Unveiling the importance of magnetic fields in the evolution of dense clumps formed at the waist of bipolar H,{sc ii} regions: a case study on Sh2-201 with JCMT SCUBA-2/POL-2. (arXiv:1912.10188v1 [astro-ph.GA])

Unveiling the importance of magnetic fields in the evolution of dense clumps formed at the waist of bipolar H,{sc ii} regions: a case study on Sh2-201 with JCMT SCUBA-2/POL-2. (arXiv:1912.10188v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Eswaraiah_C/0/1/0/all/0/1">Chakali Eswaraiah</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_D/0/1/0/all/0/1">Di Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Samal_M/0/1/0/all/0/1">Manash R. Samal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_J/0/1/0/all/0/1">Jia-Wei Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ma_Y/0/1/0/all/0/1">Yuehui Ma</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lai_S/0/1/0/all/0/1">Shih-Ping Lai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zavagno_A/0/1/0/all/0/1">Annie Zavagno</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ching_T/0/1/0/all/0/1">Tao-Chung Ching</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_T/0/1/0/all/0/1">Tie Liu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pattle_K/0/1/0/all/0/1">Kate Pattle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ward_Thompson_D/0/1/0/all/0/1">Derek Ward-Thompson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pandey_A/0/1/0/all/0/1">Anil K. Pandey</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ojha_D/0/1/0/all/0/1">Devendra K. Ojha</a>

We present the results based on magnetic fields (B-fields), probed using JCMT
SCUBA-2/POL-2 observations of polarized dust emission at 850 $mu$m, towards
two clumps (clump 1 and clump 2) formed at the waist of the bipolar H,{sc ii}
region Sh2-201. We complement these data with archival CO data from JCMT/HARP
and 21~cm radio continuum data from VLA. We find that the morphology of
B-fields in clumps are bent and compressed by the expanding H,{sc ii} region,
thereby following a bow-like morphology in clump 1. B-fields strengths are
estimated using the modified Davis-Chandrasekhar-Fermi relations to be
266$pm$32 $mu$G for clump 1 and 65$pm$6 $mu$G for clump 2. We suggest that
B-fields become stronger in accordance with the amount of H,{sc ii} emission
interacting with the clump surfaces. Comparison among the various pressure
values suggests that B-fields dominate in clump 1, whereas ionized gas thermal
pressure dominates on clump 2. Comparison between pressures imparted by the
stellar feedback (thermal pressure from expanding H,{sc{ii}} region) and the
clump internal pressure (sum of magnetic, turbulence, and gas thermal
pressures) reveals that further expansion of the H,{sc{ii}} region will be
stopped by clump 1, however, clump 2 maintains a near equilibrium with the
stellar feedback. The virial analyses reveal that clump 1 is bound by its
gravity, whereas the clump 2 is unbound. In addition, the critical mass ratios
suggest that clump 1 could be undergoing collapse as the combined contribution
from neutral gas thermal energy, turbulence, and B-fields is not sufficient to
counteract the gravity. In contrast, clump 2 is stable because of the strong
support rendered by these three factors.

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