Initial phases of high-mass star formation: a multiwavelength study towards the extended green object G12.42+0.50

Abstract

We present a multiwavelength study of the extended green object, G12.42+0.50, in this paper. The associated ionized, dust, and molecular components of this source are studied in detail employing various observations at near-, mid- and far-infrared, submillimetre, and radio wavelengths. Radio continuum emission mapped at 610 and 1390 MHz, using the Giant Meterwave Radio Telescope, India, advocates for a scenario of coexistence of an UC H II region and an ionized thermal jet possibly powered by the massive young stellar object, IRAS 18079-1756, with an estimated spectral type of B1-B0.5. Shock-excited lines of H₂ and [Fe II], as seen in the near-infrared spectra obtained with UKIRT-UIST, lend support to this picture. Cold dust emission shows a massive clump of mass 1375 M_⊙ enveloping G12.42+0.50. Study of the molecular gas kinematics using the MALT90 and JCMT archival data unravels the presence of both infall activity and large-scale outflow suggesting an early stage of massive star formation in G12.42+0.50. A network of filamentary features are also revealed merging with the massive clump, mimicking a hub-filament layout. Velocity structure along these indicates bulk inflow motion.