A near-infrared study of the star forming region RCW 34

TL;DR

This near-infrared study of RCW 34 reveals a large population of pre-main sequence stars, indicating ongoing star formation over 10 million years, with spatial distribution suggesting influence from massive stars on star formation activity.

Contribution

First near-infrared imaging analysis of RCW 34 identifying pre-main sequence stars and their spatial distribution, linking star formation activity to massive star influence.

Findings

Over 700 objects identified as likely pre-main sequence stars.

Luminosity function indicates star formation ongoing for about 10 million years.

Spatial distribution shows younger stars near massive O and B stars.

Abstract

We report the results of a near-infrared imaging study of a $7.8 \times 7.8$ arcmin$^2$ region centered on the 6.7 GHz methanol maser associated with the RCW 34 star forming region using the 1.4m IRSF telescope at Sutherland. A total of 1283 objects were detected simultaneously in J, H, and K for an exposure time of 10800 seconds. The J-H, H-K two-colour diagram revealed a strong concentration of more than 700 objects with colours similar to what is expected of reddened classical T Tauri stars. The distribution of the objects on the K {\it vs} J-K colour-magnitude diagram is also suggestive that a significant fraction of the 1283 objects is lower mass pre-main sequence stars. We also present the luminosity function for the subset of about 700 pre-main sequence stars and show that it suggests ongoing star formation activity for about $10^7$ years. An examination of the spatial distribution of the pre-main sequence stars shows that the fainter (older) part of the population is more dispersed over the observed region and the brighter (younger) subset is more concentrated around the position of the O8.5V star. This suggests that the physical effects of the O8.5V star and the two early B-type stars on the remainder of the cloud out of which they formed, could have played a role in the onset of the more recent episode of star formation in RCW 34.