5958( 12) - 09/30/96 11:57 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5958 Version: 12 Check-in Date: 30-Sep-1996 11:42:32 1.Proposal Title: HST OBSERVATIONS OF NEW GRAVITATIONAL LENS CANDIDATES ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Quasars GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: JEAN SURDEJ INSTITUT D'ASTROPHYSIQUE CoI: Sjur Refsdal Hamburg Observatory N CoI: Christian Vanderriest Canada-France-Hawaii Telescope Corporation N CoI: Jean-Francois Claeskens European Southern Observatory, La Silla N CoI: Marc Remy Institut d'Astrophysique de Liege N CoI: Benoit Pirenne Space Telescope European Coordinating N Facility, Garching bei Muenchen CoI: Almudena Prieto MPI fuer Extraterrestrische Physik, N Garching bei Muenchen ------------------------------------------------------------------------------------ 6. Abstract Two new promising cases of multiply imaged quasars (J03.13 A and B and HE1104--180 A and B) have recently been identified in the framework of systematic optical surveys for gravitational lenses carried out at the European Southern Observatory. Furthermore, following a careful re-analysis (numerical PSF subtraction) of a sample of WFPC planetary camera frames obtained for 41 selected highly luminous quasars within the HST snapshot survey, we have identified several good gravitational lens candidates among which 0956+1217. For several of these candidates, individual spectra of the resolved QSO images have never been obtained. The lens has not yet been identified for most of them. No direct imagery at high angular resolution (<= 0.1") exists for the two first candidates. The interesting structures seen for the best HST candidate need to be confirmed. Taking advantage of the excellent angular resolution of HST, we propose to obtain FOS spectra and to directly image with the WFPC2 planetary camera these new gravitational lens candidates in order to identify their real physical nature (lensed or not lensed) and to set important constraints on the lensing (or other) models. ------------------------------------------------------------------------------------ Observations Description ------------------------ We should like to image the new gravitational lens candidates described in the previous section at high angular resolution and with a dynamic range as large as possible in order to search for very faint image structures (cf. yet undetected lensed image(s), lensing galaxy, etc.) at angular separations as small as 0.1'' from the multiple QSO images. Because of the very large dynamic range requested for these observations and also the need for some direct imaging in the red (search for the lensing galaxy and/or other intervening galaxies, cluster, etc.), we find that the WFPC2 planetary camera is the most appropriate instrument for our needs. Our strategy to optimally detect faint structures at small angular separations will be to obtain at least 4 (usually 5) exposures, slightly offset, for each gravitational lens candidate, in two spectral bands (using for instance the recommended WFPC2 F555W and F814W filters which have good transmission, are very broad and are contiguous in wavelength). Multiple offset exposures are requested in order to be able to discriminate secondary images against cosmic rays, to better handle the CCD pixel response function, to better sample, construct and subtract an optimal point spread function (subsequently used for multiple images decomposition and/or image deconvolution; see Hjorth and Jensen 1993, in the proceedings of the 31st Liege International Astrophysical Colloquium, p. 103), to improve our detectability of very faint structures with an acceptable signal-to-noise ratio (S/N app. 5--10) and, to absolutely avoid saturation of the brightest QSO images. Two different spectral bands are necessary because we need to derive at least one color to discriminate for instance lensed images against intervening ones, when testing the gravitational lensing hypothesis. In addition, for the gravitational lens candidate J03.13, we shall directly check the spectral similarity (lensed? or not lensed?) of the A and B images by taking FOS spectra with the grating G650L (wide spectral coverage) and the 0.5" circular aperture. Requesting a signal-to-noise ratio of app. 20 per resolution element and considering a dark count rate of 0.013 count/sec/diode in the FOS/RED mode, the HST + FOS + COSTAR efficiency E_Lambda versus Lambda (see Fig. 1.2.1 in the HST FOS Instrument Handbook), the throughput of the 0.5'' single circular aperture (Fig. 1.2.2. in the same reference), the corresponding FOS line width of app. 25 Angstrom, a representative wavelength of 5200 Angstrom, the V apparent magnitude of the QSO images and a spectral index Alpha = +1 to characterize their spectral energy distribution, we have derived the exposure times for each QSO image. We find that for a V = 17.3, 18.1, 19.4 and 20.6 mag. QSO image, the requested exposure times are of the order of 5, 10, 30 and 90 min., respectively. The individual targets: J03.13 A & B: The brightest QSO image in this system has a visual magnitude of 17.3. In order not to saturate this (and all other) QSO image(s) on the PC frames observed with HST, we shall use the ADC channel with the 14 e/DN gain, which provides a digital full well of 53000 e. Setting the maximum number of collected electrons per pixel to 2/3 the value of the full well (i.e. 353333 e), it is easy to calculate the maximum allowable integration time when using the WFPC2 F555W and F814W filters: we find for V = 17.3 that t_max(F555W) = 200 sec. and t_max(F814W) = 600 sec. By resampling, registration and combination of the 5 (or sometimes 4) obtained CCD frames in each color, we have computed that a secondary image 7.3, 6.4 or 5 mag. fainter than the brightest QSO image should be detectable at an angular separation >= 0.4", = 0.25" or = 0.15", respectively (S/N app. 10 in the latter case). Taking into account the acquisition (and re- acquisition) of guide stars, the instrument overheads and the exposure times (5 x (200 + 600) sec.), 2 orbits are necessary to achieve the proposed direct imaging. In order to take the FOS spectra of the A and B QSO images (see above) and including the time for the acquisition (and re-acquisition) of guide stars and the instrument overheads, 3 additional orbits are necessary for the spectroscopy. A total of 5 orbits is thus requested to unravel the physical nature of this very good gravitational lens candidate. HE 1104-180 A, B &C: The brightest QSO image has a visual magnitude V = 16.5. It is then easy to estimate that t_max(F555W) = 100 sec. and t_max(F814W) = 350 sec. It is possible to record 3 (and 4) PC frames of HE 1104-180 with the F555W (and F814W) filters in just 1 orbit. 0956+1217: For this quasar, we have V = 17.6. It is then easy to calculate that t_max(F555W) = 260 sec. and t_max(F814W) = 900 sec. It is possible to record 3 (and 4) PC frames of 0956+1217 with the F555W (and F814W) filters in just 2 orbits. Real Time Justification ----------------------- Calibration Justification ------------------------- We should like to get an early acquisition for J03.13 (which could be a triple image, i.e. A be made of two close double images A' and C, separated by less than 0.2"). We wish to be able to make use of calibration PSF stars with the WFPC2 (at the recommended PC1 position) F555W and F814W filters. Additional Comments ------------------- We should like to get an early acquisition for J03.13 (which could be a triple image, i.e. A be made of two close double images A' and C, separated by less than 0.2"). We therefore request some 'Hold on' for the spectroscopic observations of J03.13. We are monitoring photometrically these gravitational lens candidates at ESO and CFH and, if necessary, we could readjust some of the proposed exposure times (mainly in order to avoid saturation of the QSO images on the PC frames and also when using the FOC). ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: Software-Version (Controller= 6.0) Preprocessor (Er, ------------------------------------------------------------------------------------ 5958( 12) - 09/30/96 11:57 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 J03.13A- GALAXY,QSO,GRAVITATIONA RA=10H 17M 23.9S +/- 0.1S,DEC=- J2000 Z = 2.55 B = 17.6+/-0.2 OFFSET L LENS, 20D 46' 58.70" +/- 1" R = 17.2+/-0.2 I = 16.9+/-0.2 Comments: Lensed QSO image (the brightest one) - coords updated 13 Sept 95 2 J03.13B GALAXY, QSO, XI-OFF=-0.82"+/- 0.02",ETA- 1950.0 Z = 2.55 B = 19.6+/-0.4 Gravitational Lens OFF=0.04"+/- 0.02",FROM 1 R = 19.3+/-0.3 I = 19.0+/-0.3 Comments: Lensed QSO image (the faintest one) 3 J03.13C GALAXY, QSO, XI-OFF=0.82"+/- 0.02",ETA-OFF=- 1950.0 Z = 2.55 B = 21.0+/-1.0 Gravitational Lens 0.04"+/- 0.02",FROM 1 R = 21.0+/-1.0 I = 21.0+/-1.0 Comments: Symetric position of B with respect to A (for contamination estimate of image B by A) 4 0956+122 GALAXY, QSO RA=09H 56M 11.1S +/- 1950.0 Z = V = 17.6+/-0.5 0.1S,DEC=12D 17' 07.0" +/- 1.5" 3.301 B-V = 0.2+/-0.2 Comments: QSO 5 HE1104-1805 GALAXY,QSO,GRAVITATIONA RA=11H 06M 33.48S +/- 0.1S,DEC=- J2000 Z = V = 16.5+/-0.5 L LENS, 18D 21' 25.0" +/- 1.0" 2.303 I = 16.1+/-0.5 Comments: Multiply imaged QSO 6 H0449-1645 GALAXY,QSO, RA=04H 52M 14.21S +/- 0.1S,DEC=- J2000.0 B = 18.0+/-1.0 16D 40' 17.0" +/- 1.0" Comments: QSO 7 J03.13A- GALAXY,QSO,GRAVITATIONA RA=10H 17M 23.839S +/- 0.02S, J2000 Z = 2.55 B = 17.6+/-0.2 OFFSET-NEW L LENS, DEC=-20D 46' 58.40" +/- 0.3", R = 17.2+/-0.2 PLATE-ID=01CQ I = 16.9+/-0.2 Comments: Lensed QSO image (the brightest one) - coords updated 22 april1996 (JS) Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1980.21 0.0 0.0 0.0 8 J03.13B-NEW GALAXY, QSO, XI-OFF=-0.845"+/- 0.02",ETA- J2000 Z = 2.55 B = 19.6+/-0.4 Gravitational Lens OFF=0.025"+/- 0.02",FROM 7 R = 19.3+/-0.3 I = 19.0+/-0.3 Comments: Lensed QSO image (the faintest one) 9 J03.13C-NEW GALAXY, QSO, XI-OFF=0.845"+/- 0.02",ETA-OFF=- J2000 Z = 2.55 B = 21.0+/-1.0 Gravitational Lens 0.025"+/- 0.02",FROM 7 R = 21.0+/-1.0 I = 21.0+/-1.0 Comments: Symetric position of B with respect to A (for contamination estimate of image B by A) 5958( 12) - 09/30/96 11:57 - [ 2] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Early Acquisition for visit 4 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 J03.13A-OFF WFPC2 IMAGE PC1 F555W CR-SPLIT=NO,ATD-GAIN=15, 1 160 S SPATIAL SCAN 1 SET SCAN-READ=ALL ------------------------------------------------------------------------------------------------------------------------------------ 2 J03.13A-OFF WFPC2 IMAGE PC1 F555W CR-SPLIT=NO,ATD-GAIN=15 1 160 S EXPAND MAX DUR 125% MIN SET DUR 75% ------------------------------------------------------------------------------------------------------------------------------------ 3 J03.13A-OFF WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD-GAIN=15 1 400 S EXPAND MAX DUR 125% MIN SET DUR 75% ------------------------------------------------------------------------------------------------------------------------------------ 4 J03.13A-OFF WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD-GAIN=15 1 400 S EXPAND MAX DUR 125% MIN SET DUR 75% END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 5 J03.13A-OFF WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD-GAIN=15, 1 400 S SPATIAL SCAN 3 SET SCAN-READ=ALL ------------------------------------------------------------------------------------------------------------------------------------ 5958( 12) - 09/30/96 11:57 - [ 3] Visit: 02 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 0956+122 WFPC2 IMAGE PC1 F555W CR-SPLIT=NO,ATD-GAIN=15, 1 160 S SPATIAL SCAN 7 SCAN-READ=ALL ------------------------------------------------------------------------------------------------------------------------------------ 2 0956+122 WFPC2 IMAGE PC1 F555W CR-SPLIT=NO,ATD-GAIN=15 1 300 S EXPAND MAX DUR 125% MIN DUR 75% ------------------------------------------------------------------------------------------------------------------------------------ 3 0956+122 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD-GAIN=15 1 500 S EXPAND MAX DUR 125% MIN DUR 75% END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 5958( 12) - 09/30/96 11:57 - [ 4] Visit: 03 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HE1104-1805 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD-GAIN=15, 1 200 S SPATIAL SCAN 7 SCAN-READ=ALL ------------------------------------------------------------------------------------------------------------------------------------ 2 HE1104-1805 WFPC2 IMAGE PC1 F814W CR-TOLERANCE=0.0,ATD-GAIN=15, 1 200 S CR-SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ 3 HE1104-1805 WFPC2 IMAGE PC1 F555W CR-TOLERANCE=0.0,ATD-GAIN=15, 1 200 S CR-SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ 5958( 12) - 09/30/96 11:57 - [ 5] Visit: 04 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 J03.13A-OFF FOS/RD ACQ/PEA 4.3 MIRROR SEARCH-SIZE-X=2,SEARCH-SIZE-Y=6, 1 2 S ONBOARD ACQ FOR 2 SET-NEW K SCAN-STEP-X=3.33,SCAN-STEP-Y=1.23 ------------------------------------------------------------------------------------------------------------------------------------ 2 J03.13A-OFF FOS/RD ACQ/PEA 1.0 MIRROR SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2, 1 2 S ONBOARD ACQ FOR 3 SET-NEW K SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61 ------------------------------------------------------------------------------------------------------------------------------------ 3 J03.13A-OFF FOS/RD ACQ/PEA 0.5 MIRROR SEARCH-SIZE-X=3,SEARCH-SIZE-Y=3, 1 2 S ONBOARD ACQ FOR 4 SET-NEW K SCAN-STEP-X=0.29,SCAN-STEP-Y=0.29 ------------------------------------------------------------------------------------------------------------------------------------ 4 J03.13A-OFF FOS/RD ACQ/PEA 0.3 MIRROR SEARCH-SIZE-X=4,SEARCH-SIZE-Y=4, 1 10 S ONBOARD ACQ FOR 5-10 SET-NEW K SCAN-STEP-X=0.17,SCAN-STEP-Y=0.17 Comments: Increase time_per_exposure from 10S to 12S, if possible ------------------------------------------------------------------------------------------------------------------------------------ 5 WAVE FOS/RD ACCUM 0.5 G650L 1 DEF ------------------------------------------------------------------------------------------------------------------------------------ 6 J03.13A-OFF FOS/RD ACCUM 0.5 G650L 1 840 S SET-NEW ------------------------------------------------------------------------------------------------------------------------------------ 7 J03.13B-NEW FOS/RD ACCUM 0.5 G650L 1 3700 S EXPAND MAX DUR 110% MIN DUR 90% ------------------------------------------------------------------------------------------------------------------------------------ 8 J03.13B-NEW FOS/RD ACCUM 0.5 G650L 1 1200 S EXPAND MAX DUR 150% MIN DUR 90% ------------------------------------------------------------------------------------------------------------------------------------ 9 J03.13C-NEW FOS/RD ACCUM 0.5 G650L 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ 10 WAVE FOS/RD ACCUM 0.5 G650L 1 DEF ------------------------------------------------------------------------------------------------------------------------------------ 5958( 12) - 09/30/96 11:57 - [ 6] Visit: 05 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 H0449-1645 WFPC2 IMAGE PC1 F814W DITHER-TYPE=BOX,CR-SPLIT=NO, 1 400 S ATD-GAIN=15 ------------------------------------------------------------------------------------------------------------------------------------ 5958( 12) - 09/30/96 11:57 - [ 7] Visit: 06 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 J03.13A-OFF WFPC2 IMAGE PC1 F814W DITHER-TYPE=BOX,CR-SPLIT=NO, 1 400 S SET-NEW ATD-GAIN=15 ------------------------------------------------------------------------------------------------------------------------------------ 2 J03.13A-OFF WFPC2 IMAGE PC1 F814W DITHER-TYPE=BOX,CR-SPLIT=0.5, 1 360 S SET-NEW CR-TOLERANCE=0.0,ATD-GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 3 J03.13A-OFF WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD-GAIN=7 1 80 S EXPAND MAX DUR 150% MIN SET-NEW DUR 60% ------------------------------------------------------------------------------------------------------------------------------------ 5958( 12) - 09/30/96 11:57 - [ 8] Scan Paramters Form ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 1 Exposure Logsheet lines: 7.001 FGS Scan: D Dwell Only: dwell points/line: 2 Seconds per dwell: 160.00 Scan width (arc-secs): 1.1400 Scan length (arc-secs): 1.1400 Angle between sides (degrees) 90.00 Number of lines: 2 Scan rate (arc-sec/sec): 0.0000 PA of first scan line (degrees) 36.100 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): Width Offset (arc-sec): ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 3 Exposure Logsheet lines: 7.005 FGS Scan: D Dwell Only: dwell points/line: 2 Seconds per dwell: 400.00 Scan width (arc-secs): 1.1400 Scan length (arc-secs): 1.1400 Angle between sides (degrees) 90.00 Number of lines: 2 Scan rate (arc-sec/sec): 0.0000 PA of first scan line (degrees) 36.100 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): Width Offset (arc-sec): ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 7 Exposure Logsheet lines: 8.001,9.001 FGS Scan: D Dwell Only: dwell points/line: 2 Seconds per dwell: 200.00 Scan width (arc-secs): 1.1400 Scan length (arc-secs): 1.1400 Angle between sides (degrees) 90.00 Number of lines: 2 Scan rate (arc-sec/sec): 0.0000 PA of first scan line (degrees) 36.100 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): Width Offset (arc-sec): ------------------------------------------------------------------------------------------------------------------------------------ 5958( 12) - 09/30/96 11:57 - [ 9] Summary Form for Proposal 5958 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 FOS/RD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ATD-GAIN=15 SCAN-READ=ALL CR-SPLIT=0.5 CR-TOLERANCE=0.0 SCAN-STEP-Y=1.23 SCAN-STEP-Y=0.61 SCAN-STEP-Y=0.29 SCAN-STEP-Y=0.17 DITHER-TYPE=BOX ATD-GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Quasars ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SPATIAL SCAN 1 EXPAND MAX DUR 125% MIN DUR 75% EXPAND MAX DUR 125% MIN DUR 75% END ORBIT SPATIAL SCAN 3 SPATIAL SCAN 7 ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 3 ONBOARD ACQ FOR 4 ONBOARD ACQ FOR 5-10 EXPAND MAX DUR 110% MIN DUR 90% EXPAND MAX DUR 150% MIN DUR 90% EXPAND MAX DUR 150% MIN DUR 60% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F814W MIRROR G650L ------------------------------------------------------------------------------------------------------------------------------------ Target Names J03.13A-OFFSET 0956+122 HE1104-1805 J03.13A-OFFSET-NEW WAVE J03.13B-NEW J03.13C-NEW H0449-1645 ------------------------------------------------------------------------------------------------------------------------------------