Detection of Lyman continuum absorption in the BL Lacertae object PKS0735+178.
Abstract
The detection of the Lyman edge in the BL Lac object PKS 0735+178 at the absorption red shift determined by optical measurements leads to a lower limit for the column density of atomic hydrogen, N(H I) not less than 4(17)/sq cm. The Lyman-alpha absorption line appears to have been detected, but only an approximate upper limit can be obtained from the data, of the order of 2(19)/sq cm. This amount of atomic hydrogen is less than that for a line of sight through the disk of a normal spiral galaxy. It is suggested that the absorbing material exists either in the halo of a galaxy or in the tenuous, extended, gaseous disk of a galaxy.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 1981
- DOI:
- 10.1086/159253
- Bibcode:
- 1981ApJ...249...13B
- Keywords:
-
- Bl Lacertae Objects;
- Lyman Spectra;
- Quasars;
- Ultraviolet Absorption;
- Absorption Spectra;
- Gas Density;
- Hydrogen Atoms;
- Iue;
- Red Shift;
- Astronomy