Embedded Young Stellar Object Candidates in the Active Star Forming Complex W51: Mass Function and Spatial Distribution

TL;DR

This study identifies and analyzes 737 candidate Young Stellar Objects in the W51 star-forming complex, revealing mass segregation and variations in the stellar mass function influenced by local molecular cloud conditions.

Contribution

It provides a detailed catalog of YSOs in W51, including their spatial distribution and mass function, highlighting environmental effects on star formation.

Findings

Mass segregation of the most massive YSOs in W51.

Variation in the YSO mass function between regions.

Identification of 69 high-mass embedded YSOs.

Abstract

We present 737 candidate Young Stellar Objects (YSOs) near the W51 Giant Molecular Cloud (GMC) over an area of 1.25 deg x 1.00 deg selected from Spitzer Space Telescope data. We use spectral energy distribution (SED) fits to identify YSOs and distinguish them from main-sequence or red giant stars, asymptotic giant branch stars, and background galaxies. Based on extinction of each YSO, we separate a total of 437 YSOs associated with the W51 region from the possible foreground sources. We identify 69 highly embedded Stage 0/I candidate YSOs in our field with masses > 5 Msun (corresponding to mid-to early-B main-sequence spectral types) 46 of which are located in the central active star forming regions of W51A and W51B. From the YSOs associated with W51, we find evidence for mass segregation showing that the most massive YSOs are concentrated on the W51 HII region complex. We find a variation in the spatial distribution of the mass function (MF) of YSOs in the mass range between 5 Msun and 18 Msun. The derived slopes of the MF are -1.26 and -2.36 in the active star-forming region and the outer region, respectively. The variation of the MF for YSOs embedded in the molecular cloud implies that the distribution of stellar masses in clusters depends on the local conditions in the parent molecular cloud.