An infrared study of the high-mass, multi-stage star-forming region IRAS~12272-6240

Abstract

IRAS 12272-6240 is a complex star forming region with a compact massive dense clump 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-IR imaging and low-resolution spectroscopy with the Baade/Magellan telescope and its camera PANIC. Mosaics of size $2\times 2$ square arcmin in the $JH{K}_s$ bands and with narrow-band filters centred in the 2.12 $\hat{I}¼$m H${}_2$ and 2.17 $\hat{I}¼$m Br${\hat{I}}^3$ lines were analysed in combination with HI-GAL/{\sl Herschel} and archive IRAC/{\sl Spitzer} and {\sl WISE} observations. We found that the compact dense clump houses two Class~I YSOs that probably form a 21 kAU-wide binary system. Its combined 1 to 1200 $\hat{I}¼$m SED is consistent with an O9V central star with a $10^{-2}{M}_{\odot }$ disc and a $1.3\times 10^4{M}_{\odot }$ dust envelope. Its total luminosity is $8.5\times 10^4{L}_{\odot }$. A series of shocked H${}_2$ 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 sub-cluster containing the YSOs. We also identified and classified the O-type central stars of two dusty radio/IR HII regions flanking the protostars. Our results confirm that these elements form a single giant young complex where massive star formation processes started some 1 million years ago and is still active.

14 pages, 13 figures, Accepted by MNRAS