Measuring Young Stars in Space and Time -- II. The Pre-Main-Sequence Stellar Content of N44

TL;DR

This study uses deep HST observations and machine learning to identify and analyze young pre-main-sequence stars in the N44 star-forming complex, revealing clustering structures and their association with known star-forming regions.

Contribution

Introduces a machine learning approach to distinguish PMS stars in extragalactic data and maps their clustering structure in N44.

Findings

Approximately 26,700 PMS candidates identified with high confidence.

Detected 18 significant PMS clustering structures, including a prominent star-forming subcluster.

Most clusters coincide with known H II regions and contain massive young stars.

Abstract

The Hubble Space Telescope (HST) survey Measuring Young Stars in Space and Time (MYSST) entails some of the deepest photometric observations of extragalactic star formation, capturing even the lowest mass stars of the active star-forming complex N44 in the Large Magellanic Cloud. We employ the new MYSST stellar catalog to identify and characterize the content of young pre-main-sequence (PMS) stars across N44 and analyze the PMS clustering structure. To distinguish PMS stars from more evolved line of sight contaminants, a non-trivial task due to several effects that alter photometry, we utilize a machine learning classification approach. This consists of training a support vector machine (SVM) and a random forest (RF) on a carefully selected subset of the MYSST data and categorize all observed stars as PMS or non-PMS. Combining SVM and RF predictions to retrieve the most robust set of PMS sources, we find $\sim26,700$ candidates with a PMS probability above 95% across N44. Employing a clustering approach based on a nearest neighbor surface density estimate, we identify 18 prominent PMS structures at $1$ $\sigma$ significance above the mean density with sub-clusters persisting up to and beyond $3$ $\sigma$ significance. The most active star-forming center, located at the western edge of N44's bubble, is a subcluster with an effective radius of $\sim 5.6$ pc entailing more than 1,100 PMS candidates. Furthermore, we confirm that almost all identified clusters coincide with known H II regions and are close to or harbor massive young O stars or YSOs previously discovered by MUSE and Spitzer observations.