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

Author(s): Alvaro Hacar Gonzalez, Jouni Kainulainen, Mario Tafalla, Henrik Beuther, Joao Alves
Abstract: Filaments play a central 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 ¹³CO and C¹⁸O (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 ~6.5 pc of length. With an internal gas kinematics dominated by thermal motions (i.e. σ_NT/c_s ≲ 1) and large-scale velocity gradients, these results reveal Musca as the longest velocity-coherent, sonic-like object identified so far in the interstellar medium. The transonic 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.
This publication is based on data acquired with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between the Max-Planck-Institut fuer Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory (ESO programme 087.C-0583).The reduced datacubes as FITS files are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via cdsarc.u-strasbg.fr/viz-bin/qcat
Organisation(s): Department of Astrophysics
External organisation(s): Observatorio Astronómico Nacional (OAN-IGN), Max-Planck-Institut für Astronomie
Journal: Astronomy & Astrophysics
Volume: 587
No. of pages: 12
ISSN: 0004-6361
DOI: https://doi.org/10.1051/0004-6361/201526015
Publication date: 03-2016
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy, 103004 Astrophysics
Keywords
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/55d89dab-448d-4b8f-9256-9df7742cf22b