The Gould's Belt Very Large Array Survey I: The Ophiuchus complex

TL;DR

This study provides a detailed, high-resolution radio survey of the Ophiuchus star-forming complex, revealing properties of young stellar objects, their emission mechanisms, and background sources with implications for future observations.

Contribution

It offers the first large-scale, deep radio imaging of the Ophiuchus complex, identifying and characterizing young stellar objects and background sources at high resolution.

Findings

189 sources detected, including 56 young stars and 4 extragalactic objects.

Most young stars show non-thermal gyrosynchrotron emission with high variability.

The radio properties follow a modified Güdel-Benz relation.

Abstract

We present large-scale ($\sim$ 2000 square arcminutes), deep ($\sim$ 20 $\mu$Jy), high-resolution ($\sim$ 1$''$) radio observations of the Ophiuchus star-forming complex obtained with the Karl G.\ Jansky Very Large Array at $\lambda$ = 4 and 6 cm. In total, 189 sources were detected, 56 of them associated with known young stellar sources, and 4 with known extragalactic objects; the other 129 remain unclassified, but most of them are most probably background quasars. The vast majority of the young stars detected at radio wavelengths have spectral types K or M, although we also detect 4 objects of A/F/B types and 2 brown dwarf candidates. At least half of these young stars are non-thermal (gyrosynchrotron) sources, with active coronas characterized by high levels of variability, negative spectral indices, and (in some cases) significant circular polarization. As expected, there is a clear tendency for the fraction of non-thermal sources to increase from the younger (Class 0/I or flat spectrum) to the more evolved (Class III or weak line T Tauri) stars. The young stars detected both in X-rays and at radio wavelengths broadly follow a G\"udel-Benz relation, but with a different normalization than the most radio-active types of stars. Finally, we detect a $\sim$ 70 mJy compact extragalactic source near the center of the Ophiuchus core, which should be used as gain calibrator for any future radio observations of this region.