7978(  1) - 04/16/98 14:04  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      7978
                                                       Version: 1
                                                       Check-in Date: 16-Apr-1998
                                                                      14:02:32

1.Proposal Title:
Extremely Faint Galaxies in STIS Slitless Grism Spectra
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2. Proposal For  3. Cycle
AR               7
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4. Investigators
                                                                                     Contact?
    PI: Kenneth M. Lanzetta               State University of New York at Stony
                                          Brook
   CoI: Sebastian Pascarelle              State University of New York at Stony         N
                                          Brook
   CoI: Hsiao-Wen Chen                    State University of New York at Stony         N
                                          Brook

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5. Abstract

The STIS slitless grism survey can verify (or otherwise) the broad-band photometric
redshift techniques at redshifts z > 5 by providing the first spectroscopically
confirmed examples of very high redshift galaxies. Here we propose to determine
redshifts of extremely faint galaxies in STIS grism spectra by means of broad-band
redshift techniques and to verify these redshifts by identifying narrow-band
emission, absorption, and continuum features in the same spectra. The deep STIS
slitless grism images can detect galaxies as faint as AB(5835) ~ 28.5, albeit at a
signal-to-noise ratio of only S/N ~ 0.3 per pixel. But integrated over a bandpass
of, say, 250 pixels or 1250 Angstrom, a signal-to-noise ratio of S/N = 0.3 per pixel
corresponds to a signal-to-noise ratio of S/N ~ 5 per bandpass element, which is
sufficient to derive ``photometric'' redshifts. We will apply a new optimal
extraction method based on the exact two-dimensional spatial profiles of the spectra
on the grism image, which are obtained from the direct image that accompanies every
grism image. We expect more than 20 galaxies per field at redshifts z > 4 and more
than three galaxies per field at redshifts z > 5.
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  Data Distribution

  Media:           ELECTRONIC
  Blocking Factor: 10
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                                                7978(  1) - 04/16/98 14:04  - [  2]

            Summary Form for Proposal  7978

  Item                         Used in this proposal
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  Proposal Category            AR
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