Distortion of Magnetic Fields in the Dense Core SL42 (CrA-E) in the Corona Australis Molecular Cloud Complex

Abstract

Detailed magnetic field structure of the dense core SL42 (CrA-E) in the Corona Australis molecular cloud complex was investigated based on near-infrared polarimetric observations of background stars to measure dichroically polarized light produced by magnetically aligned dust grains. The magnetic fields in and around SL42 were mapped using 206 stars and curved magnetic fields were identified. On the basis of simple hourglass (parabolic) magnetic field modeling, the magnetic axis of the core on the plane of sky was estimated to be $40^{\circ }\pm 3^{\circ }$. The plane-of-sky magnetic field strength of SL42 was found to be $22.4\pm 13.9$ $\mu$G. Taking into account the effects of thermal/turbulent pressure and the plane-of-sky magnetic field component, the critical mass of SL42 was obtained to be $M_{\mathrm{cr}}=21.2\pm 6.6$ M${}_{\odot }$, which is close to the observed core mass of $M_{\mathrm{core}}\approx 20$ M${}_{\odot }$. We thus conclude that SL42 is in a condition close to the critical state if the magnetic fields lie near the plane of the sky. Since there is a very low luminosity object (VeLLO) toward the center of SL42, it is unlikely this core is in a highly subcritical condition (i.e., magnetic inclination angle significantly deviated from the plane of sky). The core probably started to collapse from a nearly kinematically critical state. In addition to the hourglass magnetic field modeling, the Inoue \& Fukui (2013) mechanism may explain the origin of the curved magnetic fields in the SL42 region.

23 pages, 12 figures, accepted for publication in ApJ; For the convenience of readers, we explained our procedures of various data calibration/reduction/analysis methods again in this paper, instead of omitting detailed explanations by citing our previous papers

References in corpus (8)

• Identifying the Low Luminosity Population of Embedded Protostars in the c2d Observations of Clouds and Cores
• A Large Catalog of Accurate Distances to Local Molecular Clouds: The Gaia DR2 Edition
• Near-IR Imaging Polarimetry toward a Bright-Rimmed Cloud: Magnetic Field in SFO 74
• Distortion of Magnetic Fields in a Starless Core: Near-Infrared Polarimetry of FeSt 1-457
• Distortion of Magnetic Fields in a Starless Core II: 3D Magnetic Field Structure of FeSt 1-457
• CO Outflow Survey of 68 Very Low Luminosity Objects: a Search for Proto-Brown Dwarf Candidates
• Distortion of Magnetic Fields in a Starless Core VI: Application of Flux Freezing Model and Core Formation of FeSt 1-457
• Chemical and Physical Conditions in Molecular Cloud Core DC 000.4-19.5 (SL42) in Corona Australis

Cited by in corpus (2)

• Classification of Filament Formation Mechanisms in Magnetized Molecular Clouds
• Magnetic Properties of Star-Forming Dense Cores