The rate and latency of star formation in dense, massive clumps in the Milky Way

Heyer, M. and Gutermuth, R. and Urquhart, J. S. and Csengeri, Tímea and Wienen, M. (2016) The rate and latency of star formation in dense, massive clumps in the Milky Way. ASTRONOMY & ASTROPHYSICS, 588. ISSN 0004-6361

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Abstract

Context. Newborn stars form within the localized, high density regions of molecular clouds. The sequence and rate at which stars form in dense clumps and the dependence on local and global environments are key factors in developing descriptions of stellar production in galaxies.Aims. We seek to observationally constrain the rate and latency of star formation in dense massive clumps that are distributed through- out the Galaxy and to compare these results to proposed prescriptions for stellar production.Methods. A sample of 24μm-based Class I protostars are linked to dust clumps that are embedded within molecular clouds selected from the APEX Telescope Large Area Survey of the Galaxy. We determine the fraction of star-forming clumps, f∗, that imposes a constraint on the latency of star formation in units of a clump’s lifetime. Protostellar masses are estimated from models of circumstellar environments of young stellar objects from which star formation rates are derived. Physical properties of the clumps are calculated from 870μm dust continuum emission and NH3 line emission.Results. Linear correlations are identified between the star formation rate surface density, ΣS FR, and the quantities ΣH2 /τf f and ΣH2 /τcross , suggesting that star formation is regulated at the local scales of molecular clouds. The measured fraction of star forming clumps is 23%. Accounting for star formation within clumps that are excluded from our sample due to 24μm saturation, this fraction can be as high as 31%, which is similar to previous results. Dense, massive clumps form primarily low mass (< 1-2 M⊙) stars with emergent 24μm fluxes below our sensitivity limit or are incapable of forming any stars for the initial 70% of their lifetimes. The low fraction of star forming clumps in the Galactic center relative to those located in the disk of the Milky Way is verified.

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