Thermal balance and comparison of gas and dust properties of dense clumps in the Hi-GAL survey

M. Merello, S. Molinari, K. L.J. Rygl, N. J. Evans, D. Elia, E. Schisano, A. Traficante, Y. Shirley, B. Svoboda, P. F. Goldsmith

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


We present a comparative study of physical properties derived from gas and dust emission in a sample of 1068 dense Galactic clumps. The sources are selected from the cross-match of the Herschel Infrared Galactic Plane Survey with 16 catalogues of NH 3 line emission in its lowest inversion (1,1) and (2,2) transitions. The sample covers a large range in masses and bolometric luminosities, with surface densities above σ = 0.1 g cm -2 and with low virial parameters α < 1. The comparison between dust and gas properties shows an overall agreement between T kin and T dust at volumetric densities n ≳3 1.2 × 10 4 cm -3, and a median fractional abundance φ ‡(NH 3) = 1.46 × 10 -8. While the protostellar clumps in the sample have small differences between T kin and T dust, prestellar clumps have a median ratio T kin /T dust = 1.24, suggesting that these sources are thermally decoupled. A correlation is found between the evolutionary tracer L/M and the parameters T kin /T dust and φ ‡(NH 3) in prestellar sources and protostellar clumps with L/M < 1 L M -1. In addition, a weak correlation is found between non-thermal velocity dispersion and the L/M parameter, possibly indicating an increase of turbulence with protostellar evolution in the interior of clumps. Finally, different processes are discussed to explain the differences between gas and dust temperatures in prestellar candidates, and the origin of non-thermal motions observed in the clumps.

Original languageEnglish (US)
Pages (from-to)5355-5379
Number of pages25
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Mar 11 2019


  • ISM: clouds
  • ISM: evolution
  • catalogues
  • stars: formation
  • stars: protostars

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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