6790( 5) - 03/15/99 10:27 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6790 Version: 5 Check-in Date: 21-Oct-1997 16:09:04 1.Proposal Title: MASS DETERMINATION OF QSOs USING GRAVITATIONAL LENSING ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 6 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Jean Surdej INSTITUT D'ASTROPHYSIQUE CoI: Jean-Francois Claeskens Institut d'Astrophysique de Liege N CoI: Mike Hawkins Royal Observatory Edinburgh N CoI: Angela Iovino Osservatorio Astronomico di Brera, Milano N CoI: Marc Remy Institut d'Astrophysique de Liege N CoI: Peter Shaver European Southern Observatory, Garching N bei Muenchen ------------------------------------------------------------------------------------ 5. Abstract Only four pairs of quasars with different redshifts and angular separations smaller than 5'' are presently known. We propose to directly image with the WFPC2 planetary camera these interesting quasar associations in order to search for the presence of a secondary lensed image of the background source near the foreground quasar. The detection (or non- detection) of these putative secondary images will enable us to weigh (or significantly improve the upper limit on) the mass of the foreground quasars. These QSO mass estimates will take into account the lensing effects due to the host galaxy of the foreground quasar(s) and/or other intervening galaxies, if detected on the high quality PC images. Furthermore, one of these quasars (Q 1009- 0252) has recently been reported to be multiply imaged. The WFPC2 CCD frames will also enable us to search for the lensing object(s) and for additional macro- lensed images of the background quasar, and will thus provide essential constraints on the lensing model. ------------------------------------------------------------------------------------ 6790( 5) - 03/15/99 10:27 - [ 2] Observations Description ------------------------ In order to significantly improve the existing constraints on (or to derive) the mass of the foreground quasars in close QSO pairs, we should try to detect the presence of a secondary image of the background quasar that is as faint as possible (typically 7--6--5 magnitudes fainter than the background and/or foreground QSO image(s)) at an angular separation as small as possible (0.4"-- 0.25"--0.15", respectively) from the foreground quasar (see the calculations by Iovino and Shaver (1986) for the particular case of 1548+114 A \& B). We thus need to image the four proposed QSO pairs not only at a high angular resolution but also with a dynamic range as large as possible, in which the linearity of the detector is totally preserved. Because of the very wide dynamic range requested for these observations and also the need for some direct imaging in the red (search for the QSO host galaxy and/or other intervening galaxies, cluster), we find that the WFPC2 planetary camera is the most appropriate instrument for our needs. Our strategy to optimally search for the presence of a faint secondary QSO image will be to obtain at least 2 (usually 3 or more) exposures, slightly offset, for each QSO pair 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 and construct an optimal point spread function from the background QSO (subsequently used for multiple images decomposition and/or image deconvolution; see Hjorth and Jensen 1993), to improve our detectability of a secondary image that is as faint as possible (5--6--7 mag. fainter than the other QSOs images in the field), with an acceptable signal-to-noise ratio (S/N = 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 for the primary and secondary QSO images in order to test the gravitational lensing hypothesis. \par\medskip\noindent {\bf The individual targets}: \par\noindent \par\noindent {\bf Q 1009-0252A, B \& C}: The brightest quasar in this close QSO pair has a visual magnitude of 18.1. 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 = 18.1 that t{max}{F555W} = 400 sec. and t{max}{F814W} = 1400 sec. By resampling, registration and combination of the 3 (or sometimes 2) CCD frames obtained in each color, we have computed that a secondary image 7.3, 6.4 or 5 mag. fainter than the foreground quasar should be detectable at an angular separation >= 0.4", = 0.25" or = 0.15", respectively (S/N = 10 in the latter case). Taking into account the acquisition (and re- acquisition) of guide stars, the instrument overheads and the exposure times (3 x 400 sec. + 2 x 1400 sec.), a total number of 2 orbits is necessary to achieve the scientific goals exposed in the previous section. \par\noindent {\bf Q 1148+0055A \& B}: In this case too, the brightest QSO image A has a magnitude V(A) = 18.1 and a total number of 2 orbits is therefore also requested. \par\noindent {\bf 1548+114A \& B}: The brightest image in this system is 1548+114A with V(A) = 17.2. Furthermore, 1548+114B is known to be variable (17.6 <= V_B \leq 19.1 during the course of the ESO key programme, 1989-1993). We have estimated (under reasonable conditions) that a total number of 2 orbits is necessary in this case to obtain 4 ( and 5) frames of 600 sec. (200 sec.) each with the F814W (and F555W) filters. Because of lack of time, we shall only carry out the red observations (dithering + PC will lead to a final image approximately 4 times better in angular resolution than that obtained by Burbidge et al. ... so this should not be considered as a duplication). \par\noindent {\bf QSO-2132--4537A \& B}: The brightest QSO image has a visual magnitude V = 18.7. It is then easy to estimate that t{max}{F555W} = 700 sec. and t{max}{F814W} = 2400 sec. It is possible to record 3 (and 2) PC frames of QSO-2132--4537A \& B with the F814W (and F555W) filters in just 3 orbits. Because of a lack of (allocated) tiime, we shall only spend 2 orbits on this pair of quasars. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6790( 5) - 03/15/99 10:27 - [ 3] Data Distribution Paper Products: Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 6790( 5) - 03/15/99 10:27 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 Q1009-0252-A GALAXY, QSO, RA=10H 12M 15.90S +/- 0.10S, J2000 Z = R = 17.6 Gravitational Lens DEC=-03D 07' 01.73" +/- 1.00" 2.745 B-R = 0.6 Comments: R_B=20.0 and R_C=18.9, I_A_B_C=17.5, 19.6, 18.7, Z_C=1.62, Note that epoch = 1952.09 2 Q1148+0055-A GALAXY, QSO RA=11H 51M 15.41S +/- 0.10S, J2000 Z = R = 17.9 DEC=+00D 38' 26.5" +/- 1.00" 1.887 Comments: R_faint = 20.7, Z_A=1.89, Z_B=1.41, V_A=18.1, V_B=20.6, it was not possible to measure GASP coordinates for this QSO 3 Q1548+114-B GALAXY, QSO RA=15H 50M 43.70S +/- 0.10S, J2000 Z = R = 18.1 DEC=+11D 20' 47.70" +/- 1.00", 1.901 PLATE-ID=00J1 Comments: R_faint=18.8, Z_B=0.44, Z_A=1.90, V_B=17.2, V_A=19 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1982.3020 0.0 0.0 0.0 4 QSO-2132- GALAXY, QSO RA= 21H 32M 28.21S +/- 0.10S, J2000 Z = 1.33 V = 18.7 4537-B DEC=-45D 37' 38.3" +/- 1.00", PLATE-ID=04ZE Comments: Z_A=1.33, Z_B=0.875, V_A=19.1, V_B=18.7 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1980.6078 0.0 0.0 0.0 6790( 5) - 03/15/99 10:27 - [ 5] Visit: 01 Visit Priority: 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 Q1009-0252- WFPC2 IMAGE PC1 F555W CR-SPLIT = NO,ATD-GAIN = 15, 1 400 S SPATIAL SCAN 3 A SCAN-READ = ALL ------------------------------------------------------------------------------------------------------------------------------------ 2 Q1009-0252- WFPC2 IMAGE PC1 F814W ATD-GAIN = 15 1 2600 S A ------------------------------------------------------------------------------------------------------------------------------------ 6790( 5) - 03/15/99 10:27 - [ 6] Visit: 02 Visit Priority: 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 Q1148+0055- WFPC2 IMAGE PC1 F555W CR-SPLIT = NO,ATD-GAIN = 15, 1 400 S SPATIAL SCAN 3 A SCAN-READ = ALL ------------------------------------------------------------------------------------------------------------------------------------ 2 Q1148+0055- WFPC2 IMAGE PC1 F814W ATD-GAIN = 15 1 2600 S A ------------------------------------------------------------------------------------------------------------------------------------ 6790( 5) - 03/15/99 10:27 - [ 7] Visit: 03 Visit Priority: 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 Q1548+114-B WFPC2 IMAGE PC1 F814W CR-SPLIT = NO,ATD-GAIN = 15, 1 400 S SPATIAL SCAN 5 SCAN-READ = ALL ------------------------------------------------------------------------------------------------------------------------------------ 6790( 5) - 03/15/99 10:27 - [ 8] Visit: 04 Visit Priority: 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 QSO-2132-45 WFPC2 IMAGE PC1 F555W CR-SPLIT = NO,ATD-GAIN = 15, 1 700 S SPATIAL SCAN 1 37-B SCAN-READ = ALL ------------------------------------------------------------------------------------------------------------------------------------ 2 QSO-2132-45 WFPC2 IMAGE PC1 F814W ATD-GAIN = 15 1 2600 S 37-B ------------------------------------------------------------------------------------------------------------------------------------ 6790( 5) - 03/15/99 10:27 - [ 9] Scan Paramters Form ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 1 Exposure Logsheet lines: 04.001 FGS Scan: D Dwell Only: dwell points/line: 3 Seconds per dwell: 400.00 Scan width (arc-secs): 0.0000 Scan length (arc-secs): 0.3330 Angle between sides (degrees) 90.00 Number of lines: 1 Scan rate (arc-sec/sec): 0.0000 PA of first scan line (degrees) 45.000 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): 0.1660 Width Offset (arc-sec): 0.0 ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 3 Exposure Logsheet lines: 01.001,02.001 FGS Scan: D Dwell Only: dwell points/line: 2 Seconds per dwell: 400.00 Scan width (arc-secs): 0.2500 Scan length (arc-secs): 0.2500 Angle between sides (degrees) 90.00 Number of lines: 2 Scan rate (arc-sec/sec): 0.0000 PA of first scan line (degrees) 270.000 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): 0.0 Width Offset (arc-sec): 0.0 ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 5 Exposure Logsheet lines: 03.001 FGS Scan: D Dwell Only: dwell points/line: 2 Seconds per dwell: 400.00 Scan width (arc-secs): 0.2500 Scan length (arc-secs): 0.2500 Angle between sides (degrees) 90.00 Number of lines: 2 Scan rate (arc-sec/sec): 0.0000 PA of first scan line (degrees) 270.000 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): 0.0 Width Offset (arc-sec): 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 6790( 5) - 03/15/99 10:27 - [ 10] Summary Form for Proposal 6790 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT = NO ATD-GAIN = 15 SCAN-READ = ALL ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SPATIAL SCAN 3 SPATIAL SCAN 5 SPATIAL SCAN 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names Q1009-0252-A Q1148+0055-A Q1548+114-B QSO-2132-4537-B ------------------------------------------------------------------------------------------------------------------------------------