Theoretical quasar emission-line ratios. VIII. Implications of free-free emission for QSO clouds.
Abstract
A range of simple theoretical models is presented which explores the effects of high densities in the broad-line clouds on near-IR free-free emission. These calculations demonstrate in a qualitiative way that large near-IR fluxes can result from high densities without compromising the observed hydrogen line spectrum. It is suggested that high density in the emission-line region provides a plausible explanation of several features seen in the spectra of QSOs and active galaxies, including (1) the 3-micron bump and/or the near-IR spectral break seen in many QSOs, (2) the low observed Pa-alpha broad-line fluxes seen in some objects, and (3) the highly depressed Br-gamma broad-line fluxes seen in active galaxies. It is also found that free-free emission in such clouds can be an important coolant.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 1985
- DOI:
- 10.1086/163384
- Bibcode:
- 1985ApJ...295..394P
- Keywords:
-
- Astronomical Spectroscopy;
- Emission Spectra;
- Molecular Clouds;
- Quasars;
- Active Galaxies;
- Astronomical Models;
- Cooling;
- Gas Density;
- H Lines;
- Line Spectra;
- Astrophysics