5815(  0) - 07/18/95 18:04  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      5815
                                                       Version: **********
                                                       Check-in Date: **********

1.Proposal Title:
An HST-FOS Archival Investigation of the Origin of the NV Emission in QSO Spectra
------------------------------------------------------------------------------------
2. Scientific Category   3. Proposal For  4. Cycle
Quasars                     AR               5
------------------------------------------------------------------------------------
5. Investigators
                                                                                     Contact?
    PI: David Turnshek                    Dept. of Physics & Astronomy,   \
                                          University of Pittsburgh

------------------------------------------------------------------------------------
6. Abstract

-0.1 truein The nature of the NV emission lines observed in QSO spectra is unclear.
In most models the bulk of the NV emission is assumed to be created by collisional
excitation. However, observational constraints derived from the study of Broad
Absorption Line (BAL) QSOs are consistent with the bulk of the NV emission being
created by resonance line scattering. In the resonance line scattering model a BAL
region covering factor averaging ~ 0.1 is large enough to create observable NV
emission in both BAL QSOs and non-BAL QSOs.  Enhanced NV emission is produced by
this process because the NVLambdaLambda1238,1242 BALs scatter inner LyAlpha emission
photons in addition to the continuum photons.  We propose an HST-FOS archival study
of > 100 QSO spectra which will enable us to distinguish between these two
possibilities based on the measurement of specific emission lines.  If collisional
excitation in a photoionized gas is the dominant mechanism for the production of NV,
then the NV emission-line strength should be correlated with the HeII and probably
the CIV emission-line strengths since these lines are formed in the same region.
Alternatively, if resonance line scattering is the dominant mechanism for the
production of NV, then the NV emission-line strength should depend on the strength
of the (inner) LyAlpha broad emission line, the maximum outflow velocity of the BAL
region gas (which we assume is correlated with the broad emission line FWHM to first
order), and the BAL region covering factor (which we assume is ~ 0.1 to first
order).
------------------------------------------------------------------------------------
  Observations Description
  ------------------------


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


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


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

------------------------------------------------------------------------------------

                                                5815(  0) - 07/18/95 18:04  - [  2]

  Data Distribution

  Media:           8MM
  Blocking Factor: 10
  Ship To:         PI_Address
  Ship Via:        UPS
  Email:                                                              ,
------------------------------------------------------------------------------------

                                                5815(  0) - 07/18/95 18:04  - [  3]

            Summary Form for Proposal  5815

  Item                         Used in this proposal
------------------------------------------------------------------------------------------------------------------------------------
  Proposal Category            AR
------------------------------------------------------------------------------------------------------------------------------------
  Scientific Category          Quasars
------------------------------------------------------------------------------------------------------------------------------------