The Deep SWIRE Field I. 20cm Continuum Radio Observations: A Crowded Sky

TL;DR

This paper reports the deepest 20cm radio survey in the SWIRE field, revealing high source density and larger-than-expected source sizes, with implications for confusion limits at microJy flux levels.

Contribution

It provides the deepest radio source catalog to date in the SWIRE field, with detailed analysis of source sizes and density at very low flux levels.

Findings

Median source sizes > 1 arcsecond at low flux densities

Approximately 6 sources per square arcminute down to 15 microJy

Potential confusion limit near 1 microJy flux density

Abstract

We present results from deep radio observations taken with the VLA at a center frequency of 1400 MHz cover a region of the SWIRE Spitzer Legacy survey, centered at 10 46 00, 59 01 00 (J2000). The reduction and cataloging of the radio sources are described. The survey presented is the deepest so far in terms of the radio source density on the sky. Perhaps surprisingly, the sources down to the bottom of the catalog have median angular sizes greater than 1 arcsecond, like their cousins 10-100 times stronger. If the log N - log S normalization remains constant at the lowest flux densities, there are about 6 sources per square arcminute down to 15 microJy at 20cm. Given the finite source sizes this implies we may reach the natural confusion limit near 1 microJy.