Star formation towards the southern cometary H ii region IRAS 17256−3631

• Published in: Monthly notices of the Royal Astronomical Society Vol. 456; no. 3; p. 2425
• Main Authors: Veena, V S, Vig, S, Tej, A, Varricatt, W P, Ghosh, S K, Chandrasekhar, T, Ashok, N M
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 01-03-2016
• Subjects: Astronomy; Clouds; Clumps; Clusters; Comets; Infrared telescopes; Morphology; Radio; Spectrum analysis; Star & galaxy formation; India
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stv2832

IRAS 17256-3631 is a southern Galactic massive star-forming region located at a distance of 2 kpc. In this paper, we present a multiwavelength investigation of the embedded cluster, the H ii region, as well as the parent cloud. Radio images at 325, 610 and 1372 MHz were obtained using Giant Metrewave Radio Telescope, India while the near-infrared imaging and spectroscopy were carried out using United Kingdom Infrared Telescope and Mt. Abu Infrared Telescope, India. The near-infrared K-band image reveals the presence of a partially embedded infrared cluster. The spectral features of the brightest star in the cluster, IRS-1, spectroscopically agree with a late O or early B star and could be the driving source of this region. Filamentary H sub( 2) emission detected towards the outer envelope indicates the presence of highly excited gas. The parent cloud is investigated at far-infrared to millimetre wavelengths and 18 dust clumps have been identified. The spectral energy distributions of these clumps have been fitted as modified blackbodies and the best-fitting peak temperatures are found to range from 14 to 33 K, while the column densities vary from 0.7 to 8.5 x 10 super( 22) cm super( -2). The radio maps show a cometary morphology for the distribution of ionized gas that is density bounded towards the north-west and ionization bounded towards the south-east. This morphology is better explained with the champagne flow model as compared to the bow-shock model. Using observations at near-, mid- and far-infrared, submillimetre and radio wavelengths, we examine the evolutionary stages of various clumps.