1. Unveiling the importance of magnetic fields in the evolution of dense clumps formed at the waist of bipolar H II regions: a case study on Sh2-201 with JCMT SCUBA-2/POL-2
- Author
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Jia-Wei Wang, Di Li, Derek Ward-Thompson, Yuehui Ma, Devendra K. Ojha, Kate Pattle, Annie Zavagno, Tie Liu, Chakali Eswaraiah, Anil K. Pandey, Shih-Ping Lai, M. R. Samal, Tao-Chung Ching, National Astronomical Observatories [Beijing] (NAOC), Chinese Academy of Sciences [Beijing] (CAS), Centre Procédés, Énergies Renouvelables, Systèmes Énergétiques (PERSEE), Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Physical Research Laboratory [Ahmedabad] (PRL), Indian Space Research Organisation (ISRO), National Tsing Hua University [Hsinchu] (NTHU), Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), Academia Sinica, Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Xinjiang Institute of Ecology and Geography [Urumqi] (XIEG), National University of Ireland [Galway] (NUI Galway), Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy [Preston], University of Central Lancashire [Preston] (UCLAN), Aryabhatta Research Institute of Observational Sciences (ARIES), and Tata Institute for Fundamental Research (TIFR)
- Subjects
Physics ,H II region ,F990 ,010504 meteorology & atmospheric sciences ,Turbulence ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,01 natural sciences ,Astrophysics - Astrophysics of Galaxies ,Virial theorem ,Magnetic field ,Protein filament ,13. Climate action ,Space and Planetary Science ,[SDU]Sciences of the Universe [physics] ,Ionization ,Astrophysics of Galaxies (astro-ph.GA) ,0103 physical sciences ,010303 astronomy & astrophysics ,James Clerk Maxwell Telescope ,0105 earth and related environmental sciences ,Cosmic dust - Abstract
We present the properties of magnetic fields (B-fields) in two clumps (clump 1 and clump 2), located at the waist of the bipolar H II region Sh2-201, based on JCMT SCUBA-2/POL-2 observations of 850 $\mu$m polarized dust emission. We find that B-fields in the direction of the clumps are bent and compressed, showing bow-like morphologies, which we attribute to the feedback effect of the H II region on the surface of the clumps. Using the modified Davis-Chandrasekhar-Fermi method we estimate B-fields strengths of 266 $\mu$G and 65 $\mu$G for clump 1 and clump 2, respectively. From virial analyses and critical mass ratio estimates, we argue that clump 1 is gravitationally bound and could be undergoing collapse, whereas clump 2 is unbound and stable. We hypothesize that the interplay between thermal pressure imparted by the H II region, B-field morphologies, and the various internal pressures of the clumps (such as magnetic, turbulent, and gas thermal pressure), has the following consequences: (a) formation of clumps at the waist of the H II region; (b) progressive compression and enhancement of the B-fields in the clumps; (c) stronger B-fields will shield the clumps from erosion by the H II region and cause pressure equilibrium between the clumps and the H II region, thereby allowing expanding I-fronts to blow away from the filament ridge, forming bipolar H II regions; and (d) stronger B-fields and turbulence will be able to stabilize the clumps. A study of a larger sample of bipolar H II regions would help to determine whether our hypotheses are widely applicable., Comment: 25 pages, 10 figures, and 4 tables. Accepted for publication in ApJ
- Published
- 2022
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