Temperature structure and kinematics of the IRDC G035.39–00.33^⋆

¹ Max Planck Institute for Extraterrestrial Physics, Gießenbachstraßse 1, 85748 Garching bei München, Germany
e-mail: vsokolov@mpe.mpg.de
² European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
³ Astrophysics Research Institute, Liverpool John Moores University, Liverpool, L3 5RF, UK
⁴ Department of Astronomy, University of Florida, Gainesville, FL 32611, USA
⁵ Department of Physics, University of Florida, Gainesville, FL 32611, USA
⁶ INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
⁷ School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, UK

Received: 23 December 2016
Accepted: 27 June 2017

Abstract

Aims. Infrared dark clouds represent the earliest stages of high-mass star formation. Detailed observations of their physical conditions on all physical scales are required to improve our understanding of their role in fueling star formation.

Methods. We investigate the large-scale structure of the IRDC G035.39–00.33, probing the dense gas with the classical ammonia thermometer. This allows us to put reliable constraints on the temperature of the extended, pc-scale dense gas reservoir and to probe the magnitude of its non-thermal motions. Available far-infrared observations can be used in tandem with the observed ammonia emission to estimate the total gas mass contained in G035.39–00.33.

Results. We identify a main velocity component as a prominent filament, manifested as an ammonia emission intensity ridge spanning more than 6 pc, consistent with the previous studies on the Northern part of the cloud. A number of additional line-of-sight components are found, and a large-scale linear velocity gradient of ~ 0.2km s^-1 pc^-1 is found along the ridge of the IRDC. In contrast to the dust temperature map, an ammonia-derived kinetic temperature map, presented for the entirety of the cloud, reveals local temperature enhancements towards the massive protostellar cores. We show that without properly accounting for the line of sight contamination, the dust temperature is 2–3 K larger than the gas temperature measured with NH₃.

Conclusions. While both the large-scale kinematics and temperature structure are consistent with that of starless dark filaments, the kinetic gas temperature profile on smaller scales is suggestive of tracing the heating mechanism coincident with the locations of massive protostellar cores.