The spectrum of the QSO PHL 957.
Abstract
Results are presented for observations of PHL 957 which were made with an echelette spectrograph and an image-tube scanner. Strengths and widths are listed for the Ly-alpha, Si IV, and C IV emission lines as well as the C III intercombination line; wavelengths and approximate strengths are given for 203 absorption features in the spectral region from 3145.9 to 5528.2 A. It is shown that the profiles of the strongest emission lines are all different and give rise to uncertainties in determining the emission redshift. The density of absorption lines shortward of the Ly-alpha emission is found to be approximately 10 times greater than at longer wavelengths. Most of these lines are thought to be due to more than 100 clouds with unit Ly-alpha optical depth along the line of sight to the quasar. Two highly probable absorption redshift systems (A and K) are observed which may contain evidence for line locking, probably of He II, Ly-alpha, and Ly-beta on the He II-Lyman continuum. No 1640-A He II emission or N V absorption is detected in system A or K. Absorption system A is shown to be consistent with that expected from a pure H I region and to be a prime candidate for a system arising in an intervening galaxy.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1976
- DOI:
- 10.1086/154460
- Bibcode:
- 1976ApJ...207....1C
- Keywords:
-
- Absorption Spectra;
- Emission Spectra;
- Lyman Spectra;
- Quasars;
- Red Shift;
- H I Regions;
- Lyman Alpha Radiation;
- Lyman Beta Radiation;
- Tables (Data);
- Astrophysics