9367( 9) - 02/24/04 07:08 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9367 Version: 9 Check-in Date: 24-Feb-2004 07:05:08 1.Proposal Title: Unique Opportunities to Search for the Optical Counterparts to High-Z Damped LyAlpha Systems ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Cyril Hazard University of Pittsburgh CoI: David Turnshek University of Pittsburgh Y ------------------------------------------------------------------------------------ 5. Abstract The galaxies responsible for damped LyAlpha absorption in QSO spectra are difficult to observe against the strong background QSO emission. We propose to detect even low luminosity galaxies associated with QSO absorption line systems out to redshifts as high as z = 1.8 by observing them in the shadow cast by an even higher redshift damped LyAlpha absorber. As a result the galaxy will be observed free of contamination by the background AGN and of the uncertainties which arise when image processing techniques are required to remove the AGN emission. We propose two approaches. In the first we will attempt to detect a z = 1.8634 system seen in the optical spectrum of a high-z BL Lac object in the shadow of two higher-redshift systems seen in the same optical spectrum. In the second only the higher redshift shadowing LyAlpha system is seen in the optical spectrum and the presence of the lower- redshift systems at z = 0.713 and z = 1.0466 are inferred from the presence of strong MgII, SiII and FeII absorption lines. ------------------------------------------------------------------------------------ 9367( 9) - 02/24/04 07:08 - [ 2] Observations Description ------------------------ The z = 1.8634 system. Our primary aim will be to detect the galaxy responsible for the z = 1.8634 absorption system in H0841+1256. The F255W filter is ideally suited for this purpose with a passband confined to the interval 2000 - 3100Angstrom. This will result in the complete blanking out of the BL Lac object itself and place the peak of the response near the z = 1.8634 Lyman Limit. Taking into account the filter response and assuming (the worst case scenario) of no flux from the galaxy below 2611Angstrom will give us an effective passband of about 550Angstrom. Assuming that the galaxies are similar to those identified by Steidel et.al.(1994) with absolute B magnitudes around - 21 we would expect the absorbing galaxy to have an apparent magnitude about +24 while the observations of Rao and Turnshek (1998) would imply that the object could be fainter than +26. On the other hand, we have no information on how the brightness of these systems evolves with redshift. Thus, spectrophotometry of the Rao and Turnshek z = 0.221 galaxy suggests that it last underwent a burst of star formation several billion years ago. There is therefore a strong possibility that the higher redshift objects at some 25 percent age of the Universe will be younger star burst systems and significantly brighter, particularly in the UV. This uncertainty dictates that we should aim to achieve the lowest limiting magnitude possible. We propose observations through filter F255W using the WFPC2 camera. With this arrangement we estimate that we will attain a S/N = 5 over 0.2"x 0.2" corresponding to 23 mag arcsec^-2 in 12 orbits. By binning over 0.5"x0.5" we then reach a magnitude adequate to check if we are dealing with a luminous high redshift galactic disc. Howevever, if conventional wisdom is correct and, at high redshifts at least, the damped systems really do represent proto-galaxies, then our magnitude limits are very pessimistic since we would expect more UV emission than we assumed in our earlier estimates. The observations will provide a significant test of the standard high-redshift models and complementary information to that from the lower-redshift studies. Observations of the lower-z systems. The damped systems at z = 2.43 and 2.52, like the higher-redshift systems in H0841+1256, have Lyman limits at or above 3100Angstrom and the QSOs will be obscured in all observations at lower wavelengths. The filter F225W is therefore also ideal for these observations. However, the continuum from the z = 0.731 and 1.046 systems will now be visible to at least 1800Angstrom giving us a much wider effective bandwidth and in addition LyAlpha emission will now fall within the observing window. Taken together with their smaller distance we estimate that their images will be at least 2 magnitudes brighter than that of the z = 1.863 system. Under these circumstances we estimate that we can achieve a positive detection even for obects as faint as the Rao-Turnshek galaxies in 5 orbits. At the suggestion of STScI, we will also consider use of the more sensitive ACS camera in the event that no flux is detected in our three targets. Therefore, in the Phase 2 submission we have put completion of the program ON-HOLD after the initial WFPC2-F255W observations (3 orbits on the high-z system and 2 orbits each on the two lower-z systems). If flux from a target is not visible, we will implement the ON-HOLD observations with ACS. In this event a small amount of light from the QSO is expected to be in the image since the effective upper wavelength limit of the ACS-F250W filter falls above the Lyman Limit; this will have to be subtracted. In the event that the WFPC2-F255W observations show detections, they will be repeated, using the 15 remaining orbits. 9367( 9) - 02/24/04 07:08 - [ 3] Real Time Justification ----------------------- Calibration Justification ------------------------- Real_Time_Justification Additional Comments ------------------- ------------------------------------------------------------------------------------ 9367( 9) - 02/24/04 07:08 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 Q0841+1256 GALAXY, HIGH REDSHIFT RA=08H 44M 24.27S +/- 1.0", J2000 V = 18 GALAXY DEC=12D 45' 47.02" +/- 1.0", PLATE-ID=028I Coordinate Source: GSC_SURVEY_PLATE Comments: DLA galaxy of unknown flux; QSO has V=18 but is observed below the Lyman limit. 2 Q2343+1232 GALAXY, HIGH REDSHIFT RA=23H 46M 28.29S +/- 1.0", J2000 V = 18 GALAXY DEC=12D 48' 58.12" +/- 1.0", PLATE-ID=00JG Coordinate Source: GSC_SURVEY_PLATE Comments: DLA galaxy of unknown flux; QSO has V=18 but is observed below the Lyman limit. 3 Q2344+1228 GALAXY, HIGH REDSHIFT RA=23H 46M 46.05S +/- 1.0", J2000 V = 18 GALAXY DEC=12D 45' 26.95" +/- 1.0", PLATE-ID=00JG Coordinate Source: GSC_SURVEY_PLATE Comments: DLA galaxy of unknown flux; QSO has V=18 but is observed below the Lyman limit. 9367( 9) - 02/24/04 07:08 - [ 5] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFPC2-LINE Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.3535 Coordinate_Frame POS-TARG Pattern_Orient 45 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFPC2-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.3535 Coordinate_Frame POS-TARG Pattern_Orient 45 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 3 Primary_Pattern Secondary_Pattern Pattern_Type ACS-SBC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.472 Coordinate_Frame POS-TARG Pattern_Orient 44.40 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 9367( 9) - 02/24/04 07:08 - [ 6] 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 Q0841+1256 WFPC2 IMAGE WF2 F255W CR-SPLIT=NO 1 44 M PATTERN 1 10 ------------------------------------------------------------------------------------------------------------------------------------ 9367( 9) - 02/24/04 07:08 - [ 7] 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 ------------------------------------------------------------------------------------------------------------------------------------ 20 Q0841+1256 ACS/HR ACCUM HRC F250W CR-SPLIT=NO 1 45 M PATTERN 3 20 C ------------------------------------------------------------------------------------------------------------------------------------ 30 Q0841+1256 ACS/HR ACCUM HRC F250W CR-SPLIT=NO 1 45 M C ------------------------------------------------------------------------------------------------------------------------------------ 9367( 9) - 02/24/04 07:08 - [ 8] Visit: 03 Visit Priority: Visit Requirements: ON HOLD On Hold Comments: Conditional if target flux evaluated from Visit Number 01 goes undetected. 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 ------------------------------------------------------------------------------------------------------------------------------------ 20 Q0841+1256 ACS/HR ACCUM HRC F250W 1 45 M PATTERN 3 20 C ------------------------------------------------------------------------------------------------------------------------------------ 9367( 9) - 02/24/04 07:08 - [ 9] 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 ------------------------------------------------------------------------------------------------------------------------------------ 20 Q0841+1256 ACS/HR ACCUM HRC F250W CR-SPLIT=NO 1 45 M PATTERN 3 20 C ------------------------------------------------------------------------------------------------------------------------------------ 9367( 9) - 02/24/04 07:08 - [ 10] Visit: 05 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 ------------------------------------------------------------------------------------------------------------------------------------ 5 Q2343+1232 WFPC2 IMAGE WF2 F255W 1 44 M PATTERN 2 ------------------------------------------------------------------------------------------------------------------------------------ 9367( 9) - 02/24/04 07:08 - [ 11] Visit: 06 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 ------------------------------------------------------------------------------------------------------------------------------------ 20 Q2343+1232 ACS/HR ACCUM HRC F250W CR-SPLIT=NO 1 45 M PATTERN 3 20 C ------------------------------------------------------------------------------------------------------------------------------------ 9367( 9) - 02/24/04 07:08 - [ 12] Visit: 07 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 Q2344+1228 WFPC2 IMAGE WF2 F255W 1 44 M PATTERN 2 ------------------------------------------------------------------------------------------------------------------------------------ 9367( 9) - 02/24/04 07:08 - [ 13] Visit: 08 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: on hold visit requirement removed by PC at the request of PI. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 20 Q2344+1228 ACS/HR ACCUM HRC F250W CR-SPLIT=NO 1 45 M PATTERN 3 20 C ------------------------------------------------------------------------------------------------------------------------------------ 9367( 9) - 02/24/04 07:08 - [ 14] Summary Form for Proposal 9367 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WF2 HRC ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ACS/HRC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 10 PATTERN 3 20 ON HOLD PATTERN 2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F255W F250W ------------------------------------------------------------------------------------------------------------------------------------ Target Names Q0841+1256 Q2343+1232 Q2344+1228 ------------------------------------------------------------------------------------------------------------------------------------