Star Formation & Young Stellar Content in the W3 GMC

TL;DR

This study provides a detailed analysis of young stellar objects in the W3 GMC, revealing complex star formation processes including triggered and spontaneous events, and comparing classification methods for low and intermediate-mass stars.

Contribution

It introduces a comprehensive classification and spatial analysis of YSOs in W3 GMC, highlighting the roles of triggered and spontaneous star formation.

Findings

Clustered and distributed star formation observed

Triggered star formation dominates in certain regions

Evidence of spontaneous star formation in the GMC

Abstract

In this work we have carried out an in-depth analysis of the young stellar content in the W3 GMC. The YSO population was identified and classified in the IRAC/MIPS color-magnitude space according to the `Class' scheme and compared to other classifications based on intrinsic properties. Class 0/I and II candidates were also compared to low/intermediate-mass pre-main-sequence stars selected through their colors and magnitudes in 2MASS. We find that a reliable color/magnitude selection of low-mass PMS stars in the infrared requires prior knowledge of the protostar population, while intermediate mass objects can be more reliably identified. By means of the MST algorithm and our YSO spatial distribution and age maps we investigated the YSO groups and the star formation history in W3. We find signatures of clustered and distributed star formation in both triggered and quiescent environments. The central/western parts of the GMC are dominated by large scale turbulence likely powered by isolated bursts of star formation that triggered secondary star formation events. Star formation in the eastern high density layer also shows signs of extended periods of star formation. While our findings support triggering as a key factor for inducing and enhancing some of the major star forming activity in the HDL (e.g., W3 Main/W3(OH)), we argue that some degree of quiescent or spontaneous star formation is required to explain the observed YSO population. Our results also support previous studies claiming an spontaneous origin for the isolated massive star(s) powering KR 140.