The Musca cloud: a 6 pc-long velocity-coherent, sonic filament

Author(s)

A. Hacar, J. Kainulainen, M. Tafalla, H. Beuther, J. Alves

Abstract

Filaments play a key role in the molecular clouds' evolution, but their

internal dynamical properties remain poorly characterized. To further

explore the physical state of these structures, we have investigated the

kinematic properties of the Musca cloud. We have sampled the main axis

of this filamentary cloud in $^{13}$CO and C$^{18}$O (2--1) lines using

APEX observations. The different line profiles in Musca shows that this

cloud presents a continuous and quiescent velocity field along its

$\sim$6.5 pc of length. With an internal gas kinematics dominated by

thermal motions (i.e. $\sigma_{NT}/c_s\lesssim1$) and large-scale

velocity gradients, these results reveal Musca as the longest

velocity-coherent, sonic-like object identified so far in the ISM. The

(tran-)sonic properties of Musca present a clear departure from the

predicted supersonic velocity dispersions expected in the Larson's

velocity dispersion-size relationship, and constitute the first

observational evidence of a filament fully decoupled from the turbulent

regime over multi-parsec scales.

Organisation(s)

Department of Astrophysics

External organisation(s)

Max-Planck-Institut für Astronomie, Observatorio Astronómico Nacional (OAN-IGN)

Publication date

11-2015

Austrian Fields of Science 2012

103004 Astrophysics

Keywords

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