Physics
Scientific paper
Jul 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995hst..prop.5815t&link_type=abstract
HST Proposal ID #5815
Physics
Hst Proposal Id #5815 Quasars
Scientific paper
-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}.
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