ALMA-IRDC: dense gas mass distribution from cloud to core scales

Journal
Date Issued
2021
Author(s)
Barnes, A. T.
•
Henshaw, J. D.
•
•
Pineda, J. E.
•
Cosentino, G.
•
Tan, J. C.
•
Caselli, P.
•
Jiménez-Serra, I.
•
Law, C. Y.
•
Avison, A.
•
Bigiel, F.
•
Feng, S.
•
Kong, S.
•
Longmore, S. N.
•
Moser, L.
•
Parker, R. J.
•
Sánchez-Monge, Á.
•
Wang, K.
DOI
Abstract
Infrared dark clouds (IRDCs) are potential hosts of the elusive early phases of high mass star formation (HMSF). Here, we conduct an in-depth analysis of the fragmentation properties of a sample of 10 IRDCs, which have been highlighted as some of the best candidates to study HMSF within the Milky Way. To do so, we have obtained a set of large mosaics covering these IRDCs with Atacama Large Millimeter/submillimeter Array (ALMA) at Band 3 (or 3 mm). These observations have a high angular resolution (∼3 arcsec; ∼0.05 pc), and high continuum and spectral line sensitivity (∼0.15 mJy beam-1 and ∼0.2 K per 0.1 km s-1 channel at the N2H+ (1 - 0) transition). From the dust continuum emission, we identify 96 cores ranging from low to high mass (M = 3.4-50.9 M⊙) that are gravitationally bound (αvir = 0.3-1.3) and which would require magnetic field strengths of B = 0.3-1.0 mG to be in virial equilibrium. We combine these results with a homogenized catalogue of literature cores to recover the hierarchical structure within these clouds over four orders of magnitude in spatial scale (0.01-10 pc). Using supplementary observations at an even higher angular resolution, we find that the smallest fragments (<0.02 pc) within this hierarchy do not currently have the mass and/or the density required to form high-mass stars. None the less, the new ALMA observations presented in this paper have facilitated the identification of 19 (6 quiescent and 13 star-forming) cores that retain >16 M⊙ without further fragmentation. These high-mass cores contain trans-sonic non-thermal motions, are kinematically sub-virial, and require moderate magnetic field strengths for support against collapse. The identification of these potential sites of HMSF represents a key step in allowing us to test the predictions from high-mass star and cluster formation theories.
Volume
503
Issue
3
Start page
4601
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2021MNRAS.503.4601B
Rights
open.access
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