5821(  0) - 07/18/95 18:06  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      5821
                                                       Version: **********
                                                       Check-in Date: **********

1.Proposal Title:
Cosmic Evolution of Lyman Alpha Clouds
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2. Scientific Category   3. Proposal For  4. Cycle
Quasars                     AR               5
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5. Investigators
                                                                                     Contact?
    PI: Wei Zheng                         Johns Hopkins University
   CoI: Arthur F. Davidsen                Johns Hopkins University                      N
   CoI: Ji--Cheng Liu                     Johns Hopkins University                      N

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6. Abstract

Preliminary HST results find that the number distribution of the Ly-alpha\ forest
clouds for z < 1 is considerably different from that in high--z QSOs. The properties
of Ly- alpha\ forest clouds may evolve with epoch, and the most significant changes
take place probably at 1 < z < 2. The high --resolution FOS archive will provide a
homogeneous database which is ten times larger than that used in previous work and
enables the study to extend from z ~ 1 to z ~ 2.  By studying the distribution of
forest clouds along the line of sight, the distribution with clouds' column density,
and the extent of the proximity effect for z < 2, we hope to determine the
fundamental distribution parameters (Gamma and Beta) and the intensity of the UV
background radiation with accuracy comparable to that in optical studies.  We will
be able to picture the evolution of intergalactic medium, and possibly pinpoint the
most probable cause for such evolution. These data will be combined with the optical
spectra to produce a complete track of properties of the intergalactic medium from
the present epoch to z ~ 4.5.
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  Observations Description
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  Real Time Justification
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  Calibration Justification
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  Additional Comments
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                                                5821(  0) - 07/18/95 18:06  - [  2]

  Data Distribution

  Media:           8MM
  Blocking Factor: 10
  Ship To:         PI_Address
  Ship Via:        UPS
  Email:                                                              ,
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                                                5821(  0) - 07/18/95 18:06  - [  3]

            Summary Form for Proposal  5821

  Item                         Used in this proposal
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  Proposal Category            AR
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  Scientific Category          Quasars
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