Unveiling the Importance of Magnetic Fields in the Evolution of Dense Clumps Formed at the Waist of Bipolar H ii Regions: A Case Study of Sh 2-201 with JCMT SCUBA-2/POL-2
Eswaraiah,Chakali1,2; Li,Di1,3; Samal,Manash R.4,5; Wang,Jia-Wei2,6; Ma,Yuehui7,8; Lai,Shih-Ping2; Zavagno,Annie9,10; Ching,Tao-Chung1; Liu,Tie11; Pattle,Kate12,13; Ward-Thompson,Derek14; Pandey,Anil K.15; Ojha,Devendra K.16
Source PublicationThe Astrophysical Journal
AbstractAbstract 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 Sh 2-201, based on James Clerk Maxwell Telescope SCUBA-2/POL-2 observations of 850 μm 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-field strengths of 266 and 65 μG 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 of the thermal pressure imparted by the H ii region, the B-field morphologies, and the various internal pressures of the clumps (such as magnetic, turbulent, and gas thermal pressures) 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 that 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 ionization fronts to blow away from the filament ridge, forming bipolar H ii regions; and (d) stronger B fields and turbulence that 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.
KeywordInterstellar magnetic fields Magnetic fields H II regions Submillimeter astronomy Star formation Dust continuum emission Stellar feedback
WOS IDIOP:0004-637X-897-1-ab83f2
PublisherThe American Astronomical Society
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Document Type期刊论文
Affiliation1.CAS Key Laboratory of FAST, National Astronomical Observatories, Chinese Academy of Sciences, Datun Road, Chaoyang District, Beijing 100101, People's Republic of China;,
2.Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
3.University of Chinese Academy of Sciences (UCAS), Beijing 100049, People's Republic of China;
4.Physical Research Laboratory (PRL), Navrangpura, Ahmedabad 380 009, Gujarat, India;
5.Graduate Institute of Astronomy, National Central University, 300, Jhongli City, Taoyuan County 32001, Taiwan
6.Academia Sinica Institute of Astronomy & Astrophysics, 11F of Astronomy-Mathematics Building, AS/NTU, No.1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
7.Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, 10 Yuanhua Road, Nanjing 210033, People's Republic of China
8.University of Chinese Academy of Sciences, 19 A Yuquan Road, Shijingshan District, Beijing 100049, People's Republic of China
9.Aix-Marseille Université, CNRS, CNES, LAM, Marseille, France
10.Institut Universitaire de France, Paris, France
11.Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, People’s Republic of China
12.Institute of Astronomy, National Tsing Hua University (NTHU), 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan, R.O.C
13.Centre for Astronomy, School of Physics, National University of Ireland Galway, University Road, Galway, Ireland
14.Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
15.Aryabhatta Research Institute of Observational Sciences (ARIES), Manora-peak, Nainital, Uttarakhand, 263002, India
16.Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India
First Author AffilicationNational Astronomical Observatories, Chinese Academy of Sciences
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GB/T 7714
Eswaraiah,Chakali,Li,Di,Samal,Manash R.,et al. Unveiling the Importance of Magnetic Fields in the Evolution of Dense Clumps Formed at the Waist of Bipolar H ii Regions: A Case Study of Sh 2-201 with JCMT SCUBA-2/POL-2[J]. The Astrophysical Journal,2020,897(1).
APA Eswaraiah,Chakali.,Li,Di.,Samal,Manash R..,Wang,Jia-Wei.,Ma,Yuehui.,...&Ojha,Devendra K..(2020).Unveiling the Importance of Magnetic Fields in the Evolution of Dense Clumps Formed at the Waist of Bipolar H ii Regions: A Case Study of Sh 2-201 with JCMT SCUBA-2/POL-2.The Astrophysical Journal,897(1).
MLA Eswaraiah,Chakali,et al."Unveiling the Importance of Magnetic Fields in the Evolution of Dense Clumps Formed at the Waist of Bipolar H ii Regions: A Case Study of Sh 2-201 with JCMT SCUBA-2/POL-2".The Astrophysical Journal 897.1(2020).
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