6611( 6) - 06/26/96 06:59 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6611 Version: 6 Check-in Date: 26-Jun-1996 06:57:12 1.Proposal Title: A Group or Cluster of Ly-alpha-Absorbing Galaxies at z ~ 0.26 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle QSO Absorption Lines GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: KENNETH LANZETTA SUNY CoI: John K. Webb University of New South Wales N CoI: Xavier Barcons Instituto de Fi sica de Cantabria N ------------------------------------------------------------------------------------ 6. Abstract We have recently identified seven galaxies of a group or cluster that appears to be associated with a pair of Ly-alpha\ absorption features at z ~ 0.26 toward the QSO 3CR 323.1. Here we propose to measure the covering factor of the absorbing material by obtaining a high-resolution spectrum of the Ly-alpha\ absorption lines using the GHRS. The outcome of the proposed observation will have important implications for establishing the nature and origin of gas around galaxies: Either galaxies in groups or clusters can possess extended gaseous disks or halos, or galaxy clusters can contain cool, smoothly distributed gas. We note that 3CR 323.1 is a particularly bright QSO and that the Ly-alpha\ absorption profile occurs at the peak of Ly-alpha\ emission, where the observed flux is f_Lambda = 4 * 10^-14 erg s^-1 cm^-2 AA^-1. This makes the acquisition of a GHRS spectrum extremely practical, hence 3CR 323.1 provides a unique opportunity to study the relationship between a Ly-alpha\ absorption line and a group or cluster of galaxies. ------------------------------------------------------------------------------------ 6611( 6) - 06/26/96 06:59 - [ 2] Observations Description ------------------------ We will use the GHRS with G160M and LSA to obtain a spectrum of spectral resolution FWHM ~ 14 kms\\ and signal-to-noise ratio S/N ~ 12 per diode with a total exposure time of 10,800 s. To estimate the required exposure time, we determined the actual ultraviolet flux from the HST spectrum and used the sensitivity and dark count values quoted in the Hubble Space Telescope Goddard High Resolution Spectrograph (GHRS) Instrument Handbook, Version 6.0. At the wavelength Lambda = 1537 Angstrom\\ of interest, the observed flux is f_Lambda = 4 * 10^14 erg s^-1 cm^-2 AA^-1. Interpolating from Table 8--2 yields a count rate of 0.0189 count s^-1. ing for a dark rate of 0.008 count s^-1, the Case 2 equation on page 34 yields a signal-to-noise ratio of 12 per diode in an exposure time of 10,800 s. Our simulations have shown that this is sufficient to meet our scientific goals. Allowing for acquisition and overhead, we require five orbits to reach the required exposure time. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: Department of Earth and Space Sciences*State University of New York at Stony Brook*Stony Brook, NY 11794- 2100 Ship Via: UPS Email: lanzetta@sbastc.ess.sunysb.edu , ------------------------------------------------------------------------------------ 6611( 6) - 06/26/96 06:59 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 3CR323.1 GALAXY,QSO RA = 15H 47M 43.53S +/- 0.07S, 2000 Z = V = 16.69+/-0.3 DEC = +20D 52' 17.5" +/- 0.1", 0.264 B-V = 0.11+/-0.1 PLATE-ID=0280 U-B = -0.85+/-0.1 6611( 6) - 06/26/96 06:59 - [ 4] Visit: 01 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 3CR323.1 FOS/BL ACQ/BIN 4.3 MIRROR 1 20.0 S ONBOARD ACQ FOR 2 ARY ------------------------------------------------------------------------------------------------------------------------------------ 2 3CR323.1 HRS ACCUM 2.0 G160M 1537.0 STEP-PATT=DEF,FP-SPLIT=NO, 14 299.2 S COMB=FOUR ------------------------------------------------------------------------------------------------------------------------------------ 3 3CR323.1 HRS ACCUM 2.0 G160M 1537.0 STEP-PATT=DEF,FP-SPLIT=NO, 14 299.2 S COMB=FOUR ------------------------------------------------------------------------------------------------------------------------------------ 4 3CR323.1 HRS ACCUM 2.0 G160M 1537.0 STEP-PATT=DEF,FP-SPLIT=NO, 14 299.2 S COMB=FOUR ------------------------------------------------------------------------------------------------------------------------------------ 6611( 6) - 06/26/96 06:59 - [ 5] Summary Form for Proposal 6611 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters STEP-PATT=DEF FP-SPLIT=NO COMB=FOUR ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category QSO Absorption Lines ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G160M ------------------------------------------------------------------------------------------------------------------------------------ Target Names 3CR323.1 ------------------------------------------------------------------------------------------------------------------------------------