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KMOS User Manual

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1. WEE IFU 24 IFU 1 IFU 1 IFU 24 IFU 1 IFU 24 Figure 13 An illustration of the quality of sky subtraction on the left for the simple sky subtrac tion method and on the right using the optimal sky subtraction method following the algorithm presented in Davies 2007 The matrix shows arm to arm subtraction in the same exposure e g the sky residual in IFU using IFU to do sky subtraction in the same exposure For comparison the vector at the bottom shows the sky residual when the sky is subtracted from the same IFU but from the subsequent exposure e g IFU IFU in the classical A B sequence e Optimal sky subtraction IFU on source IFU on sky after rescaling the OH lines An improvement can be obtained by using an optimal sky subtraction in which the sky is determined as before by a subsequent exposure on the same IFU classical A B nodding but this time applying a wavelength dependent scaling of the various OH sky lines in the sky frame following the algorithm presented in Davies 2007 MNRAS 375 1099 This method gives smaller residuals and is currently being implemented in the KMOS pipeline e Cross arm sky subtraction IFU on source IFU on sky with out rescaling the OH lines Another possibility is to remove the sky background by subtracting one arm from another in the same exposure e g having only few arms dedicated to sky during the whole OB and using them to subtract the
2. e If possible use the same rotator angle for acquisition and science observations since a significant difference in the rotator angle might introduce some positioning error up to 2 3 pixels shift of the science targets on the IFU for large rotations e To avoid persistence it is recommended to observe simultaneously only sources with similar magnitudes within a range of 3 4 magnitudes Choose the DIT and NDIT using the ETC such that fluxes are at most 5 000 ADUs DIT pixel 2 500e DIT pixel even for significantly better conditions than foreseen e g using seeing 0 4 in the ETC e Do not observe sources brighter than 6th magnitude Vega in all bands because that would saturate and cause severe persistence e For observations of faint targets which will not be detected in each single exposure it might be useful to have one or two IFUs dedicated to observe a brighter star which will be detected in a single exposure and therefore can be used to cross check the registration of the frames For example if the main science targets are faint galaxies Hap 23 observed with several 300sec exposures it can be useful to dedicate one of the 24 IFUs to observe simultaneously a star of Hag 19 20 in the field e Use a AB AB or ABA ABA nodding pattern to obtain best sky subtraction sky frequency 1 or 2 e IZ and YJ observations in dark and grey time or bright time if gt 90 away from the moon H and K observati
3. DET1 SEQ DIT Integration 0 3600 10 Individual integration time time DIT in seconds for the reference stars DET1 NDIT Number of 1 100 1 Number of DITs to combine DITs before writing the data to the disk ADA GUID ALPHA RA guide star NODEFAULT RA coordinate of the guide star Need to be added by the user in P2PP and corrected for proper motion ADA GUID DELTA DEC guide star NODEFAULT DEC coordinate of the guide star Need to be added by the user in P2PP and corrected for proper motion OCS GRFI NAME GratingFilter IZ YJ H K HK NODEFAULT Grating name The following parameters need to be implemented second icon on the top panel in the target section Dec TEL TARG NAME Name NODEFAULT Name of the standard star TEL TARG ALPHA Right Ascen NODEFAULT RA coordinate of the standard sion star Need to be added by the user in P2PP TEL TARG DELTA Declination NODEFAULT DEC coordinate of the stan dard star Need to be added by the user in P2PP TEL TARG EQUINOX Equinox J2000 Equinox TEL TARG EPOCH Epoche 2000 Epoch of observation used with the next two parameters to correct for proper motion TEL TARG PMA Proper motion 0 0 Proper motion of the standard RA star in RA in arcsec yrA TEL TARG PMD Proper motion 0 0 Proper motion of the standard star in Dec in arcsec yrA NOTE The Coordinates for the standard star can be provided
4. ICE Cabinets Maintenance Trolley 8 Handling Pods Figure 2 Schematic view of KMOS on the Nasmyth platform KMOS has been designed to have effectively three independent modules each of them com prising 8 pick off systems a set of 8 Integral Field Units IFUs one spectrograph and one 2kx2k HgCdTe near IR detector The following section describes the different sub systems of KMOS in the order they are encountered along the optical path going from the telescope to the detector 2 2 Description of the instrument sub systems 2 2 1 The pick off system The selection of the pick off fields is achieved by means of 24 telescopic pick off arms which patrol the instrument focal plane of 7 2 arcmin diameter Each pick off arm contains a pick off mirror and associated relay optics which are positioned inside the telecentric instrument KMOS User Manual ESO 264148 5 Figure 3 Top one of the pick off arms Bottom the full 24 pick off arms in the front end of the KMOS cryostat KMOS User Manual ESO 264148 6 focal plane by means of an articulated arm The pick off arms are arranged into two different planes top and bottom of twelve arms each so that adjacent arms cannot interfere with each other One of the planes is placed above the nominal focal plane and one below Each layer of twelve pick off arms can patrol 100 of the field The two motions radius and theta of the pick off arms are both driven by stepping mo
5. IRIS Photometric Standards the MSSSO photometric standards a composite list of bright spectroscopic standards and the Hipparcos Catalog The majority of the standards come from the Hipparcos Catalog Although the Hipparcos Catalog is an excellent source of telluric standards for ISAAC most of the stars in the catalog do not have IR magnitudes which means that IR magnitudes have to be inferred from the spectral type Such an extrapolation leads to an uncertainty of 5 20 in the absolute flux calibration If users wish to have a more certain absolute flux calibration they should provide their own standards and should include these observations in their time request in Phase 1 Alternatively if the broad band magnitudes of the object are known the absolute flux calibration can be derived by convolving the measured spectrum with the broad band filter curves In this case the IR magnitude of the standard is irrelevant only KMOS User Manual ESO 264148 30 the spectral type is important KMOS offers two possibilities to observe a standard star 1 The template KMOS_spec_cal_stdstar allows the user to observe a standard star in only 3 IFUs one per each spectrograph Then the calibration from these 3 IFUs needs to be applied to the remaining IFUs These standard star observations will be taken automatically by the observatory and will not be charged to the user programme The telluric will be taken within 2 hours from the science observations
6. KARMA A2 A3 2 8 Al E NOTE the dither offsets are in arcsec and always referring to the initial position A5 Ap A4 A Science Pattern A1 A2 A3 A4 A5 A6 0 0 0 3 0 3 0 3 0 3 0 3 0 3 0 3 0 3 0 0 3 Object Position defined in KARMA Sky pattern B1 B2 B3 0 0 0 3 0 3 0 3 0 3 Figure 15 An illustration of the dither pattern that can be constructed with the free dither template in P2PP The sequence for just 1 IFU is shown since it will be identical for all of them This example is for 6 object frames and sky frequency 2 which gives in total 3 sky frames in the sequence ABA ABA ABA KMOS User Manual ESO 264148 25 if the target is gt 90 degrees away from the Moon Faint observations in IZ band should be performed in dark time It is always recommended not to observe targets closer than 30 degrees to the Moon to avoid problems linked to the telescope guiding 3 4 8 The influence of precipitable water vapour PWV In general the precipitable water vapour is not critical for near IR observations with KMOS By default the PWV limit in P2PP is set to 20mm If a more stringent PWV constraint than 10mm is required this can be done by a waiver 3 4 9 Rotation Optimisation Before preparing the KARMA set up file it is strongly recommended to check the status of the instrument and inactive pick off arms at the following web page http www eso org sci facilities
7. Manual ESO 264148 28 4 1 1 Darks Produced by KMOS_spec_cal_dark Dark frames with exposure times corresponding to the exposure time of the object Dark frames are used to correct for the instrument bias especially if no off or sky frames are available In addition dark frames are used to generate bad pixel maps 4 1 2 Flat field calibration Produced by KMOS_spec_cal_calunit Flat fields are used to correct for pixel to pixel sensitivity variations The flats are taken during daytime calibration using the internal flat lamp with constant intensity The flats are generated daily for all the bands that have been observed during the night and a set of flats in all bands are also taken regularly e g every week or month to run the RTD Real Time Display The flats are taken at a rotator angle as close as possible to one used during observations to reduce the effect of flexures 4 1 3 Wavelength calibration Produced by KMOS_spec_cal_wave Arc lamp frames for wavelength calibration Argon and Neon are obtained for each spectral band observed during the night As for the flats the arc lamp frames are taken at a rotator angle as close as possible to the one used during observations to reduce the effect of flexure The sky frames containing OH lines can be used to improve the wavelength calibration by removing residual flexure and obtain a better registration of the frames before combining them 4 1 4 Spectroscopic sky flats Prod
8. Telescope VLT Very Large Telescope 1 3 Scope of this document The aim of the KMOS User Manual is to provide information on the technical characteristics of the instrument its performance observing and calibration procedures and data reduction from a user astronomer perspective 1 4 KMOS in a nutshell The K band Multi Object Spectrograph KMOS is a second generation instrument designed for operation on the VLT The key feature of KMOS is its ability to perform Integral Field Spectroscopy in the near infrared bands for 24 targets simultaneously The instrument design employs 24 configurable arms that position pickoff mirrors at user specified locations in the Nasmyth focal plane The sub fields thus selected are then fed to 24 image slicer integral field units IFUs that partition each sub field into 14 identical slices with 14 spatial pixels along each slice Light from the IFUs is then dispersed by three cryogenic grating spectrometers which generate 14x14 spectra with 1000 Nyquist sampled spectral resolution elements for each of the 24 independent sub fields The patrol field of the pickoffs is 7 2 arcmin in diameter which is the diameter of the un vignetted field at the VLT Nasmyth focus thus minimising the thermal background in the K band Each IFU has a square field of view of 2 8x2 8 arcsec anamorphic magnification in the IFU foreoptics ensures uniform spatial sampling of 0 2x0 2 arcsec whilst maintaining Nyquist sampling 2
9. a dialogue panel will pop up see Figure 19 showing the required offset in RA and Dec and rotation to be applied to centre the reference stars in the IFUs At this point the user can inspect the results and have the following choices a Accept Apply the offset and proceed to the science observations without taking a new image of the reference stars after the offset b Accept new image Apply the offset but take a new image of the reference stars and recalculate the offset This iterative process can be repeated until the required centering accuracy is achieved recommended residual lt 0 1 c Accept no offset Proceed to science observations with no offset applied d Sky image Takes a sky image to increase the S N KMOS User Manual ESO 264148 39 e Repeat Takes a new image allowing the user to increase the exposure time insert ing the new value in the exposure time box and press Change Time f Abort Terminate the OB 5 Once the centering of the reference stars is completed residual offset lt 0 1 the arms are retracted and re deployed to the science targets as defined in KARMA In the following we describe in details the parameters required by the acquisition templates to be set in P2PP KMOS User Manual ESO 264148 7 2 1 KMOS_spec_acq 40 This template performs acquisition i e telescope preset and instrument setup Then a test exposure is taken From this exposure the telescope
10. and instrument misalignment is deter mined and a corresponding telescope offset is performed SCI template Parameter P2PP Label Range Default Notes DET1 SEQ DIT Integration 0 3600 10 Individual integration time time DIT in seconds for the reference stars DET1 NDIT Number of 1 100 1 Number of DITs to combine DITs before writing the data to the disk SEQ TPLSCI DURATION Duration 0 36000 3600 Duration of SCI template in seconds needed to calculate atmospheric refraction NODEFAULT TEL TARG ALPHA Right Ascen NODEFAULT RA Central coordinate of sion the acquisition position Taken automatically from the KARMA target set up file TEL TARG DELTA Declination NODEFAULT DEC Central coordinate of the acquisition position Taken automatically from the KARMA target set up file TEL TARG EQUINOX Equinox 2000 Equinox Taken automatically from the KARMA set up file SUPR OPTROT Suppress T F F Choosing True T it will not Rotation perform the rotation optimi Optimisation sation in case one or more arms allocated to targets are inactive when executing the OB See Section 3 4 9 and Ap pendix for more details OCS INS TARG SETUP KARMA target ins KARMA target set up file set up file OCS GRFI NAME GratingFilter IZ YJ H K HK Grating name KMOS User Manual ESO 264148 7 2 2 KMOS_spec_acq_mapping Al For this acquisition only telescope
11. before assembly 2 2 2 Integral Field Units and filters FUs contain the optics that collect the output beam from each of the 24 pick offs and reimage it with appropriate anamorphic magnification on the image slicers All the slices from a group of 8 sub fields are aligned and reformatted into a single slit for each of the three spectrographs KMOS User Manual ESO 264148 7 Table 2 Characteristics of the KMOS detectors Detector type Substrate removed Hawaii 2RG Operating temperature 35K QE gt 90 Number of pixels 2048 x 2048 Pixel size 18m Gain e ADU 2 08 Readout noise e 9 for short DIT 2 6 for long integration with Fowler sampling Saturation ADU gt 60 000 ADU Non linearity gt 55 000 ADU Persistence gt 5 000 ADU Hot pixels x1 in detectors 2 and 3 23 in detector 1 Minimum DIT s 2 47 The IFU sub system has no moving parts and has gold coated surfaces diamond machined from aluminium for optical performance in the near infrared and at cryogenic temperatures Each pick off arm contains a fold mirror located at the tip of the arm to divert the input beam along the arm A lens is used to collimate the beam and re image the telescope pupil onto the cold stop located in the arm A roof mirror which moves in a direction opposite to the fold mirror maintains the optical path length to the cold stop A subsequent fold mirror then directs the beam along the arm s rotational axis and away from the telescope and to
12. from the setup by rotator optimisation it is for example listed in the header which target was assigned to it but could not be observed This information is important for the user who otherwise might wonder where a target allocated in KARMA might have gone to An example fits header after rotator optimisation is given below HIERARCH ESO OCS ROT OFFANGLE 30 000 DDD TTT Rotator offset angle HIERARCH ESO OCS ROT OFFSET 30 000 deg Angle used during rotator o HIERARCH ESO OCS ARM3 ALPHA 52415 822 HHMMSS TTT Target alpha hosted HIERARCH ESO OCS ARM3 DELTA 242952 620 DDMMSS TTT Target delta hosted HIERARCH ESO OCS ARM3 NAME 328 007849 Target name hosted by arm i HIERARCH ESO OCS ARM3 PRIOR 2 Target priority hosted by arm i HIERARCH ESO OCS ARM3 ORIGARM 1 Original arm number before rotato HIERARCH ESO OCS ARM4 NAME 328 007827 Target name hosted by arm i HIERARCH ESO OCS ARM4 ORIGARM 2 Original arm number before rotato HIERARCH ESO OCS ARM4 NOTUSED Coll Reason why arm was not used HIERARCH ESO OCS ARM14 NAME Target name hosted by arm i HIERARCH ESO OCS ARM14 ORIGARM 12 Original arm number before rotato HIERARCH ESO OCS ARM14 NOTUSED NotInPAF Locked Reason why arm was not used The real rotator angle which is sent to the TCS is given by the keyword OCS ROT OFFANGLE and is the sum of the rotator angle defined in the KARMA set up file and OCS ROT OFF
13. in two equivalent formats 1 RA and Dec corrected for proper motion and set proper motions in RA and Dec 0 0 or 2 RA and Dec non corrected for proper motion and provide the values of the proper motion KMOS User Manual ESO 264148 7 2 4 KMOS_spec_acq stdstarscipatt 43 The acquisition process is very similar to the one described above The difference is that the arm pattern is the one from science observation NOTE The position of the guide star should be outside the KMOS field of view and in the annulus between 4arcmin and 12arcmin from the standard star In the target tab the coordinates of the standard star must be introduced NODEFAULT Parameter P2PP Label Range Default Notes DET1 SEQ DIT Integration 0 3600 10 Individual integration time time DIT in seconds for the reference stars DET1 NDIT Number of 1 100 1 Number of DITs to combine DITs before writing the data to the disk ADA GUID ALPHA RA guide star NODEFAULT RA coordinate of the guide star Need to be added by the user in P2PP and corrected for proper motion ADA GUID DELTA DEC guide star NODEFAULT DEC coordinate of the guide star Need to be added by the user in P2PP and corrected for proper motion OCS INS TARG SETUP KARMA target ins KARMA target setup file to set up file configure the arms OCS GRFI NAME GratingFilter IZ YJ H K HK Grating name The following parameters need to be
14. lamps Arms are set in calibration position Detector integration time and attenuator are set automatically for the used lamp s and defined erating filter combination GRFI The corresponding parameters are stored in the configu ration The default parameters can be overwritten during execution of the OB if parameter SEQ ASK ATTEN TIME is set to T Parameter P2PP Label Range Default Notes DET1 NDIT Number 1 100 1 Number of DITs to combine of DITs before writing the data to the disk SEQ ASK ATTEN TIME Ask for attenu T or F T Setting for interactive execu ator and time tion If TRUE it will ask for the level of attenuator and ex posure time during execution If FALSE it will use the default value without asking SEQ NEXPO Number of ex 1 100 1 Number of exposures at a posures given position of the rotator SEQ ROT Rotator posi 270 270 List of rotator positions at tion which the flat field is taken The default is 6 rotator posi tions separated by 60 degrees 60 0 60 120 180 240 INS FLATLAMP NAME Flatfield Lamp LAMP3 LAMP4 LAMP3 4 DE FAULT Flat field lamp to be used for the observation OCS GRFI NAME GratingFilter IZ YJ H K HK NODEFAULT Grating to be used for the ob servation KMOS User Manual ESO 264148 54 7 4 6 KMOS_spec_cal calunitflatnight Attached calibration flat taken during the night just after the science observat
15. mode For the spectroscopic observation of extended contiguous fields on the sky KMOS provides two dedicated configurations known as Mosaic mode where the individual IFUs either all 24 or a subset of 8 are arranged in such a way that with successive telescope pointings a contiguous rectangular area can be covered see section 7 3 5 and 7 3 4 For data reduction a single sky background position as in the other modes is necessary Figure 10 third column For the two existing predefined configurations the participating arms are allocated to fixed positions forming a 6 x 4 or a 4 x 2 array Figure 11 shows the positions of the IFUs red squares in these arrangements for the first telescope pointing starting in the upper left corner The observation block that you prepare will contain just this first pointing along with the appropriate arm positions All subsequent telescope offsets however will be calculated by the instrument control software automatically during the OB execution To ensure there are no gaps the spacings between the IFUs are slightly smaller than an integer multiple here three and two of the IFU size With the given configurations it is thus possible to map rectangular areas of 64 9 x 43 3 2810 sq arcsec and 32 5 x 16 3 530 sq arcsec with 16 and 9 telescope pointings respectively in a single OB In the unlikely case that even such a comparatively large field as the 6x4 one is still too small to fulfill your scie
16. or 9 5 Number of dithers dither pat of dithers tern see Figure 20 SEQ DITHER SIZE Dither size 0 2 arcsec 0 2 Dither size in arcsec SEQ SKYOBS FREQ Sky 0 100 0 Frequency of sky exposure will be observed See Section 3 4 5 for details every X science e g 0 no sky exposures 1 exposures sky after every science expo sure etc NOTE In this template the number of sky frames is determined by 2 parameters the sky fre quency SEQ SKYOBS FREQ and long sky exposure The number of science frames is determined by the of dithers SEQ DITHER NO in this template limited to 3 5 or 9 For example let s assume we need 3 science frames Number of dithers 3 of 30sec each Integration time 30 With the same convention as in Section 3 4 5 we define A the science frame and B the sky frame e If sky frequency is 0 and optional long sky exposure is 0 then no sky will be taken at all The observing sequence will be AAA e If sky frequency is 0 and optional long sky exposure is gt 0 e g 30 then a single sky frame of 30sec will be taken at the end of the science sequence e g after all science frames are taken The observing sequence will be AAAB KMOS User Manual ESO 264148 46 e If sky frequency gt 0 e g 1 and optional long sky exposure gt 0 e g 60 then sky frames of 30sec as the science frames will be taken after each science frame plus a
17. pixel of the spectral resolution element at the detector KMOS User Manual ESO 264148 2 Table 1 KMOS main specifications Wavelength coverage 0 8 um to 2 5 um Spectral bands IZ YJ H K HK Spectral resolving power R 3400 3600 4000 4200 2000 IZ YJ H K HK Number of IFUs 24 Extent of each IFU 2 8 x 2 8 Spatial sampling 0 2 x 0 2 Patrol field 7 2 arcmin diameter circle Closest approach of IFUs lt 2 IFUs separated by 6 arcsec centre to centre of the IFU depending on the details of the configuration The use of focal plane pick offarms allows considerable flexibility in selecting targets and in particular the important capacity to deal with strongly clustered or close paired sources In addition to observing multiple individual sources KMOS has the capability for integral field mapping of contiguous areas in a 9 point or 16 point dither pattern The spectral resolving power of R 3000 4000 is optimal for OH avoidance in the J amp H bands A lower spectral resolution mode is also availablein the combined H K band KMOS main specifications are summarized in Table 1 1 5 Integral Field Spectroscopy In traditional spectroscopy a slit or a single aperture is placed into the focal plane which is re imaged through the spectrograph onto the detector While this measure is necessary to arrange detector space in dispersion direction to allow the spectra spread the disadvan
18. sequence sky subtracted from the same arm in subsequent exposure e g A B and on the right for the cross arm subtraction in this case IFU1 IFU7 which are imaged onto the same detector The fluxes are in arbitrary units The top panels are for the simple subtraction and the bottom panels for the optimised method following Davies 2007 Please note the different Y axis scales on the right and left hand panels The cross arm subtraction leaves sky residuals which are a factor 2 3 higher compared to the normal nod to sky method and the residuals are even worse when using IFUs from different detectors for the sky subtraction as shown in Figure 13 will be averaged out The recommended amplitude of the dither is 0 1 0 3 and should be lt 0 6 to avoid that part of the object goes outside the IFU The offsets for dithering corresponds to the telescope positions on sky i e they are defined as absolute offsets and follow the astronomical convention i e top is North and left is East therefore the objects move in the opposite direction on the reconstructed cube In the case of the nod to sky template the dither pattern is fixed and there is a choice between 3 5 9 points dither For the free dither template the user can specify the full dither pattern as well as the frequency with which to observe the sky i e the sky frequency The dither offsets specified in P2PP are in arcsec and always refer to the initial position defined in K
19. showing the two layers of pick off arms allocated to targets with the IFU field of view for each arm shown on the right hand side e Guide stars are used by the telescope to guide the field during the exposures once the acquisition is complete They must be given in R band the guider wavelength and must be in the range 8 lt Rvega lt 12 It is preferred to provide several guide stars e It is very essential for successful KMOS observations that all entries in the user provided catalogue are on the same astrometric system and that proper motions are considered i e for bright reference targets and potential guide stars e A fits image of the field is also needed to determine a suitable sky background position for the telescope nodding e The first step is to choose one of the three observing modes available in KMOS Nod to Sky Stare or Mosaic see Section 3 4 e Then the pick off arm allocation is performed by using two predefined algorithms Hun garian and Stable Marriage or manually by the user The automated algorithms have been implemented with the aim of maximising the number of pick off arms allocated to targets considering the relative priorities and accounting for all the restrictions to avoid collisions or vignetting of the pick off arms e KARMA also allows the users to define the arm configuration for acquisition which can be done using science targets or reference targets e Finally the user creates the instrument co
20. strategies whereof two are mainly differing by the way the sky background signal is determined Nod to Sky and Stare The third allows for the observation of contiguous fields on sky Mosaic instead of multiple isolated targets See Figure 10 3 4 1 Nod to sky mode In this mode the sky background signal is obtained by moving nodding the telescope and or rotating the instrument between two previously defined positions depicted by the two schematic configurations in the left column of Figure 10 Each pick off arm IFU represented schemati cally by a black square switches between its scientific target red bullet and a corresponding own sky background position blue square The sky position has to be determined using KARMA In the process of nodding only the telescope and or instrument rotator positions are altered the pick off arm configuration remains unchanged In the nod to sky mode there is a fixed sequence AB AB where A is the science position and B is the sky position Please note that in position B some IFUs can contain science targets if they are located on KMOS User Manual ESO 264148 18 sky in position A In case that not all 24 arms can be allocated at once to scientific targets within a single telescope instrument position it is possible to assign not used arms to blank sky It is possible to introduce a small dither between each exposure effectively shifting the targets within the IFUs note the dither is the same for a
21. the helium and hydrogen absorption in the spectrum of the hot star Some hot stars also have emission lines or are in dusty regions These stars should be avoided The V I colour of the star can be used as an indicator of dust For stars hotter than AO it should be negative And lastly hot stars tend to lie near the galactic plane so there may be positions on the sky where there are no nearby hot stars available Solar analogs for the purpose of removing telluric features are stars with spectral type GOV to G4V These standards have many absorption lines in the IR particularly in the J band The features can be removed by dividing by the well known solar spectrum that has been degraded to the resolution of the observations In addition to hot stars and solar analogs IR astronomers have used other stellar types as telluric standards For example F dwarfs are commonly used We would like users to think carefully about which star is best for their program Although the observatory will automatically observe a telluric standard for service programs we cannot guarantee that we will make the best choice as this depends on the science users wish to do If you think that a specific spectral type suits your program better than others we recommend that you mention the spectral type in the Readme file and User Comment of the OB or submit calibration OBs which are charged to the user The observatory selects telluric standards from four catalogs the
22. to calibrate all IFUs is sufficient at the level of precision of a few percent KMOS User Manual ESO 264148 32 5 Instrument features and known problems 5 1 Ghosts Because KMOS works in second order for all of the high dispersion gratings it is susceptible to first order Littrow grating ghosts Figure 17 shows an image in the YJ band obtained with only one arm in its calibration position fully illuminated with the Argon Neon lamps The remaining 7 arms are parked in the field outside the calibration position A ghost image is clearly visible on the left of the array The colour scale has been enhanced to show the ghost since the level of the ghost is less than 1 part in 100 for all bands YJ band Illuminated IFU uonoaup jesjoeds Figure 17 Image in the YJ band with one single IFU illuminated with a Argon Neon calibration lamp on the right The ghost is visible on the left side of the array The colour scale has been enhanced to show the ghost since the level of the ghost is less than 1 for all bands This ghost image has been predicted by modelling and it is produced by light reflected from the detector and re dispersed by the grating By design KMOS gratings IZ YJ H and K work in 2 order The light reflected by the detector is dispersed back in 1 order by the grating and produces an in focus image of the science spectrum at lower spectral resolution and with the wavelengths reversed The ghost appears on the opposite si
23. 00 1600 1800 2000 2200 2400 2600 Wavelength nm Figure 12 Sky emission as a function of wavelength frame at all but it can be modified to allow more sky frames by setting the sky frequency parameter to a value larger than zero Note that with the sky frequency parameter the exposure time for the sky frames is always the same as for the science frames e g 300 sec on science and 300 sec on sky Defining A the object observations and B the sky observations the following object sky sequences are recommended here shown for the free dither mode e AB AB one sky frame for each object frame sky frequency 1 e ABA ABA one sky frame for 2 object frames sky frequency 2 e AABAA AABAA one sky frame for 4 object frames sky frequency 4 NOTE The sky frequency MUST be lt the number of object frames e g for an OB with 4 science frames the sky frequency parameter must be lt 4 It is recommended to use always the closest sky frame to the object frame to perform sky subtraction this is done automatically by the pipeline The frequency of sky frames depends on the sky subtraction accuracy needed and the brightness of the targets For faint targets a sky frame every one or two object frames is recommended sky frequency 1 or 2 while for bright sources e g mag lt 17 18 it is possible to reduce the number of sky frames to 1 sky every 4 object frames or even more sky frequency gt 4
24. 10mas per year then the corrections must be calculated and included in the catalogue positions for guide stars reference stars and science targets e Science targets as well as guide and reference stars must be on the same astrometric reference frame with an accuracy of 0 2 arcsec or better e Check the instrument news web page for locked arms in your foreseen observing pe riod http www eso org sci facilities paranal instruments kmos news html KMOS User Manual ESO 264148 17 El y Y a 2 9 v ZS Telescope at Sky position Figure 10 Schematics of the three observation modes configurable by KARMA Nod to Sky Stare and Mosaic Depending on the current telescope position an arm is either allocated to a science target or to sky background The offsets between Science and Sky position are performed by the telescope alone while the pick off arms remain fixed at their positions in the focal plane Only a few IFUs are depicted Not drawn to scale Avoid high priority e g 1 or 2 science targets on those arms when creating an arm configuration by disabling the locked arms within KARMA 3 4 Observing modes Although KMOS is a rather complex instrument it offers essentially only a single observation mode Integral Field Spectroscopy at least as far as the term observation mode is usually understood within the context of VLT instrumentation Beyond that however KMOS allows three different observing
25. 2 MS spec OBS DOAISEY circa ra Dae AR 7 3 3 KMOS spec obs freedither 1 be ee REE REDE E RHEE ioe WMO Spee abs ENEE o e ehh ew ERG EERE ERR EH ES tao KMOB spec obs Mappingll 4 2 542 454 ee debe ede ee ees TA Calibration Templates gt o 2460254 Pedi a Decd oe cud deed ee TAL TO DO CASARSE erh E A eR ORE SEES AA Fa KMOSspeccalstdstatscipatt s A A ese erent e TAS KMOSspeccalskylat os a AAA AAA we EN 7 4 4 KMOS spec caldark coses iris as e TAS EM Eemer caltalunibe o ie hae ed RA A 746 KMOS speccalcalunitfatnight s ccc ocara ctrca croen TA KMOSspeccal wave oaao amaran a Oe eRe A ee OR eS vi 27 27 28 28 28 28 28 30 32 32 34 34 35 35 35 35 36 KMOS User Manual ESO 264148 vii TAS KMOS speccalwavenight cis e6e eee eee we e 55 FED KMOS speccallinearity 2 2 aoe ed ae eh a we Re menera e 55 8 Appendix 56 Cok Tier CUI cid OE POSS E RES 56 SL Fits DANS s core rs E AA eS a 56 8 2 Total instrument transmission 59 KMOS User Manual ESO 264148 1 1 Introduction 1 1 Applicable Documents AD1 VLT MAN KMO 146606 002 KMOS KARMA user manual AD2 1 2 Abbreviations and acronyms AD Applicable Document ESO European Southern Observatory FWHM Full Width at Half Maximum IFU Integral Field Unit KMOS K Band Multi Object Spectrometer PAE Provisional Acceptance Europe PSF Point Spread Function RD Reference Document RTD Real Time Display TBC To Be Confirmed TBD To Be Decided UT Unit
26. ARMA they are NOT cumulative offsets i e relative to the previous position as for other VLT instruments Objects and sky positions are both dithered The dithering pattern is specified in P2PP but the sequences are followed independently according to the frequency of sky observations Figure 15 shows an example with free dither template 6 object frames and 3 sky frames in the pattern ABA ABA ABA 3 4 7 The influence of the Moon Moonlight can produce an increase of the continuum sky background especially at short wavelengths The effect of the Moonlight on a specific observation can be quantified using the KMOS Exposure Time Calculator As a guideline observations in H and K band are not noticeably affected by Moonlight and therefore can be performed in any condition including bright time Observations in the YJ band can be affected by Moonlight especially when the target is very close to the Moon e g observations at 15 degrees away from the Moon have a background 3 times higher compared to 90 degrees away from Moon Therefore it is recommended to perform YJ observations of faint targets in grey time or in bright time KMOS User Manual ESO 264148 24 Dither sequence defined in P2PP DITHER Pattern in ALPHA 0 0 3 0 3 0 3 0 3 0 B24 A Bi DITHER Pattern in DELTA 0 0 3 0 3 0 3 0 3 0 3 Sky observed every X science 2 B1 Object sky sequence A B A A3B A As BzAs 2 8 Sky Position defined in
27. EUROPEAN SOUTHERN OBSERVATORY ES Organisation Europ ene pour des Recherches Astronomiques dans l H misph re Austral O Europ ische Organisation ftir astronomische Forschung in der s dlichen Hemisph re ESO European Southern Observatory Karl Schwarzschild Str 2 D 85748 Garching bei Miinchen Very Large Telescope Paranal Science Operations KMOS User Manual Doc No ESO 264148 Issue 1 7 Date 19 07 2015 M Cirasuolo R Sharples L Schmidtobreick Prepared A IE Date Signature A Smette Approved eg Ee wet ses a Date Signature S Mieske Released e HKG PES EE Raw ke Date Signature KMOS User Manual ESO 264148 This page was intentionally left blank KMOS User Manual ESO 264148 ill Change Record Issue Rev Date Section Parag affected Reason Initiation Documents Remarks 2014 12 21 all converted from Word format KMOS User Manual ESO 264148 This page was intentionally left blank KMOS User Manual ESO 264148 Contents 1 Introduction Aid 1 2 1 3 14 1 5 Applicable Documents sss a e E A BE O RE A Abbreviations and acronyms SOONG of this COIE s ss RA oS ESHER RER ER GREER DEH KMOS ties xs clicar BeOS Ee SE EE KES RS Integral Field Spectroscopy eo opos 6 peed een be ea wba wee g 2 Technical description of the instrument CN 2 2 E 2 4 Overview OF the imstrument lt lt kb REDE SERRE SE Ree SERGE a Descriptio
28. OLE SEQ SKYOBS FREQ Sky 0 100 0 Frequency of sky exposure will be observed See Section 3 4 5 for details every X science e g 0 no sky exposures 1 exposures sky after every science expo sure etc KMOS User Manual ESO 264148 52 7 4 Calibration Templates 7 4 1 KMOS_spec cal stdstar This template works together with KMOS_spec_acq stdstar see 7 2 3 After acquisition the standard star is located in the first IFU With the template KMOS_spec_cal stdstar the star is observed only in 3 pre defined IFUs one per each spectrograph With telescope offsets the star is observed in sequence through the 3 IFUs and at the end again through the first Parameter P2PP Label Range Default Notes DET1 SEQ DIT Integration 0 3600 10 Individual integration time time DIT in seconds for the science targets DET1 NDIT Number 1 100 1 Number of DITs to combine of DITs before writing the data to the disk OCS TARG FLUXSTD Magnitude of NODEFAULT Magnitude in the Vega system the standard of the standard star in the ob star Vega served band OCS TARG TELLUR Spectral type of NODEFAULT Spectral type of the standard standard star star see section 4 1 5 for de tails 7 4 2 KMOS_spec_cal stdstarscipatt The actions are very similar as in KMOS_spec_cal_stdstar above The difference here is that the position of the IFUs is as in the science observation The calibratio
29. OS User Manual ESO 264148 57 offset in degrees which was calculated during rotator optimisation any value different from 0 indicates that a real rotator optimisation took place i e that the targets were assigned to new arms For each arm the fits header holds all the information which was available in the KARMA set up file for the original arm i e the arm holding the same target before rotator optimisation Additional information is given by the following two keywords e OCS ARMi ORIGARM This keyword holds the number of the arm to which the target was assigned originally in the KARMA set up file e OCS ARMi NOTUSED If this keyword is present arm i was not used for the observation There are several possibilities why this might be the case No target was assigned to the original arm in the KARMA set up file and this information was rotated on to arm i Arm i is locked Arm i would collide go into a limit switch or be eclipsed by a lock arm The spectrograph connected with arm i is not useable Of course several of these things may happen simultaneously The value given in the fits header for the keyword tries to summarize these things in a short text message but the really important information is if the keyword is present or not It should be noted that the OCS ARMi NOTUSED keyword has no influence on the rest of the information given for an arm in the fits header i e even if an arm was removed
30. PRESET and instrument SETUP are performed no align ment is done Note that no acquisition exposure is executed for this template NODEFAULT Parameter P2PP Label Range Default Notes TEL TARG ALPHA Right Ascen NODEFAULT RA Central coordinate of sion the acquisition position Taken automatically from the KARMA target set up file TEL TARG DELTA Declination NODEFAULT DEC Central coordinate of the acquisition position Taken automatically from the KARMA target set up file TEL TARG EQUINOX Equinox 2000 Equinox Taken automatically from the KARMA set up file OCS INS TARG SETUP KARMA target ins KARMA target set up file set up file OCS GRFI NAME GratingFilter IZ YJ H K HK Grating name KMOS User Manual ESO 264148 7 2 3 KMOS_spec_acq stdstar 42 Three arms are positioned near the centre of the FoV The telescope is positioned in such a way that the standard star will be located in first of the used arms Then the alignment process with one star is performed NOTE The position of the guide star should be outside the KMOS field of view and in the annulus between 4arcmin and 12arcmin from the standard star In the target tab it is possible to insert the coordinates of the standard star already corrected for proper motion or the J2000 coordinates and the value of the proper motion in arcsec per year Parameter P2PP Label Range Default Notes
31. SET KMOS User Manual ESO 264148 58 We can see here that during the rotator optimisation an offset of 30 0 deg was calculated OCS ROT OFFSET i e each target was shifted to the next arm in the same layer Obviously a rotator angle of 0 was defined in the KARMA set up file since the angle sent to the TCS OCS ROT OFFANGLE is identical with the rotator optimisation offset The following lines display the fits header information for three different arms 3 4 and 14 e Arm3 was used during the observation the OCS ARM3 NOTUSED keyword is not present the arm holds the target 328 007849 which was assigned in the PAF file to arml as can be seen from the OCS ARM3 ORIGARM keyword e Arm4 was not used during the observation the OCS ARM4 NOTUSED keyword is present and tells us that the arm would have collided if it had moved to its position The target which was assigned to this arm but could not be observed was assigned in the KARMA set up file to arm2 OCS ARM4 ORIGARM e ARM14 was again not used during the observation the OCS ARM14 NOTUSED is present and tells us the reasons for this There was no target assigned in the PAF file to the original arm NotInPAF The arm is locked and hence cannot be used for an observation Locked The corresponding original arm 12 is again given by the OCS ARM14 ORIGARM key word The following reasons for an arm not to be used in an observation can appear i
32. The key parameter to define the object sky sequence is the sky frequency labelled in P2PP as Sky observed every X science exposures Table 8 illustrates the possible combinations of object and sky frames that can be obtained e Simple sky subtraction IFU on source IFU on sky All the discussions so far assume a simple sky subtraction in which the sky in a given IFU is subtracted from the same IFU in a subsequent exposure to sky e g the classical A B nodding KMOS User Manual ESO 264148 21 Table 8 Illustration of the possible sequences that can be obtained in P2PP with the combination of object frames and sky frequency The sequences are shown for up to 6 object frames but it can be extended to a larger number of frames science frames Sky frequency Object sky pattern 2 1 AB AB Recommended 2 2 ABA Recommended 3 1 AB AB AB Recommended 3 2 ABAA 3 3 ABAA 4 1 AB AB AB AB Recommended 4 2 ABA ABA Recommended 4 3 ABAAA 4 4 AABAA 5 1 AB AB AB AB AB Recommended 5 2 ABA ABAA 5 3 ABAA AA 5 4 AABAA A 5 5 AABAAA 6 1 AB AB AB AB AB AB Recommended 6 2 ABA ABA ABA Recommended 6 3 ABAA ABAA 6 4 AABAA AA 6 5 AABAA AA 6 6 AAABAAA KMOS User Manual ESO 264148 22 Simple sky subtraction Optimal sky subtraction Scaled from 0 to 150 Scaled from 0 to 75 IFU 24 Sky residuals Wwe low high IFU 1 E
33. and difference in airmass of lt 0 2 However it is possible for the user to submit his her own preferred standard star for the programme The accuracy in the calibration that can be achieved by observing the standard star only in 3 IFU of course will introduce some uncertainty in the other IFUs due to the IFU to IFU variation but the accuracy is in the range of 2 to 5 2 For more accurate calibration it is possible to use the KMOS_spec_cal_stdstarscipatt tem plate in which the standard star is observed sequentially through all IFUs The larger overheads for this template depend on the exposure time needed in each IFU For a given exposure time the overall time needed to execute this template will be a factor 8 10 longer compared to the previous KMOS_spec_cal_stdstar template For a 10sec exposure in each IFU the overheads are 10min including preset and acquisition In this case this must be requested by the user in the proposal and the total execution time will be charged to the programme 4 1 6 Attached calibrations Produced by KMOS spec cal calunitflatnight and KMOS spec cal wavenight The daytime calibrations provide flatfield and arc which are slightly shifted on the detector compared to the night time science observations due to the grating repeatability This shift is very small with a standard deviation of 0 2 pixels This has no impact on the reconstruction except to shift everything by that amount and to produce smal
34. c guidelines for Phase 2 and the P2PP software can be found at the following links e http www eso org sci observing phase2 SMGuidelines html e http www eso org sci observing phase2 P2PP3 html KMOS observations are all coded via templates and two or more templates make up an Observing Block OB which contains all the necessary information to execute the observing sequence KMOS specific templates for acquisitions science observations and calibrations are described in detail in Section 7 For the vast majority of projects the night time OBs will contain only one science template and the mandatory target acquisition template The usual darks arc for wavelength calibration and lamp for flat field exposures are taken during day time as part of the calibration plan see Section 4 1 If for some observations flats and arc data are needed immediately after the science exposure this can be obtained by attaching specific calibration templates at the end of the OB The following sections describe the observing modes available for KMOS and some highlights on how to prepare the OBs 3 2 KARMA the observation preparation tool for KMOS The P2PP software is predominantly intended for the specification of simple parameters like exposure time filter band or other settings which essentially are common to the majority of VLT instruments However the nature of a multi object spectrometer in general and the complexity of KMOS in particular r
35. ction However since the sky lines vary with time some residual will remain as for any other OH sky line Therefore it is recommended not to use too long exposure e g gt gt 600 sec 5 2 Stray light There is a low level of diffuse scattered light at each side of an IFU when illuminated with a source of light At a distance of 4 pixels from the edge of the IFU the level is lt 2 in all bands being weaker at long wavelengths 2 in IZ 1 5 in YJ 1 in H 0 8 in K and 0 8 in HK At a distance of 100 pixels from the edge of the IFU the stray light level drops to values lt 0 5 in all bands Therefore the scattered light will only affect science observations when a bright extended source completely filling the IFU is observed with other faint ones For this reason it is recommended to observe simultaneously only sources with similar magnitudes within a range of 3 4 magnitudes Please note that in some specific configurations when one arm is in park position and the neighbouring arms are deployed in the field some scattered light is visible in the arm in the park position This is of course scientifically irrelevant since the scattered light is only visible in the arm in the park position which is outside the field of view and not allocated to any science or sky target KMOS User Manual ESO 264148 35 5 3 Flexures Three different types of flexure can affect observations with KMOS 1 the flexure of the bench 2 the fl
36. d counts in each pixel are computed by fitting the slope of the signal vs time In addition Threshold Limited Integration TLI mode is used to extend the dynamical range for long exposure times if one pixel is illuminated by a bright source and reaches an absolute value above a certain KMOS User Manual ESO 264148 8 Figure 5 Top Perspective view of a single KMOS spectrograph module Bottom the three spectrographs mounted in the KMOS cryostat KMOS User Manual ESO 264148 9 Signal SIG2 EXT LEVEL SIG1 DIT Figure 6 Extrapolation threshold for nondestructive sampling and extrapolation of detector signal for high flux levels For pixels with high flux red only readout values below EXTLEVEL or ange rectangles are taken into account in the calculation of the slope and values written in the FITS files are extrapolated to the full DIT SIG2 For low flux pixels blue all nondestructive readouts are used light blue rectangles This is a modified figure from Finger at al 2008 A document explaining in detail this readout mode and its different regimes with their conse quences is available at http www eso org sci facilities paranal instruments xshooter doc reportNDreadoutpublic pdf threshold close to detector saturation only detector readouts before the threshold is reached are used to compute the slope and the counts written in the FITS image for this pixel are extrapolated to the entire exposure tim
37. d light pipe KMOS User Manual ESO 264148 10 Figure 7 View of the internal calibration unit showing the 24 output apertures or ports illuminated by the flat field tungsten lamp 2 2 6 Infrastructure and electronics The instrument housekeeping electronics IHE are mounted on the Nasmyth Platform in two electronics cabinets The instrument control electronics ICE are mounted in a further three electronics cabinets which co rotate with the instrument An instrument specific cable co rotator CACOR see Fig 2 is used to house the ICE cabinets and interface the cables to the instrument able to rotate 270 degrees This sits on an instrument handling carriage which slides on rails allowing the instrument to be pulled back to give access to the Nasmyth Rotator during maintenance operations The controller for the cable rotator mechanism is located in a fifth electronics cabinet mounted on the Nasmyth Platform to one side of the CACOR 2 3 Overall performances 2 3 1 Image quality Figure 8 shows one full detector illuminated with the arc calibration lamp argon and neon in the H band Each detector collects the light from 8 IFUs marked at the top of the image As in the traditional long slit spectrographs the spectrum across the array is curved by design however this slit curvature is relatively straightforward to correct in software and it is done as part of the data reduction pipeline As shown in the zoom in image in the right pan
38. de of the array with respect to the position of the arm that generates it For example in the Figure 17 only one IFU on the right side of the array is illuminated and the ghost is visible to the left side symmetrical with respect to the centre of the array When all the IFUs are illuminated their ghosts will fall onto pixels that contain science data Figure 18 shows the ghost level defined as the intensity of the ghost image divided by the intensity of the source that has generated it for all three detectors and all bands The results can be summarised as follows KMOS User Manual ESO 264148 33 Log Ghost level 1 0 1 2 0 25 Wavelength micron Figure 18 Ghost level as a function of wavelength for all three detectors The ghost level is defined as the intensity of the ghost image divided by the intensity of the source that has generated it The coloured boxes identify the full wavelength coverage in each band IZ YJ H K The horizontal error bars denote the fraction of the band affected by the ghost It can be noted that the level is less than 1 part in 100 and only affects a fraction of the wavelengths especially in the IZ and YJ bands The ghost is not present in the HK band KMOS User Manual ESO 264148 34 e The ghost is present in all 3 detectors and for all 24 arms e It is present in the IZ YJ H K bands but not in HK band as predicted as this latter grating works already in first order e The intens
39. detectors and all five bands
40. e This is an effective way to remove cosmic rays on these devices see Finger et al 2008 Proc SPIE Vol 7021 for a more detailed description Important Warning adjacent pixels can follow different regimes by using this readout mode one can follow the normal regime and its neighbour can follow and extrapolated regime if the counts reach the extrapolation threshold This may lead to bad line profiles which could then affect chemical abundances determinations for example Therefore we strongly recommend to select the shortest possible DITs so that the typical counts in a single frame are of the order of few thousands ADUs in the ETC This means that the counts will not be extrapolated and it will also limit persistence 2 2 5 Calibration Unit The internal Calibration Unit is located inside the cryostat and provides a quasi uniform light distribution simultaneously to all 24 fields via an 180 mm diameter integrating sphere having 24 output apertures or ports These ports are divided into sets of 12 corresponding to the upper and lower arms and the light from a specific port is directed toward its corresponding pick off field via one of 24 calibration mirrors located above the focal plane and just outside the patrol field All calibration sources tungsten lamp for flat fielding and spectral lamps argon and neon for wavelength calibration are located inside a second external integrating sphere connected to the internal sphere via a gold coate
41. e eS ONN OA BRA Rh a php D D D k HROoOOoOo Oo KMOS User Manual ESO 264148 4 Calibrating and reducing KMOS data 41 KMOS calibration Dll 2 cae ee eee haw AA LRE MA EE 412 Flat feld calibration lt sc lt s soeces rs A EN a e Al Wavelength calibration EEN ENEE NEE E ATA Spectroscopic sky late lt ss ses ss dwc eoa dired dr Koras 4 1 5 Spectro photometric Calibration and telluric standards 4 1 6 Attached calibrations 44 26 265 bee 4A Oe NN A ee EE Ee 5 Instrument features and known problems 5 1 5 2 5 3 GIO E we AR EEE ES DEED ORM CRE ERE ee E 5 1 1 Impact of ghost on science observations A o IE 5 3 1 Flexure of the bench and pick off arms 5 3 2 Flexure of the spectrograph lt 2 2 4545 4402 bea de Ee eae 5 3 0 Impact of flexure on science 6 55 ee o lt 2 2 6 Summary of hints and tips for preparing observations 7 Templates reference 7 1 Notes on some common parameters he Acquisition Templates dao beh oe hw ES Aw RMA ROR EN Tal AMV S0CC Red lt lt we EG re daa Se ERE A sa T22 MEIS spec ageet mapping cce secde ee REDDER EDR See m23 KMOS spec ac sister lt sos wide ewe bo See ERE eRe R 7 2 4 KMOS spec acqustdstarecipabt lt lt c ede 0 020524 T20 KMOSspecacgskyflat 22 kee bebe ee cr A Dok CWS Templates Au ek ET eier A A E RA ee eS Tad BIMOR Spee ae Sete cas hed ee dtor he ee eA RR HES 7 3
42. e g 30 then a single sky frame of 30sec will be taken at the end of the science sequence e g after all science KMOS User Manual ESO 264148 49 frames are taken The observing sequence will be AAAAB e If sky frequency is gt 0 e g 1 and optional long sky exposure is 0 then only the sky frames of 30sec as the science frames will be taken after every science frame for sky frequency 1 and the observing sequence will be ABABABAB e If sky frequency gt 0 e g 2 and optional long sky exposure gt 0 e g 60 then sky frames of 30sec as the science frames will be taken every 2 science frame plus an additional long sky frame of 60sec at the end In this case the observing sequence will be ABA ABA Beo sec NOTE The sky frequency MUST be lt the number of object frames e g for an OB with 4 science frames the sky frequency parameter must be lt 4 KMOS User Manual ESO 264148 50 7 3 4 KMOS_spec_obs_mapping8 With this template 8 arms are positioned as shown in Figure 21 Using the pre defined set of dithers with 9 pointings uninterrupted coverage of 32 5 x 16 3 530 sq arcsec is achieved See Section 3 4 4 for details Using the keyword Part of mosaic to be observed it is possible to split the mosaic and observe only a fraction of it This feature is needed if for example the individual exposures are long and it will take more than 1 hour to complete the 9 pointings f
43. ec_obs_nodtosky KMOS spec obs freedither KMOS spec_acq_mapping KMOS _spec_obs_mapping8 KMOS spec_obs_mapping24 KMOS_spec_acq stdstar KMOS_spec cal_stdstar KMOS_spec_acq stdstarscipatt KMOS_spec_cal_stdstarscipatt KMOS_spec_acq skyflat KMOS_spec_cal_skyflat KMOS spec cal dark KMOS _spec_cal_calunit KMOS_spec cal_wave KMOS spec cal_calunitflatnight KMOS spec_cal_wavenight Table 11 gives a summary of KMOS acquisition science and calibration templates It shows also the correspondence between science or calibration templates with corresponding acquisi tion templates The calibration templates for dark calunit flats and arcs do not need acquisi tion templates The acquisition templates using KARMA setup files do not need the specifica tion of the target RA and Dec and proper motion except for the standard star science pattern stdstarscipatt where the coordinates of the standard star have to be entered by the user 7 1 Notes on some common parameters DIT and NDIT are the user defined Detector Integration Time and the number of DITs to be integrated before writing the data to the disk KMOS User Manual ESO 264148 38 7 2 Acquisition Templates KMOS does not have an imaging mode and all data is taken in the format of an integral field spectrograph the slices sorted in x direction and the light dispersed in y direction on the detector Interactive acquisition procedur
44. el of Figure 8 the image quality in both spectral and spatial directions is good across the entire array The measured FWHM of the spectral lines is 2 pixels providing a good Nyquist sampling In the spatial direction the image of an unresolved pinhole point source no seeing included shows a FWHM of lt 1 pixel 0 2 arcsec in the direction across the slices and 1 3 pixels 0 25 arcsec in the spatial direction within the slices 2 3 2 Spectral bands KMOS allows observations across five bands mostly corresponding to the atmospheric win dows in the near infrared Due to the spectral curvature not all the IFUs have the same wavelength coverage The IFUs imaged at the centre of the array have a slightly different KMOS User Manual ESO 264148 11 u0 99 1p eoeds Spatial direction Figure 8 One full detector showing the light from the arc calibration lamp argon neon in the H band The location of the edges of the 8 IFU imaged onto the detector is shown at the top of the image The yellow squares on the image mark 9 positions for which a zoom in is provided in the right panel Table 3 Spectral coverage guaranteed in all three detectors Band Wavelength Coverage um IZ 0 779 1 079 YJ 1 025 1 344 H 1 456 1 846 K 1 934 2 460 HK 1 484 2 442 wavelength coverage compared to the IFUs at the edge of the array For completeness the wavelength coverage for IFUs at the cent
45. equire that the standard P2PP tool must be complemented by an additional piece of software which allows a more detailed configuration including the individual robotic pick off arm positions to be specified The optimal allocation of the pick off arms to their target positions is achieved by a dedicated tool called KARMA which also takes into account the target priorities and several mechanical and optical constraints Detailed information on how to download install and run the KARMA software can be found here http www eso org sci observing phase2 SMGuidelines KARMA html In the following we briefly describe the essential steps performed by KARMA to create the instrument configuration files to be attached to the OBs e As input KARMA requires a catalogue in ASCII format containing the coordinates of the science targets their relative priority and a list of potential reference and telescope guide stars e The reference stars are used for acquisition and alignment of the IFU on the target objects The magnitudes must be specified in the KARMA file and be of sufficient brightness to be observed in lt 60s see section 3 3 for details and should refer to a band as close as possible to the observing band for the science exposure KMOS User Manual ESO 264148 15 IT se DN a O mag B select object scroll image measure WCS Control H select region Figure 9 KARMA graphical interface
46. es are done on the reconstructed images These images are calculated in real time on the instrument control workstations The main function of the acquisition template is to preset the telescope to setup the in strument e g choose wave band move arms in position etc and perform the acquisition from reference stars which can be science targets themselves if the stars are bright enough mag lt 14 This acquisition is necessary to correct for any mis alignment between the as trometry of the catalogue provided by the user and the actual telescope position and rotator angle of the instrument Alignment Results Telescope and Rotator Offsets Target INS SYSTEM DETDATA KMOS_SPEC_ACQ114_0001 fits Accept Sky Accept new image y arcsec z aresec Rot Degrees Offsets 0 134 0 180 0 054 Repeat Calculation ETE Avg residual arcsec 0 658 Details Sky image Rotational offset was calculated green yes red no D Repeat Exposure time s Change Time New exposure time s Abort Figure 19 Screen shot of the gui for the acquisition The acquisition sequence is important for astronomers in visitor mode 1 Retract the arms to park position 2 Preset the telescope and simultaneously move the arms to acquire the reference stars as defined in KARMA 3 Take an exposure reconstruct the cubes and show images in the RTD 4 At the end of the integration
47. exure of the pick off arms 3 the flexure of the spectrographs The first two affect the spatial position of the source on the IFUs while the last one produces a shift mainly in the spectral direction However all of them are small and their effect is mostly corrected in software 5 3 1 Flexure of the bench and pick off arms The flexure of the bench and pick off arms subject to gravity has the net effect of spatially displacing the targets on the IFUs However this shift is always in the opposite direction to the gravity vector and during a complete rotation 360 the image of the source moves on the field of view of the IFU describing a well defined ellipse with semi major axis 1 5 pixels The effect of this flexure is compensated for in software In fact at the start of any OB the flexure at that specific rotator angle position is removed during acquisition In this phase the 3 or more acquisition sources are centred in the 3 IFUs effectively removing the flexure of the bench and the pick off arms Therefore during the execution of the OB the maximum uncorrected image movement due to the flexure of the bench and pick off arms corresponds to the rotation angle in the longest DIT At 10 zenith distance an integration of 10 15min gives a maximum instrument rotation of 13 20 The maximum image motion in such integration time is only 0 1 0 2 pixels This gives a negligible effect on the image quality 5 3 2 Flexure of the s
48. g the OB preparation In KARMA it is also set a maximum distance for the nodding 6 arcmin necessary to retain the guide star during the OB The frequency with which the sky measurements are obtained depends on the observing band the brightness of the source and on the accuracy of sky subtraction required Figure 12 shows the sky emission as a function of wavelength across the range observed by KMOS In the science templates the number of sky frames is determined by 2 parameters the sky frequency and the optional long sky exposure see Section 7 3 The sky frequency parameter in P2PP labelled as Sky will be observed every X science exposures sets the intervals with which sky frames are taken with respect to the science frames and it is described in details below The optional long sky exposure on the other hand is simply an additional sky frame of user specified length that can be taken at the end of the template after all the science frames In the nod to sky template the sky frequency parameter is fixed to one meaning that a sky frame is taken after each object frame In the other templates it is possible to specify the frequency of the sky observations In the stare mode the default value is 0 e g no sky KMOS User Manual ESO 264148 20 800000 700000 600000 500000 400000 300000 ph s m2 micron arcsec2 200000 100000 800 1000 1200 14
49. implemented in the target section second icon on the top panel Dec TEL TARG NAME Name NODEFAULT Name of the standard star TEL TARG ALPHA Right Ascen NODEFAULT RA coordinate of the standard sion star Need to be added by the user in P2PP TEL TARG DELTA Declination NODEFAULT DEC coordinate of the stan dard star Need to be added by the user in P2PP TEL TARG EQUINOX Equinox J2000 Equinox TEL TARG EPOCH Epoche 2000 Epoch of observation used with the next two parameters to correct for proper motion TEL TARG PMA Proper motion 0 0 Proper motion of the standard RA star in RA in arcsec yrA TEL TARG PMD Proper motion 0 0 Proper motion of the standard star in Dec in arcsec yrA NOTE The Coordinates for the standard star can be provided in two equivalent formats 1 RA and Dec corrected for proper motion and set proper motions in RA and Dec 0 0 or 2 RA and Dec non corrected for proper motion and provide the values of the proper motion Note especially visitors When you transfer the obx files you will need to re edit the coordinates of the standard star after you imported the OB KMOS User Manual ESO 264148 7 2 5 KMOS_spec_acq skyflat 44 This acquisition consists of telescope preset without guiding and instrument setup as it was done for science observation same arm pattern No alignment is performed Parameter P2PP Label Range Default N
50. inearity This template acquires images for assessment of detector linearity Parameter P2PP Label Range Default Notes DET1 NDIT Number 1 100 1 Number of DITs to combine of DITs before writing the data to the disk SEQ EXPO TIME LIST List of exposure times s 2 47624 43200 2 5 5 0 7 5 10 0 12 5 15 15 12 5 10 0 7 5 5 0 2 5 List of exposures expressed in seconds INS ATTEN NAME Attenuator Block x1 x0 5 x0 1 x0 05 x0 01 x0 1 Attenuator position x1 fully open x0 01 open to 1 Block all light is blocked INS FLATLAMP NAME Flatfield lamp LAMP3 LAMP4 LAMP3 4 DEFAULT Flat Lamp to be used for the observation OCS GRFI NAME GratingFilter IZ YJ H K HK NODEFAULT Grating to be used for the ob servation KMOS User Manual ESO 264148 56 8 Appendix 8 1 Rotator optimisation KMOS is able to do observations even in the case of restricted hardware availability e g locked pick off arms or locked devices in one of the spectrographs The user should check the KMOS news page for the current instrument arm status http www eso org sci facilities paranal instruments kmos news html The idea is to create a rotated setup at the time of the observation i e to do a suitable rotation of the instrument and to recalculate the mapping between pickoff arms and science targets in order to reach optimized observation efficiency e
51. ined set of dithers with 16 pointings uninterrupted coverage of 64 9 x 43 3 2810 sq arcsec is achieved See Section 3 4 4 for details Using the keyword Part of mosaic to be observed it is possible to split the mosaic and observe only a fraction of it This feature is needed if for example the individual exposures are long and it will take more than 1 hour to complete the 16 pointings full mosaic In this case the observations can be broken down into several OBs and in each of them observe one fourth of the mosaic The parameters are the same as for KMOS_spec_obs_mapping8 above The exception is the parameter SEQ MAP PART which has different optional values Parameter P2PP Label Range Default Notes DETLSEQ DIT Integration 0 3600 10 Individual integration time time DIT in seconds for the science targets DET1 NDIT Number 1 100 1 Number of DITs to combine of DITs before writing the data to the disk SEQ DET1 DIT Option long sky 0 3600 0 Exposure time for a long expo exposure Time sure on sky if 0 then no ad ditional sky exposure if 4 0 additional exposure with this specified duration will be exe cuted at the end of template SEQ MAP PART Part of mosaic WHOLE Part of mosaic to be observed to be observed HALF1 This keyword allows to observe HALF2 the whole mosaic or just a frac QUARTI tion of it the first third the QUART2 second third or last third QUARTS QUART4 WH
52. ion see Section 4 1 6 NOTE The grating must be the same as for the science observation posures Parameter P2PP Label Range Default Notes DET1 NDIT Number 1 100 1 Number of DITs to combine of DITs before writing the data to the disk SEQ NEXPO Number of ex 1 100 1 Number of exposures at a given position of the rotator INS FLATLAMP NAME Flatfield Lamp LAMP3 LAMP4 Flat field lamp to be used for LAMP3 4 the observation DEFAULT OCS GRFI NAME GratingFilter IZ YJ H K HK Grating to be used for the ob NODEFAULT servation 7 4 7 KMOS_spec_cal_ wave Wavelength calibration spectra are taken using internal lamps with the arms in calibration position Detector integration time and attenuator are set automatically for the used lamp s and defined grating filter combination GRFI The corresponding parameters are stored in the configuration The default parameters can be overwritten during execution of the OB if parameter SEQ ASK ATTEN TIME is set to T NODEFAULT Parameter P2PP Label Range Default Notes DET1 NDIT Number 1 100 1 Number of DITs to combine of DITs before writing the data to the disk SEQ ASK ATTEN TIME Ask for attenu T or F T Setting for interactive execu ator and time tion If TRUE it will ask for the level of attenuator and ex posure time during execution If FALSE it will use the default value w
53. ithout asking SEQ NEXPO Number of ex 1 100 1 Number of exposures at a posures given position of the rotator SEQ ROT Rotator posi 270 270 List of rotator positions at tion which the arcs are taken The default is 60 0 60 120 180 240 INS FLATLAMP NAME Wave Lamp Ar Ne Ar Ne Arc lamp to be used for the Ar Ne observation There is an Ar gon lamp and a Neon lamp which can be used simultane ously Ar Ne the latter being recommended OCS GRFI NAME GratingFilter IZ YJ H K HK Grating to be used for the ob servation KMOS User Manual ESO 264148 7 4 8 KMOS_spec_cal_ wavenight 59 Attached calibration flat taken during the night just after the science observation see Section 4 1 6 NOTE The grating must be the same as the same as in the science observation NODEFAULT Parameter P2PP Label Range Default Notes DET1 NDIT Number 1 100 1 Number of DITs to combine of DITs before writing the data to the disk SEQ NEXPO Number of ex 1 100 1 Number of exposures at a posures given position of the rotator INS FLATLAMP NAME Wave Lamp Ar Ne Ar Ne Arc lamp to be used for the Ar Ne observation There is an Ar gon lamp and a Neon lamp which can be used simultane ously Ar Ne This latter Ar Ne is the default and it is the recommended mode OCS GRFI NAME GratingFilter IZ YJ H K HK Grating to be used for the ob servation 7 4 9 KMOS _spec_cal_l
54. ity of the ghosts vary slightly from detector to detector but on average it is 0 6 in IZ band 0 4 in YJ 0 06 in H and 0 2 in K e The ghost covers only a fraction of the observable wavelength especially in the IZ and YJ bands 5 1 1 Impact of ghost on science observations The potential science impact of the ghost is that bright OH lines are re imaged onto pixels that should contain only continuum from in between OH lines therefore increasing the background The ghosts produced by bright OH lines are in the vast majority of the cases well below the level of the intra OH continuum except for the very brightest OH lines In a more quantitative way the average ratio between strong OH lines and intra line continuum is 50 in the YJ band and significantly higher 500 in the H band Therefore using the values of the intensity for the ghosts described above the ghost of OH lines will be 50 x 4 01078 0 2 of the continuum in the YJ band and 500 x 6 0107 0 3 of the continuum in the H band Quantitatively lt 0 5 of the wavebands is affected by ghost lines with flux comparable to the intra OH continuum and lt 1 1 5 of the wavebands is affected by ghost lines with flux gt 0 5xthe flux of intra OH continuum It is worth noticing that he ghost spectrum will only contribute in increasing the noise in regions in between the OH sky lines In fact the lines themselves produced by the ghost will be subtracted off during sky subtra
55. ky if 0 then no ad ditional sky exposure if 4 0 additional exposure with this specified duration will be exe cuted at the end of template SEQ DITHER NO Number 3 5 or 9 5 Number of dithers dither pat of dithers tern see Figure 20 SEQ DITHER SIZE Dither size 0 2 arcsec 0 2 Dither size in arcsec SEQ SKYOBS FREQ Sky 0 100 0 Frequency of sky exposure will be observed See Section 3 4 5 for details every X science e g 0 no sky exposures 1 exposures sky after every science expo sure etc NOTE A KARMA file prepared for the Stare mode can be used as well for the Nod to Sky mode in P2PP KMOS User Manual ESO 264148 7 3 3 KMOS_spec_obs freedither 48 In this template the user can define any dither pattern it is not limited to 3 5 or 9 as in the stare or nod to sky template See Section 3 4 5 and 3 4 6 for details on the sky subtraction strategy and offset dithering will be observed every X science exposures Parameter P2PP Label Range Default Notes DET1 SEQ DIT Integration 0 3600 10 Individual integration time time DIT in seconds for the science targets DET1 NDIT Number 1 100 1 Number of DITs to combine of DITs before writing the data to the disk SEQ DET1 DIT Option long sky 0 3600 0 Exposure time for a long expo exposure Time sure on sky if 0 then no ad ditional sky exposure if 4 0 additional exposu
56. l edge effects at the ends of the slitlets If the user requires more accuracy it is possible to include arc and or flat calibra tions in an OB The attached calibration template MUST be placed after the corresponding science template because it will use the same setup of the instrument performed by the sci ence template e g without moving the grating These calibrations are charged to the user programme KMOS User Manual ESO 264148 31 IFU 24 V _ 0 94 0 022 iy a L ARA H E iJ un i e SECH FU 23 20 0 99 0 025 pool ME 4 i hs dl ae an he KI M na ratio with offset 1 1 6 1 7 1 8 wavelength micron Figure 16 Comparison between the measurements of the 3 arm standard star template and all 24 arms sciencepattern standard star template Davies et al 2013 A amp A 558 A56 In the 3 arm standard star the IFUs used are number 3 12 and 20 one per each spectrograph The green curve in the background shows the extracted spectrum for a standard star in the H band The overplotted blue curves are the ratio in arbitrary scales and offsetted between the spectra in each IFU respect to those taken in just 3 reference arms 3 12 20 taken via the 3 arm standard star template as labelled on the left hand side For each IFU on the right the mean ratio and the standard deviation are indicated for regions where the signal to noise is above a minimum threshold This suggests that using just 3 arms
57. ll IFUs A choice of a 3 5 9 points dither with a fixed pattern and user specified sizes is available as described in details in section 7 3 2 and illustrated in Figure 20 3 4 2 Stare mode The characteristic feature of this mode is that the telescope always points stares to the same position and the instrument rotation angle doesn t change upper part of second column in Figure 10 The sky background then will be obtained by dedicated sky arms which in contrast to the Nod to Sky mode deliver a signal which is picked not by the same IFU as for the scientific target All pick off arms allocated to science targets can however serve for sky background subtraction simultaneously if their IFUs contain a sufficient number of empty sky pixels A dedicated sky position where all arms are on blank sky in addition is necessary only once lower part of second column in Figure 10 As for the nod to sky mode there is the possibility to introduce a dither patter with 3 5 9 points More details are given in section GGL 3 4 3 Free dither mode A hybrid mode can be obtained by using the free dither template in which the user can specify the size and the pattern of the dither for each exposure as well as the frequency with which to observe the sky see sections 3 4 5 3 4 6 and 7 3 3 From the KARMA preparation point of view either nod to sky or stare mode can be used since the specific setup for the free dither is only done in P2PP 3 4 4 Mosaic
58. mmended brightness for reference stars for ac quisition is Jvega lt 14 mag for 1min integration Note that the reference stars MUST be observed in the same band as the science targets The following table gives some guidelines for the J band but these apply to the other bands as well IZ H K Magnitude of acquisition targets Typical exposure time for acquisition 6 lt Jyega lt 10 3sec DIT 3sec NDIT 1 10 lt Jvega lt 12 10sec DIT 2 5sec NDIT 4 Jvega 13 25sec DIT 8sec NDIT 3 Jvega 14 60sec DIT 20sec NDIT 3 e Please also remember that the magnitude range for guide stars for the VLT is 8 lt Rvega lt 12mag NOTE the use of R band for guide stars is mandatory in KARMA e Saturation and strong persistence must be avoided at any time Please take care To exclude any risk of artefacts produced by detector persistence DITs and NDIT must be selected using the ETC such that fluxes are at most 5 000 ADUs DIT pixel 2 500 e DIT pixel even for significantly better conditions than foreseen e g using seeing 0 4 in the ETC e IMPORTANT Accurate astrometry is essential for KMOS observations In case of reference and guide stars as well as for stellar science targets it is important to correct the coordinates for proper motions For this we recommend to use the latest UCAC catalogue UCAC4 that can be queried via Vizier Proper motions for stellar sources must be checked and if they are greater than
59. n additional ong sky frame of 60sec at the end In this case the observing sequence will be AB AB AB Beosec NOTE The sky frequency MUST be lt the number of object frames e g for an OB with 5 science frames the sky frequency parameter must be lt 5 NOTE A KARMA file prepared for the Nod to Sky mode can be used as well for the Stare mode in P2PP O O O O g O O D O Q O O O O Q Figure 20 The standard KMOS dither patterns 3 5 and 9 point dither KMOS User Manual ESO 264148 47 7 3 2 KMOS_spec_obs_nodtosky This is another possibility to do observations with KMOS The parameters are the same as for KMOS spec obs stare except for the parameter SEQ SKYOBS FREQ This parameter is set for KMOS_spec_obs_nodtosky frozen and equal to 1 whereas for KMOS_spec_obs_stare it can be freely defined in P2PP Hence for the nod to sky mode there is a fixed sky frequency with a sky frame taken after every science frame e g AB AB AB As for the stare mode it is possible to take an optional long sky exposure at the end of the observing sequence Parameter P2PP Label Range Default Notes DET1 SEQ DIT Integration 0 3600 10 Individual integration time time DIT in seconds for the science targets DET1 NDIT Number 1 100 1 Number of DITs to combine of DIT s before writing the data to the disk SEQ DET1 DIT Option long sky 0 3600 0 Exposure time for a long expo exposure Time sure on s
60. n every com bination as value of OCS ARMi NOTUSED Acronym Meaning NotInPaf No target was assigned in KARMA to the original arm Locked The arm is locked Coll The arm would collide if going to its target position BrghObj The arm would hit a bright object this should never occur see above Ecl The arm is eclipsed Spectr The spectrograph belonging to the arm is not useable Cal The arm is not used during calibration LimitSw The arm would run into a limit switch This is a special case which can only occur during the creation of the lookup tables ATC and has no meaning for the normal observer operator KMOS User Manual ESO 264148 59 8 2 Total instrument transmission Figure 23 shows the derived total efficiencies as measured for one arm in each of the three spectrographs These measured values include the contribution of the atmosphere telescope optics and detector Note that YJ is calibrated using only the J band while HK uses both H and K bands The IZ band was calibrated using the monochromatic flux density calculated for 0 99 1 0u4m These measurements were repeated several times during Commissioning 2 and Commissioning 3 to obtain final data for the ETC throughput throughput throughput 8 S er YJ 3 D L L 1 20 o 1 12 20 12 12 20 FU FU A FU Figure 23 Total instrument transmission for the three
61. n of the instrument sub systems 2al The mice Syren AMI 2 2 2 Integral Field Units and filter ooo 44245 te eae ew Re eS 229 SEENEN circa arar AA 224A VIS asa AA A A AAA 229 Cabano Unit e sa se gruo dru arar 2 2 6 Infrastructure and electronics EEN a Overall PErorTmane s pidas a a we ere eS ee eS OS ai fon magegualiy cr cs serea ee tae Se DED ee Wed AA eR Lil eee Re oe ek oe eS Be eee E A et ee EN 2 3 3 Spectral resolving power oe OUI e are a a a OEE GS ERS SRR SHES 23 0 Recommended DITS lt 4 4 25 44444 Seb eb eae ew EES 2 3 6 Saturation and persistence limits 00000 ee The Exp s re Time Calculator A cosg oea anoe ew Re Sw eS Re oS 3 Observing with KMOS 3 1 3 2 3 3 3 4 3 5 A Le a ae A ee OR E a E Ee i a E ee a KARMA the observation preparation tool for KMOS Target POM s e y coos e E ee EES EEA ERE eS Observing Modes A se cn kasra ah E ae A ES AE K RS Oa Nod tobky MOUS 22424 ec a ee srl eu ta Sage e a 3A2 ptre mode e ie Oe eRe OE e Re BR ek A 343 Fre edither mode cecs sose ie die RE pie EG Se AR SAA Moio mode osoro so ee OEM OO ANE ARNE R a REE BS 34 5 Strategy for sky subtraction osc Tesi e E a 3 4 6 Offsetting and dithering ici a 3 4 7 The influence of the Moon 3 4 8 The influence of precipitable water vapour PWV 349 Rotation Optimisation se sss so dra we be a ee ae ewe eS IR soe ace II D e e a a a a a a e a E D e E a N FPF F
62. n star is positioned sequentially in all IFUs and spectra are taken The parameters are the same as for KMOS_spec cal stdstar 7 4 3 KMOS_spec_cal skyflat Sky flats are taken with the arm pattern as defined in the KARMA file in the acqusition KMOS_spec_acq skyflat see 7 2 5 Skyflats are either taken before sunset with the telescope fixed in zenith position or dithering is performed to improve signal to noise Parameter P2PP Label Range Default Notes DET1 SEQ DIT Integration 0 3600 10 Individual integration time time DIT in seconds for the science targets DET1 NDIT Number 1 100 1 Number of DITs to combine of DITs before writing the data to the disk SEQ DITHER NO Number of 3 5 or 9 5 Number of dithers dither pat dithers tern see Figure 20 SEQ DITHER SIZE Dither size 0 2 arcsec 1 0 Dither size in arcsec KMOS User Manual ESO 264148 53 7 4 4 KMOS_spec _cal dark Simple darks are taken lamps are off filter wheels are in position block Parameter P2PP Label Range Default Notes DET1 SEQ DIT Integration 0 3600 10 Individual integration time time DIT in seconds for the science targets DET1 NDIT Number 1 100 1 Number of DITs to combine of DITs before writing the data to the disk SEQ NEXPO Number of ex 1 100 1 Number of dark exposures to posures take 7 4 5 KMOS_spec cal calunit Internal flats are taken using calibration
63. nfiguration file and finding chart to be used in P2PP in order to complete the observation preparation KMOS User Manual ESO 264148 16 All the previous steps are supported by a graphical interface as shown in Figure9 3 3 Target acquisition Before any science observation it is necessary to perform the target acquisition a mandatory step to correct for any mis alignment between the astrometry of the catalogue provided by the user and the actual telescope position and rotator angle of the instrument Since KMOS does not have an imaging mode the target acquisition is obtained by observing bright reference stars with short exposures and the Quick Reduction and Real Time Display RTD to iteratively centre the reference objects in the IFUs For this task it is necessary to allocate at least 2 and preferably 3 or more pick off arms to reference targets provided by the user along with the input catalogue If the science targets stars only are bright enough they can be used directly for acquisition otherwise bright reference stars must be used In this latter case during the OB execution KMOS will first allocate the arms specified to the corresponding reference targets and allow the alignment of telescope and instrument Then the arms will be retracted again and finally deployed to their science positions IMPORTANT e To reduce overheads during acquisition we recommend exposure times for acquisition to be in the range 10s 60s The reco
64. ntific requirements KMOS and KARMA open up the possibility to combine more than one of these rectangular areas leading to an equivalent number of PAF files and OBs The size of your super field must KMOS User Manual ESO 264148 19 E 9 64 9 Figure 11 Left The size of the continuous area 0 8 sq arcmin covered by a single OB in Mosaic mode with the large configuration with 24 IFUs which requires 16 telescope pointings The red squares indicate the IFU positions at the start of the OB Right The small Mosaic configuration with 8 IFUs which requires 9 telescope pointings to cover the rectangular area of 0 15 sq arcmin be specified in KARMA It is worth noticing that depending on the exposure time in each tile the full OB might exceed the one hour limit e g 16 pointings x DIT sky positions Hence there exists the possibility to break down the mosaic and execute in one OB just a fraction of the mosaic The small mosaic can be split in 3 OBs the large mosaic in 4 3 4 5 Strategy for sky subtraction Unlike long slit spectrographs the field of view of each KMOS IFU is too small 2 8 x 2 8 to nod and keep the target within the field of view Thus the classical nod along the slit cannot be performed and therefore sky measurements must be obtained by nodding the telescope to offset sky fields The scale of the offset e g how many arcsec from the science targets and rotator angle can be specified in KARMA durin
65. ons in any conditions e Background dominated observations are reached for exposures longer than 300 sec KMOS User Manual ESO 264148 37 7 Templates reference All scientific and calibration observations with ESO instruments are prepared as observing blocks OBs with the Phase 2 Proposal Preparation tool P2PP The scheduling of these OBs is then done on the site with the Broker of Observing Block BOB and the Visitor Observ ing Tool VOT in visitor mode and with BOB and the Observation Tool OT during service mode observation runs Observing blocks consist of the target information a small number of user selected templates the constraints sets and the scheduling information The observ ing templates which are described below are lists of keywords parameters of the respective templates to define the configuration and setup to be used for the respective observations Parameters can be either selectable by users or they are hidden to the user to compact and to simplify the appearance of the parameter lists Hidden parameters cannot be changed by the users but only by the instrument operators Since the hidden parameters will be rarely changed during science observation runs we do not provide an explanation here in the template reference section Table 11 Summary of KMOS acquisition science and calibration templates Acquisition templates Science and calibration templates KMOS_spec_acq KMOS_spec_obs_stare KMOS_sp
66. otes OCS INS TARG SETUP KARMA target set up file ins KARMA target setup file to allow the arms to be config ured in the field The actual RA and Dec defined in the KARMA files will be ignored and only the arm configuration will be retained OCS GRFI NAME GratingFilter IZ YJ H K HK NODEFAULT Grating name KMOS User Manual ESO 264148 45 7 3 Science Templates The five science templates provide various observation modes e g mosaics or individual arms allocations as well as various strategies for nodding between object and sky position and jitter offsets between the images 7 3 1 KMOS_spec_obs_stare This observing mode is recommended only for bright objects and or very compact objects for which the sky background can be determined within the same IFU See Section 3 4 5 for details on the sky subtraction strategy Parameter P2PP Label Range Default Notes DET1 SEQ DIT Integration 0 3600 10 Individual integration time time DIT in seconds for the science targets DET1 NDIT Number 1 100 1 Number of DITs to combine of DIT s before writing the data to the disk SEQ DET1 DIT Option long sky 0 3600 0 Exposure time for a long expo exposure Time sure on sky if 0 then no ad ditional sky exposure if 4 0 additional exposure with this specified duration will be exe cuted at the end of template SEQ DITHER NO Number 3 5
67. paranal instruments kmos news html However it might happen that one or more arms become inactive e g locked in park position after the user has submitted the OBs This might result in loosing some high priority targets priority 1 In this case there is an option to re optimise the allocation when the OB is executed by rotating the instrument and maximising the number of priority 1 targets that are allocated to active pick off arms In fact the KMOS focal plane is symmetric for 30 degrees rotations angle which is necessary to move a target from one pick off arm to the next in the same level During optimisation all 12 possible rotated setups are checked for their observation efficiency considering how many targets can be observed and what is the priority of the observable targets The setup that maximises the number of priority 1 targets is selected This procedure has the advantage of recovering high priority targets that would have otherwise not been observed penalising lower priority targets A detailed description of the optimisation how to identify which arm is allocated to which target after optimisation via keywords in the fits headers can be found in the Appendix To fully exploit this optimisation feature it is recommended to carefully choose the priority of the science targets priority 1 2 and 3 However there are some risks associated with the rotation optimisation In fact having a rotator offset between acquisition and
68. pectrograph The spectrograph flexure does not affect spatial image quality but produces a shift in the spectral direction of 1 pixel in a complete rotation of 360 To compensate for this effect day time calibrations flat field and arcs are carried out at a number of different rotator positions every 60 to ensure that the flat field is valid for all rotator angles Otherwise there is no effect on the spectral image quality as the effect in an observation is much less than the linewidth Co added frames can be fitted together using sky lines to remove the image displacement using the reduction pipeline 5 3 3 Impact of flexure on science There is no major impact of flexure on science observations since KMOS software and the data reduction pipeline take into account and correct the effect of flexure KMOS User Manual ESO 264148 36 6 Summary of hints and tips for preparing observations e Astrometry Make sure that science targets guide stars and reference stars are all on the same coordinate system UCAC4 on Vizier can be used to find stars with accurate astrometry or use stars extracted from the same images as the science targets e Always correct for proper motion e Choose Telescope Guide stars with magnitudes in the R band 8 lt Rvega lt 12 e Choose at least 3 4 Reference stars in the magnitude range 8 14 in the same band as the science observations However the more stars you provide the better the alignment will be
69. re and edge of the array for all three detectors are reported in Table4 and Table5 The common wavelength coverage for each of these bands that is observed in all IFUs is reported in Table3 2 3 3 Spectral resolving power 2 3 4 Sensitivity The total efficiency of KMOS in all bands has been measured on sky using several standard stars observed during commissioning Based on these values the expected limiting Vega mag nitudes in 1 hour on source observation for S N of 5 per spectral bin are given in Table7 See Appendix 8 2 for the instrument transmission as a function of wavelength in each of the three detectors KMOS User Manual ESO 264148 Table 4 Spectral coverage at the centre of each detector Band Wavelength Coverage jum Spectrograph A Spectrograph B Spectrograph C IZ 0 778 1 092 0 779 1 094 0 771 1 085 YJ 1 022 1 359 1 025 1 361 1 015 1 352 H 1 452 1 866 1 456 1 870 1 443 1 857 K 1 921 2 460 1 922 2 461 1 919 2 460 HK 1 474 2 471 1 484 2 481 1 458 2 456 Table 5 Spectral coverage at the edge of each detector Band Wavelength Coverage um Spectrograph A Spectrograph B Spectrograph C IZ 0 772 1 086 0 773 1 087 0 764 1 079 YJ 1 014 1 351 1 016 1 353 1 007 1 344 H 1 441 1 855 1 445 1 859 1 432 1 846 K 1 932 2 472 1 934 2 473 1 931 2 472 HK 1 465 2 462 1 470 2 442 1 445 2 442 Table 6 The measured spec
70. re with this specified duration will be exe cuted at the end of template SEQ DITHER ALPHA DITHER pat 100 100 Dither pattern within the IFU tern in ALPHA NO DEFAULT in RA Expressed in arcsec and always referred to the initial position See Section 3 4 6 for details SEQ DITHER DELTA DITHER pat 100 100 Dither pattern within the IFU tern in DELTA NO DEFAULT in Dec Expressed in arcsec and always referred to the ini tial position See Section 3 4 6 for details SEQ SKYOBS FREQ Sky 0 100 0 Frequency of sky exposure See Section 3 4 5 for details e g 0 no sky exposures 1 sky after every science expo sure etc NOTE In this template the number of sky frames is determined by 2 parameters the sky frequency SEQ SKYOBS FREQ and optional long sky exposure The number of science frames is determined by the number of dithers set by the DITHER pattern For example let s assume we need 4 science frames with 0 2 arcsec dither around the central position DITHER pattern ALPHA 0 2 0 2 0 2 0 2 DITHER pattern DELTA 0 2 0 2 0 2 0 2 of 30sec each Integration time 30 With the same convention as in Section 3 4 5 we define A the science frame and B the sky frame e If sky frequency is 0 and optional long sky exposure is 0 then no sky will be taken at all The observing sequence will be AAAA e If sky frequency is 0 and optional long sky exposure is gt 0
71. rming a large pseudo slit with the dissection in the second dimension happening by the detector pixels similar to a classical long slit spectrograph In the case of KMOS each target is dissected in 14 slices each dispersed on 14 pixels KMOS User Manual ESO 264148 Two dimensional original o gt E ney slicing of the on sky image Die 22007 Spectral dipersion of the sliced image e ke Computer reconstruction of the 3D data cube Spatial in Y a 3 e Spatial in X Computer reconstructed image Figure 1 Example of Integral Field Unit Spectroscopy A 2 dimensional image will first be sliced the slices then dispersed on a common slit and finally a 3D data cube is reconstructed from the obtained spectra In KMOS the image is sliced in14 elements instead of 6 as in this figure KMOS User Manual ESO 264148 4 2 Technical description of the instrument 2 1 Overview of the instrument From a hardware perspective the instrument partitions into the following key subsystems e Pickoff subsystem e IFU subsystem e Spectrograph subsystem e Detector subsystem e Infrastructure subsystems and electronics The opto mechanical parts of the instrument are all contained within a cryostat operated at a temperature of 120K while the electronics are on the Nasmyth platform and inside the cable rotator CACOR see Figure 2 and Section 2 2 6 Instrument Cryostat CACOR VLT Nasmyth Adaptor Rotator
72. science observations might introduce some positioning error with a shift of the science targets within the IFU up to 2 3 pixels depending on the rotation applied In preparing the OBs in P2PP the users can decide if they want to suppress the rotation optimisation in case one or more arms allocated to targets are not active even if that would mean loosing priority 1 targets This can be done by setting the keyword SUPR OPTROT to True i e tick the checkbox in the acquisition template see Section 7 2 On the other hand if the users decide to accept the rotation optimisation it is worth noting that the procedure is fully automated it will be performed at the telescope when the OB is executed without any control from the users on which targets are re allocated or at which rotator angle If selected the algorithm for optimisation will simply choose the rotator angle that maximises the number of priority 1 targets that are observed without further user inputs KMOS User Manual ESO 264148 Table 9 Typical values for telescope and instrument overheads 26 Action Time min Preset of the telescope 5 10 Acquisition MOSAIC setup 0 Acquisition non MOSAIC setup without exposure time per cycle 2 cycles usually necessary read out writing image to disk 0 1 interaction image reconstruction 0 58 Acquisition 2nd OB in a concatenation MOSAIC and non MOSAIC setups arms parking and deplo
73. sky in all the other IFUs This can be done with or without applying the optimal rescaling of the OH sky lines Based on preliminary results obtained during commissioning this cross arm subtraction leaves sky residuals which are a factor 2 3 higher compared to the normal nod to sky method A B described before see Figure 13 Figure 14 In this case is recommended to use at least one IFU on sky per each of the three spectrographs 3 4 6 Offsetting and dithering On top of the nodding between object and sky position that is defined in KARMA it is also possible in P2PP to define small dithers between different exposures essentially moving the source within the IFU after each exposure This small dithering within the IFU is particularly useful for faint sources because the small offsets will result in different parts of the array being used for the same target hence small cosmetic artefacts which are not removed by flat fielding KMOS User Manual ESO 264148 23 Subtraction from subsequent Example of arm to arm exposures IFU 1 IFU 1 subtraction IFU 1 IFU 7 3 soeSsimple s E simple ie 5 0 2 an 200 1 10 1 15 1 20 1 25 1 30 1 10 115 1 20 1 25 1 30 wovelength micron wavelength micron a Be _ 200 ti 2 E optimal oe Kg 3 SE 3 100 20 Y 200 1 10 115 1 25 1 30 1 10 1 15 1 20 1 25 1 30 1 20 wavelength micron wavelength micron Figure 14 Example of residual sky on the left for the classical nod to sky
74. ss and with the same instrument setup as that used for of the science target Furthermore the strength of the telluric lines varies with time so it is also necessary to observe the standard soon after or soon before the science target The spectrum of the telluric standard is divided directly into that of the science target Ideally the spectrum of the telluric standard should be known so that features belonging to it can be removed However this is normally not the case so one has to use standards for which the spectrum is approximately known In general we use hot stars AO or earlier as telluric standards but solar analogs are also available on demand on best effort basis and generally these stars are selected from the Hipparcos Catalog The spectra of stars hotter than B4 are relatively featureless and are well fit by blackbody curves So by knowing the spectral type of the star one uses a blackbody curve with the appropriate temperature to fit the continuum of the standard The spectra of stars that are cooler than AO start to have many more features and cannot be fit with a blackbody curve for wavelengths below 1 Du Unfortunately hot stars do contain some features usually lines of hydrogen and helium that can be difficult to remove If the regions around the hydrogen and helium lines are of interest then one can also observe a late type star which should have weak hydrogen and helium lines This star is then used to correct for
75. subsequent observations For this reason targets should not be brighter than 6 th magnitude in J H K bands The detectors can show a strong persistence effect even after being illuminated below the saturation level typically gt 40 000 ADUs DIT pixel equivalent to 20 000 e DIT pixel Therefore to exclude any risk of artefacts produced by detector persistence DITs and NDIT must be selected using the ETC such that fluxes are at most 5 000 ADUs DIT pixel even for significantly better conditions than foreseen e g using seeing 0 4 in the ETC 2 4 The Exposure Time Calculator The KMOS Exposure Time Calculator ETC can be found at the following link http www eso org observing etc It returns a realistic estimation of the integration time on source needed to achieve a given S N as a function of the band selected and the atmospheric conditions In building the OB please remember to add the overheads for time spent on sky and telescope instrument setting as described in section 3 5 The parameters to be provided for the input are self explanatory The magnitudes for the targets can be specified for a point source or for an extended source Results can be given as exposure time on source needed to reach a given S N or as the S N reached in a given exposure time on source KMOS User Manual ESO 264148 14 3 Observing with KMOS 3 1 Overview As for all ESO instruments the P2PP software is used to prepare KMOS observations The generi
76. tage is that only a point or in case of a slit a line through the object is sampled at the same time To cover an object two dimensionally requires several consecutive exposures with altered slit positions This method is not only time consuming but also prone to errors in pointing and in stability as all sorts of changes can happen while these lots of exposures are done Integral field spectroscopy aims at addressing these problems by allowing spectroscopy of a two dimensional area of the image plane in a simultaneous way As the spectrum of each spatial element also referred to as a spaxel to distinguish from the detector pixels is taken at the same time the result is stable with respect to temporal changes Furthermore effects of pointing errors and atmospheric dispersion can be addressed later during data reduction as no light is lost if the field covered is large enough Each spaxel can be referred to as being a slit However as the spectra of several adjacent spaxels can be added together there are no slit losses caused e g by bad seeing conditions There are different techniques to realize an integral field unit IFU technically and in KMOS this is performed by using image slicers see Figure 1 for an illustration With this technique the image of the object hits a mirror array that dissects slices of the image to send them to different channels Eachslice is re imaged onto a slit via a pupil mirror and imaged along a row fo
77. tors which are modified for cryogenic operation Whilst the positioning of the arms is open loop via step counting from datum switches there is a linear variable differential transformer LVDT encoder on each arm which is used to check for successful movement In addition a hardware collision detection system is also implemented as a third level of protection which can sense if any two arms have come into contact and stop the movement of arms within 10m All 24 arms can be commanded to move simultaneously and a typical arm movement takes 120 seconds The reconfiguration of all 24 arms from one science field to another requires typically 4 mins Pickoff Mirror rr Roof Input Focal Plane Lens Mirror 45 Cold Mirror K Mirror i Off Axis Assembly gt Parabola Filter Intermediate Focal Plane SOLID MODEL CRYO KMOS PICKOFF ARM OPTICS CENTRE FOR ADVANCED INSTRUMENTATION MON MAR 12 18 46 14 2007 UNIVERSITY OF DURHAM NETPARK RESEARCH INSTITUTE COMBINED ZMX CONFIGURATION 4 OF 8 Le y Ze PER BE Ken PA E E a e an A E AAA O e O Figure 4 Top left Optical path in the KMOS pick off system Top right one of the 3 front segments showing the 8 pick off arms on top of the plate and the filter wheel and mirrors of the IFU sub system underneath the plate Bottom One of three complete sets of IFU mirrors
78. tral resolving power in all 5 bands Band Pixel scale nm pixel Resolving power Short wavelength Band centre Long wavelength IZ 0 143 2795 3406 3773 YJ 0 165 3089 3582 4088 H 0 203 3570 4045 4555 K 0 266 3809 4227 4883 HK 0 489 1514 1985 2538 Table 7 Limiting magnitude Band Magnitude Vega IZ YJ H HK K 19 9 20 1 19 8 19 8 17 9 KMOS User Manual ESO 264148 13 2 3 5 Recommended DITs For short exposures the minimum DIT is 2 47s and to reduce the calibration load and share calibrations with other projects we recommend especially in service mode the following DIT values for bright targets 2 5s 3s 4s 5s 10s 15s 20s 30s 60s or 100s For long exposures on faint targets with no risk of saturation we recommend to work with NDIT 1 and a DIT depending on the frequency of sky frames needed To avoid excessive daytime calibrations only a limited choice of DIT values for longer exposures is recommended in service mode DIT 300s 450s 600s 900s 1200s allowed only for IZ For DIT values different from these a waiver is required It is worth noting that background limited performance between the OH lines is reached in 300s Therefore exposure times gt 300s are recommended for faint sources 2 3 6 Saturation and persistence limits Saturation should be avoided at any time since it produces persistence artefacts that can last up to several hours and severely affect
79. uced by MOS spec cal_skyflat Twilight spectroscopic skyflats are taken regularly by the observatory monthly and must be used to determine the illumination correction especially important in the mosaic mode to produce uniform images Based on the initial measurements this should deliver an illumination correction good to a few percent level If the user requires a higher accuracy for the illumination correction it is possible to request twilight sky flats in Phase 1 in the special calibration section of the proposal 4 1 5 Spectro photometric Calibration and telluric standards Produced by KMOS_spec_cal_stdstar Calibration of spectroscopic data in the IR is a complicated procedure that requires care It is generally done in three steps The first step removes telluric features with what is commonly called a telluric standard the second step removes the spectral features of the telluric standard that are imprinted onto the science spectrum because of the first step and the third step sets the absolute scale with what one may call a spectroscopic flux standard In general the spectroscopic standard and the telluric standard are the same star but this does not need to be the case KMOS User Manual ESO 264148 29 The most prominent features in IR spectra are the telluric lines of the Earth s atmosphere Unfortunately many of the telluric lines do not scale linearly with airmass so it is necessary to observe a standard at the same airma
80. ull mosaic in service mode OBs and in each of them observe a third of the mosaic In this case the observations can be broken down into several Parameter P2PP Label Range Default Notes DET1 SEQ DIT Integration 0 3600 10 Individual integration time time DIT in seconds for the science targets DET1 NDIT Number 1 100 1 Number of DITs to combine of DITs before writing the data to the disk SEQ DET1 DIT Option long sky 0 3600 0 Exposure time for a long expo exposure Time sure on sky if 0 then no ad ditional sky exposure if 4 0 additional exposure with this specified duration will be exe cuted at the end of template SEQ MAP PART Part of mosaic WHOLE Part of mosaic to be observed to be observed ONETHIRD1 This keyword allows to observe ONETHIRD2 the whole mosaic or just a frac ONETHIRD3 tion of it the first third the WHOLE second third or last third SEQ SKYOBS FREQ Sky 0 100 0 Frequency of sky exposure will be observed See Section 3 4 5 for details every X science e g 0 no sky 1 sky after exposures every science etc Figure 21 Positions of arms during observations with template KMOS_spec_obs_mapping8 left side and KMOS_spec_ obs_mapping24 right side KMOS User Manual ESO 264148 51 7 3 5 KMOS_spec_obs_mapping24 This template is very similar to the previous one In this case all 24 arms are positioned as shown in Figure 21 Using the pre def
81. ven with constrained hardware This process is called rotator optimisation see Figure 22 Arm 3 Arm 5 Arm 1 Arm 7 Figure 22 The idea behind the rotator optimisation Let Arm 1 be locked e g after a hardware failure Left In the original configuration given by the KARMA set up file the red target cannot be observed Right After rotating the instrument and recalculating the mapping between targets and arms all targets are observable An optimisation like this might be of special interest if the red target has higher priority than the others As can be seen from the figure rotator optimisation always takes place in steps of 30 degrees angle which is necessary to move a target from one pick off arm to the next in the same level During optimisation all 12 possible rotated setups are checked for their observation efficiency considering how many targets can be observed and what is the priority of the observable targets Then the best of these setups is selected A detailed description of the optimisation is given in the KMOS Instrument Software User and Maintenance Manual VLT MAN KMO 146606 001 From the user point of view what is important is the information given in the fits headers when the rotator optimisation is performed 8 1 1 Fits headers The information if a rotated setup as compared to the KARMA set up file was used for an exposure is given by the keyword OCS ROT OFFSET This keyword holds the rotational KM
82. wards the K mirror assemblies These are used to focus the pick off fields onto the intermediate focal plane and also to orient each of the 24 fields correctly onto the IFU s image slicer A set of band pass filters is used to select the appropriate waveband for each observation As the filters are located in the converging beam produced by the K mirrors they are also utilised to correct the chromatic aberrations focus induced by the collimating lens in the arm 2 2 3 Spectrographs The spectrograph sub system is comprised of three identical units which supply three de tectors sub systems Each spectrograph uses a single off axis toroidal mirror to collimate the incoming light which is then dispersed via a reflection grating and refocused using a 6 element transmitting camera The five available gratings IZ YJ H K HK are mounted on a 5 position wheel which allows optimized gratings to be used for the individual bands A blank position in the filter wheel is used for calibrations 2 2 4 Detectors KMOS uses 3 Teledyne substrate removed HgCdTe 2kx2k 18m pixel Hawaii 2RG detectors one for each spectrograph The detectors are operated at a temperature of 35K while the rest of the cryostat is at 120K Typical characteristics and performances are given in Table 2 Sample up the ramp non destructive readout is always used This means that during inte gration the detector is read out at regular short intervals without resetting it an
83. xel variation loca Taken at optimised rotator as needed tion of the slits on the array angles based on night obser vations Arcs Daily Wavelength calibration Taken at optimised rotator Argon Neon as needed angles based on night obser vations Flats Daily Pixel to pixel variation loca Taken at 6 different rotator as needed tion of the slits on the array angles every 60 to correct for flexure Arcs Daily Wavelength calibration Taken at 6 different rotator Argon Neon as needed angles every 60 to correct for flexure Attached On demand template attached to Science arc flat OB by user charged to user Telluric as needed Correct for telluric absorp Within 2 hours of the science standars tion correct response curve data airmass difference of 0 2 3 IFUs only absolute flux calibration Maximum S N 100 Telluric on demand Correct for telluric absorp OB prepared by user charged standars tion correct response curve to user all IFUs absolute flux calibration Spectroscopic Monthly Twilight spectroscopic flats skyflats Radial veloc On demand Accurate radial velocity cali OB prepared by user charged ity standards bration to user NOTE Flat and arcs at optimised rotator angles are not available yet but will be in the near future Currently only flat and arcs at six fixed rotator angles are provided In the following the individual calibrations are discussed in more detail KMOS User
84. yment 4 Read out writing image to disk 0 1 Image reconstruction 0 33 Offset dither i e within individual IFUs 0 15 Offset to sky 0 75 3 5 Overheads The telescope and instrument overheads are summarised in Table 9 The table gives over heads assuming a typical scenario for catalogues with good astrometry in which two cycles of acquisition offsets are required The total time for the acquisition cycle is dependent on the exposure time selected The set up for grating and filter wheel is included within the time to park and deploy the arms For a normal OB for which the acquisition and re centering of the reference stars is straightforward e g only one iteration the total initial overheads are 10min including presetting acquisition and reconfiguration of the arms The readout time is very short few seconds For OBs in which the astrometry of the catalogue is not very good and the acquisition process requires several iterations or in the case the reference stars are too faint gt 14mag requiring longer exposures then the overheads can be much longer KMOS User Manual ESO 264148 27 4 Calibrating and reducing KMOS data 4 1 KMOS calibration plan A summary of the calibration plan is given in Table 10 Table 10 Summary of KMOS calibration plan Calibration Frequency Purpose Notes Darks Daily Master dark bad pixel map DIT 60s Flats Daily Pixel to pi

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