7973(  1) - 04/16/98 14:02  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      7973
                                                       Version: 1
                                                       Check-in Date: 16-Apr-1998
                                                                      14:01:15

1.Proposal Title:
Lyman-Alpha Absorbers and Large Scale Structure
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2. Proposal For  3. Cycle
AR               7
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4. Investigators
                                                                                     Contact?
    PI: Chris Impey                       University of Arizona
   CoI: Cathy Petry                       University of Arizona                         N

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5. Abstract

We propose to use quasar spectra from the HST archive to measure the coherence
length of Lyman-Alpha absorbers as a function of redshift, extending our previous
work on the size and shape of the absorbers. Coincident absorbers along the line-of-
sight to quasar pairs and groups can reveal the geometry of the diffuse but highly
ionized gas on scales of 1 h_100^-1 kpc to 50 h_100^-1 Mpc. We will use automated
line selection and fitting software to identically measure HST spectra and spectra
extracted from SPH supercomputer simulations. A direct cross-check will be made with
line lists from the Quasar Absorption Line Key Project. Lyman-Alpha absorption is an
effective way to measure large scale structure because the gas represents the
majority of the baryons and it traces the underlying dark matter distribution. The
simple physical history of these low density regions of the universe means that HST
quasar spectra can be used to derive the shape and amplitude of the power spectrum
of mass fluctuations. We will also derive estimators of large scale structure that
are sensitive to the variation of cosmological parameters in the simulations.
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                                                7973(  1) - 04/16/98 14:02  - [  2]

            Summary Form for Proposal  7973

  Item                         Used in this proposal
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  Proposal Category            AR
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