J/MNRAS/465/559 IC 63 and IC 59 magnetic field structure (Soam+, 2017)
Magnetic field structure of IC 63 and IC 59 associated with H II region Sh 185.
Soam A., Maheswar G., Lee C.W., Neha S., Andersson B.-G.
<Mon. Not. R. Astron. Soc., 465, 559-568 (2017)>
=2017MNRAS.465..559S 2017MNRAS.465..559S (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Molecular clouds ; Polarization
Keywords: polarization - ISM: general - ISM: magnetic fields
Abstract:
Bright-rimmed clouds (BRCs) are formed at the periphery of HII regions
as the radiation from the central star interacts with dense gas. The
ionization and resulting compression of the clouds may lead to cloud
disruption causing secondary star formation depending on the stellar
and gas parameters. Here we use R-band polarimetry to probe the
plane-of-the sky magnetic field for two nearby BRCs, IC 59 and IC 63.
Both nebulae are illuminated by γ Cas with the direction of the
ionizing radiation being orientated parallel or perpendicular to the
local magnetic field, allowing us to probe the importance of magnetic
field pressure in the evolution of BRCs. Because of the proximity of
the system (∼200pc), we have acquired a substantial sample of over 500
polarization measurements for stars that form the background to the
nebulae. On large scales, the magnetic field geometries of both clouds
are anchored to the ambient magnetic field. For IC 63, the magnetic
field is aligned parallel to the head-tail morphology of the main
condensation, with a convex morphology relative to the direction of
the ionizing radiation. We estimate the plane-of-the-sky magnetic
field strength in IC 63 to be ∼90µG. In IC 59, the projected
magnetic field follows the M-shape morphology of the cloud. Here,
field lines present a concave shape with respect to the direction of
the ionizing radiation from γ Cas. Comparing our observations to
published theoretical models, we find good general agreement,
supporting the importance of magnetic fields in BRC evolution.
Description:
The optical polarimetric data towards IC 63 and IC 59 were collected
using the Aries Imaging Polarimeter (AIMPOL) mounted at the Cassegrain
focus of the 104-cm Sampurnanand telescope, India. The images were
obtained using a 1024x1024pixel2 CCD chip (Tektronix TK1024) out
of which the central 325x325pixel2 area was used for the imaging.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
ic59pol.dat 43 236 Bright-rimmed cloud IC59 optical polarization
ic63pol.dat 43 308 Bright-rimmed cloud IC63 optical polarization
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Byte-by-byte Description of file: ic59pol.dat ic63pol.dat
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Bytes Format Units Label Explanations
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2- 11 F10.6 deg RAdeg Right ascension (J2000)
14- 23 F10.6 deg DEdeg Declination (J2000)
27- 29 F3.1 % P Fraction of polarization
33- 35 F3.1 % e_P Uncertainties in fraction of polarization
37- 39 I3 deg PA Polarization position angle measured from
North increasing towards east
42- 43 I2 deg e_PA Uncertainties in polarization position angle
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Acknowledgements:
Archana Soam, asoam(at)usra.edu
(End) Patricia Vannier [CDS] 12-Mar-2019