In:
Research in Astronomy and Astrophysics, IOP Publishing, Vol. 20, No. 5 ( 2020-05-01), p. 077-
Abstract:
We present a pilot H i survey of 17 Planck Galactic Cold Clumps (PGCCs) with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). H i Narrow Self-Absorption (HINSA) is an effective method to detect cold H i being mixed with molecular hydrogen H 2 and improves our understanding of the atomic to molecular transition in the interstellar medium. HINSA was found in 58% PGCCs that we observed. The column density of HINSA was found to have an intermediate correlation with that of 13 CO, following ( N (HINSA)) = (0.52 ± 0.26) ( N 13 CO ) + (10 ± 4.1). H i abundance relative to total hydrogen [H i ]/[H] has an average value of 4.4 × 10 –3 , which is about 2.8 times of the average value of previous HINSA surveys toward molecular clouds. For clouds with total column density N H 〉 5 × 10 20 cm –2 , an inverse correlation between HINSA abundance and total hydrogen column density is found, confirming the depletion of cold H i gas during molecular gas formation in more massive clouds. Non-thermal line width of 13 CO is about 0-0.5 km s −1 larger than that of HINSA. One possible explanation of narrower non-thermal width of HINSA is that HINSA region is smaller than that of 13 CO. Based on an analytic model of H 2 formation and H 2 dissociation by cosmic ray, we found the cloud ages to be within 10 6.7 – 10 7.0 yr for five sources.
Type of Medium:
Online Resource
ISSN:
1674-4527
DOI:
10.1088/1674-4527/20/5/77
Language:
Unknown
Publisher:
IOP Publishing
Publication Date:
2020
detail.hit.zdb_id:
2511247-8
SSG:
6,25
SSG:
16,12
Permalink
