7977(  1) - 04/16/98 14:03  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      7977
                                                       Version: 1
                                                       Check-in Date: 16-Apr-1998
                                                                      14:02:21

1.Proposal Title:
Evolution of the EUV Continuum of Quasars
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2. Proposal For  3. Cycle
AR               7
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4. Investigators
                                                                                     Contact?
    PI: Wei Zheng                         Johns Hopkins University
   CoI: Gerard Kriss                      Johns Hopkins University                      N
   CoI: Arthur Davidsen                   Johns Hopkins University                      N

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5. Abstract

Based on the archival FOS data we constructed a composite quasar spectrum and found
that the continuum between ~ 350 Angstrom\ and 1000 Angstrom\ can be approximated
with a power law of f_Nu \propto nu^-1.8 which may well connect with the soft X-ray
flux level. However, uncertainties were significant at shorter wavelengths as the
number of high-z quasars in the merged spectrum was small. A database of all FOS
spectra, plus some archival STIS spectra, will increase the number of z > 1.5
quasars by nearly an order of magnitude. Accurate measurements of the quasar EUV
continuum will be used to derive the shape of the UV background field in the early
universe. In particular, the redshift dependence of the quasar continuum shape
between z ~ 1.0 and 4.0 will offer a key input to models of the intergalactic
medium. The results will also be used to improve photoionization calculations for
AGN and to search for new EUV emission lines. A set of composite quasar continua at
different redshifts and with different radio properties will be made available to
the astronomy community.
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  Data Distribution

  Media:           ELECTRONIC
  Blocking Factor: 10
  Ship To:         PI_Address
  Ship Via:
  Email:
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                                                7977(  1) - 04/16/98 14:03  - [  2]

            Summary Form for Proposal  7977

  Item                         Used in this proposal
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  Proposal Category            AR
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