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1. RA or X 0 10 5 DECorY 2 7 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 if 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 to the position of the first 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 to the position of the first 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 im Table 2 3 Only standard filter grism combinations are allowed as ind
2. European Southern Observatory anisation Europ enne pour des Recherches Astronomiques dans PH misph re Austral ers me Or rga mn ion fiir astronomische Forschung in der siidlichen Hemis Sph re VLT PROGRAMME Paranal Observatory Very Large Telescope VIsible Multi Object Spectrograph VIMOS User Manual Doc No VLT MAN ESO 14610 3509 Issue 78 1 Date June 6 2006 VLT Paranal Observatory x Telephone 56 55 435000 x Fax 56 55 435001 ii VIMOS User Manual Issue 78 1 Change Record Issue Rev date sections affected Reason 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 I 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 IT and P75 Phase T 5 0 Nov 26 2004 all release for P75 phase II and P76 Phase I 76 0 Mar 21 2005 2 7 3 5 7 3 6 6 updated release for P76 Phase I 3 7 7 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 for P77 Phase T EZ Dec 01 2005 Appendix release for P77 Phase II 78 0 Mar 01 2006 none release for P78 Phase T 78 1 Jun 06 2006 all release for P78 Phase II Editors G Marconi ESO Paranal Science Operations e mail gma
3. FF uu 46 Efficiency curve of the high resolution grisms FF uu AT Efficiency curve of the high resolution grisms FF uu 48 vi List of Tables 2 1 2 2 2 3 2 4 2 5 2 1 2 8 2 9 2 10 SH 3 1 3 2 3 3 4 1 Al VIMOS opto mechanical characteristics FF ee 4 VIMOS Imaging characteristics and performance FFF eens 6 Standard grism filter combinations 7 MOS spectral resolution and spectral ranges observed using the mask for spectrophotometric standard lt ppa e bh we wee IR YN DAU A WW DE AGO OE WIU a ARG aR SS 8 Spectral coverage AA for three positions of the slit in field of view MOS mode 8 EE MOES te aa Nr AN AA IAE gd SAR eo eee 8 Spectral characteristics in IPU mode e EEN OR ED a GA Rd bd 10 IFU spectral coverage in the various quadrants I I ug 10 Basic characteristics of the VIMOS CCDS o 2 NN RR GA as ANE yd 11 Detector Readout Modes o aa aca a a a a a E A ae E bee x 11 Detector read out noise and conversion factors 1 0 FF 12 VIMOS Calibration Plan IMG Mode 2 2 I GG I I ee 19 VIMOS Calibration Plan MOS Mode 22 VIMOS Calibration Plans IFU Mode e occa eeGaw Ab 4 E AWA GS a ee e 24 Science and Nighttime Calibration Templates 26 Characteristics of the VIMOS filters 39 vil viii VIMOS User Manual Issue 78 1 Chapter 1 Introduction 1 1 Scope The VIMOS User s Manual is intended to provide information o
4. 1 gunlacamirte Helease 1 29 1 2 DIES me nw Graphis Ompect des TAF ALR Y raro Valua Pus El Herald annes 1 renns emm Min LL Me 1Jes Ds fw Luw 127 Hg 6336 Auw Sul Cul Levels zack Z z S SH Figure 3 1 Guidecam Graphical User Interface Superimposed to the field of view are the VIMOS field of view layout Guide Probe drawing and USNO selected stars in the field and the Guide Probe at the Nasmyth focal plane of the telescope 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 Webpages for detailed informations If no guide star is provided by the user i e 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 sel
5. e GG I r a a 3 5 7 MOS mode attached night time calibrations 3 5 8 MOS mode calibration plan 3 5 9 MOS mode pipeline 3 5 10 MOS mode Exposure Time Calculator I eee 3 6 Integral Field Unit IFU 3 6 1 Acquisition accuracy 3 6 2 Dithering jitter pattern 3 6 3 IRL mode grism filter Setup e sasea a da a HR PR RAA A WW Ga E a WR A 3 6 4 IFU mode attached night time calibrations FF a 3 6 5 IFU mode calibration plan 3 6 6 IFU mode pipeline 3 6 7 IFU mode Exposure Time Calculator FF ug do VIMOS overheads occiso AAA Be Ra A A 4 VIMOS templates SH kescht ia a a e e a a ee WYR B8 4 2 TEMiplate Maes osa a od Ra A A a NF 43 Things to know Reminder 4 FR RE Y GW RR A a a RR yR A dA lise OF GRID EE ums a A A A 4 5 Acquisition templates 4 5 1 VIMOS img acq Preset 4 5 2 VIMOS_mos acq Mask 4 5 3 VIMOS_mos_acq Standard 4 5 4 VIMOS ifu acq Preset 4 6 Science templates 4 6 1 VIMOS img obs Offset 4 6 2 VIMOS mos obs Offset 4 6 3 VIMOS fu obs Offset 4 7 Calibration Templates 4 7 1 Nighttime Imaging Calibrations lt lt Eb FRO AH ER UNO 4 7 1 1 VMO Simgcal Photomi ociosos bee ee gd hee y FR LLL VIMOS meca ASO eo nen a E oe Dee Ble A RF DDD Ba HS 47 2 Nighttime MOS Calibrations ec FFF RA as RG AR 4 4 7 2 1 VIMOS moscal NighiCalib oe ee o mala aaa wee yu aS 4 72 2 VIMOS mos cal Standard o coscc 564 444 64 a RF EE RAA Ars Nigbhtime IPU C
6. of the R filter for preimaging 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 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 VIMOS User Manual Issue 78 1 19 Table 3 1 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 filters Photom Std 4 quadrants Daily Night time Zero Point 5 U BVRI filters Photom Std 1 quadrant Weekly Night time Extinction coeff 10 U BVRI filters high airmass Astrometric fields 4 6 months Night time Distortion map 1 pixel R filter 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 2 In special cases it may be possible to deviate from these rules i
7. star is 505 745 nm 3 With HR red grisms the spectral range in guadrant 1 for a standard star is 650 865 nm 4 New HR_red VPHG grisms have been installed from October 5 2005 Table 2 5 Spectral coverage AA for three positions of the slit in field of view MOS mode Grism Order sorting AA AA AA filter CCD center CCD top CCD bottom LR red OS red 550 950 nm 550 950nm 550 950 nm LR blue OS blue 360 670nm 360 670nm 360 670nm MR GG475 500 1000 nm 500 1000nm 500 950 nm HR blue Free 415 620 nm 468 674nm 370 566nm HR red GG475 630 870nm 690 930nm 570 805 nm HR orange GG435 520 760 nm 577 817nm 463 703nm slit to the spectrograph at the mask focal plane location Each IFU mask one for each channel of VIMOS has a set of 4 fibre slits or pseudo slits for a total of 6400 fibers The special arrangement of fibers for VIMOS IFU head is showed in Fig 2 3 The fibers numbering 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 2 4 The detailed IFU table is distributed to the users toghether 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 th
8. E CATALOGUE Get Guide Star From TEL GS1 ALPHA 0 240000 Guide Star RA TEL GS1 DELTA 900000 900000 Guide Star Dec INS ADP1 file name Name of 1st 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 ifu_acq_Preset 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 HR orange HD red 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 IF
9. 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 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 CAL FLAG 14 1 or 4 quadrants VIMOS fu cal NightCalib Keyword Ra nge Label in p2pp SEO FLATFIELD F SEO ARC F T Night Arc SEO FLATFIELD NEXPO 1 1000000 T Night Flat Field No of scrrenflats Appendix D Abbreviations and Acronyms The following abbre
10. MOS 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 This template is used for acquisition of a field in imaging mode for both imaging and pre imaging OBs Figure 4 1 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 T wo options are offered for this parameter CATALOGUE This is the default option
11. NS 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 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 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 52 VIMOS User Manual Issue 78 1 VIMOS mos acq Standard Keyword Range Label in p2pp DET WIN1 UIT1 1 1000000 Exposure time seconds
12. STNUME VIMOS OCS CON QUAD Y IMS FOCUT EMP AE INS ADT TVPE MOST INS ADENFRSI N MM seet ett INS ADF UNIT PIXEL INS ADIID Tomas USEM vn Ady Der reel om INS ADF COMMENT IMSM SEK LD I VELA ILLBIINAML ANS ODIAN USLIVAL TPLFILE REEP PT DATE oBs 2008 1 1 1 1T06 22 23 637 2 1 TEL TARG EQUINOX 20007 ILL ARG NAL mf INS ADE GRISM NAME MR 145 ADF GRISM SPECT EN SIS DN arasz aer mi Zorn er A ada O AA IMS SHU2FO SH 21110 VOLO MASS SY FY RE 11 Uebst PRO CCD MASK TEMP 40259544 E MASK a 132 3336671 D2 Figure 4 3 P2PP VIMOS ADP browser window 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 4 3 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 offsetted in the 10x10 arc seconds acquisition box in quadrant 1 and then centered by the Night Time Sup
13. U magnification in arcsec fiber INSIFUS MODE FT IFU Shutter TEL TARG ADDVELALPHA 15 15 Additional Velocity RA TEL TARG ADDVELDELTA 15 15 Additional Velocity DEC 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 VIMOS User Manual Issue 78 1 51 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 SEO NOFF 1 1000000 Number of telescope offsets SEO 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 fu obs Offset Keyword Range Label in p2pp DET WIN1 UIT1 1 100000 Exposure time seconds I
14. VIMOS img cal Photom This template is for acquisition of photometric data zero points in Imaging mode The acquisition template to use with this template is VIMOS img acq 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 calibration OB the filter in the first observation template following the acquisition template should be the same as the one in the acquisition template Number of exposures per telescope offset This parameter defines how many exposures are taken at each offset position 1 or 4 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 sequentially in the 4 quadrants by applying the appropriate offsets from the coordinates of the star field defined in the target p
15. a a 1 g 0 6 l S z 0 4 0 2 E E EFE E E ES ug o gw er ee Cf yng o z 400 500 600 700 400 500 600 700 Wl nm wl nm TWR 0 500 600 700 800 900 100900 600 700 800 900 1000 Wl nm Wl nm Figure A 3 OS blue OS red transmission curves VIMOS User Manual Issue 78 1 A OS LS LS 600 800 1000 Wl nm 600 800 1000 Wl nm T T T T T T TIE rer TT pata ad I T L 1 L 500 600 700 800 500 Wavelength nm 1 1 600 700 Figure A 4 GG435 GG475 transmission curves 43 Appendix 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 44 VIMOS User Manual Issue 78 1 45 100 L Desir J Blase LORRED utile L Central W Min Gpee Peak Fff x EN 2 HI El i A pg si nh 1 iR WL microns ico LUWBLU units Denircd Rare En Centro al Min Speu Peak Elf ET E an Ba a 40 BAD 0 4 o s 0 8 1 Wl microre Figure B 1 Efficiency curve of the low resolution grisms LR red LR blue The vertical lines mark the desired blaze and the central wavelenghs 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 th
16. ackage of the acquisition template As many exposures as defined in Number of exposures per telescope offset 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 VIMOS User Manual Issue 78 1 35 4 7 1 2 VIMOS img cal Astrom This template is for acquisition of astrometric data in Imaging mode The acquisition template to use with this template is VIMOS img acg Preset The coordinates to define in the acquisition template are those of the astrometric field Offsets from these coordinates to position 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 calibration 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 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 offs
17. acy 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 seguences 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 adeguate template see Sect 4 Attached flat and arcs calibrations are mandatory for all IFU observations At tached arcs are mandatory for MOS science observations with grisms LR blue and HR blues and highly recommended for MOS science observations with grisms MR HR red HR orange and HR red Execution time is charged to the user program 18 VIMOS User Manual Issue 78 1 i Site Paranal o 2 00 arcsec Dec 20 FN E E e Tstart 2 hrs J Tend 2 hrs 2 eng _ 45micron D D D 4 0 Se ge seg J 37micron E 4 o 67micron 2 Gi E Es geck m E o gt 2 EN BE SH 5 J o S J a o E Ba SES sea i A S 8 1 5 J 1 A 4 A A 1 A A A A 1 A A A A 1 A L A A 1 d 10 5 O 5 10 RA arcmi
18. alibrations a da 00 NN RW RW barca aa 4 7 3 1 VIMOS ni cal Specphot 2 0 65655554004 RR RG A 41 32 VIMOS Hu cal Nigh alli 005055 664294 6 E des E y ar aa A A VIMOS Filters B VIMOS Grisms C Template Signature Files for Observation and Acguisition C 1 Acquisition Template C 2 Observation Template C 3 Template Signature Files for Calibrations VIMOS User Manual Issue 78 1 D Abbreviations and Acronyms 53 List of Figures VIMOS Opto Mechanical back bo eee ee aa 4 Gee OPENED Sua ee BE le eee OH eek hE da eo ed 5 IFU head View from the telescope and detail of the fiber modules 9 IFU mode fibers numbering on the masks o o eee 9 QE curve of one VIMOS COD 9 RR DF RR ER aa A 11 Guidecam Graphical User Interface 16 Atmospheric Dispersion Example I GL GG GG I 18 VMMPS Graphical User Interface 2 2 25 ca is aa RE DA E a O BB 21 P2PP example of a preimagine OB o corsa sina YR RR UG UN RA a EGO na 27 PPP Example ofa MOS OB lt o 04 242 240 8845 een RR ok RE a RA A AD A 28 P2PP VIMOS ADP browser window aa saoao YDD aaa 004404 E do ddd UR 44 29 Mer Tang OCULAR Ai A 40 Alter transmission CUNA AA 41 Order Sorting Filter transmission curves EE eg 42 Order Sorting Filter transmission curves EF Gu ud 43 Efficiency curve of the low resolution grisms FF uu 45 Efficiency curve of the medium resolution grism
19. and back side illuminated Table 2 9 indicates the basic characteristics of the VIMOS CCDs Figure 2 5 shows the quantum efficiency curve of one of the CCDs VIMOS User Manual Issue 78 1 11 Table 2 9 Basic characteristics of the VIMOS CCDs Parameter Value Number of pixels 2048 x 4096 Pixel size um 15 Dark current at 120 C e px h lt 7 Deviation from Linearity Full well lt 0 5 Charge transfer efficiency gt 0 999999 0 E Es ha e o A Al mE s 300 350 400 450 500 580 600 50 700 750 BOD 50 900 950 1000 1050 1102 Wavalangih nm Figure 2 5 QE curve of one VIMOS CCD 2 5 1 Detector read out 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 image The default readout modes are indicated in Table 2 10 Table 2 10 Detector Readout Modes and Characteristics VIMOS Mode Size Speed Binning Gain Port Windowing Readout time Imaging 4x2kx2k 225kpx sf 1x1 Low 1 port Not supported 30s 15s Spectroscopy 4x2kx4k 225kpx s 1x1 High 1 port Not supported 45s 20s 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 Tabl
20. ange 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 4 VIMOS User Manual Issue 78 1 Table 2 1 VIMOS opto mechanical characteristics Instrument Location Opto mechanical layout Wavelength coverage Detectors Spectral Resolution Filters Grism Flexures Masks Multiplex Integral Field Unit Nasmyth B VLT UT3 Melipal 4 beams each a complete focal reducer F 1 88 output 0 37 to 1 microns 4 x 2048 x 4096 15 um pixel R 180 to 2500 1 arcsec slit 10 per channel U BVRIz OS red OS blue GG435 GG475 170mm diameter 6 per channel LR red LR blue MR HR blue HR orange HR red H Passive compensation motion of 2 pixels over 360 rotation 15 masks simultaneously loaded in instrument at maximum per channel D Slits of any position and shape width gt 0 6 length lt 30 840 simultaneous slits 10 long at R 200 210 simultaneous slits 10 long at R 2000 2500 54 x 54 field 6400 fibers with 0 67 sampling 27 x 27 field 6400 fibers with 0 33 sampling 1 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 appl
21. ault values 0 28 VIMOS User Manual Issue 78 1 K UbsBlock Ho Name VIMUIS mp us ya i o Gesond V0 Esper Urnu cundo Filur See Eli de Sas fran O Ean oert rR TE O CR tS SQM T use sto I O I 1 RE SE E zdltlonc ve 2c tu gt a yL nbere Te e e Of s3ts F zdltlonc ve 2c tv DEC Jet of officts orcseo along thz silt 9 1 ADF ei fenas useri wmz MI adg BOF lle Z formas use z vm 2H adr ADF Flle E fornaz use 3 vm 3M 1 ade SLE ile 4 fornas usei ymi 4M ade Figure 4 2 P2PP Example of a MOS OB 4 5 2 VIMOS mos acqg 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 2148x2444 pixels of each of the 4 CCDs whereas the spectroscopic images use the full CCD size 2148x4096 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 concerning the target coordinates and equinox are taken from the ADP files and are automatically loaded in the P2PP target package when including the first ADP file in the template Figure 4 2 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 t
22. ber of slits along the dispersion direction to avoid reduce multiple overlaps The multiplex can be reduced by increasing the distance between slits 2 4 Integral Field Unit IFU 2 4 1 Fiber arrangement and spatial characteristics 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 8 VIMOS User Manual Issue 78 1 Table 2 4 MOS spectral resolution and spectral ranges observed using the mask for spectrophotometric standard stars Grism Default Order Spectral Number Spectral Res Dispersion Spectral sorting filter range of pixels 1 slit pixel multiplex LR blue OS Blue 370 670 nm 550 180 5 3 4 LR red OS Red 550 950 nm 550 210 73 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 520 760 nm 4096 2150 0 6 1 HR red GG475 630 870nm 4096 2500 0 6 1 1 With HR blue grims the spectral range in quadrant 1 for a standard star is 400 620 nm 2 With HR orange grims the spectral range in guadrant 1 for a standard
23. ction 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 VIMOS 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 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 3 3 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 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 supp
24. d 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 parameters should be left to their default values 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 preimaging the use of R filter is mandatory e Return to Origin T F This parameter defines if after a dithered set of observations the telescope will return at the position at beginning of template or not As an example this parameter should be set to I when the aim of the OB is to execute multi color imaging observations with the same pattern of offsets on the same field using 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 offsets during the template The number of exposu
25. d the y axis oriented E The wavelength axis in spectroscopy is the y axis with wavelength increasing with y 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 The gap between the quadrants is approximately 2 The pointing coordinates correspond approximately to the center of the gap 6 VIMOS User Manual Issue 78 1 Table 2 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 0205 pixel Image Quality 80 encycled energy in 0 4 within the whole field Filters U Bessel BVRI Gunn z see section A F ratio 1 88 Limiting Magnitudes in 1h exp V 27 7 1 26 6 50 detection for a point source V 26 5 I 25 4 50 detection in 3 for a galaxy Table 2 2 summarizes the main characteristics of the imaging mode 2 2 1 Image Quality For the most updated information please 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 co
26. e 2 11 indicates the readout noise and gain values for the 4 chips Note that these values are subject to change and are indicated here only for reference Exact values have to be found in the image headers RON and conversion factor monitoring is available through the OC1 WEB pages 2 5 4 Fringing With the z Gunn and Bessel T 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 12 VIMOS User Manual Issue 78 1 Table 2 11 Detector read out noise and conversion factors For reference only subject to change Chip Read out Mode RON e rms K e adu CCD 1 225 kpxs low gain IMG mode 5 3 1 70 CCD 2 225 kpxs 1 low gain 5 2 1 86 CCD 3 225 kpxs low gain 5 3 1 95 CCD 4 225 kpxs 1 low gain 4 9 1 80 CCD 1 225 kpxs high gain MOS and IFU modes 4 3 0 51 CCD 2 225kpxs high gain 4 6 0 56 CCD 3 225kpxs high gain 4 7 0 57 CCD 4 225 kpxs 1 high gain 43 0 52 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 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 informa
27. e blue 46 VIMOS User Manual Issue 78 1 Desirec Mare INTE units central Wavelength Efficiency T Wl microns Figure B 2 Efficiency curve of the medium resolution grisms MR The vertical lines mark the desired blaze and the central wavelenghs 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 Issue 78 1 47 100 ynu ag SE pe HIGHBLU units Desired Blaze cenirel Wl Efficiency ac 0 6 ER 1 1 8 WI m crons F dlGHURA nijta J 80 Desired Blaze Efficiency Z 04 0 8 0 8 1 1 2 Wl mierons Figure B 3 Efficiency curve of the high resolution grisms HR blue HR orange The vertical lines mark the desired blaze and the central wavelenghs 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 48 VIMOS User Manual Issue 78 1 VIMOS Efficiency 500 550 600 350 700 750 sao 850 900 960 1000 Wavelenght nm Figure B 4 Efficiency curve of the high resolution grisms HR red VPHG The spectral range and efficiency refers to the slit in the center of the field The cutoff wavelength is in most cas
28. e d 10 ea Multiples characteristics 444 4444 20 4464 62 245446 ee a aaa da 4 2s 10 2o tbe ss ssa a RE hE OAS EE O EW AED A DG DDR RH 10 Al Detector read out modes osc s sys ee ras aa eae EE A a 11 Boe Conros o Ga Ra ee ee Ea Ea OE Segre ee SEA EFO ee eS 11 2 5 3 Read out noise and conversion facto 11 25M a NA 11 a III 12 2 040 More information s i dias aa a dd da aaa 12 26 Ca OD DS a A RU AAA GADW eee ee CR OW da e A 12 24 UTES A cs deito ed Sa ne GR a EER EEE e O RY Bod ee yd o e GS 13 3 Observing with VIMOS 15 3 1 Interaction with the telescope 15 3 1 1 Guide stars and Guidecam software tool FI ee 15 ola Guide Stars Poley usas 24 444 4440 AAA A BR DERE ewe DD UG 16 Sula Cumalative Geeks cerciorarse 17 3 1 4 Telescope and Instrument Focus e y 17 go Apnospherie Dispersion oe ee ew OEE ARRAS e e DROE ode a a 17 oo ingne And FIG adi AA AA e da DS EES 17 a AMO ce ERAN 18 Sl Presa o e ENN A RES he Ee E A A 18 Tt CERCO MOADE pasmo gpa DRA E AF FANA O RO eee 19 iii lv VIMOS User Manual Issue 78 1 3 4 3 IMG mode calibration plan 3 4 4 IMG mode pipeline 3 4 5 IMG mode Exposure Time Calculator FF eee eee 3 5 Multi Object Spectroscopy MOS 3 5 1 Pre imaging 3 5 2 Rotator on sky 3 5 3 VIMOS Mask Preparation Software VMMPS oo o 3 5 4 Finding charts 3 5 5 Visitors using MOS 3 5 6 MOS mode grism Hfilter setup
29. e hosted simoultaneously into the cabinets Until P77 only 8 masks can be simoultaneously 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 recommended for all setups Users may also attach screenflats The execution time for these nighttime calibrations is always subtracted from the total allocated time 3 5 8 MOS mode calibration plan Table 3 2 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 f
30. e of the large field of view VIMOS optical path is split into four channels The four quadrants of the instrument are operated in parallel i e 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 2 1 A schematic opto mechanical layout is shown in Fig 2 1 The focal plane is divided in 4 identical channels and is equipped with the mask exchange units MEU which host up to 15 pre punched masks for MOS spectroscopy per quadrant the IFU fiber head and the IFU masks The folding mirror section hosts the four folding mirrors and the flexure compensators The Filter Camera Section the beam section hosts optical analyzers filters and or grisms the camera and the exposure shutter in front of the CCD 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 GEU the grism exch
31. e on the ESO WEB pages http www eso org observing etc 20 VIMOS User Manual Issue 78 1 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 3 5 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 coordinates of bright objects stars in the field of view These objects stars after dete
32. ected by the user In addition it may happen that a guide star suitable for preimaging observations will not be usable for the spectroscopic follow up if e g the seeing has changed VIMOS User Manual Issue 78 1 17 e It is requested that the users selecting a guide star for their observations use Guidecam to generate the finding chart to be delivered as 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 appropiate 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 Defocussing 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 atmo spheric dispersion will be mostly noticed in MOS mode In imaging
33. ed 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 Transmission curves are available in Appendix A for the filters and Appendix B for the grisms Table 2 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 VIMOS User Manual Issue 78 1 7 Table 2 3 Standard grism filter combinations for MOS and IFU modes Grism Filter Default Allowed LR blue OS blue Free LR red OS red Free MR GG475 OS red OS blue HR blue Free HR red GG475 HR orange GG435 1 The grism filter configuration MR OS blue is not supported by the pipeline 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 2 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 obtai
34. es given by the order separation filters the red CCD limit or the limit of the VIMOS optics in the blue Appendix C Template Signature Files for Observation and Acguisition C 1 Acquisition Template The following tables list the parameters of the VIMOS acquisition templates C 2 C 3 VIMOS img acg 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 EOUINOX 2000 3000 Eguinox 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 Observation Template Template Signature Files for Calibrations 49 50 VIMOS User Manual Issue 78 1 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 SETUPFIL
35. et from the coordinates of the field defined 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 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 Nighttime MOS Calibrations 4 7 2 1 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 I 3 screen flats will be taken e Night Arc T F If T an arc spectrum will be taken 4 7 2 2 VIMOS mos cal Standard This template is used for the observation of a standard star in mode MOS This template can
36. f there is a valid scientific reason in that case a waiver must be specifically requested to ESO before you submit your Phase II information 3 4 2 Science imaging Observation Category SCIENCE It is mandatory to set the Observation Category to SCIENCE in the observation template 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 3 1 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 gc pipeline status html for the information concerning the latest status 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 exposure time calcu lator availabl
37. 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 VIMOS User Manual Issue 78 1 27 g t pr maging Zegt pr raging Alpha nf5 1 pet ott zc Bw A po E Expusures pat Ta ue Or Ge anal y rele city 24 Addr onal v elc cit JEL E EL mn dE Guid 5 ar Ra GU Scart Dew o arreguia A Figure 4 1 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 RA and Guide Star DEC Coordinates of the guide star when the SETUPFILE 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 moving targets If no additional velocity is needed these parameters should be left to their def
38. gs are 0 67 arcsec fiber and 0 33 arcsec fiber To produce a valid OB the magnification should be the same in 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 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
39. h the VIMOS ifu acg Preset acquisition 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 OS blue OS red GG435 GG 475 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 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 template of the OB 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 T
40. he one selected in the acquisition template 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 arcsec fiber To produce a valid OB the magnification should be the same in every template of the OB 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 maks 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 observations the telescope will return at the reference position or not Th
41. he 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 to choose the same filter as the one used for the pre imaging Waiver is requested differently 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 Velocity 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 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 produced by VMMPS The files 1 to 4 correspond to the 4 quadrants of the instrument and should be set in the right order VIMOS User Manual Issue 78 1 29 K Sninrt File PAFHDRSTART mr OUT MEDO EES O pamte lln 2271 9 0 Y DO 3 4 Marks ADO P amp D A 9D31442 1 2002 11 16T1 7 45 12001 1 ite wrias asiri Ymo Ii au TALES E ADM Aperture Definition File in Disel AT CDTT AAMT mum mys 2 40 PAF CRTE DAYTIM 2002 11 16717 95 1 6 001 PARLCHGMAME IT PAFACHG DAYTIM PAF CHCK MAME TALAI DAY IIM T PAF CHCKCHFCKSUM PARHOREMD IN
42. icated in Table 2 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 e Return to Origin T F This parameter defines if after a dithered set of observations 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 offsets during the template The number of exposures taken at each telescope position is determined by the next param eter Number of exposures per telescope offset 7 The pattern of offset is defined in the List of offsets arcsec along the slitand List of offsets arcsec perpendicular to the slit pa rameters e Number of exposures per telescope offset This parameter defines how many exposures are taken at each offset position 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 posit
43. ion the template will return at the beginning of the list of offsets and apply them again For example if 3 telescope offsets are defined Number of Telescope Uffsets together with the following series of offsets VIMOS User Manual Issue 78 1 33 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 1 2 0 Offsets arcsec perpendicular to the slit 0 0 0 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 respeect to the second 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 2 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 t
44. is 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 accomodated 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 2 6 shows the spatial characteristics of the IFU mode Table 2 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 x 27 40 x 40 1 LR blue LR red OFF 0 33 fibre 20 x2 80 x 80 4 LR blue LR red ON 0 33 fibre 13 x 137 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 VIMOS User Manual Issue 78 1 VIMOS field Mask 2 Mask 1 Channel 2 Channel 1 Mask 3 Mask 4 Channel 3 Channel 4 IFU head View from the telescope VS SO E DES EE E E E ES a on DAM HEAD e AR GEM A MES AS ze OS AU O eee y ES EE Madules of the line A for mask 4 Figure 2 3 IFU head View from the telescope and detail of the fiber modules Mask 2 Mask 1 2a E ES OA Y For all modules of the 80 For all module
45. is parameter is in general to be left in the default value 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 offsets 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 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 34 VIMOS User Manual Issue 78 1 List of offsets arcsec List of offsets between exposures Offsets are defined relative 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 together 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 RA 0 10 5 0 10 DEC A 10 0 5 4 7 Calibration Templates 4 7 1 Nighttime Imaging Calibrations 4 7 1 1
46. lways possible to find a guide star such that the Telescope Guide Probe is not vignetting the VIMOS field of view Therefore users are 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 3 1 shows the Guidecam Graphical User Interface displaying the geometry of the VIMOS field of view 15 16 VIMOS User Manual Issue 78 1
47. m will be taken 37 38 VIMOS User Manual Issue 78 1 Appendix A VIMOS Filters Table A 1 lists the characteristics of the VIMOS filters The transmission curves are given in the following figures Table A 1 Characteristics of the VIMOS filters Filter Ao nm FWHM nm U 370 50 B BESS 430 97 0 V_BESS 546 89 0 D 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 99 40 VIMOS User Manual Issue 78 1 el va el 360 380 400 pet figo Ti r 1 I ij I 1 l I 1 if D H l d 1 l 1 l 1 l 1 U I l l l l 1 l Norm T 0 8 0 6 Norm T 0 4 0 2 Norm T i 1 550 600 500 550 600 Wl nm wi nm Figure A 1 U B V filter transmission curves VIMOS User Manual Issue 78 1 Norm T Norm T 600 Wavelength nm HHHH Hiiren Tr n TT 1 1 800 900 1000 Wavelength nm Figure A 2 R Lz filter transmission 1 900 1000 curves 41 42 VIMOS User Manual Issue 78 1 te 1 E 2 0 8 Sc is e a o io Fr a E g 0 6 E d 1 20 4 0 2 E T ak ae e Lr da 4 oak Tr et ge EE ell a br AD Va iri
48. 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 status of the ESO pipeline 24 VIMOS User Manual Issue 78 1 Standard Star Table 3 3 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 in HR Orange Monitoring Screen Arc 1 Daily Day time IFU Arc in HR Orange Monitoring 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 quadrants Daily Night time Response function 10 All grism filter 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 screenflats and arcs is charged to the user 3 6 7 IFU mode Exposure Time Calculator The approximate limiting magnitudes in IFU mode can be obtained from the exposure time calculator available o
49. n 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 Consequently 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 Chapter 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 observations 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 i
50. n the following topics e Overall description of the instrument Sect 2 e Observing with VIMOS 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 html 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 Departement usd help eso org 2 VIMOS User Manual Issue 78 1 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 78 1 5 Version notes change track 1 5 1 Version 78 1 Version 78 1 c
51. ncentration effects are in any case small and negligible for flat field and photometric calibrations 2 2 2 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 Figures A 1 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 A 1 and Figs Alto A 4 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 separat ing 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 2 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 allow
52. ned with a 1 slit width with the various grisms is given in Table 2 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 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 D order contamination between different layers of slits For faint objects order overlap is usually not a problem only the sky will contribute significantly 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 recommended to reduce the multiplex num
53. ng 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 setup 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 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 images for HR grism 3 screenflats are mandatory for the other cases 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 3 3 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
54. nutes Figure 3 2 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 wavelengths 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 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 It is 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 distorsions is derived from R filter observations only To minimize the slit losses due the distorsion of the instrument the use
55. only be used following the VIMOS_mos_acq Standard acquisition template and not 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 GG 475 e Grism The available grisms are LR blue LR red MR HR blue HR orange HR red 36 VIMOS User Manual Issue 78 1 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 standar 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 e 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 2 5 5 0 Once the user select the slit width the rest is totally automatic the star will be offsetted 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 3 Nightime IFU Calibrations 4 7 3 1 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 wit
56. ontains more detailed and accurate information about the spectral range that can be observed in spectroscopic modes MOS and IFU with the various grisms Table 2 11 has been updated Hyperlinks have been added to the text The various sections of the manual have been re arranged 1 6 Acknowledgements The following institutes have participated to the development of VIMOS e Laboratoire d Astrophysique de Marseille Marseille France Observatoire de Haute Provence Saint Michel Observatoire France e Laboratoire d Astrophysique de PObservatoire Midi Pyr n es Toulouse France Osservatorio Astronomico di Capodimonte Napoli Italy Istituto di Fisica Cosmica e Tecnologie Relative Milano Italy Osservatorio Astronomico di Brera Milano Italy Istituto di Radioastronomia Bologna Italy Osservatorio Astronomico di Bologna Bologna Italy The first edition of this User Manual was delivered by the VIRMOS Consortium P I O Le F vre Chapter 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 the 0 37 1 micron domain in 3 main observing modes direct imaging IMG multi slit spectroscopy MOS and integral field spectroscopy IFU Becaus
57. or 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 status of the ESO pipeline VIMOS User Manual Issue 78 1 23 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 stro
58. ort VIMOS User Manual Issue 78 1 NGC2243 259 0 2428 0 327 07 59 57 125 1 10 40 07 01 000 259 16 Figure 3 3 VMMPS Graphical User Interface Example of ADP file superimposed to field of view 21 22 VIMOS User Manual Issue 78 1 Table 3 2 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 quadrants Daily Night time Response function 10 All grism filter Standard Star setups used 1 Internal accuracy not considering instrument flexures see Sect 2 7 IMPORTANT NOTE The execution time for all attached night time calibrations screenflats and arcs is charged to the user is guaranteed for mask preparation on the mountain 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 b
59. port Astronomer IMPORTANT the user have to provide coordinates accurate enough to have the selected stan dard visible in the acquisition box 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 standard 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 Tt is recommended to choose 30 VIMOS User Manual Issue 78 1 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 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 acqui
60. ral range covered in IFU modes by the various grisms as obtained by the automatic pipeline when reducing the spectrophotometric standard star With low and intermediate resolution grisms the spectral coverage is independent of the position of the IFU pseudo slits With the high resolution grisms the spectral coverage is determined 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 2 8 2 4 3 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 66 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 Hflter combinations is given in Table 2 7 2 4 4 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
61. rconi eso org S Bagnulo M Rejkuba ESO Paranal Science Operations ESO User Support Department e mail sbagnulo eso org e mail mrejkuba eso org Contents 1 Introduction 1 TAL SOUR ao A O ME ME nam Ges po AA A A yddu a NF amp amp A 1 L2 More Information om VIMOS cosida e ee a o a A a tata RW A dr 1 13 Contact Dar DA YR swim EE a A RG E A Do Da A A E RES 1 L Period of Validity of this Manual e s a sa aora RR RR RR YG EU aa 2 16 Version notes change track o posar ss eps bri ER E E a gg E 2 od Vemos ses aa dd CG RH eee eh ee eee EDM GRE aD Oe bed 2 10 Ackaowledeements cre mp ee hh RO ee eR OE ee ee 4 2 2 Instrument Characteristics 3 Li e qua eR ok ek OO ew EO a I E ee Rae oe Oo BR ew we 3 21 1 Instrument modes i ee ociosa ad ede dee SOO e 3 2 1 2 Field of view Orientation supe ALE EE eer eGR Ede DD RG RR 5 22 oe Ae ee EEE ER AEE KA Re ee eae eee ee wg 8 9 Ha 0 o AAA 6 2 22 Imaging Filters ecc sea as a ee ee e A 6 2 3 Multi Object Spectroscopy MO 6 Brook Opectral range cocos ee ED YU GRI Bee RR GEG EU AE AR UF GYR 7 23 2 mpectral resoluti n vo cc e toded a So O ede ea Gabe o e n 7 233 Multiplex characteristics 224 e050 22k A e ee RR E ES 7 2 4 Integral Field Dam PU 4 6495 ia 2444 484 Uh oa ate ee e Goa do 7 2 4 1 Fiber arrangement and spatial characteristics 2 2 o 7 PA DEL ronge cated ka E BM a CER aaa 10 Bao Dpechral TESOMIION ssa sis A AEE A REU E O dyd we e
62. res taken at each telescope position is determined by the next pa rameter Number of exposures per telescope offset 7 The pattern of offsets is defined in the pa rameters 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 RA and List of offsets arcsec in Y or DEC List of off sets 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 32 VIMOS User Manual Issue 78 1
63. rue 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 maks shutter option should be the same in every template of the OB This parameter is ignored when MR or HR grisms are used 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 standar star field will be positioned in one or four of the quadrants of the IFU As many exposures as defined in Number of exposures per telescope offset will be taken at each telescope position 1 or 4 4 7 3 2 VIMOS fu 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 VIMOS User Manual Issue 78 1 e Night Flat Field T F If set to I 3 screen flats will be taken e Night Arc T F If T an arc spectru
64. s related to the observing mode The users will fill out the parameter fields keywords of the templates e g grisms filters 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 preparation 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 relevant 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 magnitude 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 a
65. s of the E mask 2 mask 1 hee Acie 74 WE 8 SS Line A UCI RO Line A For all modules of the 80 For all modules of the mask 3 80 SE mask 4 LD Tre TETO 1 Lineb bBmelir r 4 3i 74 75 bec Lie Das Tr Tr 3 Hmeb Mask 3 Mask 4 View from the telescope Figure 2 4 IFU mode fibers numbering on the masks 10 VIMOS User Manual Issue 78 1 Table 2 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 2 8 IFU spectral coverage in the various quadrants Grism Ql Q2 Q3 Q4 LR blue OS blue 390 670nm 395 675nm 400 680nm 400 680nm LR red OS red 570 915 nm 580 930 nm 590 930nm 585 930 nm MR GG475 485 1015nm 490 1020nm 490 1020nm 490 1015nm HR blue free 415 620nm 415 620nm 415 620nm 415 620nm HR orange GG435 525 745 nm 525 745 nm 525 745nm 525 740 nm HR red GG475 635 860nm 635 865 nm 635 860nm 645 875 nm 2 4 2 Spectral range Table 2 7 shows the spect
66. s the mode of the instrument either img mos ifu type is the type of the template either acg obs or cal description is a string identifying the purpose of the template Offset for an observation Preset for a preset NightCal for attached night calibrations etc 4 3 Things to know Reminder e See Sect 2 1 2 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 25 26 VIMOS User Manual Issue 78 1 coordinates e g X Y or in RA DEC All offsets are to be defined in arcseconds The offsetts 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 and Table 2 3 4 4 List of templates Table 4 1 lists the VIMOS templates Table 4 1 Science and Nighttime Calibration Templates Type Name VIMOS_img acq Preset Acquisition VIMOS_mos_acq Mask templates VIMOS mos acq Standard VIMOS ifu acg Preset Science VIMOS img obs Offset templates VIMOS mos obs Offset VIMOS ifu obs Offset VIMOS img cal Photom VIMOS mg cal Astrom Calibraton VI
67. sition 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 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 as the one selected here 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 2 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 as the one selected here 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 samplin
68. 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 LR 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 are 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 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 3 2 shows a worst case scenario of MOS observations with LR blue spectral coverage 370 670 nm for a field with declination 20 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 076 are not allowed e Accur
69. the East on the right A rotation of 90 degrees will put East up and North left see Fig 2 2 Optional additional offsets in alpha and delta Alpha Offset and Delta offset with 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 T wo options are offered for this parameter VIMOS User Manual Issue 78 1 31 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 SETUPFILE option of the Get Guide Star From field is selecte
70. tion on detector characteristics cosmetic and performance on sky at http www eso org projects 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 OTH50 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 could be find at http www eso org instruments vimos inst atlas index html VIMOS User Manual Issue 78 1 13 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 14 VIMOS User Manual Issue 78 1 Chapter 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 template
71. viations and acronyms are used in this manual ACQ ADP ADU CCD DEC ESO ETC FEU FIERA FWHM GEU HR IFU IMG MEU MOS OB os PSF P2PP RA RMS RON TSF VIMOS VMMPS VLT e cm h kpx min mm nm px Acquisition Aperture Definition in Pixels Analogue to Digital Unite Charge Coupled Device Declination European Southern Observatory Exposure Time Calculator Filter Exchange Unit Fast Imager Electronic Readout Assembly Full Width Half Maximum Grism Exchange Unit High Resolution Integral Field Unit Imaging Mask Exchange Unit Multi Object Spectroscopy Observation Block Order Sorting Point Spread Function Phase 2 Proposal Preparation Right Ascension Root Mean Square Read Out Noise Template Signature File Visible Multi Object Spectrograph Vimos Mask Manifacturing Preparation Software Very Large Telescope Angstrom Electron Centimeter Hour KiloPixel Minute Millimeter Nanometer Pixel Second Micrometer 53 54 VIMOS User Manual Issue 78 1
72. y 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 Figure 2 1 VIMOS Opto Mechanical layout VIMOS User Manual Issue 78 1 5 7 58 o gt DN 0 zi 61 x Q2 i o ych a 55 7 58 E l i IFU SE S Z Q3 94 yA y A l i Figure 2 2 Image orientation Layout of the imaging field of view Indicated are the orientation on sky for different rotator angles the image and wavelength axes the location of the IFU head IMG mode uses broadband filters U BVRIz MOS and IFU modes share the set of grisms and order sorting filters given in Table 2 3 In MOS mode a set of four laser punched masks made of INVAR is inserted in 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 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 1 2 Field of view orientation Figure 2 2 shows the orientation of the field of view of the instrument At 09 rotator angle the z axis of the CCDs is oriented E and the y axis is oriented N Increasing rotator angle moves the compass counterclockwise e g at 909 rotator angle the x axis is oriented S an

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