Distribution of HNCO 5₀₅−4₀₄ in massive star-forming regions

¹ Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, 200030 Shanghai, PR China
e-mail: lijuan@shao.ac.cn
² Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, 210008 Nanjing, PR China
³ School of Astronomy & Space Science, Nanjing University, 22 Hankou RD, 210093 Nanjing, PR China
⁴ Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, 210093 Nanjing, PR China

Received: 18 December 2012
Accepted: 6 May 2013

Abstract

Aims. The goal of this paper is to study the spatial distribution of HNCO in massive star-forming region and to investigate both its spatial association with infrared sources and physical conditions in region of HNCO emission.

Methods. We mapped nine massive star-forming regions in HNCO 5₀₅–4₀₄ with the Purple Mountain Observatory 13.7 m telescope. The C¹⁸O maps of these sources were obtained simultaneously.

Results. The HNCO emission shows compact distribution, with the emission peak centered 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 find a good correlation between the integrated intensities, linewidths, and LSR velocities of HNCO and HC₃N emission, implying similar excitation mechanisms for these two species. As such, collisional excitation is likely to be the dominant excitation mechanism for HNCO 5₀₅ − 4₀₄ emission in galactic massive star-forming regions.