In Search of Infall Motion in Molecular Clumps. III. HCO+ (1-0) and H13CO+ (1-0) Mapping Observations toward Confirmed Infall Sources
Abstract
The study of infall motion helps us to understand the initial stages of star formation. In this paper, we use the IRAM 30 m telescope to make mapping observations of 24 infall sources confirmed in previous work. The lines we use to track gas infall motions are HCO+ (1-0) and H13CO+ (1-0). All 24 sources show HCO+ emissions, while 18 sources show H13CO+ emissions. The HCO+ integrated intensity maps of 17 sources show clear clumpy structures; for the H13CO+ line, 15 sources show clumpy structures. We estimated the column density of HCO+ and H13CO+ using the RADEX radiation transfer code, and the obtained [HCO+]/[H2] and [H13CO+]/[HCO+] of these sources are about 10-11-10-7 and 10-3-1, respectively. Based on the asymmetry of the line profile of the HCO+, we distinguish these sources: 19 sources show blue asymmetric profiles, and the other sources show red profiles or symmetric peak profiles. For eight sources that have double-peaked blue line profiles and signal-to-noise ratios greater than 10, the RATRAN model is used to fit their HCO+ (1-0) lines, and to estimate their infall parameters. The mean V in of these sources is 0.3-1.3 km s-1, and the ${\dot{M}}_{\mathrm{in}}$ is about 10-3-10-4 M ⊙ yr-1, which is consistent with the results of intermediate or massive star formation in previous studies. The V in estimated from the Myers model is 0.1-1.6 km s-1, and the ${\dot{M}}_{\mathrm{in}}$ is within 10-3-10-5 M ⊙ yr-1. In addition, some identified infall sources show other star-forming activities, such as outflows and maser emissions. Especially for those sources with a double-peaked blue asymmetric profile, most of them have both infall and outflow evidence.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2021
- DOI:
- 10.3847/1538-4357/ac22ab
- arXiv:
- arXiv:2109.07221
- Bibcode:
- 2021ApJ...922..144Y
- Keywords:
-
- Star formation;
- Interstellar medium;
- Molecular clouds;
- Collapsing clouds;
- 1569;
- 847;
- 1072;
- 267;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- doi:10.3847/1538-4357/ac22ab