Magnetic field structure of IC 63 and IC 59 associated to H II region - Sh 185

Abstract

Bright-rimmed clouds (BRCs) are formed at the periphery of H II 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 in the two near-by BRCs IC\,59 and IC\,63. Both nebulae are illuminated by $\gamma$ Cas with the direction of 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 ($\sim$200pc) we have acquired a substantial sample of over 500 polarization measurements for stars 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 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 $\sim 90\mu$G. 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 $\gamma$ Cas. Comparing our observations to published theoretical models we find good general agreement, supporting the importance of magnetic fields in BRC evolution.

11 pages, 6 figures, Accepted for publication in MNRAS

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• The Cassiopeia Filament: A Blown Spur of the Local Arm
• On the collisional disalignment of dust grains in illuminated and shaded regions of IC 63
• Investigation of Rocket Effect in BRC 18 using Gaia EDR3
• Tracing the magnetic field morphology of the LDN 1172/1174 cloud complex
• High Resolution Observations of HI in the IC 63 Reflection Nebula
• Optical polarimetry study of Lambda-Orionis star-forming region
• Physics and Chemistry of Radiation Driven Cloud Evolution. [C II] Kinematics of IC 59 and IC 63
• Research on the Interstellar Medium and Star Formation in the Galaxy: An Indian Perspective