Distribution of HNCO 5$_{05}-4_{04}$ in Massive Star-forming Regions

TL;DR

This study maps HNCO emission in nine massive star-forming regions, revealing its compact distribution, association with infrared sources, and similar excitation mechanisms to HC3N, primarily driven by collisions.

Contribution

It provides the first detailed spatial mapping of HNCO in multiple massive star-forming regions and analyzes its physical association with infrared sources and other molecules.

Findings

HNCO emission is compact and peaks near water masers.

Most HNCO clumps are associated with infrared sources.

HNCO and HC3N show correlated emission properties, indicating similar excitation mechanisms.

Abstract

The goal of this paper is to study the spatial distribution of HNCO in massive star-forming regions, and investigate its spatial association with infrared sources, as well as physical conditions in region of HNCO emission. We have mapped nine massive star-forming regions in HNCO 5$_{05}-4_{04}$ with the Purple Mountain Observatory 13.7m telescope. The C18O maps of these sources were obtained simultaneously. The HNCO emission shows compact distribution, with emission peak centred on water masers. Nearly all the HNCO clumps show signs of embedded mid-infrared or far-infrared sources. The FWHM sizes of HNCO clumps are significantly smaller than C18O clumps but rather similar to HC3N clumps. We also found good correlation between the integrated intensities, linewidths and LSR velocities of HNCO and HC3N emission, implying similar excitation mechanism of these two species. As such, collisional excitation is likely to be the dominant excitation mechanism for HNCO 5$_{05}-4_{04}$ emission in galactic massive star-forming regions.