Observations of CA II Absorption along the Nearly Parallel Lines of Sight toward 3C 273 and SN 1991T
Abstract
We present high S/N, high-resolution observations of the Ca II absorption toward 3C 273 and SN 1991T in a sensitive metal-line probe of the interstellar and intergalactic gas out to the Virgo Cluster over pathlengths separated by only 1.4^deg^ on the sky. In addition to marked differences in the low-velocity gas, we detect weak Ca II components at V_LSR_ = -87, +215, and +263 km s^-1^ toward SN 1991T that are absent in the 3C 273 spectrum. Given the velocity (V_LSR_ = 1733 km s^-1^) of the SN 1991T host galaxy (NGC 4527), we ascribe these features to the Galactic high-velocity cloud (HVC) phenomenon primarily observed in H I 21 em emission. Although the metal-line counterparts to HVCs have been rarely observed, our ability to detect these weak Ca II components is beyond the sensitivity of almost all previous absorption-line work on extragalactic sources outside the vicinity of the Magellanic Clouds. We discuss the possibility that metal-absorbing HVCs of low column density could be common throughout the Galactic halo and the resulting implications for the halo interpretation of multicomponent QSO absorption-line systems.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1991
- DOI:
- 10.1086/186236
- Bibcode:
- 1991ApJ...383L..41M
- Keywords:
-
- Absorption Spectra;
- Calcium;
- Intergalactic Media;
- Interstellar Matter;
- Milky Way Galaxy;
- Quasars;
- Line Of Sight;
- Line Spectra;
- Magellanic Clouds;
- Radial Velocity;
- Astrophysics;
- GALAXIES: INDIVIDUAL ALPHANUMERIC: 3C 273;
- GALAXIES: INDIVIDUAL NGC NUMBER: NGC 4527;
- GALAXIES: INTERGALACTIC MEDIUM;
- GALAXIES: THE GALAXY;
- INTERSTELLAR: MATTER;
- QUASARS