A new method to unveil embedded stellar clusters

TL;DR

This paper introduces a new infrared-based statistical method to identify and analyze embedded stellar clusters within dark molecular clouds, effectively distinguishing young stars from background stars and correcting for extinction effects.

Contribution

The novel method combines star counting with luminosity function analysis and extinction correction, improving cluster detection in embedded regions compared to previous techniques.

Findings

Successfully applied to Orion A and B complexes

Results agree with deep Spitzer and Chandra data

Reveals spatial distribution of unobscured clusters

Abstract

In this paper we present a novel method to identify and characterize stellar clusters deeply embedded in a dark molecular cloud. The method is based on measuring stellar surface density in wide-field infrared images using star counting techniques. It takes advantage of the differing $H$-band luminosity functions (HLFs) of field stars and young stellar populations and is able to statistically associate each star in an image as a member of either the background stellar population or a young stellar population projected on or near the cloud. Moreover, the technique corrects for the effects of differential extinction toward each individual star. We have tested this method against simulations as well as observations. In particular, we have applied the method to 2MASS point sources observed in the Orion A and B complexes, and the results obtained compare very well with those obtained from deep Spitzer and Chandra observations where presence of infrared excess or X-ray emission directly determines membership status for every star. Additionally, our method also identifies unobscured clusters and a low resolution version of the Orion stellar surface density map shows clearly the relatively unobscured and diffuse OB 1a and 1b sub-groups and provides useful insights on their spatial distribution.