Cosmology from angular size counts of extragalactic radio sources.
Abstract
Cosmological implications of observed angular sizes of extragalactic radio sources are investigated using the log N-log theta relation (N = number of sources with angular size greater than theta) and the median angular size vs flux density relation derived from several surveys. A technique is outlined for estimating the expected relations for a uniform distribution of sources in space. It is found that for angular sizes of at least 100 arcsec, the slope of the N(theta) relation is almost independent of cosmological model and source-size distribution but depends strongly on the radio luminosity function. It is shown that the angular-size data give independent evidence for evolution in source properties with epoch. Data for simple evolutionary schemes are fitted to the steady-state and Einstein-de Sitter cosmologies. It is found that the steady-state model cannot easily explain the data, while the Einstein-de Sitter model gives reasonable fits.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- September 1975
- DOI:
- 10.1093/mnras/172.3.513
- Bibcode:
- 1975MNRAS.172..513K
- Keywords:
-
- Astronomical Models;
- Cosmology;
- Extragalactic Radio Sources;
- Quasars;
- Size Determination;
- Angular Distribution;
- Galactic Evolution;
- Luminous Intensity;
- Radio Galaxies;
- Stellar Luminosity;
- Astrophysics