8673(  5) - 03/08/01 14:13  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      8673
                                                       Version: 5
                                                       Check-in Date: 08-Mar-2001
                                                                      14:12:53

1.Proposal Title:
The Properties of Ly-Alpha Absorbers at Redshifts Between 0.9<z<1.5
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2. Proposal For  3. Cycle
GO               9
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4. Investigators
                                                                                     Contact?
    PI: Buell Jannuzi                     National Optical Astronomy Observatories,
                                          AURA
   CoI: Prof. John Bahcall                Institute for Advanced Study                  N
   CoI: Prof. Jill Bechtold               University of Arizona                         N
   CoI: Prof. Donald Schneider            The Pennsylvania State University             N
   CoI: Dr. Jeff Valenti                  Space Telescope Science Institute             N
   CoI: Prof. David Weinberg              Ohio State University                         N
   CoI: Dr. Ray Weymann                   The Observatories of the Carnegie             N
                                          Institution of Washington

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5. Abstract

We propose to use STIS to obtain new Echelle resolution (10 km/ sec) spectra of
three bright quasars which, when combined with archived and scheduled observations,
will be used to characterize the properties of Ly-Alpha absorbers in the redshift
range 0.9<z<1.6. A well measured sample of approximately 300 Ly-Alpha absorbers,
comparable in size to some of the samples being used successfully to characterize
the properties of absorbers at higher redshifts, is the immediate objective of this
program. The physical characteristics of the final sample will be compared to the
expected properties derived from analysis of the ever increasing number of
simulations of the IGM and Ly-Alpha absorbers at z~1 (e.g., Zhang et al. 1997; Dave
et al. 1998; Riediger et al. 1998; and Theuns et al. 1998). While the simulations
have all managed to reproduce the general observed properties of z~3 absorbers, they
make different predictions for these properties at z~1. These differences arise
because the expansion history of the universe and the rate of structure formation
depend on the values of Omega and Lambda, and both affect the evolution of
statistical properties of the absorbers. More broadly, comparison between the
properties at z~1 and those at higher redshifts can test whether structure in the Ly
-Alpha forest is evolving in the manner predicted by gravitational instability
theories.
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  Observations Description
  ------------------------

     We have selected 3 bright quasars (with known UV fluxes previously determined
     by HST) whose redshifts (z>1.3) place the wavelength region between the quasar
     Ly-Alpha and Ly-Beta emission lines within the coverage of the most efficient
     setting of the E230M Echelle grating (centered at 2707 Angstroms and producing
     a spectrum covering 2303 to 3111 Angstroms). The observations would be made
     using 0.2x0.2'' apt. in ACCUM mode. The resulting spectra will have a spectral
     resolution of 10 km/s. We have used the STIS cycle 9 ETC to determine the
     necessary exposure times to achieve a SNR of 13-15 (the choice of SNR is
     discussed below) at 2400 Angstroms for each observation. For each object the
     SNR redward of 2400 Angstroms will increase until about 2800 Angstroms, where
     it will start to decline to 13 at 3111 Angstroms.

  Real Time Justification
  -----------------------

     None

  Calibration Justification
  -------------------------


  Additional Comments
  -------------------

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TARGET LIST    Fixed Targets
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Tar|   Target   |         Target        |            Target              |Coord   | Radial |             Flux data
No |    Name    |       Description     |           Position             |Eqnx    |  Vel.  |
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1   PG0117+213   GALAXY, QSO, EXT-       RA=01H 20M 17.252S +/- 0.1S,     J2000             F(2400)=4.0e-15
                 MEDIUM, ABSORPTION LINE DEC=21D 33' 46.24" +/- 1.0",                       V = 16.1
                 SYSTEM - EXTRAGALACTIC  PLATE-ID=021K
    Coordinate Source: GSC_SURVEY_PLATE

2   PKS0232-04   GALAXY, QSO, EXT-       RA=02H 35M 7.3S +/- 0.1S, DEC=-  J2000             F(2400)=4.0e-15
                 MEDIUM, ABSORPTION LINE 04D 2' 6.0" +/- 1.0", PLATE-                       V = 16.4
                 SYSTEM - EXTRAGALACTIC  ID=027W
    Coordinate Source: GSC_SURVEY_PLATE

3   PG1630+377   GALAXY, QSO, EXT-       RA=16H 32M 1.101S +/- 0.2",      J2000             F(2400)=5.0e-15
                 MEDIUM, ABSORPTION LINE DEC=37D 37' 49.35" +/- 0.2",                       V = 16.4
                 SYSTEM - EXTRAGALACTIC  PLATE-ID=01RW
    Coordinate Source: GSC_SURVEY_PLATE

                                                8673(  5) - 03/08/01 14:13  - [  4]

Visit: 01
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
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Exposure|   Target  |Instr | Oper. | Aper  |Spectral|Central|             Optional            |Num|  Time |       Special
 Number |    Name   |Config| Mode  |or FOV |Element |Waveln.|            Parameters           |Exp|       |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
110      PG0117+213  STIS/C ACQ     F28X50L MIRROR                                             1   2 S
                     CD             P
   Comments:  Onboard ACQ for 120
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120      PG0117+213  STIS/N ACCUM   0.2X0.2 E230M    2707                                      5   40 M    EXPAND
                     UV-MAM
                     A
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                                                8673(  5) - 03/08/01 14:13  - [  5]

Visit: 02
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
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Exposure|   Target  |Instr | Oper. | Aper  |Spectral|Central|             Optional            |Num|  Time |       Special
 Number |    Name   |Config| Mode  |or FOV |Element |Waveln.|            Parameters           |Exp|       |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
210      PG0117+213  STIS/C ACQ     F28X50L MIRROR                                             1   2 S
                     CD             P
   Comments:  Onboard ACQ for 220
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220      PG0117+213  STIS/N ACCUM   0.2X0.2 E230M    2707                                      5   40 M    EXPAND
                     UV-MAM
                     A
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                                                8673(  5) - 03/08/01 14:13  - [  6]

Visit: 03
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
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Exposure|   Target  |Instr | Oper. | Aper  |Spectral|Central|             Optional            |Num|  Time |       Special
 Number |    Name   |Config| Mode  |or FOV |Element |Waveln.|            Parameters           |Exp|       |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
310      PG0117+213  STIS/C ACQ     F28X50L MIRROR                                             1   2 S
                     CD             P
   Comments:  Onboard ACQ for 320
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320      PG0117+213  STIS/N ACCUM   0.2X0.2 E230M    2707                                      5   40 M    EXPAND
                     UV-MAM
                     A
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                                                8673(  5) - 03/08/01 14:13  - [  7]

Visit: 04
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
------------------------------------------------------------------------------------------------------------------------------------
Exposure|   Target  |Instr | Oper. | Aper  |Spectral|Central|             Optional            |Num|  Time |       Special
 Number |    Name   |Config| Mode  |or FOV |Element |Waveln.|            Parameters           |Exp|       |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
410      PKS0232-04  STIS/C ACQ     F28X50L MIRROR                                             1   2 S
                     CD             P
   Comments:  Onboard ACQ for 420
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420      PKS0232-04  STIS/N ACCUM   0.2X0.2 E230M    2707                                      5   40 M    EXPAND
                     UV-MAM
                     A
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                                                8673(  5) - 03/08/01 14:13  - [  8]

Visit: 05
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
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Exposure|   Target  |Instr | Oper. | Aper  |Spectral|Central|             Optional            |Num|  Time |       Special
 Number |    Name   |Config| Mode  |or FOV |Element |Waveln.|            Parameters           |Exp|       |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
510      PKS0232-04  STIS/C ACQ     F28X50L MIRROR                                             1   2 S
                     CD             P
   Comments:  Onboard ACQ for 520
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520      PKS0232-04  STIS/N ACCUM   0.2X0.2 E230M    2707                                      5   40 M    EXPAND
                     UV-MAM
                     A
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                                                8673(  5) - 03/08/01 14:13  - [  9]

Visit: 06
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
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Exposure|   Target  |Instr | Oper. | Aper  |Spectral|Central|             Optional            |Num|  Time |       Special
 Number |    Name   |Config| Mode  |or FOV |Element |Waveln.|            Parameters           |Exp|       |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
610      PKS0232-04  STIS/C ACQ     F28X50L MIRROR                                             1   2 S
                     CD             P
   Comments:  Onboard ACQ for 620
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620      PKS0232-04  STIS/N ACCUM   0.2X0.2 E230M    2707                                      5   40 M    EXPAND
                     UV-MAM
                     A
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                                                8673(  5) - 03/08/01 14:13  - [ 10]

Visit: 07
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
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Exposure|   Target  |Instr | Oper. | Aper  |Spectral|Central|             Optional            |Num|  Time |       Special
 Number |    Name   |Config| Mode  |or FOV |Element |Waveln.|            Parameters           |Exp|       |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
710      PG1630+377  STIS/C ACQ     F28X50L MIRROR                                             1   2 S
                     CD             P
   Comments:  Onboard ACQ for 720
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720      PG1630+377  STIS/N ACCUM   0.2X0.2 E230M    2707                                      5   40 M    EXPAND
                     UV-MAM
                     A
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                                                8673(  5) - 03/08/01 14:13  - [ 11]

Visit: 08
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
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Exposure|   Target  |Instr | Oper. | Aper  |Spectral|Central|             Optional            |Num|  Time |       Special
 Number |    Name   |Config| Mode  |or FOV |Element |Waveln.|            Parameters           |Exp|       |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
810      PG1630+377  STIS/C ACQ     F28X50L MIRROR                                             1   2 S
                     CD             P
   Comments:  Onboard ACQ for 820
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820      PG1630+377  STIS/N ACCUM   0.2X0.2 E230M    2707                                      5   40 M    EXPAND
                     UV-MAM
                     A
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                                                8673(  5) - 03/08/01 14:13  - [ 12]

Visit: 09
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
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Exposure|   Target  |Instr | Oper. | Aper  |Spectral|Central|             Optional            |Num|  Time |       Special
 Number |    Name   |Config| Mode  |or FOV |Element |Waveln.|            Parameters           |Exp|       |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
910      PG1630+377  STIS/C ACQ     F28X50L MIRROR                                             1   2 S
                     CD             P
   Comments:  Onboard ACQ for 920
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920      PG1630+377  STIS/N ACCUM   0.2X0.2 E230M    2707                                      2   40 M    EXPAND
                     UV-MAM
                     A
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                                                8673(  5) - 03/08/01 14:13  - [ 13]

            Summary Form for Proposal  8673

  Item                         Used in this proposal
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  Apertures                    F28X50LP 0.2X0.2
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  Configurations               STIS/CCD STIS/NUV-MAMA
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  Opmodes                      ACQ ACCUM
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  Proposal Category            GO
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  Special Requirements         EXPAND
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  Spectral Elements            MIRROR E230M
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  Target Names                 PG0117+213 PKS0232-04 PG1630+377
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  Wavelengths                  2707
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