Radio and Millimeter Continuum Surveys and their Astrophysical Implications

TL;DR

This paper reviews radio and millimeter sky surveys, discussing source populations, evolutionary models, rare sources, large-scale structure studies, and future telescope prospects, highlighting recent findings and unresolved issues in the field.

Contribution

It provides a comprehensive overview of radio source populations, compares local luminosity functions, and discusses the implications of recent surveys and models for astrophysics.

Findings

Exponential decline of source densities at high redshift.

Good match of evolutionary models with observed source counts.

Identification of rare source classes like GHz Peak Spectrum and ADAF/ADIOS.

Abstract

We review the statistical properties of the main populations of radio sources, as emerging from radio and millimeter sky surveys. Recent determinations of local luminosity functions are presented and compared with earlier estimates still in widespread use. A number of unresolved issues are discussed. These include: the (possibly luminosity-dependent) decline of source space densities at high redshifts; the possible dichotomies between evolutionary properties of low- versus high-luminosity and of flat- versus steep-spectrum AGN-powered radio sources; and the nature of sources accounting for the upturn of source counts at sub-mJy levels. It is shown that straightforward extrapolations of evolutionary models, accounting for both the far-IR counts and redshift distributions of star-forming galaxies, match the radio source counts at flux-density levels of tens of microJy remarkably well. We consider the statistical properties of rare but physically very interesting classes of sources, such as GHz Peak Spectrum and ADAF/ADIOS sources, and radio afterglows of gamma-ray bursts. We also discuss the exploitation of large-area radio surveys to investigate large scale structure through studies of clustering and the Integrated Sachs-Wolfe effect. Finally we briefly describe the potential of the new and forthcoming generations of radio telescopes. A compendium of source counts at different frequencies is given in an appendix.