Embedded stellar populations towards young massive star formation regions - I. G305.2+0.2

Abstract

We present deep, wide field J, H and Ks images taken with Infrared Imager and Spectrometer 2 (IRIS2) on the Anglo-Australian Telescope, towards the massive star formation region G305.2+0.2. Combined with 3.6, 4.5, 5.8 and 8.0 mu m data from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) survey on the Spitzer Space Telescope, we investigate the properties of the embedded stellar populations. After removing contamination from foreground stars, we separate the sources based on their infrared (IR) colour. Strong extended emission in the GLIMPSE images hampers investigation of the most embedded sources towards the known sites of massive star formation. However, we find a sizeable population of IR excess sources in the surrounding region free from these completeness effects. Investigation reveals the recent star formation activity in the region is more widespread than previously known. Stellar density plots show the embedded cluster in the region, G305.24+0.204, is offset from the dust emission. We discuss the effect of this cluster on the surrounding area and argue it may have played a role in triggering sites of star formation within the region. Finally, we investigate the distribution of IR excess sources towards the cluster, in particular their apparent lack towards the centre compared with its immediate environs.