Abstract

Poster - Splinter MassiveStars   (S23)

A Multiscale Study of Fragmentation and the Role of Magnetic Field in IRDC SDC18.624-0.070

Han-Tsung Lee, Ya-Wen Tang, Patrick Koch
I. Physikalisches Institut, Universität zu Köln; Academia Sinica Institute of Astronomy and Astrophysics

We present a multiscale study of the magnetic field toward the filamentary infrared dark cloud SDC18.624-0.070 and its two clumps SDC18-N and SDC18-S using dust polarization continuum observations at 850 μm and 1.3 mm with various resolutions from JCMT and SMA from 10 pc to 0.01 pc scales, which are central to investigate the impact of the magnetic field on fragmentation. We find a magnetic field which is preferentially perpendicular to the major axes of all structures (filament, clumps, and cores). While its mean orientation is preserved within about 20-30 deg, a systematically increasing field dispersion toward smaller scales indicates a growing impact of gravity. We find the magnetic field strength scales with the volume density with a power index of 0.35-0.40. All these features suggest that the magnetic field constrains the direction of accretion and initial contraction as predicted by strong-field models. A multiscale energy analysis of gravity, magnetic field, and turbulence quantifying their relative importance shows that SDC18-S, displaying less fragmentation, has a larger field strength than SDC18-N which harbors more fragments. A faster (SDC18-N) and slower transition (SDC18-S) to a gravity-dominated regime is found to explain the different fragmentation patterns, with the stronger magnetic field in SDC18-S suppressing fragmentation more.