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This paper presents a multiwavelength investigation of the Galactic H  ii  region IRAS 17149 − 3916. Using the Giant Meterwave Radio Telescope, India, first low-frequency radio continuum observations at 610 and 1280 MHz for this region are presented. The ionized gas emission displays an interesting cometary morphology, which is likely powered by the early-type source, E4 (IRS-1). The origin of the cometary morphology is discussed under the framework of the widely accepted bow shock, champagne flow, and clumpy cloud mechanisms. The mid- and far-infrared data from Spitzer -GLIMPSE and Herschel -Hi-GAL reveal a complex network of pillars, clumps, bubble, filaments, and arcs suggesting the profound influence of massive stars on the surrounding medium. Triggered star formation at the tip of an observed pillar structure is reported. High-resolution ALMA continuum data show a string of cores detected within the identified clumps. The core masses are well explained by thermal Jeans fragmentation and support the hierarchical fragmentation scenario. Four 'super-Jeans' cores are identified which, at the resolution of the present data set, are suitable candidates to form high-mass stars. [ABSTRACT FROM AUTHOR]

A multiwavelength analysis of star formation associated with the extended green object, G19.88-0.53 is presented in this paper. With multiple detected radio and millimetre components, G19.88-0.53 unveils as harbouring a protocluster rather than a single massive young stellar object. We detect an ionized thermal jet using the upgraded Giant Meterwave Radio Telescope, India, which is found to be associated with a massive, dense and hot ALMA 2.7 mm core driving a bipolar CO outflow. Near-infrared spectroscopy with UKIRT–UIST shows the presence of multiple shock-excited H2 lines concurrent with the nature of this region. Detailed investigation of the gas kinematics using ALMA data reveals G19.88-0.53 as an active protocluster with high-mass star-forming components spanning a wide evolutionary spectrum from hot cores in accretion phase to cores driving multiple outflows to possible UCH  ii regions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]