A Significant Population of Candidate New Members of the Rho Ophiuchi Cluster

TL;DR

This study introduces a new method to identify young stars in star-forming regions, applied to Rho Ophiuchi, revealing a threefold increase in known members and highlighting the prevalence of disks among candidates.

Contribution

The paper presents a novel, unbiased technique combining near-infrared imaging and spectral energy distribution fitting to identify low-mass members in star-forming regions.

Findings

Identified 948 candidate members in Rho Ophiuchi.

Increased known young stellar objects by a factor of three.

81% of candidates show infrared excess indicating disks.

Abstract

We present a general method for identifying the pre-main-sequence population of any star-forming region, unbiased with respect to the presence or absence of disks, in contrast to samples selected primarily via their mid-infrared emission from Spitzer surveys. We have applied this technique to a new, deep, wide-field, near-infrared imaging survey of the Rho Ophiuchi cloud core to search for candidate low mass members. In conjunction with published Spitzer IRAC photometry, and least squares fits of model spectra (COND, DUSTY, NextGen, and blackbody) to the observed spectral energy distributions, we have identified 948 candidate cloud members within our 90% completeness limits of J=20.0, H=20.0, and K_S=18.50. This population represents a factor of ~3 increase in the number of known young stellar objects in the Rho Ophiuchi cloud. A large fraction of the candidate cluster members (81% +/- 3%) exhibit infrared excess emission consistent with the presence of disks, thus strengthening the possibility of their being bona fide cloud members. Spectroscopic follow-up will confirm the nature of individual objects, better constrain their parameters, and allow an initial mass function to be derived.