9498( 5) - 03/26/02 09:02 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9498 Version: 5 Check-in Date: 26-Mar-2002 09:01:21 1.Proposal Title: The Nature of the Close Binary Quasar LBQS 0103-2753 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Vesa Junkkarinen University of California - San Diego CoI: Dr. Ross Cohen University of California, San Diego N CoI: Prof. Gregory Shields University of Texas N CoI: Prof. Frederick Hamann University of Florida N ------------------------------------------------------------------------------------ 5. Abstract We propose STIS spectroscopic and ACS imaging observations of the small--separation quasar pair LBQS 0103-2753 A/B (= CT 344). This quasar pair with z = 0.85, has a projected separation of only 0.3 arcsec or 2.3 kpc. The brighter member of the pair (V = 18.2) is a BAL quasar while the fainter (V = 19.4) is a quasar at a similar redshift without BALs. It is very likely that the two quasars are a binary quasar, and not a chance superposition along the line of sight or a gravitational lens (Junkkarinen et al. 2001). The goals of the STIS spectroscopic observations are to accurately measure the systemic redshifts and redshift difference, to search for variability, and to quantify the emission line differences between the two quasars. Deep ACS WFC images, in the F606W and F814W filters, will be used to provide information on the host galaxy morphologies, to look for the signatures of a merger/interaction -- in particular disturbed isophotes and tidal tails, and to study any cluster of galaxies around this quasar pair. These observations will test the lensing versus binary hypothesis and help differentiate between merging and a high relative velocity galaxy--galaxy interaction. Studies of binary quasars with such close separations will put constraints on merger timescales and duty cycles for AGN fueling at these separations. ------------------------------------------------------------------------------------ 9498( 5) - 03/26/02 09:02 - [ 2] Observations Description ------------------------ The ACS WFC with the F606W and F814W filters will be used to observe the quasar pair field for low level extended structure. The goal is to measure the host morphology and detect distortions in the isophotes and any tidal tails. The desired S/N is 3 per 0.1x0.1 arcsec region (2X2 pixels at 0.05 arcsec per pixel) for a surface brightness (in R) corresponding to m(AB) ~ 25.0 per square arcsec. This roughly corresponds to detecting a 2X2 pixel region with an enclosed flux of m(AB) ~ 30.0 at a S/N = 3. At 0.5 to 1.5 arcsec from the quasar point sources (10 to 30 pixels), the dominant sources of noise are root N noise from the sky, imperfect PSF subtraction, and root N noise from the PSF (the PSF is faint compared to sky at r >= 10 pixels under these conditions). The root N noise from the sky is the dominant noise source over most of this range of separation from the bright sources. The target S/N can be obtained with 4 orbits with the ``LOW'' background option. In order to better sample the PSF and remove defects, the observations will be dithered by using a standard set of 4 closely spaced pointings. With the reduced visibility due to the ``LOW'' flag and taking into account all the overheads, the proposed observations will consist of four 900 s integrations with the F606W filter followed by four 900 s integrations with F814W filter. Each 900 s integration will be split into two 450 s integration with the CRSPLIT=1 option to independently remove cosmic rays (the cosmic rays using 4 900 s integrations can be removed with interpolation, but using 8 450 s integrations will probably result in a substantially cleaner image at a cost of a little overhead). The ACS WFC observation will be packed into 4 orbits with 1800 s of science time per orbit. The brighter quasar image (V = 18.2) will be saturated with predicted electrons in the brightest pixel of 160, 000 and 100, 000 for the F606W and F814W respectively (per 450 s image compared to a full well of 80, 000). The saturation will involve at most a pixel or two. The fainter quasar image is about a factor of 3 fainter in the red and will not be saturated. The F606W and F814W filters were chosen for the ACS WFC observations because they are wide and have high throughput. The central wavelengths of the two filters, 6060 Angstroms and 8140 Angstroms, correspond to 3280 Angstroms and 4400 Angstroms at z = 0.85. The STIS/CCD G430L spectroscopy will consist of one orbit and 1800 s total integration time (with the normal CR split). The target S/N at 5000 Angstrom on LBQS 0103-2753 B (V = 19.4) is 15. The C III] 1909 and Mg II 2798 emission lines and limits on any absorption will be measured from these spectra. The STIS G430L spectrum will cover rest wavelengths from 1570 Angstroms to 3080 Angstroms at z = 0.85. The STIS/CCD G750L spectroscopy will consist of two orbits with a fringe flat in the middle. Total integration time will be 3600 s and the target S/N on LBQS 0103-2753 B at 9300 Angstroms is 15. The lines of interest around 9300 Angstrom are H Beta and O III 5007. The STIS G750L spectrum will cover rest wavelengths from 2840 Angstroms to 5500 Angstroms at z = 0.85. We chose the 52X0.1 slit with the higher overhead in order to keep the resolution at two pixels for forbidden lines and to reduce spectral smearing if there are spatially extended narrow emission lines. The STIS/NUV G230L will be used for a one orbit observation with the 52X0.2 slit. This duplicates the wavelengths of a previous STIS observation of this target. The composite spectrum has previously shown time variability. For all of the STIS observations, the STIS slit PA will be chosen to cover both of the quasars so that simultaneous spectra of both are obtained. Real Time Justification ----------------------- We request the ``LOW'' option for the 4 orbits dedicated to the ACS WFC imaging. The ``LOW'' background option is required since most of the morphology information (spiral arms etc.) and possible tidal tails will be at very low light levels in the 0.5 to 1.5 arcsec region from the quasar point sources (4 to 12 kpc at z = 0.85). The target S/N is 3 for a 2 by 2 pixel region at R = 25 mag per square arcsec. Away from the bright sources, this light level is completely ``sky'' limited with or without the ``LOW'' option. Without the ``LOW'' option, the broad F606W and F814W filters produce images that have sky levels about three times higher than with the ``LOW'' option (based on the ACS ETC with the Earth in shadow option) and the noise is about 3^0.5 higher. Without the ``LOW'' option more than 6 orbits would be needed to reach the target S/N for these sky-limited observations. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9498( 5) - 03/26/02 09:02 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 CT344 GALAXY, QSO RA=01H 5M 34.77S +/- 1", DEC=- J2000 Z = V = 17.8+/-0.6 27D 36' 58.4" +/- 1", PLATE- 0.848 B = 18.1+/-0.3 ID=00DA B-V = 0.3+/-0.4 Coordinate Source: GSC_SURVEY_PLATE Comments: The target consists of close pair of QSOs, the separation is 0.3 arcsec, the PA is 30.1 degrees 9498( 5) - 03/26/02 09:02 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.265 Coordinate_Frame POS-TARG Pattern_Orient 20.67 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 9498( 5) - 03/26/02 09:02 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 320D TO 10D ORIENT 50D TO 100D ORIENT 140D TO 190D ORIENT 230D TO 290D On Hold Comments: Additional Comments: ACS WFC observations of QSO pair at PA = 30.1 deg. Orientation to avoid QSOs aligned with rows or columns and diffraction spikes. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 CT344 ACS/WF ACCUM WFC F606W CR-SPLIT=2 1 1020 S PATTERN 1 10 LOW-SKY C ------------------------------------------------------------------------------------------------------------------------------------ 20 CT344 ACS/WF ACCUM WFC F814W CR-SPLIT=2 1 1020 S PATTERN 1 20 LOW-SKY C ------------------------------------------------------------------------------------------------------------------------------------ 9498( 5) - 03/26/02 09:02 - [ 6] Visit: 02 Visit Priority: Visit Requirements: ORIENT 75.1D TO 75.1D ORIENT 255.1D TO 255.1D On Hold Comments: Additional Comments: PA of two QSOs is 30.1 degrees, separation is 0.3 arcsec, STIS slit aligned to obtain spectra of both QSOs, STIS point source ACQ worked in a previous cycle on this QSO pair. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 CT344 STIS/C ACQ F28X50L MIRROR 1 15 S CD P Comments: ACQ for Observation number 20. ------------------------------------------------------------------------------------------------------------------------------------ 20 CT344 STIS/N ACCUM 52X0.2 G230L 2376 1 2300 S EXPAND END ORBIT UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9498( 5) - 03/26/02 09:02 - [ 7] Visit: 03 Visit Priority: Visit Requirements: ORIENT 75.1D TO 75.1D ORIENT 255.1D TO 255.1D On Hold Comments: Additional Comments: PA of two QSOs is 30.1 degrees, separation is 0.3 arcsec, STIS slit aligned to obtain spectra of both QSOs, STIS point source ACQ plus ACQ/PEAK worked in a previous cycle on this QSO pair. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 CT344 STIS/C ACQ F28X50L MIRROR 1 15 S CD P Comments: ACQ for Observation numbers 20 - 80 ------------------------------------------------------------------------------------------------------------------------------------ 20 CT344 STIS/C ACQ/PEA 52X0.1E MIRROR 1 20 S CD K 1 Comments: ACQ/PEAK for exposure No. 30 to 80. Using offset "aperture" near edge of CCD. ------------------------------------------------------------------------------------------------------------------------------------ 30 CT344 STIS/C ACCUM 52X0.1E G750L 7751 CR-SPLIT=2 1 1834 S END ORBIT EXPAND CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 40 CCDFLAT STIS/C ACCUM 52X0.05 G750L 7751 2 DEF CD Comments: Long Slit CCDFLAT for 2 objects separated by 0.3 arcsec on slit. ------------------------------------------------------------------------------------------------------------------------------------ 50 CT344 STIS/C ACCUM 52X0.1E G750L 7751 CR-SPLIT=2 1 2762 S EXPAND END ORBIT CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 60 CCDFLAT STIS/C ACCUM 52X0.1 G750L 7751 2 DEF CD Comments: Long Slit CCDFLAT for 2 objects separated by 0.3 arcsec on slit. ------------------------------------------------------------------------------------------------------------------------------------ 70 CCDFLAT STIS/C ACCUM 0.2X0.0 G750L 7751 2 DEF CD 6 Comments: Fringe flat for center of slit. ------------------------------------------------------------------------------------------------------------------------------------ 80 CT344 STIS/C ACCUM 52X0.1E G430L 4300 CR-SPLIT=2 1 2856 S EXPAND END ORBIT CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 9498( 5) - 03/26/02 09:02 - [ 8] Summary Form for Proposal 9498 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC F28X50LP 52X0.2 52X0.1E1 52X0.05 52X0.1 0.2X0.06 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC STIS/CCD STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ACQ ACQ/PEAK ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 320D TO 10D ORIENT 50D TO 100D ORIENT 140D TO 190D ORIENT 230D TO 290D PATTERN 1 10 LOW-SKY PATTERN 1 20 LOW-SKY ORIENT 75.1D TO 75.1D ORIENT 255.1D TO 255.1D EXPAND END ORBIT END ORBIT EXPAND ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W F814W MIRROR G230L G750L G430L ------------------------------------------------------------------------------------------------------------------------------------ Target Names CT344 CCDFLAT ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 2376 7751 4300 ------------------------------------------------------------------------------------------------------------------------------------