! Proposal 6426, submission 1 ! PI: Emilio Falco ! Received Thu Feb 8 15:20:31 EST 1996 ! From: falco@jupiter.harvard.edu ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6426,v 6.1 1997/05/14 19:45:21 pepsa Exp $ ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6426,v 6.1 1997/05/14 19:45:21 pepsa Exp $ ! ! Refer to the HST Phase II Proposal Instructions to fill this out ! ! Anything after a "!" is ignored, and may be deleted ! ! All keywords with multiple entries are comma delimited except the ! Visit_Requirements and Special_Requirements keywords which can be ! delimited with carriage returns or semi-colons, but not commas ! ! For help call your Program Coordinator: Lucas ! Phone: 410-338-4716 , E-mail: lucas@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Name of Phase I Proposal: archive-0089.falco.prop ! Date generated: Fri Dec 22 16:27:18 EST 1995 ! Proposal_Information ! Section 4 Title: A Search For Multiple Images of QSOs Seen Through Damped Ly-alpha Absorbers Proposal_Category: GO Scientific_Category: COSMOLOGY Cycle: 6 Investigators PI_name: Emilio Falco PI_Institution: Smithsonian Astrophysical Observatory CoI_Name: Abraham Loeb CoI_Institution: Harvard University Contact: N ! Y or N (designate at most one contact) CoI_Name: Matthias Bartelmann CoI_Institution: Max-Planck Institut fuer Astrophysik Contact: N ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) We propose to obtain high-resolution images of a sample of QSOs with strong damped Ly-alpha absorption in their spectra. The observations would determine whether these QSOs are multiply imaged by gravitational lensing. It is widely believed that damped Ly-alpha absorption occurs in HI disks of spiral galaxies. Gravitational lensing is then inevitable for lines of sight passing close to the centers of these systems. For typical spiral galaxies, the resulting image separation is expected to be in the range 0.1''--0.5'' and can only be detected with HST at optical wavelengths. Because the neutral -hydrogen column density increases on average towards the center of galaxies, strong Ly-alpha absorption provides an efficient ``flag'' for gravitationally lensed QSOs with small image separations. Bartelmann & Loeb (1995, ApJ, in press) have shown that the frequency of multiple images is enhanced by 1--2 orders of magnitude in samples of QSOs with strong damped Ly-alpha absorption (N_ HI>~ 10^21 cm^-2), compared to the overall QSO population. For this proposal, we have selected those QSOs most likely to exhibit gravitational lensing, from the published list of QSOs with damped Ly-alpha absorption. If lensing is found in this QSO sample, it will have important cosmological implications. First, it will confirm the association of damped Ly-alpha systems with galactic potential wells. Second, the magnification bias associated with lensing would make the appearance of damped systems more likely, and therefore affect estimates of the neutral-hydrogen fraction in the Universe (Bartelmann & Loeb 1995). Third, the cosmological history of HI is linked to the process of galaxy formation and evolution (Lanzetta, Wolfe, & Turnshek 1995, ApJ, 440, 435). Finally, the lensing frequency provides a sensitive probe of the cosmological constant. Questions ! Free format text (please update) Observing_Description: We have selected a sample of QSOs with damped Ly-alpha absorption from the literature. Table 1 shows the list of objects that would be most likely to exhibit multiple images. The table shows the QSO brightness, its redshift, the limits of the redshift interval surveyed for damped Ly-alpha absorption, the absorber redshift, its HI column density, and the estimated probability of occurrence of image splitting. The probability P is computed from the redshift interval surveyed for damped Ly-alpha absorption, the quasar brightness, the redshifts of the QSO and the damped Ly-alpha absorption, and the absorber column density, following Bartelmann & Loeb (1995). begintable begincenter QSO V z_QSO z_min z_max z_abs N P t_1 t_2 t_3 PG1329+412 16.30 1.935 0.485 0.632 0.519 6.31 49 5 15 3 2223-052 17.19 1.404 0.416 0.631 0.492 7.94 37 11 38 8 PG2112+059 15.52 0.466 0.111 0.451 0.204 2.51 10 20 7 21 0000-263 18.00 4.111 2.389 4.060 3.395 19.95 9 4 8 18 1209+093 18.50 3.297 2.175 3.254 2.581 25.12 7 7 14 15 PG0935+417 16.20 1.937 1.062 1.550 1.369 2.00 6 5 15 3 0058-292 18.47 3.093 1.778 3.052 2.673 15.85 6 7 14 15 0302-223 16.00 1.400 1.008 1.376 0.969 1.00 3 34 11 37 0347-382 17.30 3.228 2.044 3.186 3.025 6.31 2 12 43 9 129 105 165 129 B0218+35.7 20.00 0.94(?) - - 0.68 >= 10? 100 35 8 23 The proposed sample of QSOs with known damped Ly-alpha absorption, as well as the known lens, B0218+35.7. For a given QSO, V is its apparent V magnitude, z_QSO is its redshift, z_min and z_max are the boundaries of the redshift interval surveyed for damped Ly-alpha absorption, z_abs is the absorber redshift, N its HI column density, P is the estimated probability for the occurrence of a multiple image of the QSO, given these redshifts, the QSO brightness, and the column density of the absorption, and t_i, with i = 1, 2, 3 is the exposure time in minutes that we estimated with FOCSIM for filters F175W, F342W and F480LP, respectively (in combination with neutral- density filters F2ND, F4ND and F6ND wherever necessary). The absorption system in 0302-223 consists of three damped Ly -alpha systems separated by about 5000 km/s. This may indicate that the absorbers are part of a larger system, like a filament, which by its additional mass might increase the chance of lensing. For B0218+35.7, z_QSO is tentatively based on possible absorption lines because its spectrum is that of a BL Lac (Browne et al. 1993); N is a rough estimate, because as of yet there is no measurement. endcenter endtable We propose to observe the sample of QSOs shown in Table 1 with three filters, F175W, F342W and F480LP. An initial estimate of colors of possible lensed images would aid the interpretation, and because the sample is bright, the total time requested remains small, even with three filters, which also help to fill out the orbits efficiently. The initial lensing signature that we will search for is multiple images, most likely pairs, with separations <1''. With this observed sample in hand, we plan to proceed to propose spectroscopic follow-up observations with HST. We estimated imaging exposures for each QSO with FOCSIM. We assumed that the QSO spectrum is a continuum with slope ~ -0.5 (Francis et al. 1991, ApJ 373, 465). Thus, we neglected line absorption, which is further in the blue than the limits of our filters for the redshifts involved, and the flux in emission lines that would only add a small upward correction to our flux estimates. For each object, we calculated the exposure time necessary to reach S/N ~ 30, or a dynamic range for image flux ratios of ~ 3.7 mag. It was necessary to include neutral -density filters F2ND, F4ND and F6ND in various combinations with F175W, F342W and F480LP, to maintain count rates at acceptable levels. We also propose to obtain a low -resolution, objective-prism (FUVOP) spectrum of B0218+357, to determine directly the HI column density of the lens. We propose to orient the dispersion axis so as to simultaneously disperse (but spatially separate) both images of the quasar, to measure their individual UV spectra. We found it necessary to include F275W and F1ND in the optical path, to maintain acceptable count rates; we estimated a total of about 40 minutes would suffice to obtain a spectrum with S/N > 50, again based on the FOCSIM simulations. We trimmed most of our exposure times to fit all of our observations in the 10 orbits that we were allotted. In particular, we eliminated several of the F175W exposures where, as pointed out by the TAC, the QSO light would be absent due to the Ly-alpha absorption. Although it would still be interesting to try to detect any lensing galaxies, we opted for eliminating the F175W exposures for sample QSOs with Ly-alpha absorption at redshifts > 1. The TAC also pointed out that 0000-263 and 0347-382 were observed previously with HST. However, the archived observations are only pre-refurbishment, were between 100 and 350 seconds long, and were conducted at best under coarse lock. Therefore, the extant data are not very useful. Because 0347-382 had the lowest lensing probability and we were short on orbits, we decided to eliminate it from our sample. We decided however to keep 0000-263, to obtain a much improved image with FOC. Real_Time_Justification: Calibration_Justification: ! Move text from Real_Time_Justification Additional_Comments: We plan to conduct ground-based follow-up observations of interesting candidates wherever possible, to confirm the occurrence of lensing. SAO reference number: P3554-9-95 Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: PG1329+412 Alternate_Names: Description: GALAXY, QSO, Lyman Alpha Cloud, Gravitational Lens Position: RA=13H 31M 41.13S +/- 0.03S, DEC=+41D 01' 58.0" +/- 0.5" Equinox: J2000 RV_or_Z: Z=1.930 RA_PM: 0.0 ! Units are seconds of time per year Dec_PM: 0.0 ! Units are seconds of arc per year Epoch: Annual_Parallax: 0.0 Flux: V=16.3 +/- 0.1 ! Include at least V and B-V Comments: Target_Number: 2 Target_Name: 2223-052 Alternate_Names: 3C446 Description: GALAXY, QSO, Lyman Alpha Cloud, Gravitational Lens Position: RA=22H 25M 47.321S +/- 0.03S, DEC=-04D 57' 01.4" +/- 0.5" Equinox: J2000 RV_or_Z: Z=1.404 RA_PM: 0.0 ! Units are seconds of time per year Dec_PM: 0.0 ! Units are seconds of arc per year Epoch: Annual_Parallax: 0.0 Flux: V=17.2 +/- 0.1 ! Include at least V and B-V Comments: Target_Number: 3 Target_Name: PG2112+059 Alternate_Names: Description: GALAXY, QSO, Lyman Alpha Cloud, Gravitational Lens Position: RA=21H 14M 52.51S +/- 0.03S, DEC=+06D 07' 42.5" +/- 0.5" Equinox: J2000 RV_or_Z: Z=0.466 RA_PM: 0.0 ! Units are seconds of time per year Dec_PM: 0.0 ! Units are seconds of arc per year Epoch: Annual_Parallax: 0.0 Flux: V=15.5 +/- 0.1 ! Include at least V and B-V Comments: Target_Number: 4 Target_Name: 0000-263 Alternate_Names: Description: GALAXY, QSO, Lyman Alpha Cloud, Gravitational Lens Position: RA=00H 03M 22.87S +/- 0.03S, DEC=-26D 03' 17.0" +/- 0.5" Equinox: J2000 RV_or_Z: Z=4.098 RA_PM: 0.0 ! Units are seconds of time per year Dec_PM: 0.0 ! Units are seconds of arc per year Epoch: Annual_Parallax: 0.0 Flux: V=18.0 +/- 0.1 ! Include at least V and B-V Comments: Target_Number: 5 Target_Name: 1209+093 Alternate_Names: Description: GALAXY, QSO, Lyman Alpha Cloud, Gravitational Lens Position: RA=12H 11M 34.90S +/- 0.03S, DEC=+09D 02' 22.8" +/- 0.5" Equinox: J2000 RV_or_Z: Z=3.297 RA_PM: 0.0 ! Units are seconds of time per year Dec_PM: 0.0 ! Units are seconds of arc per year Epoch: Annual_Parallax: 0.0 Flux: V=18.5 +/- 0.1 ! Include at least V and B-V Comments: Target_Number: 6 Target_Name: PG0935+417 Alternate_Names: Description: GALAXY, QSO, Lyman Alpha Cloud, Gravitational Lens Position: RA=09H 38M 57.02S +/- 0.03S, DEC=+41D 28' 21.3" +/- 0.5" Equinox: J2000 RV_or_Z: Z=1.937 RA_PM: 0.0 ! Units are seconds of time per year Dec_PM: 0.0 ! Units are seconds of arc per year Epoch: Annual_Parallax: 0.0 Flux: V=16.2 +/- 0.1 ! Include at least V and B-V Comments: Target_Number: 7 Target_Name: 0058-292 Alternate_Names: Description: GALAXY, QSO, Lyman Alpha Cloud, Gravitational Lens Position: RA=01H 01M 04.57S +/- 0.03S, DEC=-28D 58' 01.1" +/- 0.5" Equinox: J2000 RV_or_Z: Z=3.093 RA_PM: 0.0 ! Units are seconds of time per year Dec_PM: 0.0 ! Units are seconds of arc per year Epoch: Annual_Parallax: 0.0 Flux: V=18.5 +/- 0.1 ! Include at least V and B-V Comments: Target_Number: 8 Target_Name: 0302-223 Alternate_Names: 1E0302-223 Description: GALAXY, QSO, Lyman Alpha Cloud, Gravitational Lens Position: RA=03H 04M 49.82S +/- 0.03S, DEC=-22D 11' 52.0" +/- 0.5" Equinox: J2000 RV_or_Z: Z=1.400 RA_PM: 0.0 ! Units are seconds of time per year Dec_PM: 0.0 ! Units are seconds of arc per year Epoch: Annual_Parallax: 0.0 Flux: V=16.0 +/- 0.1 ! Include at least V and B-V Comments: Target_Number: 9 Target_Name: B0218+35.7 Alternate_Names: MGJ0221+3555 Description: GALAXY, QSO, Lyman Alpha Cloud, Gravitational Lens Position: RA=02H 21M 05.44S +/- 0.03S, DEC=+35D 56' 13.9" +/- 0.5" Equinox: J2000 RV_or_Z: Z=0.940 RA_PM: 0.0 ! Units are seconds of time per year Dec_PM: 0.0 ! Units are seconds of arc per year Epoch: Annual_Parallax: 0.0 Flux: V=20.0 +/- 0.1 ! Include at least V and B-V Comments: Solar_System_Targets Generic_Targets Scan_Data ! Appendix B Visits ! Section 6 Visit_Number: 01 Visit_Requirements: ! Section 7.1 On_Hold_Comments: Visit_Comments: Exposure_Number: 101 ! Section 6.5 Target_Name: PG1329+412 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F4ND, F1ND, F342W Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 10M Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 102 ! Section 6.5 Target_Name: PG1329+412 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F2ND, F1ND, F480LP Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 568S Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 103 ! Section 6.5 Target_Name: PG1329+412 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F2ND, F1ND, F175W Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 14M Special_Requirements: ! Section 7.2 END ORBIT MAX DUR 15M MIN DUR 13M Comments: Visit_Number: 02 Visit_Requirements: ! Section 7.1 On_Hold_Comments: Visit_Comments: Exposure_Number: 201 ! Section 6.5 Target_Name: 2223-052 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F2ND, F175W Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 970S Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 202 ! Section 6.5 Target_Name: 2223-052 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F2ND, F480LP Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 6M Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 203 ! Section 6.5 Target_Name: 2223-052 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F4ND, F342W Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 440S Special_Requirements: ! Section 7.2 Comments: Visit_Number: 03 Visit_Requirements: ! Section 7.1 On_Hold_Comments: Visit_Comments: Exposure_Number: 301 ! Section 6.5 Target_Name: PG2112+059 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F6ND, F342W Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 10M Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 302 ! Section 6.5 Target_Name: PG2112+059 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F4ND, F175W Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 10M Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 303 ! Section 6.5 Target_Name: PG2112+059 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F4ND, F480LP Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 548S Special_Requirements: ! Section 7.2 Comments: Visit_Number: 04 Visit_Requirements: ! Section 7.1 On_Hold_Comments: Visit_Comments: Exposure_Number: 401 ! Section 6.5 Target_Name: 0000-263 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F1ND, F480LP Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 20M Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 402 ! Section 6.5 Target_Name: 0000-263 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F4ND, F342W Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 950S Special_Requirements: ! Section 7.2 Comments: Visit_Number: 05 Visit_Requirements: ! Section 7.1 On_Hold_Comments: Visit_Comments: Exposure_Number: 501 ! Section 6.5 Target_Name: 1209+093 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F2ND, F1ND, F342W Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 1060S Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 502 ! Section 6.5 Target_Name: 1209+093 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F1ND, F480LP Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 1080S Special_Requirements: ! Section 7.2 Comments: Visit_Number: 06 Visit_Requirements: ! Section 7.1 On_Hold_Comments: Visit_Comments: Exposure_Number: 601 ! Section 6.5 Target_Name: PG0935+417 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F2ND, F1ND, F480LP Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 20M Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 602 ! Section 6.5 Target_Name: PG0935+417 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F4ND, F1ND, F342W Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 1060S Special_Requirements: ! Section 7.2 Comments: Visit_Number: 07 Visit_Requirements: ! Section 7.1 On_Hold_Comments: Visit_Comments: Exposure_Number: 701 ! Section 6.5 Target_Name: 0058-292 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F2ND, F1ND, F342W Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 20M Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 702 ! Section 6.5 Target_Name: 0058-292 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F1ND, F480LP Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 965S Special_Requirements: ! Section 7.2 Comments: Visit_Number: 08 Visit_Requirements: ! Section 7.1 On_Hold_Comments: Visit_Comments: Exposure_Number: 801 ! Section 6.5 Target_Name: 0302-223 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F4ND, F480LP Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 1180S Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 802 ! Section 6.5 Target_Name: 0302-223 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F6ND, F342W Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 965S Special_Requirements: ! Section 7.2 Comments: Visit_Number: 09 Visit_Requirements: ORIENT 301D TO 81D ! Section 7.1 On_Hold_Comments: Visit_Comments: Exposure_Number: 901 ! Section 6.5 Target_Name: B0218+35.7 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F2ND, F342W Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 900S Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 902 ! Section 6.5 Target_Name: B0218+35.7 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F175W Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 1045S Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 903 ! Section 6.5 Target_Name: B0218+35.7 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F130LP, PRISM1 Wavelength: 2750 Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 2641S Special_Requirements: ! Section 7.2 POS TARG 0, -3.7 Comments: Visit_Number: 56 Visit_Requirements: ! Section 7.1 On_Hold_Comments: Visit_Comments: Auto-repeat of Visit 06 after previous failure. Exposure_Number: 651 ! Section 6.5 Target_Name: PG0935+417 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F2ND, F1ND, F480LP Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 20M Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 652 ! Section 6.5 Target_Name: PG0935+417 Config: FOC/96 Opmode: IMAGE Aperture: 512x512 Sp_Element: F4ND, F1ND, F342W Wavelength: Optional_Parameters: PIXEL=25x25 Number_of_Iterations: 1 Time_Per_Exposure: 1060S Special_Requirements: ! Section 7.2 Comments: Data_Distribution ! 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