Using magnetic fields to probe the core-fragmentation model of binary formation

2022 Fiscal Year Final Research Report

• Project/Area Number: 18K13586
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 16010:Astronomy-related
• Research Institution: National Astronomical Observatory of Japan
• Principal Investigator: HULL CHARLES 国立天文台, アルマプロジェクト, 特別客員研究員 (70814755)
• Project Period (FY): 2018-04-01 – 2023-03-31
• Keywords: Star formation / Radio astronomy / Binary stars / Protostars / Polarization / Magnetic fields / Dust

Outline of Final Research Achievements

The results of this study were published in Hull et al. 2020a (ApJ, 892, 152). In that work, we presented 1.3 mm ALMA observations of polarized dust emission toward the wide-binary protostellar system BHR 71 IRS1 and IRS2. IRS1 features what appears to be a natal, hourglass-shaped magnetic field. In contrast, IRS2 exhibits a magnetic field that has been affected by its bipolar outflow. Toward IRS2, the polarization is confined mainly to the outflow cavity walls. Along the northern edge of the redshifted outflow cavity of IRS2, the polarized emission is sandwiched between the outflow and a filament of cold, dense gas traced by N2D+, toward which no dust polarization is detected. This suggests that the origin of the enhanced polarization in IRS2 is the irradiation of the outflow cavity walls, which enables the alignment of dust grains with respect to the magnetic field -- but only to a depth of approximately 300 au, beyond which the dust is cold and unpolarized.

Free Research Field

Astronomy

Academic Significance and Societal Importance of the Research Achievements

Studying the formation of stars gives us a view into where we, as human beings, came from, because by studying how stars form, we are studying the environments in which solar systems like our own form. Studying binary stars is important since half of the stars in the Milky Way are binaries.