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VIMOS User Manual

1. VIMOS mos acq Standard Keyword Range Label in p2pp DET WIN1 UIT1 1 1000000 Exposure time seconds INS FILT NAME UBVRIz Filter TEL TARG EQUINOX 2000 3000 Equinox TEL TARG EPOCH 2000 3000 Epoch TEL TARG PMA 10 10 proper Motion Alpha TEL TARG PMD 10 10 proper Motion Delta TEL TARG ADDVELALPHA 15 15 Additional Velocity RA TEL TARG ADDVELDELTA 15 15 Additional Velocity DEC VIMOS mos cal Standard Keyword Range Label in p2pp DET WIN1 UIT1 1 100000 Exposure time seconds INS FILT NAME UBVRIz Filter OS red OS blue GG435 GG475 INS GRIS NAME LR_blue LR_red MR HR_blue Grism HR orange HR red INS SLIT NAID 0 8 1 0 1 2 1 5 1 8 2 2 5 5 0 1 0 SEQ NEXPO 1 1000000 Number of exposure per telescope offset SEQ CAL FLAG 14 1 or 4 quadrants VIMOS ifu cal Specphot Keyword Range Label in p2pp DET WIN1 UIT1 1 100000 Exposure time seconds INS FILT NAME UBVRIz Filter OS red OS blue GG435 GG475 INS GRIS NAME LR_blue LR_red MR HR_blue Grism HD orange HR red INS IFUE NAME 0 33 0 67 IFU magnification in arcsec fiber INS IFUS MODE FT IFU Shutter SEQ NEXPO 1 1000000 Number of exposure per telescope offset SEQ CAL FLAG 14 1 or 4 quadrants VIMOS User Manual VLT MAN ESO 14610 3509 VIMOS ifu cal NightCalib Keyword Range Label i
2. 700 E RR RT E 500 600 Wl nm GM 400 y 400 CP ere pi 500 600 700 Wi nm 0 ir ria EE E PEA OA DEE Do EE 500 600 700 800 900 100800 600 700 800 900 1000 Wl nm Wi nm Figure 16 OS blue OS red transmission curves VIMOS User Manual VLT MAN ESO 14610 3509 0 8 E 0 6 20 4 O EE 20 4 o E 600 800 1000 600 800 1000 Wi nm Wi nm sl 1 1 1 1 1 fi 1 500 600 700 800 500 600 700 800 avelength nm Figure 17 GG435 GG475 transmission curves 47 VIMOS User Manual VLT MAN ESO 14610 3509 48 100 T T T T T T T T T T L Dusired Elie LORRED wuilu L Central W Dr Min Sper Peak Fff F ol D 2 F E Ant 20 np 1 L A A 1 A 1 1 nA 1 if WL microns LGWBLU units Deniro Raro su Centro W Min Spec Poak Elf op Gut ER E Y E Ba au 40 sb o i A A L 1 D A 0 4 0 8 0 8 1 WI microre Figure 18 Efficiency curve of the low resolution grisms LR red LR blue The vertical lines mark the desired blaze and the central wavelengths The spectral range refers to the slit in the center of the field The cutoff wavelength is in most cases given by the order separation filters the red CCD limit or the limit of the VIMOS optics in the blue VIMOS User Manual VLT MAN ESO 14610 3509 49 LL a Desirec Mare INVES units d Central Wavelength 80 z A A EE
3. K UbsBlock No Name WIMU 3 AYU ALE SCHO als us DL val VIHO any obs Ofisst Flur Ro cule erer ze Retr te ln et Wi RUE A CR E aditlonz ve 27 w n aditlonz ve 27 w DEC ADE Net Jrermancusesi emo MI ade ADE lle Z SDF le SLE ile 4 fernaz use o vmC2u1 ade Figure 12 P2PP Example of a MOS OB 4 5 2 VIMOS_mos_acq Mask This template is used for the acquisition of a field to be observed in MOS mode Note that the acquisition image covers only the central 2048 x 2400 pixels of each of the 4 CCDs whereas the spectroscopic images use the full CCD size 2048x4096 pixels Preparing a MOS acquisition template requires that masks have been prepared with VMMPS The output of VMMPS are Aperture Definition Files in Pixels ADP files Information con cerning the target coordinates and equinox are taken from the ADP files and are automati cally loaded in the P2PP target package when including the first ADP file in the template Figure 12 shows the P2PP window with an example of a MOS Acquisition The parameters specific to this template are e Exposure time in seconds This is the integration time for the acquisition image that will be taken through the mask to check the position of the reference stars and of the science target A typical value is 60s depending on the brightness of the reference stars defined with VMMPS e Filter This filter is the one to be used for the acquisition image It is mandatory
4. 43 Table 16 lists the characteristics of the VIMOS filters The transmission curves are given in the following figures Table 16 Characteristics of the VIMOS filters Filter Ao nm FWHM nm U 370 50 B BESS 430 97 0 V BESS 546 89 0 R_BESS 648 5 130 0 I 830 80 0 z GUNN 950 160 GG475 edge filter high pass gt 475 nm GG435 edge filter high pass gt 435 nm OS red box filter band pass 550 950 OS blue box filter band pass 370 670 VIMOS User Manual VLT MAN ESO 14610 3509 44 Norm T OF ar 1 380 400 360 Wavelength nm LGL LH e ISA ai a E E E 550 600 500 550 600 Wi nm Wi nm gs 500 Figure 14 U B V filter transmission curves B VIMOS Grisms This appendix contains the efficiency curves of all standard grisms available for VIMOS and the approximate wavelength range for a slit which is located in the field centre VIMOS User Manual VLT MAN ESO 14610 3509 45 Norm T fi 1 1 fi 600 700 600 700 Wavelength nm KE Ee 700 800 900 700 800 900 wifnm Wi nm 1 1 1 800 900 1000 800 900 1000 Wavelength nm Figure 15 R l z filter transmission curves VIMOS User Manual VLT MAN ESO 14610 3509 0 8 E 0 6 3 Z 0 4 S z 0 4 0 8 E 0 6 S z 0 4 S 2 0 4 CH
5. 1 The grism filter configuration MR OS blue is not supported by the pipeline Transmission curves are available in Appendix A for the filters and Appendix B for the grisms Table 4 shows the spectral range covered in MOS modes by the various grisms as obtained by the automatic pipeline when reducing the spectrophotometric standard star This spectral range is valid for slits close to the center of the field 2 3 1 Spectral range In MOS mode slits can be positioned at any position in the imaging field of view With high resolution grisms the observed spectral range changes slightly according to the position of the slit Table 5 shows the spectral ranges covered by the detector for each grism and default order sorting filter for the slits located at three different positions in the field of view With low resolution grisms the spectral coverage is independent of the position of the slit 2 3 2 Spectral resolution The spectral resolution obtained with a 1 slit width with the various grisms is given in Table 4 2 3 3 Multiplex characteristics A particular feature of the MOS mode is the possibility of stacking multiple layers of slits along the dispersion direction This is only possible with the low resolution grisms up to four slits along the dispersion direction and the intermediate resolution grisms up to two slits for which the spectra are short enough in number of pixels to allow stacking With the high resolution grisms
6. Failure to do so will result in delays to process and deliver the pre imaging data and may result in MOS observations not being carried out Rotator on sky The rotator on sky otherwise called position angle on sky cannot be freely selected by the user This is in order to minimize the slit losses due to atmospheric dispersion Sect 3 2 The default value assigned to this parameter in P2PP should therefore not be modified The default value is 90 and corresponds to an orientation of the field with E to the top N to the left see Fig 2 In special cases it may be possible to deviate from these rules 1f there is a valid scientific reason in that case a waiver must be specifically requested to ESO before you submit your Phase II information VIMOS User Manual VLT MAN ESO 14610 3509 21 Table 12 VIMOS Calibration Plan IMG Mode Calibration Number Frequency When Products Accuracy Comment Bias 5 Daily Day time Master Bias RON Darks 3 Monthly Day time Dark current Sky Flats 5 3 7 days Twilight time Master Flat 2 U BVRIz Photom Std 4 quadrants Daily Night time Zero Point 5 U BVRI Photom Std 1 quadrant Weekly Night time Extinction coeff 10 U BVRI high airmass Astrometric fields 4 6 months Night time Distortion map 1 pixel R filter 3 4 2 Science imaging Observation Category SCIENCE It is mandatory to set the Observation Category to SCIENCE in the observation template
7. to choose the same filter as the one used for the pre imaging Waiver is requested in order to allow the selection of a different filter but see Sect 3 4 1 of this manual The available filters are U B V R I z OS blue OS red GG435 GG475 and no filter e Optional additional velocity moving targets in alpha and delta Additional Velocit y VIMOS User Manual VLT MAN ESO 14610 3509 32 Spin Fle PARHDRSTART ee GORE 5 ran VEL parameter eseu Becken AD PAFID 6D 3 90314 2 4 2002 14 18T1 7 45 14001 1 PRRNAME ernas aseri m Ima prt PATDCSC ADM Aperture Detiaition File tn Muck PALCHICAAME Tomimps 2 1 PAF CRTE DAYTIM 2002 11 161 17385 1 6 001 PLC GM AME PAFACHG DAYTIM PAF CHCK NAME PAL AIS Ln PAF CHCK CHFCRSUM ua mA eech vn air BELA ILE BI AME ANS MOD IAN Ustuap TPLFILE REEP PT DATE 985 2002 11 1 1T05 23 29 637 TT G51 ALPHA NAP A1 mr TELAS DELTA 354244 875937 INS ADI SIYALG 2 INS REF MO 2 AS ARCANO YU INSS LIT O 37 arasz er ml NT nda INS SHUNO 2 148 5 HUT PO SL WU Haly LARA MDA SID SY AI A o PRO CCO MASK TEMP 40259544 PROSCCD MA SKXO 132333667102 Figure 13 P2PP VIMOS ADP browser window RA and Additional Velocity DEC This velocity should be expressed in arcsec sec These parameters are mostly intended for imaging and possibly IFU programmes of moving targets and a priori unlikely to be of much use in MOS mode If no additional velocity
8. 2 Rotator on sky Because of the atmospheric dispersion effects Sect 3 2 the orientation on sky for MOS and pre imaging observations is not a parameter set by the user but is forced by the system to be 90 All service and visitor mode users who have particular constraints for the orientation of their fields should request a waiver 3 5 3 VIMOS Mask Preparation Software VMMPS The use of VMMPS Sect 3 5 3 is compulsory for the creation of the so called ADP Aperture Definition in Pixels files which are subsequently loaded into p2pp when preparing Observation Blocks ADP files will be used in Paranal to manufacture the masks Here are some general features of VMMPS for a quick reference guide Consult the VIMOS web page for instructions to retrieve the package and the documentation e VMMPS allows to define a mask in two situations From a contributed catalogue consisting of list of targets with accurate relative astrometry better than 0 3 rms Input catalog is a list of RA DEC coordinates This catalogue needs to have with the same relative astrometric accuracy coor dinates of bright objects stars in the field of view These objects stars after detection on the pre images will be used to register the target coordinates to the VIMOS coordinate reference frame Some of these bright stars will be used as reference for acquisition From a catalog of target positions in pixel coordinates extracted from a VI MOS
9. 7 IMPORTANT NOTE The execution time for all attached night time calibrations screen flats and arcs is subtracted from the total allocated time 3 5 10 MOS mode Exposure Time Calculator The approximate limiting magnitudes in MOS mode can be obtained from the exposure time calculator available on the ESO WEB pages http www eso org observing etc 3 6 Integral Field Unit IFU 3 6 1 Acquisition accuracy In IFU mode acquisition is blind i e limited by the accuracy of the telescope pointing 3 accuracy 3 6 2 Dithering jitter pattern With the large field of view of the VIMOS IFU techniques equivalent to shift and add classically used in imaging are a possible mode of operations Dithering jitter pattern is a list of differential pointing positions around a central position Several short images with exposure times set to have sky background limited exposures are taken at each position of a dithering pattern which are combined to reconstruct an image with the total required exposure time This allows to eliminate the sky contribution cosmic rays the CCD fringing particularly strong in the red cosmetic defects on the detectors and to produce very accurate flat fielding for correction of pixel to pixel variations The dithering pattern depends on the mean size of the observed objects it should be larger than the mean size of the objects for the method to work efficiently 3 6 3 IFU mode grism filter set
10. VIMOS field Mask 1 Channel 1 Rotator 0 N Mask 4 Channel 4 IFU head View from the telescope Modules of the lines B C D for mask Figure 5 IFU head details of the fiber modules Low transmission fiber blocks are marked with white rectangles Line B Line C Line D For rotator angle 0 North is to the right East to the top Mask 2 Mask 1 Line D Ria es ea SE ine Ee the 80 EE EE EE ike de lt mask 1 A LS A d E Line A 123 45 54 32 1 meA For all modules of the 80 For all modules of the mask 3 l 80 mask 4 CLAS RS TO Lane O TEPEDE risa T Lie C Line D SA ES ee Mask 4 View from the telescope VS Mask 3 Figure 6 IFU mode fibers numbering on the masks VIMOS User Manual VLT MAN ESO 14610 3509 12 Table 6 Integral Field Unit spatial characteristics Spatial sampling Field of view Number Pseudo slits Grism Shutter arcsec fibre arcsec of fibres per quadrant LR blue LR red OFF 0 67 fibre 54 x 54 80 x 80 4 LR blue LR red ON 0 67 fibre 27 x2 40 x 40 1 LR blue LR red OFF 0 33 fibre 27 x 27 80 x 80 4 LR blue LR red ON 0 33 fibre 13 x 13 40 x 40 1 MR HR blue HR orange HR red ON 0 67 fibre 27 x 27 40 x 40 1 MR HR blue HR orange HR red ON 0 33 fibre 13 x 13 40 x 40 1 2 4 3 Spectral range Table 7 shows the spectral range covered in IFU modes by the various grisms as
11. adequate template see Sect 4 Attached flat and arc calibrations are mandatory for all IFU observations Attached arcs are mandatory for MOS science observations with grisms LR blue and HR blue and highly recommended for MOS science observations with grisms MR HR red HR orange and HR red Execution time is subtracted from the total allocated time 3 4 Imaging IMG Imaging mode is used for both pre imaging runs and science imaging runs In both cases users are requested to use Guidecam for the selection of guide stars See Sect 3 1 1 concerning Guidecam and Sect 3 1 2 concerning the policy regarding Guide Stars 3 4 1 Pre imaging VIMOS pre imaging is mandatory prior to MOS follow up Pre imaging is carried out in service mode only The following instructions for preparation of pre imaging OBs should be strictly followed Program ID Itis mandatory for Phase I to request a specific pre imaging run in the proposal form and for Phase II to prepare the pre imaging OBs by using the corresponding Program ID Filter used The correction of the distortions is derived from R filter observations only To minimize the slit losses due the distortion of the instrument the use of the R filter for pre imaging is mandatory Pre imaging with filters other than R may be requested with a waiver Observation Category PRE IMAGE It is mandatory to set the Observation Category to PRE IMAGE in the observation template VIMOS img obs Offset see Sect 4
12. center of the IFU need to be entered in the Target Package at the bottom left of the main P2PP window The parameters for this template are e Filter This should be the same filter as the one used in the first observation template following this acquisition template In order to produce a valid OB the filter in the first observation template following this acquisition template should be the same The available filters are U B V R I z OS blue OS red GG435 GG475 and no filter Only standard filter grism combinations are allowed as indicated in Table 3 Other combinations should be requested with a waiver e Grism This is the grism that is used in the first observation template following this acquisition template In order to produce a valid OB the grism in the first observation template following this acquisition template should be the same The available grisms are LR_blue LR_red MR HR_blue HR_orange HR_red e IFU Magnification This parameter defines the sampling and correspondingly the field of view of the IFU The 2 available samplings are 0 67 arcsec fiber and 0 33 arc sec fiber To produce a valid OB the magnification should be the same in VIMOS User Manual VLT MAN ESO 14610 3509 34 every template of the OB Observations requiring different samplings on the same field should resort to several OBs e IFU Shutter This parameter is only meaningful when using the LR grisms In LR spectroscopy there are 4
13. characteristics of the VIMOS CCDs Figure 7 shows the quantum efficiency curve of one of the CCDs VIMOS User Manual VLT MAN ESO 14610 3509 13 Table 7 Spectral characteristics in IFU mode Grism Default Order Spectral range Spectral Res Dispersion Spectral sorting filter common to all quadrants 1 slit A pixel multiplex LR blue OS Blue 400 670 nm 220 5 3 4 LR red OS Red 590 915 nm 260 7 3 4 MR GG475 490 1015 nm 720 2 5 1 HR blue None 415 620 nm 2550 0 51 1 HR orange GG435 525 740 nm 2650 0 6 1 HR red GG475 645 870 nm 3100 0 6 1 Note new HR red VPHG grisms have been installed fon October 5 2005 Table 8 IFU spectral coverage in the various quadrants Grism Q1 Q2 Q3 Q4 LR blue OS blue 390 670nm 395 675nm 400 680nm 400 680 nm LR red OS red 570 915nm 580 930nm 590 930nm 585 930 nm MR GG475 485 1015nm 490 1020nm 490 1020nm 490 1015 nm HR blue free 415 620nm 415 620nm 415 620nm 415 620nm HR orange GG435 525 745nm 525 745nm 525 745nm 525 740 nm HR red GG475 635 860nm 635 865nm 635 860nm 645 875nm Table 9 Basic characteristics of the VIMOS CCDs Parameter Value Number of pixels 2048 x 4096 Pixel size um 15 Dark current at 120 C e7 px h lt T Deviation from Linearity Full well lt 0 5 Charge transfer efficiency gt 0 999999 2 5 1 Detector read o
14. field The cutoff wavelength is in most cases given by the order separation filters the red CCD limit or the limit of the VIMOS optics in the blue VIMOS User Manual VLT MAN ESO 14610 3509 92 C Template Signature Files for Observation and Acqui sition C 1 Acquisition Templates The following tables list the parameters of the VIMOS acquisition templates VIMOS_img_acq_Preset Keyword Range Label in p2pp INS FILT NAME UBVRIz Filter TEL ROT OFFANGLE 180 180 Rotator on sky TEL TARG OFFSETALPHA 3600000 3600000 Alpha Offset TEL TARG OFFSETDELTA 3600000 3600000 Delta Offset TEL AG GUIDESTAR SETUPFILE CATALOGUE Get Guide Star From TEL GS1 ALPHA 0 240000 Guide Star RA TEL GS1 DELTA 900000 900000 Guide Star Dec TEL GS1 PPOS POS NEG Guide Probe Position TEL TARG ALPHA RA of the Field Center TEL TARG DELTA DEC of the Field Center TEL TARG EQUINOX 2000 3000 Equinox TEL TARG EPOCH 2000 3000 Epoch TEL TARG PMA 10 10 proper Motion Alpha TEL TARG PMD 10 10 proper Motion Delta TEL TARG ADDVELALPHA 15 15 Additional Velocity RA TEL TARG ADDVELDELTA 15 15 Additional Velocity DEC VIMOS mos acq Mask Keyword Range Label in p2pp DET WIN1 UIT1 1 1000000 Exposure time seconds INS FILT NAME UBVRIz Filter TEL AG GUIDESTAR SETUPFILE CATALOGUE Get Guide Star From TEL GS1 ALPHA 0 240000 Guide S
15. images for HR grism 3 screen flats are mandatory for the other cases the user can choose the number as well as 1 arc taken at the same rotator position of the science target The execution time for these nighttime calibrations is always subtracted from the total allocated time 3 6 5 IFU mode calibration plan Table 14 indicates the nature frequency and accuracy of VIMOS calibrations expected to be taken as part of the calibration plan Only calibration frames required for the reduction of science data are reported More calibrations will be taken by the operation staff for the purpose of maintaining and monitoring the instrument configuration and performance e g mask to CCD transformations etc These calibrations are not reported here Calibration monitoring data can be found on the pages of the Quality Control group http www eso org observing dfo quality 3 6 6 IFU mode pipeline See http www eso org qc pipeline status html for the information concerning the latest sta tus of the ESO pipeline VIMOS User Manual VLT MAN ESO 14610 3509 27 3 6 7 IFU mode Exposure Time Calculator The approximate limiting magnitudes in IFU mode can be obtained from the exposure time calculator available on the ESO WEB pages http www eso org observing etc 3 7 VIMOS overheads The current overall efficiency of VIMOS is around 65 70 depending which mode is used The way in which some functions are operated may change at any time Con
16. is needed these parameters should be left to their default values e ADP files 1 to ADP file 4 These 4 parameters are the names of the ADP files pro duced by VMMPS The files 1 to 4 correspond to the 4 quadrants of the instrument and should be set in the right order When selecting an ADP file entry in P2PP a browser window opens up allowing to locate the file on the local disk This window is presented in Figure 13 4 5 3 VIMOS_mos_acq_ Standard This template is used for the acquisition in mode MOS using the specially designed set of calibrations masks provided by Paranal This set of masks contains a series of slits of different width that can be used for all calibrations that requires the use of a standard star i e spectrophotometric radial velocity or metallicity standard Since the template is using a pre defined set of masks no ADP need to be provided by the user No reference stars are used for the acquisition The standard star whose coordinate are provided by the user in the template will be offset in the 10x10 arc seconds acquisition box in quadrant 1 and then centered by the Night Time Support Astronomer IMPORTANT the user have to provide coordinates accurate enough to have the selected standard visible in the acquisition box VIMOS User Manual VLT MAN ESO 14610 3509 33 Note differently to the mos science acquisition where the coordinate of the field come from the ADP files produced by VMMPS the coordinates of the stan
17. obtained by the automatic pipeline when reducing the spectrophotometric standard star With low and intermediate resolution grisms the spectral coverage is independent of the po sition of the IFU pseudo slits With the high resolution grisms the spectral coverage is de termined also by the fixed positions of the pseudo slits in the focal plane but it varies slightly from quadrant to quadrant The spectral coverage for each quadrant derived from the automatic reduction of standard star observations with VIMOS pipeline is listed in the Table 8 2 4 4 Spectral resolution In IFU mode spectral resolution is fixed by the combination grism fiber size the fiber FWHM is about 3 2 pixels corresponding to 0 67 The spectral resolution is about 1 25 times the spectral resolution obtained in MOS mode with a 1 slit width The spectral resolution for various grism filter combinations is given in Table 7 2 4 5 Multiplex characteristics The same multiplex capability described in MOS mode is also used in IFU mode With the low resolution grisms there are 4 pseudo slits of fibers along the dispersion direction With intermediate and high resolution grisms only the central pseudo slit is used in practice by masking the entrance field of the IFU so that the other pseudo slits do not receive sky light 2 5 Detectors The detector mosaic of VIMOS consists of four 2kx4k EEV44 CCDs thinned and back side illuminated Table 9 indicates the basic
18. of view are the VIMOS field of view layout Guide Probe drawing and USNO selected stars in the field VIMOS User Manual VLT MAN ESO 14610 3509 18 3 1 2 Guide Stars Policy Starting from P72 ESO applies the following policy regarding guide stars e Selection of a Guide Star for VIMOS observations is mandatory for MOS and IMG mode to assess and control the amount and position of vignetting that may be introduced by the Guide Probe see Phase 2 Web pages for detailed informations e If no guide star is provided by the user ie the option CATALOGUE of the Get Guide Star From P2PP parameter of the VIMOS ifu acq Preset template is selected the guide star will be selected by the Telescope Operator at execution time e If the user provides a guide star by selecting the option SETUPFILE of the Get Guide Star From P2PP parameter of the VIMOS img acq Preset template efforts will be made to use this guide star for imaging pre imaging and for the subsequent MOS observations although this cannot be entirely guaranteed Observing conditions seeing Moon etc may indeed force to select a different guide star than the one selected by the user In addition it may happen that a guide star suitable for pre imaging observations will not be usable for the spectroscopic follow up if e g the seeing has changed e It is requested that the users selecting a guide star for their observations use Guidecam to generate the finding chart to be delivered a
19. plane in the same position as occupied by the INVAR masks in the MOS mode The spectral characteristics of the two spectroscopic modes are therefore similar but not identical 2 2 Imaging Direct imaging is used to produce wide field images VIMOS is the largest imager on the VLT using broad band filters This mode has two functions produce science images and produce the mandatory pre images needed to prepare masks see Sect 3 Table 2 summarizes the main characteristics of the imaging mode 2 2 1 IMG mode orientation of the field of view Figure 2 shows the orientation of the instrument field of view At 0 rotator angle the x axes of the CCDs are oriented E and the y axes are oriented N top panels Increasing rotator angle moves the compass counterclockwise At 90 rotator angle the x axes are oriented S and the y axes are oriented E bottom panels Note that position angle increases as rotator angle Figure 3 shows the instrument FoV keeping fixed the detectors with x axes increasing to the right and y axes increasing to the top Top right panels refer to the situation with the rotator at 0 and bottom right panels refer to the situation with rotator at 90 The corresponding positions of the detectors on sky are shown in the left panels The gap between the quadrants is approximately 2 The pointing coordinates correspond approximately to the center of the gap 2 2 2 Image Quality For the most updated information p
20. the 0 37 1 0 ym domain in three main observing modes direct imaging IMG multi slit spectroscopy MOS and integral field spectroscopy IFU Because of the large field of view VIMOS optical path is split into four channels The four quadrants of the instrument are operated in parallel De it is not possible to mix modes or filters or grisms between quadrants The field of view of the four channels is 4 x 7 x 8 in IMG and MOS and up to 54 x 54 in IFU mode in low resolution spectroscopy It provides an image scale of 0 205 pixel in MOS and 0 67 resolution element in IFU mode Each of the 4 channels has a 2048 x 4096 pixels EEV CCD with the 4k pixels being used along the dispersion to maximize the spectral coverage VIMOS is installed on the Nasmyth B focus of UT3 Melipal The VIMOS mechanical and optical characteristics are summarized in Table 1 A schematic opto mechanical layout is shown in Fig 1 VIMOS User Manual VLT MAN ESO 14610 3509 A Figure 1 VIMOS Opto Mechanical layout e The focal plane is divided in 4 identical channels and is equipped with the mask ex change units MEU which host up to 15 pre punched masks for MOS spectroscopy per quadrant the IFU fiber head and the IFU masks e The folding mirror section hosts the four folding mirrors and the flexure compensators e The Filter Camera Section the beam section hosts optical analyzers filters and or grisms the camera and the exposure shu
21. value means that the mask is not in place and the full IFU field of view is available To produce a valid OB the mask shutter option should be the same in every template of the OB This parameter is ignored when MR or HR grisms are used Number of exposures per telescope offset This parameter defines how many exposures are taken for each offset position 1 or 4 quadrants This determines whether the standard star field will be posi tioned in one or four of the quadrants of the IFU As many exposures as defined in Number of exposures per telescope offset 7 will be taken at each telescope po sition 1 or 4 VIMOS User Manual VLT MAN ESO 14610 3509 42 4 7 6 VIMOS ifu cal NightCalib This template is to be used when screen flats or wavelength calibrations are needed during the night right after a science observation This template doesn t contain any setup definition and the data will be taken with exactly the same instrument setup as used in the previous observation template This template is to be used in a science OB after observation templates It can not be used alone in an OB after an acquisition template The exposure time parameters are automatically defined by the instrument setup The parameters of the template are e Night Flat Field T F If set to T 3 screen flats will be taken e Night Arc T F If T an arc spectrum will be taken VIMOS User Manual VLT MAN ESO 14610 3509 A VIMOS Filters
22. 20 760 nm 4096 2150 0 6 1 HR red GG475 630 870nm 4096 2500 0 6 1 1 With HR blue grism the spectral range in quadrant 1 for a standard star is 400 620 nm 2 With HR orange grism the spectral range in quadrant 1 for a standard star is 505 745 nm 3 With HR red grisms the spectral range in quadrant 1 for a standard star is 650 865 nm 4 New HR red VPHG grisms have been installed from October 5 2005 Table 5 Spectral coverage AA for three positions of the slit in field of view MOS mode Grism Order sorting AX AA AA filter CCD center CCD bottom CCD top LR red OS red 550 950nm 550 950nm 550 950nm LR blue OS blue 360 670nm 360 670nm 360 670nm MR GG475 500 1000nm 500 1000nm 500 950 nm HR blue Free 415 620nm 468 674nm 370 566 nm HR red GG475 630 870nm 690 930nm 570 805 nm HR orange GG435 520 760nm 577 817nm 463 703nm ommended to reduce the multiplex number of slits along the dispersion direction to avoid reduce multiple overlaps The multiplex can be reduced by increasing the distance between slits 2 3 4 MOS mode orientation of the field of view The orientation of the instrument field of view in MOS mode can be inferred from Figs 2 and 3 taking into account that not tilted slits are oriented along the x axes and that wavelength dispersion is along the y axis with wavelength increasing with y 2 4 Integral Field U
23. 78 1 contains more detailed and accurate information about the spectral range that can be observed in spectroscopic modes MOS and IFU with the various grisms Table 11 has been updated Hyperlinks have been added to the text The various sections of the manual have been re arranged All changes by S Bagnulo and M Rejkuba comments received by G Marconi and L Christensen 1 5 2 Version 79 0 VIMOS manual has been ported to the standard format for VLT manuals Changes by S Bagnulo 1 5 3 Version 79 1 Substantial chances to the description of the instrument field of view Changes by S Bagnulo and M Rejkuba Dr S L Morris is acknowledged for having improved Fig 5 An error in Table 5 has been corrected 1 6 Acknowledgments The following institutes have participated to the development of VIMOS e Laboratoire d Astrophysique de Marseille Marseille France e Observatoire de Haute Provence Saint Michel l Observatoire France e Laboratoire d Astrophysique de l Observatoire Midi Pyr n es Toulouse France e Osservatorio Astronomico di Capodimonte Napoli Italy e Istituto di Fisica Cosmica e Tecnologie Relative Milano Italy e Osservatorio Astronomico di Brera Milano Italy e Istituto di Radioastronomia Bologna Italy e Osservatorio Astronomico di Bologna Bologna Italy VIMOS User Manual VLT MAN ESO 14610 3509 3 Table 1 VIMOS opto mechanical characteristics Instrument Location Nasmyth B VLT UT3 Melipal Opt
24. DEC will be ignored VIMOS User Manual VLT MAN ESO 14610 3509 30 OBSBIOCK Targct_prcimuging VIMOS g t pr magir gi id SEET Zegt DEZ magina Alpha n fs 1 posi time Ceronra Letz oft zc B beervatizn Ctezore Arri anal v ele city 24 Addr onal elect JEL Gel Gu de sta un 5 Guid Star Ra is aras n Y or DEC GU Scart Dew urn 3 Orig n ZI fF dasal fin Lrrega 2743 Figure 11 P2PP example of a pre imaging OB SETUPFILE If this option is selected the guide star that will be used is the one for which the coordinates are defined in the Guide Star RA DEC fields A dedicated tool Guidecam is delivered by ESO to help the users to determine the best possible guide star This option is mandatory for service mode imaging and pre imaging OBs e Guide Star RAand Guide Star DEC Coordinates of the guide star when the SETUP FILE option of the Get Guide Star From field is selected e Guide Star PPOS Position of the Guide Probe when the SETUPFILE option of the Get Guide Star From field is selected e Optional additional velocity moving targets in alpha and delta Additional Velocity RA and Additional Velocity DEC This velocity should be expressed in arcsec sec These parameters are mostly intended for imaging or possibly IFU programmes of mov ing targets If no additional velocity is needed these parameters should be left to their default values 0 VIMOS User Manual VLT MAN ESO 14610 3509 31
25. E eds RRA EE BES Boe BEE a Acguisition T A gosa Ae KE PRES CR LTD ARS EP A EO 451 VIMOS ime aer Presa e pu cue PE REE ER ERM Ow ERE Be vi VIMOS User Manual VLT MAN ESO 14610 3509 4 6 4 7 4 5 2 4 5 3 4 5 4 VIMOS te EEN VIMOS ses aed Standard rsrsrsr SEE dar VIMOS aa PIE ssa pra Rw aena a whe wR E Science templates ise un FECAL A AA A E Eo 4 6 1 4 6 2 4 6 3 VIMOS sie obs Oleh o gt cc re dat ad fen c ra eee E Ki dd VIMOS mos obs Offset ss 62 sr dno ese rou rrp as VIMOS ifu obs Offset Calibration Templates Ae rss a 4 7 1 4 7 2 4 7 3 4 7 4 4 7 5 4 7 6 VIMOS ame og PROMO cus oe bd Oe ee a ee ee VIMOS Inca LSO A E ER SS REM e VIMOS mes maligna sy esso be whee a A A VIMOS moscal Standard lt s ce cet bee eae cb pad de ee bx VIMOS if cal Specphot A set eee a RR ES VIMOS aia Niet dee ss ps ee ra Ewe A VIMOS Filters VIMOS Grisms Template Signature Files for Observation and Acquisition CI egene Templates e kc asas SESE E Re A OL Eas te Observ tion Templates o m s roe dS we PERM ROE OER EER e Co Template Signature Files for Calibrations lt lt camas Abbreviations and Acronyms vil 43 44 52 52 53 53 57 VIMOS User Manual VLT MAN ESO 14610 3509 1 1 Introduction 1 1 Scope The VIMOS User s Manual is intended to provide information on the following topics e Overall description of the instrument Sect 2 e Observing with VIMOS
26. EUROPEAN SOUTHERN OBSERVATORY ES Organisation Europ ene pour des Recherches Astronomiques dans H misph re Austral Europ ische Organisation ftir astronomische Forschung in der s dlichen Hemisphare ESO European Southern Observatory Karl Schwarzschild Str 2 D 85748 Garching bei Miinchen Very Large Telescope Paranal Science Operations VIMOS User Manual Doc No VLT MAN ESO 14610 3509 Issue 79 Date 13 12 2006 G Marconi S Bagnulo M Rejkuba IPOD ALC EE Date Signature A Kaufer PROVE HE Date Signature O Hainaut o et ce et es ert A AS IIA Se De ee he Date Signature VIMOS User Manual VLT MAN ESO 14610 3509 This page was intentionally left blank VIMOS User Manual VLT MAN ESO 14610 3509 111 Change Record Issue Rev Date Section Parag affected Reason Initiation Documents Remarks draft Oct 24 2002 all Draft delivered by VIRMOS Consortium 1 0 Feb 11 2003 all first release for P71 phase II and P72 Phase 1 1 1 July 14 2003 all release for P72 phase II and P73 Phase I 1 2 Jan 12 2004 all release for P73 phase II and P74 Phase I 1 3 Jun 14 2004 all release for P74 phase II and P75 Phase I 5 0 Nov 26 2004 all release for P75 phase II and P76 Phase 1 76 0 Mar 21 2005 2 7 3 5 7 3 6 6 3 7 7 release for P76 Phase I 76 1 June 30 2005 2 1 2 2 2 3 2 6 3 4 3 5 3 6 3 7 4 6 release for P76 Phase II 77 0 Aug 31 2005 3 6 1 3 7 2 release f
27. R HR blue HR orange HR red e Return to Origin T F This parameter defines if after a dithered set of obser vations the telescope will return at the position at beginning of template or not This parameter is in general to be left in the default value in service mode If another value is desired in service mode a waiver should be requested e Number of Telescope Offsets This parameter defines the number of telescope off sets during the template The number of exposures taken at each telescope position is determined by the next parameter Number of exposures per telescope offset The pattern of offset is defined in the List of offsets arcsec along the slit and List of offsets arcsec perpendicular to the slit parameters e Number of exposures per telescope offset This parameter defines how many exposures are taken at each offset position VIMOS User Manual VLT MAN ESO 14610 3509 37 e List of offsets arcsec along the slit and List of offsets arcsec perpendicular to the slit Offsets are defined relative to the previous telescope position Offsets are defined in detector coordinates along or perpendicular to the slits Usually only offsets along the slits need to be defined If the first image is to be taken at the preset coordinates the first set of offset should be 0 0 If there are less offset values than the required number of offset position the template will return at the beginning of the list of offsets and appl
28. RE EE RAR a A co re AERO AE EE E ERE WERE E 343 IMG mode calibration plan ssoi dr gas We A ug E k 3 4 4 IMG mode pipeline EE Ee EE EE eR ED 3 4 5 IMG mode Exposure Time Calculator 06 Multi Object Spectroscopy MOS aaa St PERRA A e e ee EE ee e Be Be ee ee o 20a Rotor OS ek ms PE II ee e eee Oh BEE 3 5 3 VIMOS Mask Preparation Software VMMPS SoA Mass Day OER Re eR eS 3 55 Visitors usine MOS a s eae eb Be ee Dee EA EA E ka Ee RO 3 5 6 MOS mode grism filter setup 3 5 7 MOS mode attached night time calibrations 3 5 9 MOS mode calibration plan gt e s s a scen Ra eR Ee 046208 dos MOS mode pipeline lt lt bbe eS Be eee ee ee ees 3 5 10 MOS mode Exposure Time Calculator 400 been Fidd Un voca os Oe a Ke ee A o E SKI Acquisition accuracy os s ee EA ACRE RARA A 2 0 2 Ditherine jitter patter Ee Pew bab arrij de das 3 6 3 IFU mode prisma filter sep 24 66 6646 eocen 444284 E 3 6 4 IFU mode attached night time calibrations 3 0 0 IFU mode calibration plan s sei aceso ee bed ee ed ees 360 TU moda Pipeline e be ere be eee SERS Shee eA 3 6 4 IFU mode Exposure Time Calculator os ec 2842 ae0e 8 894 es VIMOS CAS a a Sm EE ee eH eee ee AA eee A VIMOS templates ode 5 24644446444 26 BE DAE SEA DAE A EES RH Template A Things to know Reminder 2 sc s se pages eeu ba eee Da we ee List of templates si ee ee E R
29. Sect 3 e Observing and calibration templates Sect 4 1 2 More Information on VIMOS All VIMOS Manuals are available on the VIMOS instrument WEB pages together with the most updated informations on the instrument http www eso org instruments vimos Information and software tools for the preparation of service and visitor mode observations with VIMOS are available at http www eso org observing p2pp ServiceMode html http www eso org observing p2pp VIMOS VIMOS P2PP htm1 In particular information concerning mask preparation with VMMPS and guide star selection with Guidecam is given in the following additional manuals VVMPS Guidecam Visiting astronomers will find further instructions on the Paranal Science Operations WEB page and the Paranal Observatory home page http www eso org paranal http www eso org paranal sciops 1 3 Contact Information In case of specific questions related to Service Mode observations and proposal preparation please contact the ESO User Support Department usd help eso org For visitor mode observations please contact the Paranal Science Operations Team paranal eso org 1 4 Period of Validity of this Manual This manual is valid for Phase II preparation of Period 79 VIMOS User Manual VLT MAN ESO 14610 3509 2 1 5 Version notes change track The first edition of this User Manual was delivered by the VIRMOS Consortium P I O Le F vre 1 5 1 Version 78 1 Version
30. This template is used for acquisition of a field in imaging mode for both imaging and pre imaging OBs Figure 11 shows the P2PP window with an example of a pre imaging Observing Block OB The coordinates of the target have to be entered in the Target window at the bottom of the P2PP window The parameters for this template are the following e Filter This filter should be the same as for the subsequent imaging template The available filters are U B V R I z e Rotator on sky This parameter defines the orientation of the instrument on sky This parameter should always be set to 90 for pre imaging templates unless a waiver is requested The orientation corresponding to 90 degrees is such that the slits will be oriented N S for the spectroscopic follow up e Alpha offset and Delta offset These are optional additional offsets in alpha and delta added to the coordinates of the object specified in the target panel at the bottom of the main p2pp window The coordinates at the center of the instrument i e the central point between the four quadrants are the coordinates specified in the Target Package plus the offsets here specified e Get Guide Star From Two options are offered for this parameter CATALOGUE This is the default option for which the guide star will be searched through a catalog and will be selected at the telescope by the Telescope Operator If this option is selected the subsequent fields Guide Star RA
31. VIMOS img obs Offset see Sect 4 otherwise data will be treated as pre imaging and will not be processed as regular imaging data Rotator on sky Users are encouraged but not forced to use the default value of the rotator angle i e 90 3 4 3 IMG mode calibration plan Table 12 indicates the nature frequency and accuracy of VIMOS calibrations expected to be taken as part of the calibration plan Only calibration frames required for the reduction of science data are reported More calibrations will be taken by the operation staff for the purpose of maintaining and monitoring the instrument configuration and performance e g mask to CCD transformations etc These calibrations are not reported here Calibration monitoring including photometric zero points can be found on the pages of the Quality Control group http www eso org observing dfo quality 3 4 4 IMG mode pipeline See http www eso org qc pipeline status html for the information concerning the latest sta tus of the ESO pipeline 3 4 5 IMG mode Exposure Time Calculator The approximate limiting magnitudes in direct imaging mode can be obtained from the expo sure time calculator available on the ESO WEB pages http www eso org observing etc 3 5 Multi Object Spectroscopy MOS 3 5 1 Pre imaging Pre imaging is mandatory for all MOS observations Pre imaging is carried out in service mode see Sect 3 4 1 VIMOS User Manual VLT MAN ESO 14610 3509 22 3 5
32. ameters List of offsets arcsec in X or RA and List of offsets arcsec in Y or DEC Offsets are defined relative to the previous telescope position e Number of exposures per telescope offset This parameter defines how many exposures are taken at each offset position e Offset coordinates This parameter defines the coordinate system used to define telescope offsets If the SKY option is selected telescope offsets are in RA and DEC if DETECTOR is selected telescope offsets are in X and Y on the detector In both cases the offsets are given in arcsec e List of offsets arcsec in X or RAandList of offsets arcsec in Y or DEC List of offsets between exposures Offsets are defined relative to the previous telescope position The offsets are defined in RA DEC or X Y on detector depending on which option is selected for the Offset coordinates field If the first image is to be taken at the preset coordinates the first set of offsets should be 0 0 If there are less offset values than the defined number of offset positions the template will return at the beginning of the list of offsets and apply them again For example if 5 telescopes offsets are defined number of telescope offsets together with the following series of offsets RA or X 0 10 5 DECorY 2 7 VIMOS User Manual VLT MAN ESO 14610 3509 36 the offsets applied to the telescope will be RA or X 0 10 5 0 10 DEC or Y 2 7 2 7 2 i e i
33. ca a Min Spec Peak EH _ Le BOE E j Y Al j 20 d L i o A 1 i Mi microns Figure 19 Efficiency curve of the medium resolution grisms MR The vertical lines mark the desired blaze and the central wavelengths The spectral range refers to the slit in the center of the field The cutoff wavelength is in most cases given by the order separation filters the red CCD limit or the limit of the VIMOS optics in the blue VIMOS User Manual VLT MAN ESO 14610 3509 Efficiency 7 Efficiency 100 80 50 100 SSS Sa HIGHBLU units 80 4 Desired Blaze e Sentrel 4 7 Min Spec Peak Ei 0 otra ea a Al a SE 0 6 2g 1 W m crons AMHURA nita Desired Blaze Mim fines Peak D 03 0 8 0 8 1 d WI mizrons Figure 20 Efficiency curve of the high resolution grisms HR blue HR orange The vertical lines mark the desired blaze and the central wavelengths The spectral range refers to the slit in the center of the field The cutoff wavelength is in most cases given by the order separation filters the red CCD limit or the limit of the VIMOS optics in the blue VIMOS User Manual VLT MAN ESO 14610 3509 51 VIMOS e248 Efficiency 750 ooo esa soc 350 1000 Wavelenght nm Figure 21 Efficiency curve of the high resolution grisms HR red VPHG The spectral range and efficiency refers to the slit in the center of the
34. dard star should be set by the user in the target sub window Note the rotator angle is fixed for this template at 90 corresponding to the set of slits in the masks being oriented N S The parameters of the template are e Exposure time seconds This is the integration time for the acquisition image that will be taken through the mask to check its positioning e Filter This filter is the one to be used for the acquisition image It is recommended to choose the right combination filter exptime to avoid the saturation of the star in the acquisition image The available filters are U B V R I z OS blue OS red GG435 GG475 and no filter e Optional additional velocity moving targets in alpha and delta Additional Velocity RA and Additional Velocity DEC This velocity should be expressed in arcsec sec These parameters are mostly intended for imaging and possibly IFU programs of moving targets and a priori unlikely to be of much use in MOS mode If no additional velocity is needed these parameters should be left to their default values 4 5 4 VIMOS_ifu_acq_Preset This template is for the acquisition of a field to be observed with the Integral Field Unit Unlike the MOS acquisition template the IFU acquisition template requires to define the filter grism combination that will be used in the following observation template This is to optimize the setup of the instrument at acquisition time The coordinates of the field at the
35. e time seconds This is the integration time in seconds per exposure Filter The available filters are U B V R I z OS blue OS red GG435 GG475 Grism The available grisms are LR blue LR red MR HR blue HR orange HR red In order to produce a valid OB the filter and the grism in the first observation template following the acquisition template should be the same as the one selected in the acquisition template IFU Magnification This parameter defines the sampling and correspondingly the field of view of the IFU The 2 available samplings are 0 67 arcsec fiber and 0 33 arcsec fiber To produce a valid OB the magnification should be the same in every tem plate of the OB IFU Shutter This parameter is only meaningful when using the LR grisms In LR spectroscopy there are 4 rows of fibers along the dispersion direction whereas in MR and HR modes only one slit of fibers is used hence the variation of field of view between LR and MR and HR modes In case the object of interest is of limited size in LR mode and if only the central 1 4 x 1 4 of the field of view is needed it is possible with the IFU Shutter option to mask the outer part of the IFU always masked in MR and HR modes This allows to avoid second order overlap due to sky and or background objects between the 4 adjacent slits along the dispersion direction True means that the shutter is in place and masks the external part of the IFU False the default
36. efined in the target package of the acquisition template If the 4 quadrant option is selected the astrometric field will be positioned sequentially in the 4 quadrants by applying the appropriate offsets from the coordinates of the field defined in the target package of the acquisition template As many exposures as defined in Number of exposures telescopes offset 7 will be taken at each telescope position 1 or 4 At the end of the template the telescope will offset again to return to its position at the beginning of the template 4 7 3 VIMOS mos cal NightCalib This template is to be used when screen flats or wavelength calibrations are needed during the night right after a science observation This template doesn t contain any setup definition and the data will be taken with exactly the same instrument setup as used in the previous science template This template is to be used in a science OB after a science templates It can not be used alone in an OB after an acquisition template The exposure time parameters are automatically defined by the current instrument setup The parameters of the template are e Night Flat Field T F If set to T 3 screen flats will be taken e Night Arc T F If T an arc spectrum will be taken 4 7 4 VIMOS mos cal Standard This template is used for the observation of a standard star in mode MOS This template can only be used following the VIMOS mos ac Standard acquisition template and n
37. etc All the preparations are done with the Phase II proposal preparation tool p2pp In addition VIMOS masks have to be prepared with the VIMOS mask manufacturing prepa ration software VVMPS The strategy behind observing blocks and templates is to prepare the observations well in advance to minimize any interactive steps during the observations optimization and service mode compatibility The execution of the OBs will be mostly automatic and the execution will be done by telescope and instrument operators and staff astronomers Direct interaction at execution time is only required for the target acquisition and to assess the quality of the data The preparation of visitor and service mode observations requires special care and the rele vant documentation should be consulted See Sect 1 for instructions on how to retrieve the corresponding information 3 1 Interaction with the telescope 3 1 1 Guide stars and Guidecam software tool For telescope guiding and active optics correction it is necessary to find a guide star of mag nitude in the range 11 13 5 within the Nasmyth field of view The guide star is picked up by the Guide Probe which is attached to the telescope adapter Note that the adapter is independent of the telescope rotator to which the instrument is attached In IMG and MOS mode it is not always possible to find a guide star such that the Telescope Guide Probe is not vignetting the VIMOS field of view Therefore users a
38. f SKY option for coordinates is used after the preset the first offset will be applied to place the target at 2 arcsec North 0 offset in RA and then the first exposure will be taken after that the target will be moved further 10 arcsec West and 7 arcsec North with respect to the position of the previous exposure etc until the number of exposures is reached If DETECTOR option is used the first exposure will be taken at pixels x 0 y 10 offset is 2 which is approximately 10 pixels then the target will be moved further 10 West and 7 North with respect to the position of the previous exposure etc until the number of exposures is reached e Observation Category PRE IMAGE is for a pre imaging program SCIENCE is for a regular science imaging program It is critical that users define PRE IMAGE for pre imaging programs Failure to do so will result in slow processing and delivery possibly till the end of the period of the data 4 6 2 VIMOS mos obs Offset The parameters of this template are e Exposure time in seconds This is the integration time in seconds per exposure e Filter The available filters are U B V R I z OS blue OS red GG435 GG475 and no filter The standard grism filter configurations are given in Table 3 Only standard filter grism combinations are allowed as indicated in Table 3 Other combinations should be requested with a waiver e Grism The available grisms are LR blue LR red M
39. f photometric data zero points in Imaging mode The acquisition template to use with this template is VIMOS img ac Preset The coordinates to define in the acquisition template are those of the standard star field Offsets from these coordinates to position the star field in one or the four quadrants of the instrument will be applied automatically by the template The parameters of this template are e Exposure time seconds This is the integration time in seconds per exposure e Filter The available filters are U B V R I z To produce a valid calibra tion OB the filter in the first observation template following the acquisition template should be the same as the one in the acquisition template e Number of exposures per telescope offset This parameter defines how many exposures are taken at each offset position 1 or 4 e 1 or 4 quadrants This parameter allows to define if the standard star image will be taken in 1 or 4 quadrants If the 1 quadrant option is selected the standard star field will be positioned in only one quadrant by applying an appropriate offset from the coordinates of the star field defined in the target package of the acquisition template If the 4 quadrant option is selected the standard star field will be positioned sequen tially in the 4 quadrants by applying the appropriate offsets from the coordinates of the star field defined in the target package of the acquisition template As many expos
40. image e VMMPS maximizes the number of slits that can be assigned to the targets in the input catalogue in one or more masks depending on user s choice e Upon realization of a first mask definition VMMPS allows manual interaction to unselect targets define curved slits tilted slits etc However note that manual modification of the mask definition should be done only by experienced users and with care e VMMPS allows to define some objects as compulsory e VMMPS requires that some bright stars are defined as reference targets for acquisition purposes Figure 10 shows the VMMPS Graphical User Interface 3 5 4 Finding charts Finding charts for service mode OBs need to be prepared with VMMPS and show all targets with slits overplotted VIMOS User Manual VLT MAN ESO 14610 3509 23 Figure 10 VMMPS Graphical User Interface Example of ADP file superimposed to field of view VIMOS User Manual VLT MAN ESO 14610 3509 24 3 5 5 Visitors using MOS Visitors using the MOS mode are requested to prepare Observation Blocks ahead of their scheduled visitor run and upon completion of their pre imaging observations like in service mode This is to guarantee that visitors will have a sufficient knowledge of the VIMOS Mask Preparation Software VMMPS Sect 3 5 3 prior to their visit at Paranal and to allow mask manufacturing ahead of time Limited additional support is guaranteed for mask preparation on the mounta
41. in up to 3 masks per night to be prepared at least 48 hrs in advance The instrument has a capacity of 15 masks per quadrant loaded simultaneously one slot is normally occupied by a mask dedicated to observations of spectrophotometric standard stars However some restrictions may apply for technical reasons in the number of masks which can be hosted simultaneously into the cabinets Until P77 only 8 masks can be simultaneously accommodated in the instrument cabinet 1 of which is the mandatory spectroscopic mask and the same is currently foreseen for P78 Please refer to the Call for Proposals and to the instrument WEB pages for the updated status of the instrument situation Note that masks cannot be exchanged at night 3 5 6 MOS mode grism filter setup In MOS mode only one filter grism combination per OB is permitted the only filter exchange allowed is the one between acquisition and science template Users who want to observe the same targets with different filter grism combinations are requested to submit separate OBs for different filter grism combinations and to consider the respective overheads 3 5 7 MOS mode attached night time calibrations To correct for instrument flexures the use of attached nighttime arcs see Sect 3 5 8 is MANDATORY for all MOS OBs using LR blue and HR blue grisms and strongly recom mended for all setups Users may also attach screen flats The execution time for these nighttime calibrations is alwa
42. in p2pp DET WIN1 UIT1 1 100000 Exposure time seconds INS FILT NAME UB VE dz Filter OS red OS blue GG435 GG475 INS GRIS NAME LR blue LR red MR HR blue Grism HR orange HR red INS IFUE NAME 0 33 0 67 IFU magnification in arcsec fiber INS IFUS MODE FT IFU Shutter SEQ NEXPO 1 1000000 Number of exposure per telescope offset SEQ NOFF 1 1000000 Number of telescope offsets SEQ RETURN FT Return to Origin T F SEQ OFFSET COORDS SKY LENSLET Offset Coordinates SEQ OFFSET1 LIST List of offsets arcsec in X or RA SEQ OFFSET2 LIST List of offsets arcsec in Y or DEC VIMOS img cal Photom Keyword Range Label in p2pp DET WIN1 UIT1 1 100000 Exposure time seconds INS FILT NAME UBVRIz Filter SEQ NEXPO 1 1000000 Number of exposure per telescope offset SEQ CAL FLAG 14 1 or 4 quadrants VIMOS img cal Astrom Keyword Range Label in p2pp DET WIN1 UIT1 1 100000 Exposure time seconds INS FILT NAME UBVRIz Filter SEQ NEXPO 1 1000000 Number of exposure per telescope offset SEQ CAL FLAG 14 1 or 4 quadrants VIMOS User Manual VLT MAN ESO 14610 3509 59 VIMOS_mos_cal_NightCalib Keyword Range Label in p2pp SEQ FLATFIELD FT Night Flat Field SEQ ARC FT Night Arc SEQ FLATFIELD NEXPO 1 1000000 No of scrrenflats
43. ion in arcsec fiber INS IFUS MODE FT IFU Shutter TEL TARG ADDVELALPHA 15 15 Additional Velocity RA TEL TARG ADDVELDELTA 15 15 Additional Velocity DEC C 2 Observation Tem plates VIMOS img obs Offset Keyword Range Label in p2pp DET WIN1 UIT1 1 100000 Exposure time seconds INS FILT NAME UBVRIz Filter SEQ NEXPO 1 1000000 Number of exposure per telescope offset SEQ NOFF 1 1000000 Number of telescope offsets SEQ RETURN FT Return to Origin T F SEQ OFFSET COORDS SKY DETECTOR Offset Coordinates SEQ OFFSET1 LIST List of offsets arcsec in X or RA SEQ OFFSET2 LIST List of offsets arcsec in Y or DEC SEQ CATG PRE IMAGE SCIENCE Observation Category C 3 Template Signature Files for Calibrations VIMOS User Manual VLT MAN ESO 14610 3509 54 VIMOS_mos_obs_Offset Keyword Range Label in p2pp DET WIN1 UIT1 1 100000 Exposure time seconds INS FILT NAME UBVRIz Filter OS red OS blue GG435 GG475 INS GRIS NAME LR_blue LR_red MR HR_blue Grism HR_orange HR_red SEQ NEXPO 1 1000000 Number of exposure per telescope offset SEQ NOFF 1 1000000 Number of telescope offsets SEQ RETURN FT Return to Origin T F SEQ OFFSET1 LIST List of offsets along the slit arcsec SEQ OFFSET2 LIST List of offsets perpendicular to the slit arcsec VIMOS ifu obs Offset Keyword Range Label
44. lease have a look at the Quality Control and Data Flow Operations Web pages The focal plane of VIMOS is not strictly flat because of the complexity of the optical elements involved This results in slight focus variations across the field which translates in a variable PSF from the center to the periphery The sky concentration effects are in any case small and negligible for flat field and photometric calibrations VIMOS User Manual VLT MAN ESO 14610 3509 6 Orientation ON SKY VIMOS FoV IMAGING MOS MODE Rotator angle PA O Q2 641 IFU 6 48 6 59 Figure 2 Orientation of the VIMOS field of view on sky for position angles 0 and 90 in IMG and MOS mode 2 2 3 Imaging Filters VIMOS provides positions for 10 broadband filters in any of the four channels Presently installed filters inside the instruments are U Bessel BVRI Gunn z and some order separation filters Only the U BVRIz filters are available for imaging programmes The special U is not a standard Bessel filter see Figure 14 With the Bessel J and Gunn z filters the CCDs show fringes of approximately 7 The complete list of filters together with the transmission curves are presented in Appendix A see Table 16 and Figs 14 to 17 ESO will not accept requests for user s supplied filters for VIMOS 2 3 Multi Object Spectroscopy MOS A variety of grisms with different wavelength ranges and dispersions is available in MOS mode Order sepa
45. lengths during the exposure Atmospheric spectra start with N E orientation and move to N W through a N S orientation while crossing the Meridian The maximum amplitude of the dispersion is 2 at 2 hrs from Meridian Slits clearly have to be oriented N S as a default orientation to minimize the slit losses assuming that all MOS observations will be carried out within 2 hrs from Meridian 3 3 Fringing and Flexures The amount of flexures reported in Sect 2 7 has a number of operational consequences e The accuracy of the slit positions determined from pre imaging depends on the rotator position This is for the time being one of the reasons why slit widths narrower than 0 6 are not allowed e Accuracy of sky subtraction flat fielding due to fringing at red wavelengths accuracy of sky subtraction flat fielding may be limited by flexures With dithering jittering VIMOS User Manual VLT MAN ESO 14610 3509 20 sequences median running sky frames can be built in imaging or spectroscopy allowing accurate sky subtraction and or flat fielding of the data e In spectroscopy arcs and flats are taken during daytime and at constant rotator angle Depending on the variation in rotator angle between daytime calibrations and night time observations some flat field residuals and wavelength calibration offsets may be introduced due to the flexures In order to minimize eliminate these effects night time calibrations can be taken with an
46. meters should be left to their default values VIMOS User Manual VLT MAN ESO 14610 3509 35 4 6 Science templates 4 6 1 VIMOS_img_obs_Offset This template is used for Imaging mode observation both for Science and Pre imaging The parameters of this template are the following e Exposure time in seconds This is the integration time in seconds per exposure e Filter The available filters are U B V R I z In order to produce a valid OB the filter in the first observation template following the acquisition template should be the same as the one selected in the acquisition template For pre imaging the use of R filter is mandatory e Return to Origin T F This parameter defines if after a dithered set of obser vations the telescope will return at the position at beginning of template or not As an example this parameter should be set to 7 when the aim of the OB is to execute multi color imaging observations with the same pattern of offsets on the same field us ing different templates This parameter is in general to be left to its default value in service mode If another value is desired in service mode a waiver should be requested e Number of Telescope Offsets This parameter defines the number of telescope off sets during the template The number of exposures taken at each telescope position is determined by the next parameter Number of exposures per telescope offset 7 The pattern of offsets is defined in the par
47. n observation Preset for a preset NightCal for attached night calibrations etc 4 3 Things to know Reminder e See Sect 2 2 1 for a description of the orientation on sky of VIMOS e The default orientation on sky for MOS and pre imaging templates is 90 see Sect 3 2 Any departure from this value should be requested with a waiver e Offset convention The templates make extensive use of telescope offsets which are entered manually as lists The convention is that offsets are relative In some templates the offsets can be defined in detector coordinates e g X Y or in RA DEC All offsets are to be defined in arcseconds The offsets refer to the target Examples are provided further down in the description of the templates e Only some combinations of filters and grisms are allowed See Sect 2 3 and Table 3 4 4 List of templates Table 15 lists the VIMOS templates VIMOS User Manual VLT MAN ESO 14610 3509 29 Table 15 Science and Nighttime Calibration Templates Type Name VIMOS_img_acq_Preset Acquisition VIMOS_mos_acq_Mask templates VIMOS mos acq Standard VIMOS ifu acq Preset Science VIMOS mg obs Offset templates VIMOS mos obs Offset VIMOS ifu obs Offset VIMOS img cal Photom VIMOS mg cal Astrom Calibration VIMOS mos cal NightCalib templates VIMOS mos cal Standard VIMOS ifu cal NightCalib VIMOS ifu cal Specphot 4 5 Acquisition templates 4 5 1 VIMOS img acg Preset
48. n p2pp SEQ FLATFIELD FT Night Flat Field SEQ ARC FT Night Arc SEQ FLATFIELD NEXPO 1 1000000 No of scrrenflats 56 VIMOS User Manual VLT MAN ESO 14610 3509 57 D Abbreviations and Acronyms The following abbreviations and acronyms are used in this manual ACQ Acquisition ADP Aperture Definition in Pixels ADU Analogue to Digital Unite CCD Charge Coupled Device DEC Declination ESO European Southern Observatory ETC Exposure Time Calculator FEU Filter Exchange Unit FIERA Fast Imager Electronic Readout Assembly FWHM Full Width Half Maximum GEU Grism Exchange Unit HR High Resolution IFU Integral Field Unit IMG Imaging MEU Mask Exchange Unit MOS Multi Object Spectroscopy OB Observation Block OS Order Sorting PSF Point Spread Function P2PP Phase 2 Proposal Preparation RA Right Ascension RMS Root Mean Square RON Read Out Noise TSF Template Signature File VIMOS Visible Multi Object Spectrograph VMMPS Vimos Mask Manifacturing Preparation Software VLT Very Large Telescope A Angstrom em Electron cm Centimeter h Hour kpx KiloPixel min Minute mm Millimeter nm Nanometer px Pixel S Second um Micrometer
49. nge and are indicated here only for reference Exact values have to be found in the image headers Table 11 Detector read out noise and conversion factors For reference only subject to change Chip Read out Mode RON Je rms K e7 adu CCD 1 225 kpxs low gain IMG mode 5 3 1 70 CCD 2 225 kpxs low gain 5 2 1 86 CCD 3 225kpxs low gain 5 3 1 95 CCD 4 225kpxs low gain 4 9 1 80 CCD 1 225kpxs high gain MOS and IFU modes 4 3 0 51 CCD 2 225 kpxs high gain 4 6 0 56 CCD 3 225kpxs high gain 4 7 0 57 CCD 4 225kpxs high gain 4 3 0 52 RON and conversion factor monitoring is available through the QCI WEB pages VIMOS User Manual VLT MAN ESO 14610 3509 15 2 5 4 Fringing With the z Gunn and Bessel filters the fringing amplitude is around 7 in imaging and in spectroscopy the amplitude of fringing is of the order of 7 8 at maximum Despite this relatively strong fringing it is important to note that the structure is quite stable and dithered images taken in a sequence can easily remove the structure see Sect 3 3 2 5 5 Shutters The shutter one for each CCD camera guarantees uniform illumination of the CCD to the 1 level or better for exposure times as short as 1 sec the shortest possible exposure time 2 5 6 More information More updated information on detector characteristics cosmetics and performance on sky at http www eso org projec
50. nit IFU The Integral Field Unit IFU is a dedicated opto mechanical system aimed at producing spectra of a contiguous area of up to 54 x 54 arcsec The sky image is projected onto a micro lens array with a choice of two spatial samplings magnifications 0 33 or 0 67 per resolution element fibre Each 2D input micro lens is coupled to an optical fiber The output of the fibers is re arranged on a linear set of micro lenses to produce an entrance slit to the spectrograph at the mask focal plane location Each IFU mask one for each channel of VIMOS User Manual VLT MAN ESO 14610 3509 10 VIMOS IFU ORIENTATION ON SKY Rotator angle PA 0 Rotator angle PA 90 AN 1 4 E aeh An 2 3 1 2 Figure 4 Orientation of the VIMOS IFU field of view on sky for position angles 0 and 90 in IFU mode VIMOS has a set of 4 fibre slits or pseudo slits for a total of 6400 fibers 2 4 1 IFU mode orientation of the field of view Figure 4 shows the orientation of the instrument field of view in IFU mode for the four quadrants On the detectors wavelength dispersion is along the y axis with wavelength increasing with y The increasing position angle on the sky east of north corresponds to the positive rotator angle Spatial characteristics are described in the Section below As for IMG MOS modes the pointing coordinates in the header correspond to the center of the VIMOS field of view Due to offse
51. o mechanical layout 4 beams each a complete focal reducer F 1 88 output Wavelength coverage 0 37 to 1 microns Detectors 4 x 2048 x 4096 15 um pixel Spectral Resolution R 180 to 2500 1 arcsec slit Filters 10 per channel U BVRIz OS red OS blue GG435 GG475 170mm diameter Grisms 6 per channel LR red LR blue MR HR blue HR orange HR red H Flexures Passive compensation motion of 2 pixels over 360 rotation Masks 15 masks simultaneously loaded in instrument at maximum per channel 2 Slits of any position and shape width gt 0 6 length lt 30 Multiplex 840 simultaneous slits 10 long at R 200 210 simultaneous slits 10 long at R 2000 2500 Integral Field Unit 54 x 54 field 6400 fibers with 0 67 sampling 27 x 27 field 6400 fibers with 0 33 sampling Ul From October 2005 a set of four new and more efficient HR red VPHG grisms is installed and available in the 4 channels 2 Some restrictions apply in operations currently the number of masks that can be mounted at the instrument cabinet is 8 Please refer to the VIMOS web pages for updates 2 Instrument Characteristics 2 1 Overview VIMOS is the Visible Multi Object Spectrograph for the Very Large Telescope VLT of the European Southern Observatory ESO This instrument has been built to provide the ESO community with a wide field spectrograph with high throughput and multiplex dedicated to deep surveys VIMOS operates in
52. only one slit can be placed along the dispersion direction However please note that in the multi layer mode there is some order overlap the second order of one slit may overlap with the first order of the adjacent slit There is also OD order contamination between different layers of slits For faint objects order overlap is usually not a problem only the sky will contribute signif icantly to the overlap with a contribution that cannot be distinguished from the first order This however constrains the positioning of the slits in the focal plane stacked slits along the dispersion direction have to be strictly parallel and of the same length to allow the second orders to overlap nicely with the first order of the adjacent slits With the low resolution grisms the use of no filter instead of the default order sorting filters OS blue and OS red will result in longer spectra and second order overlap It is strongly rec VIMOS User Manual VLT MAN ESO 14610 3509 9 Table 4 MOS spectral resolution and spectral ranges observed using the mask for spectropho tometric standard stars Grism Default Order Spectral Number Spectral Res Dispersion Spectral sorting filter range of pixels 1 slit A pixel multiplex LR blue OS Blue 370 670 nm 550 180 5 3 4 LR red OS Red 550 950 nm 550 210 7 3 4 MR GG475 480 1000 nm 2000 580 2 5 2 MR OS red 550 970 nm 2000 580 2 5 2 HR blue Free 415 620 nm 4096 2050 0 51 1 HR orange GG435 5
53. or P77 Phase I 77 2 Dec 01 2005 Appendix release for P77 Phase II 78 0 Mar 01 2006 none release for P78 Phase I 78 1 Jun 06 2006 all release for P78 Phase II 79 0 Aug 23 2006 front page and fonts release for P79 Phase I 79 1 Dec 13 2006 Added clarifications about instrument FoV Phase II release for P79 Phase II VIMOS User Manual VLT MAN ESO 14610 3509 This page was intentionally left blank VIMOS User Manual VLT MAN ESO 14610 3509 Contents 1 Introduction A es ee ee Be ee et a E et ee ot A 1 2 More Information om VIMOS 2 26446 nee ee reas ds Teo Contact OM s sad san oe PKS EA EEE HREM GE Le Feed Validity of this Mam E E sesa 44 Rd A HGR a LS Version motes change track lt eco sc s ee eae ee ge ee a Ea ae we A Lal VOI Fi fants Gok ee E ee a ee eke E a Ee Be TOS Version a ee etd bw ee E E e ES ee Be E Lido Version TL sus oho ae RAR RA OO ee a H D 1 6 Acknowledgments causa ma AE EE ARA A A E RA O 2 Instrument Characteristics DL MEO a ue a ad e e a EA E SCH Instrument mod s s crime E E e MO surgidas ga sd be DG db EG He EE Ad 2 2 1 IMG mode orientation of the field of view Se Image QUS o c poce rs SB sa AE E e we ER goose Mme RO ooo ee oe hae eae S DED ee Med Se Re ee BS 29 Multi Object Spectroscopy MOS o srs go ser aa wh ee bee CN A E o c era sene sed be e E Ee EE E 23 4 Ope ctralyresolutioi s ss hes ps coace SE EN pa AN E 2 0 3 Multi
54. ot using the VIMOS mos acq Mask This template can only use the specifically designed standard mask from the repository The parameters of this template are e Exposure time seconds This is the integration time in seconds per exposure e Filter The available filters are U B V R I z OS blue OS red GG435 GG475 e Grism The available grisms are LR blue LR red MR HR blue HR orange HR red e Number of exposures per telescope offset This parameter defines how many exposures are taken for each offset position e 1 or 4 quadrants This determines whether the standard star will be positioned in one or four of the quadrants of the instrument As many exposures as defined in Number of exposures per telescope offset will be taken at each telescope position 1 or 4 VIMOS User Manual VLT MAN ESO 14610 3509 41 Slit Width Define which of the slits available in the masks will be used The width of the available slits are 0 8 1 0 1 2 1 5 1 8 2 0 2 5 5 0 Once the user select the slit width the rest is totally automatic the star will be offset from the acquisition box to the selected slit in the first quadrant and then moved to the same slit in the other quadrants 4 7 5 VIMOS ifu cal Specphot This template is used for the observation of a spectrophotometric standard star in IFU mode It is to be used in a OB with the VIMOS_ifu_acq Preset acquisition template The parameters of the template are Exposur
55. plex characteristics lt o s sacra 65 obese eee ewe a 2 3 4 MOS mode orientation of the field of view 24 Inega Feld Umt FU ceace be rr 2 4 1 IFU mode orientation of the field of view 24 2 Fiber arrangement and spatial characteristics 2 43 Spectral rang gt e c cosc sess AL E A dA e REA E RS 24A Spectral resolution s e s se doo EEE A A A E dE EE Ee 245 Multiplex characteristics lt ss soet 448244 25 44 E DER ER RH do DeeS o ece ro ea ee eee e ee ed aaa 2 5 1 Detector read out modes 266 ee ee wma Rs ERS EA eRe Es LS CONOS A e e paras DEE AAA 2 5 0 Read out noise and conversion factor 0 lt lt es 204 DOE cos ie ta AAA AAA E A IEEE 250 Meio 4 6 24864 44 8 eS oo 2 a KGS KA EGR HS 20 Cahbration UE a oo ea ee ea a Ge pag pd wae bee ee bala eS A cc ek borra Beek ee ook ee eS Sb BS ee Be Boe 3 Observing with VIMOS N MM MM KF e KF Ra Fe O oO oO o CO On CO HTH On FW G VIMOS User Manual VLT MAN ESO 14610 3509 3 1 3 2 3 3 3 4 3 9 3 6 3 7 4 1 4 2 4 3 4 4 4 5 Interaction with the telescope 3 1 1 Guide stars and Guidecam software tool ol Gude Stars EE ss e mess Be ee ee AA EA 3 1 3 Cumulative offsets ao ss ee ew E a eR Be E Eo 3 1 4 Telescope and Instrument Focus 0 0008 wee Atmospheric Dispersion ANEN EEN EN RNA A HSE A ALA a ener and Vea AE ER O kn p redd ad Ae A E E e e SL PESIMA oscura PE
56. rating filters are available to eliminate the overlap for a given slit between orders 1 the order used for science and order 2 always present on the detector This is done by restricting the wavelength range of a particular grism to less than one octave in wavelength The Oth order contamination is present only in multi layered mode i e when observing with the LR and the MR grisms Table 3 indicates the recommended and allowed grism filter combinations Any other combinations of grisms and filters should be requested with a waiver Defining in the OBs combinations not allowed and for which a waiver was not requested will result in these OBs being rejected by the User Support Department ESO will not accept requests for user s supplied grisms or filters for VIMOS VIMOS User Manual VLT MAN ESO 14610 3509 7 VIMOS FoV ORIENTATION ON SKY ON DETECTOR Rotator angle PA 0 aie l Rotator angle PA 90 E N Q2 QL Q2 Q3 e E N l l Figure 3 A comparison of the orientation of the VIMOS field of view as seen on sky left panels and on detector right panels for position angles 0 and 90 in IMG and MOS mode VIMOS User Manual VLT MAN ESO 14610 3509 8 Table 3 Standard grism filter combinations for MOS and IFU modes Grism Filter Default Allowed LR blue OS blue Free LR red OsS red Free MR GG475 OS red OS blue HR blue Free HR red GG475 HR orange GG435
57. re asked to select the guide star for their observations The choice of the guide star is mandatory for pre imaging for imaging and for MOS programs In fact the guide star for MOS is selected at the time of pre imaging guide star coordinates and position of guide probe whether positive or negative is stored in the pre image headers and subsequently propagated by VMMPS see Sect 3 5 3 the VIMOS Mask Preparation Software into the Aperture Definition in Pixel ADP files At the time of the MOS acquisition this information is extracted from the ADP files and the same guide star as used for pre imaging will be re used for the MOS observations Only in some exceptional cases the telescope operator may have to select another guide star see Sect 3 1 2 Users need not select the guiding star for observations carried out in IFU mode The position and the amount of the vignetting introduced in the field of view by the guide probe can be controlled with the help of the Guidecam software that allows one to visualize the geometry of the VIMOS field of view and of the Telescope Guide Probe and allows users to select the guide star most suitable to their observation Figure 8 shows the Guidecam Graphical User Interface displaying the geometry of the VIMOS field of view and the Guide Probe at the Nasmyth focal plane of the telescope VIMOS User Manual VLT MAN ESO 14610 3509 17 Figure 8 Guidecam Graphical User Interface Superimposed to the field
58. re performed close to meridian the slits need to be oriented N S forcing the rotator angle to be set at 90 This rotator angle is the default one to be used for pre imaging and the same rotator angle will be used during spectroscopic follow up The VIMOS operational scenario VIMOS User Manual VLT MAN ESO 14610 3509 19 foresees to carry out MOS observations as close as possible to Meridian within 2 hrs Although this represents a major operational constraint this is the only safe mode to ensure that slit losses are minimized in a systematic way for the blue setups provided that slits are oriented N S More information and simulations can be found on the VIMOS web page Figure 9 shows a worst case scenario of MOS observations with LR_blue spectral coverage 370 670 nm for a field with declination 20 T T T T T T T T T T T T T T T T T T T T T 1 Site Paranal o 2 00 orcsec J Dec 20 o o a Tstart 2 hrs a J Tend 2 hrs ge a Kee Sei 45micron HU H e Se BS a E J 37micron e 4 2 67micron 2 E Es Pi ER e E CH D gt 4 2 a SE SC E D ka o w a p Fe R gt 6 Soe SS E Bi 4 p pi p SC o a bosco csstoa soso dy 10 5 0 5 10 RA arcminutes Figure 9 Example of atmospheric dispersion at Paranal for a field at declination 20 observed with the LR_blue grism from 2 hrs from Meridian The blue and red trails show the evolution of the blue and red wave
59. respect to the coordinates of the object The coordinates at the center of the IFU are the coordinates specified in the Target Package plus the offsets here specified This can be useful e g to define small offsets between the initial pointings on the same field over several OBs e Get Guide Star From Two options are offered for this parameter CATALOGUE This is the default option for which the guide star will be searched through a catalog and will be selected at the telescope by the Telescope Operator If this option is selected the subsequent fields Guide Star RA DEC will be ignored Given that the quasi total Nasmyth field of view is accessible to choose a guide star in IFU mode the users can safely use this option SETUPFILE If this option is selected the guide star that will be used is the one for which the coordinates are defined in the Guide Star RA DEC fields As indicated above it is unlikely that this option is required in IFU mode Note that Guidecam tool is not intended to be used to select guide stars for the IFU mode but only for the IMG and MOS mode of VIMOS e Guide Star RA and Guide Star DEC Coordinates of the guide star when the SETUP FILE option of the Get Guide Star From field is selected e Optional additional velocity moving targets in alpha and delta Additional Velocity RA and Additional Velocity DEC This velocity should be expressed in arcsec sec If no additional velocity is needed these para
60. rows of fibers along the dispersion direction whereas in MR and HR modes only one slit of fibers is used hence the variation of field of view between LR and MR and HR modes In case the object of interest is of limited size in LR mode and if only the central 1 4 x 1 4 of the field of view is needed it is possible with the IFU Shutter option to mask the outer part of the IFU always masked in MR and HR modes This allows to avoid second order overlap due to sky and or background objects between the 4 adjacent slits along the dispersion direction True means that the shutter is in place and masks the external part of the IFU False the default value means that the mask is not in place and the full IFU field of view is available To produce a valid OB the mask shutter option should be the same in every template of the OB This parameter is ignored when MR or HR grisms are used e Rotator on Sky This parameter defines the orientation of the instrument on sky The IFU has a square geometry with the sides oriented N S and E W With a rotator angle of zero the orientation of the IFU on the sky is with the North up and the East to the right The increasing positive position angle on the sky east of north corresponds to the positive rotator angle Therefore the value of this keyword should be equal to the desired position angle PA on the sky see Fig 4 e Optional additional offsets in alpha and delta Alpha Offset and Delta offset with
61. s part of their Phase II material 3 1 3 Cumulative offsets For small telescope offsets the telescope may keep the same guide star However observations involving cumulative offsets greater than about 30 often result in significant vignetting of the guide probe or even in the loss of the guiding star For these reasons all dither positions for offset patterns used in the OBs must fit inside a 30 x 30 size box If larger offsets are necessary users need to prepare separate OBs and use appropriate guide star for each of them 3 1 4 Telescope and Instrument Focus The telescope focus is automatically set by the active optics system No intervention is required by the observer Defocusing of the telescope is not possible during the observations The instrument focus is corrected automatically for the different thickness of the various filters and for temperature variations autofocus 3 2 Atmospheric Dispersion VIMOS is not equipped with Atmospheric Dispersion Corrector in none of its modes The impact of atmospheric dispersion will be mostly noticed in MOS mode In imaging some image elongation may be noticed at high airmasses in the U or B band In IFU the effect will mostly be noticed with the LP blue grism and with the 0 33 fiber sampling In MOS mode the effects can lead to severe slit losses if some precautions are not taken To minimize atmospheric dispersion effects at high airmass and assuming that the observations a
62. sequently we cannot give here an estimate of the overheads that is reliable on the long term The user is referred to the current Call for Proposals and to the VIMOS web pages for the most updated estimate of the overheads http www eso org instruments vimos overview html VIMOS User Manual VLT MAN ESO 14610 3509 28 4 VIMOS templates 4 1 Introduction This section describes the VIMOS templates Templates are to be used during phase II for service and visitor programmes Templates are characterized by signatures to be filled in by the users with P2PP Templates are grouped together to build an Observation Block OB which typically consists of one acquisition template and one or more observing or calibration templates At the telescope OBs are passed to the instrument and executed according to the user defined parameter values Unless specified otherwise the information provided in this part applies to both service and visitor modes 4 2 Template names VIMOS templates are divided in groups according to the instrument mode and to the obser vations to be performed This is reflected in the name of the various templates The template naming scheme is the following VIMOS_ lt mode gt _ lt type gt _ lt description gt tsf where mode is the mode of the instrument either img mos ifu type is the type of the template either acq obs or cal description is a string identifying the purpose of the template Offset for a
63. spondingly the field of view of the IFU The 2 available samplings are 0 67 arcsec fiber and 0 33 arcsec fiber To produce a valid OB the magnification should be the same in every tem plate of the OB VIMOS User Manual VLT MAN ESO 14610 3509 38 e IFU Shutter This parameter is only meaningful when using the LR grisms In LR spectroscopy there are 4 rows of fibers along the dispersion direction whereas in MR and HR modes only one slit of fibers is used hence the variation of field of view between LR and MR and HR modes In case the object of interest is of limited size in LR mode and if only the central 1 4 x 1 4 of the field of view is needed it is possible with the IFU Shutter option to mask the outer part of the IFU always masked in MR and HR modes This allows to avoid second order overlap due to sky and or background objects between the 4 adjacent slits along the dispersion direction True means that the shutter is in place and masks the external part of the IFU False the default value means that the mask is not in place and the full IFU field of view is available To produce a valid OB the mask shutter option should be the same in every template of the OB This parameter is ignored when MR or HR grisms are used e Return to Origin T F This parameter defines if after a dithered set of obser vations the telescope will return at the reference position or not This parameter is in general to be left in the default val
64. t position of IFU with respect to the center the relevant header keywords which contain the information of the pointing of the IFU are HIERARCH ESO TEL TARG ALPHA and HIERARCH ESO TEL TARG DELTA 2 4 2 Fiber arrangement and spatial characteristics The special arrangement of fibers for VIMOS IFU head is shown in Fig 5 The fibers num bering has been arranged following the scheme mask line module fiber i e 4 B 5 67 The arrangement of the fibers into the 4 pseudo slits mask one for each channel is reported in Fig 6 The detailed IFU table is distributed to the users together with the data release A masking shutter IFU shutter is provided in front of the input micro lens array this allows the exclusive use of the central 1 4 of the field when IFU is used with intermediate and high spectral resolution grisms In this configuration only 1 fiber slit per quadrant mask is used for a total of 1600 fibers The templates for IFU mode offer the option to insert a shutter to limit the field to the central part also for low resolution grisms When small field can be accommodated this avoids second order contamination by the sky or background objects from the 3 pseudo slits corresponding to the outer part of the field of view Table 6 shows the spatial characteristics of the IFU mode VIMOS User Manual 11 VLT MAN ESO 14610 3509 Mask 2 Mask 3 Channel 3 Channel 2 Modules of the line A for mask 4
65. tar RA TEL GS1 DELTA 900000 900000 Guide Star Dec INS ADP1 file name Name of Ist quadrant ADP File INS ADP2 file name Name of 2nd quadrant ADP File INS ADP3 file name Name of 3rd quadrant ADP File INS ADP4 file name Name of 4th quadrant ADP File TEL TARG EQUINOX 2000 3000 Equinox TEL TARG EPOCH 2000 3000 Epoch TEL TARG PMA 10 10 proper Motion Alpha TEL TARG PMD 10 10 proper Motion Delta TEL TARG ADDVELALPHA 15 15 Additional Velocity RA TEL TARG ADDVELDELTA 15 15 Additional Velocity DEC VIMOS User Manual VLT MAN ESO 14610 3509 93 VIMOS _ifu_acq_Preset HR_orange HR red Keyword Range Label in p2pp DET WIN1 UIT1 1 1000000 Exposure time seconds INS FILT NAME UBVRIz Filter OS red OS blue GG435 GG475 INS GRIS NAME LR blue LR red MR HR_blue Grism TEL TARG ALPHA RA of the Field Center TEL TARG DELTA DEC of the Field Center TEL TARG EQUINOX 2000 3000 Equinox TEL TARG EPOCH 2000 3000 Epoch TEL TARG PMA 10 10 proper Motion Alpha TEL TARG PMD 10 10 proper Motion Delta TEL ROT OFFANGLE 180 180 Rotator on sky TEL TARG OFFSETALPHA 3600000 3600000 Alpha Offset TEL TARG OFFSETDELTA 3600000 3600000 Delta Offset TEL AG GUIDESTAR SETUPFILE CATALOGUE Get Guide Star From TEL GS1 ALPHA 0 240000 Guide Star RA TEL GS1 DELTA 900000 900000 Guide Star Dec INS IFUE NAME 0 33 0 67 IFU magnificat
66. ts odt http www eso org observing dfo quality 2 6 Calibration Units VIMOS has three calibration units illuminating a calibration screen at the back of the Nasmyth shutter closing the Nasmyth tunnel Each unit has the following lamps e Flatfield lamps QTH10 halogen lamp for imaging screen flats in VRIz and MOS spectroscopic screen flats in LR red and blue QTH50 halogen lamp for imaging screen flats in U B MOS screen flats in MR HR red and blue and all IFU screen flats e Arc lamps He Ar Ne The updated atlas of the spectral lines for the different grisms can be found at http www eso org instruments vimos inst atlas index html 2 7 Flexures The passive flexure compensation of VIMOS is optimized to reach a reasonable compromise in every position of the Nasmyth rotator An astatic compensator system is installed in quadrants 2 3 and 4 Image motion due to instrument flexures under gravity are currently within 2 pixels for the four channels See Sect 3 3 for recommendations on how to deal with fringing and flexures VIMOS User Manual VLT MAN ESO 14610 3509 16 3 Observing with VIMOS All observations with VIMOS are done via observing blocks OBs OBs consist of one acquisition template including target information followed by observing templates related to the observing mode The users will fill out the parameter fields keywords of the templates e g grisms filters
67. tter in front of the CCD e FEU the filter exchange units one for each channel are located below the main body of the instrument below the Filter Camera Section each unit hosts a juke box of 10 filters permanently mounted e GEU the grism exchange units are located below the Filter Camera Section they host a carousel of six grisms permanently mounted 2 1 1 Instrument modes VIMOS offers the following modes for observations e Imaging IMG see Sect 2 2 e Multi Object Spectroscopy MOS see Sect 2 3 e Integral Field Spectroscopy IFU see Sect 2 4 IMG mode uses broadband filters U BVRIz MOS and IFU modes share the set of grisms and order sorting filters given in Table 3 In MOS mode a set of four laser punched masks VIMOS User Manual VLT MAN ESO 14610 3509 5 Table 2 VIMOS Imaging characteristics and performance Field of view 4x7 x 8 separated by 2 gaps illuminated CCD area 2048 x 2350 pix slightly vignetted on the corners outside 8 Pixel scale 0 205 pixel Image Quality 80 encircled energy in 0 4 within the whole field Filters U Bessel BVRI Gunn z see section A F ratio 1 88 Limiting Magnitudes in lh V 27 7 1 26 6 50 detection for a point source V 26 5 1 25 4 50 detection in 3 for a galaxy made of INVAR is inserted im the focal plane In IFU mode fibers are arranged along pseudo slits in the so called IFU masks IFU masks may be inserted in the instrument focal
68. ue T in service mode If another value is desired in service mode a waiver should be requested e Number of Telescope Offsets This parameter defines the number of telescope off sets during the template The number of exposures taken at each telescope position is determined by the next parameter Number of exposures per telescope offset 7 The pattern of offset is defined in the List of offsets arcsec CORRECT LABEL and List of offsets arcsec CORRECT LABEL parameters e Number of exposures per telescope offset This parameter defines how many exposures are taken for each offset position e List of offsets arcsec List of offsets between exposures Offsets are defined rela tive to the previous telescope position The offsets are defined in RA DEC If the first image is to be taken at the preset coordinates the first set of offset should be 0 0 If there are less offset values than the defined number of offset positions the template will return at the beginning of the list of offsets and apply them again For example if 5 telescope offsets are defined Number of Telescope Offsets to gether with the following series of offsets in RA DEC RA 0 10 5 DEC 0 5 10 the offsets applied to the telescope will be see also Sect 4 6 1 RA O 10 5 0 10 DEC 0 5 10 0 5 VIMOS User Manual VLT MAN ESO 14610 3509 39 4 7 Calibration Templates 4 7 1 VIMOS img cal Photom This template is for acquisition o
69. up In IFU mode only one filter grism combination per OB is permitted Users who want to observe the same targets with different filter grism combinations are requested to submit separate OBs for different filter grism combinations and to consider the respective overheads VIMOS User Manual VLT MAN ESO 14610 3509 26 Table 14 VIMOS Calibration Plan IFU Mode Calibration Number Frequency When Products Accuracy Comment Bias 5 Daily Day time Master Bias RON Darks 3 Monthly Day time Dark current Screen Flats 3 Daily Day time IFU Flat with Monitoring HR Orange Screen Arc 1 Daily Day time IFU Arc with Monitoring HR Orange Screen Flats 1 to 3 Attached to all IFU Flat 5 science OBs Screen Arcs 1 Attached to all Dispersion coeff 0 3 pix science OBs Specphot 4 Daily Night time Response 10 All grism filter Standard Star quadrants function setups used 1 Internal accuracy not considering instrument flexures see Sect 2 7 2 With grism HR blue 3 screen flats are always mandatory IMPORTANT NOTE The execution time for all attached night time calibrations screen flats and arcs is subtracted from the total allocated time 3 6 4 IFU mode attached night time calibrations To better take into account the effects of instrument flexure the use of attached nighttime calibrations arcs and flats see Sect 3 6 5 is MANDATORY for all IFU OBs This template will provide 1 or 3 flat field
70. ures as defined in Number of exposures per telescope offset 7 will be taken at each telescope position 1 or 4 At the end of the template the telescope will offset again to return to its position at the beginning of the template 4 7 2 VIMOS img cal Astrom This template is for acquisition of astrometric data in Imaging mode The acquisition tem plate to use with this template is VIMOS_img_acq_Preset The coordinates to define in the acquisition template are those of the astrometric field Offsets from these coordinates to posi tion the field in one or the four quadrants of the instrument will be applied automatically by the template The parameters of the template are e Exposure time seconds This is the integration time in seconds per exposure e Filter The available filters are U B V R I z To produce a valid calibra tion OB the filter in the first observation template following the acquisition template should be the same as the one in the acquisition template e Number of exposures per telescope offset This parameter defines how many exposures are taken at each offset position 1 or 4 VIMOS User Manual VLT MAN ESO 14610 3509 40 e 1 or 4 quadrants This parameter allows to define if the astrometric field image will be taken in 1 or 4 quadrants If the 1 quadrant option is selected the astrometric field will be positioned in only one quadrant by applying an appropriate offset from the coordinates of the field d
71. ut modes The CCDs have two read out ports but only one is used This increases the read out time but as a benefit the gain offset and read out noise are constant along the entire CCD In spectroscopic mode the full CCDs 2048x4096 pixels are read out in imaging mode readout is windowed to 2048x2400 pixels In fact in both spectroscopic mode and in imaging mode the CCDs are vignetted by some hardware In spectroscopic mode the illuminated area is about 1970x4096 pixels and in imaging mode the illuminated area is about 1970x2300 pixels The actual values depend on the individual CCDs The default readout modes are indicated in Table 10 VIMOS User Manual VLT MAN ESO 14610 3509 300 350 400 450 500 5 600 AZ am 280 900 950 1000 4050 1102 Figure 7 QE curve of one VIMOS CCD Table 10 Detector Readout Modes and Characteristics 14 VIMOS Mode Size Speed Binning Gain Port Windowing Readout time Imaging Ax2kx2k 225kpx s 1x1 Low 1 port Not supported Im Spectroscopy 4x2kx4k 225kpx s 1x1 High 1 port Not supported Im 2 5 2 Controllers The 4 CCDs are controlled by two FIERA controllers The detectors of channel 2 and 3 are controlled by FIERA A VIMOSA the detectors of channel 1 and 4 by FIERA B VIMOSB 2 5 3 Read out noise and conversion factor Table 11 indicates the readout noise and gain values for the 4 chips Note that these values are subject to cha
72. y them again For example if 3 telescope offsets are defined Number of Telescope Offsets to gether with the following series of offsets List of offsets arcsec along the slit 1 2 0 List of offsets arcsec perpendicular to the slit 0 the offsets applied to the telescope will be Offsets arcsec along the slit Offsets arcsec perpendicular to the slit SS i e the first exposure is taken at 1 from the pointing position along the slit then the second exposure is taken 2 up along the slit with respect to the previous exposure and the third exposure is taken at the same position as the second 4 6 3 VIMOS ifu obs Offset This template is to be used for observation with the Integral Field Unit The parameters of this template are e Exposure time in seconds This is the integration time in seconds per exposure e Filter The available filters are U B V R I z OS blue OS red GG435 GG475 and no filter Only standard filter grism combinations are allowed as indicated in Table 3 Other combinations should be requested with a waiver e Grism The available grisms are LR blue LR red MR HR blue HR orange HR red In order to produce a valid OB the filter and the grism in the first observation template following the acquisition template should be the same as the one selected in the acquisition template e IFU Magnification This parameter defines the sampling and corre
73. ys subtracted from the total allocated time 3 5 8 MOS mode calibration plan Table 13 indicates the nature frequency and accuracy of VIMOS calibrations expected to be taken as part of the calibration plan Only calibration frames required for the reduction of science data are reported More calibrations will be taken by the operation staff for the purpose of maintaining and monitoring the instrument configuration and performance e g mask to CCD transformations etc These calibrations are not reported here Calibration monitoring data can be found on the pages of the Quality Control group http www eso org observing dfo quality 3 5 9 MOS mode pipeline See http www eso org qc pipeline status html for the information concerning the latest sta tus of the ESO pipeline VIMOS User Manual VLT MAN ESO 14610 3509 25 Table 13 VIMOS Calibration Plan MOS Mode Calibration Number Frequency When Products Accuracy Comment Bias 5 Daily Day time Master Bias RON Darks 3 Monthly Day time Dark current Screen Flats 5 Daily Day time MOS Flat 5 All used masks Screen Arcs 1 Daily Day time Dispersion coeff 0 3 pix All used masks Screen Arcs 1 Attached to science Dispersion coeff 0 3 pix All used masks OB with HR or LR blue Specphot 4 Daily Night time Response 10 All grism filter Standard Star quadrants function setups used 1 Internal accuracy not considering instrument flexures see Sect 2

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