Star formation towards the southern Cometary HII region IRAS 17256-3631

TL;DR

This study provides a comprehensive multiwavelength analysis of the star-forming region IRAS 17256-3631, revealing its embedded cluster, ionized gas morphology, and dust properties, and suggesting an evolutionary sequence for its clumps.

Contribution

It presents the first detailed multiwavelength investigation of IRAS 17256-3631, combining radio, infrared, and submillimeter data to analyze its structure, star formation activity, and evolutionary stages.

Findings

The ionized gas exhibits a cometary morphology consistent with the champagne flow model.

Eighteen dust clumps identified with temperatures 14-33 K and varying column densities.

Spectroscopic analysis suggests the brightest star is a late O or early B type.

Abstract

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 HII region, as well as the parent cloud. Radio images at 325, 610 and 1372 MHz were obtained using GMRT, India while the near-infrared imaging and spectroscopy were carried out using UKIRT 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 agrees with a late O or early B star and could be the driving source of this region. Filamentary H_2 emission detected towards the outer envelope indicates presence of highly excited gas. The parent cloud is investigated at far-infrared to millimeter wavelengths and eighteen dust clumps have been identified. The spectral energy distributions (SEDs) of these clumps have been fitted as modified blackbodies and the best-fit peak temperatures are found to range from 14-33 K, while the column densities vary from 0.7-8.5x10^22 cm^-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, submillimeter and radio wavelengths, we examine the evolutionary stages of various clumps.