The $\rho$ Oph region revisited with Gaia EDR3

TL;DR

This study uses Gaia EDR3 data to identify and analyze young stellar objects in the $ ho$ Oph region, revealing two distinct populations with different ages and motions, and discovering new candidate members.

Contribution

It provides the most complete catalog of YSOs in $ ho$ Oph, including new candidates, and uncovers two populations with different ages and kinematics using Gaia data.

Findings

191 new YSO candidates identified

Two distinct populations with different proper motions

Dispersed older population possibly from Upper Sco

Abstract

Context. Young and embedded stellar populations are important probes of the star formation process. Paradoxically, we have a better census of nearby embedded young populations than the slightly more evolved optically visible young populations. The high accuracy measurements and all-sky coverage of Gaia data are about to change this situation. Aims. This work aims to construct the most complete sample to date of YSOs in the $\rho$ Oph region. Methods. We compile a catalog of 1114 Ophiuchus YSOs from the literature and crossmatch it with the Gaia EDR3, Gaia-ESO and APOGEE-2 surveys. We apply a multivariate classification algorithm to this catalog to identify new, co-moving population candidates. Results. We find 191 new high-fidelity YSO candidates in the Gaia EDR3 catalog belonging to the $\rho$ Oph region. The new sources appear to be mainly Class III M-stars and substellar objects and are less extincted than the known members. We find 28 previously unknown sources with disks. The analysis of the proper motion distribution of the entire sample reveals a well-defined bimodality, implying two distinct populations sharing a similar 3D volume. The first population comprises young stars' clusters around the $\rho$ Ophiuchi star and the main Ophiuchus clouds (L1688, L1689, L1709). In contrast, the second population is older ($\sim$ 10 Myr), dispersed, has a distinct proper motion, and is possibly from the Upper Sco group. The two populations are moving away from each other at about 4.1 km/s, and will no longer overlap in about 4 Myr. Finally, we flag 17 sources in the literature as impostors, which are sources that exhibit large deviations from the average distance and proper motion properties of the $\rho$ Oph population. Our results show the importance of accurate 3D space and motion information for improved stellar population analysis. (Abridged)