An infrared study of the high-mass, multistage star-forming region IRAS 12272−6240

Abstract

ABSTRACT IRAS 12272−6240 is a complex star-forming region with a compact massive dense clump (DC) and several associated masers, located at a well-determined distance of d = 9.3 kpc from the Sun. For this study, we obtained sub-arcsec broad- and narrow-band near-infrared (near-IR) imaging and low-resolution spectroscopy with the Baade/Magellan telescope and its camera PANIC. Mosaics of size 2 × 2 arcmin2 in the JHKs bands and with narrow-band filters centred in the 2.12 μm H2 and 2.17 μm Br γ lines were analysed in combination with Hi-GAL/Herschel and archive IRAC/Spitzer and WISE observations. We found that the compact DC houses two Class I young stellar objects (YSOs) that probably form a 21000 -au-wide binary system. Its combined 1–1200 μm spectral energy distribution is consistent with an O9V central star with a $10^{-2} \, \mathrm{M}_\odot$ disc and a $1.3 \times 10^4 \, \mathrm{M}_\odot$ dust envelope. Its total luminosity is $8.5 \times 10^4 \, \mathrm{L}_\odot$. A series of shocked H2 emission knots are found in its close vicinity, confirming the presence of outflows. IRAS 12272−6240 is at the centre of an embedded cluster with a mean age of 1 Myr and 2.6 pc in size that contains more than 150 stars. At its nucleus, we found a more compact and considerably younger subcluster containing the YSOs. We also identified and classified the O-type central stars of two dusty radio/IR H ii regions flanking the protostars. Our results confirm that these elements form a single giant young complex where massive star formation processes started some 1 Myr ago and are still active.