Physical conditions in the absorbing regions associated with the QSO 1756+237

Details Physical conditions in the absorbing regions associated with the QSO 1756+237 Physical conditions in the absorbing regions associated with the QSO 1756+237

Jun 1979

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1979apj...230..330t&link_type=abstract

Astrophysical Journal, Part 1, vol. 230, June 1, 1979, p. 330-339.

Astronomy and Astrophysics

Astrophysics

24

Absorption Spectroscopy, Astronomical Spectroscopy, Quasars, Continuous Spectra, Fine Structure, Line Spectra, Photoionization, Plasma Clouds

Scientific paper

Observations of the QSO 1756+237 indicate that four separate absorption-line systems are present; two of which show strong, low-ionization lines, including C II at 1334.5 A. The lack of detectable C II at 1335.7-A fine-structure absorption makes it possible to set limits of less than 3 per cu cm on the maximum density of nucleons in the gas in either absorbing region. Consideration of the effects of photoionization by the QSO dictates that the minimum distance between the absorbing regions and the QSO is about 750 kpc. The energy required for ejection episodes which could place absorbing clouds at such distances is estimated to be of the order of 10 to the 64th ergs. In addition, reasonable assumptions concerning the spectral energy distribution for the continuum source of the QSO lead to tight constraints on computed photoionization models. These results point to two independent conclusions: (1) it is unlikely that the absorbing clouds were ejected by the QSO, and (2) photoionization by the QSO probably is not the dominant ionization mechanism. The absorbing gas is more likely ionized by thermal radiation from hot stars than by the continuum of the quasar.

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