The GOODS-N Jansky VLA 10 GHz Pilot Survey: Sizes of Star-forming μJY Radio Sources

• Published in: The Astrophysical journal Vol. 839; no. 1; p. 35
• Main Authors: Murphy, Eric J., Momjian, Emmanuel, Condon, James J., Chary, Ranga-Ram, Dickinson, Mark, Inami, Hanae, Taylor, Andrew R., Weiner, Benjamin J.
• Format: Journal Article
• Language: English
• Published: Philadelphia IOP Publishing 10-04-2017
• Subjects: Astrophysics; Dust emission; Emission measurements; Image detection; Radio frequency; Red shift; Scattering; Spectra; Star formation; Stars & galaxies; Wavelengths
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/aa62fd

Abstract
Our sensitive (
), high-resolution (FWHM
), 10 GHz image covering a single Karl G. Jansky Very Large Array (VLA) primary beam (FWHM
) in the GOODS-N field contains 32 sources with
and optical and/or near-infrared (OIR) counterparts. Most are about as large as the star-forming regions that power them. Their median FWHM major axis is
, with rms scatter
. In units of the effective radius
that encloses half their flux, these radio sizes are
, with rms scatter
. These sizes are smaller than those measured at lower radio frequencies, but agree with dust emission sizes measured at mm/sub-mm wavelengths and extinction-corrected H
α
sizes. We made a low-resolution (
) image with
better brightness sensitivity, in order to detect extended sources and measure matched-resolution spectral indices
. It contains six new sources with
and OIR counterparts. The median redshift of all 38 sources is
. The 19 sources with 1.4 GHz counterparts have a median spectral index of
, with rms scatter
. Including upper limits on
α
for sources not detected at 1.4 GHz flattens the median to
, suggesting that the
μ
Jy radio sources at higher redshifts—and hence those selected at higher rest-frame frequencies—may have flatter spectra. If the non-thermal spectral index is
, the median thermal fraction of sources selected at median rest-frame frequency
is ≳48%.