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Massive 70μm quiet clumps I: evidence of embedded low/intermediate-mass star formation activity

Traficante, A., Fuller, G.A., Billot, N., Duarte Cabral, Ana, Merello, M., Molinari, S., Peretto, Nicolas and Schisano, E. 2017. Massive 70μm quiet clumps I: evidence of embedded low/intermediate-mass star formation activity. Monthly Notices of the Royal Astronomical Society 470 (4) , pp. 3882-3923. 10.1093/mnras/stx1375

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Abstract

Massive clumps, prior to the formation of any visible protostars, are the best candidates to search for the elusive massive starless cores. In this work we investigate the dust and gas properties of massive clumps selected to be 70μ quiet, therefore good starless candidates. Our sample of 18 clumps has masses 300 ≲ M ≲ 3000 M⊙, radius 0.54 ≤ R ≤ 1.00 pc, surface densities Σ ≥ 0.05 g cm−2 and luminosity/mass ratio L/M≤0.3. We show that half of these 70μ quiet clumps embed faint 24μ sources. Comparison with GLIMPSE counterparts shows that 5 clumps embed young stars of intermediate stellar mass up to ≃ 5.5 M⊙. We study the clump dynamics with observations of N2H+ (1−0), HNC (1−0) and HCO+ (1−0) made with the IRAM 30m telescope. Seven clumps have blue-shifted spectra compatible with infall signatures, for which we estimate a mass accretion rate 0.04≲M˙≲2.0×10−3 0.04≲M˙≲2.0×10−3 M⊙ yr−1, comparable with values found in high-mass protostellar regions, and free-fall time of the order of tff ≃ 3 × 105 yr. The only appreciable difference we find between objects with and without embedded 24μ sources is that the infall rate appears to increase from 24μ dark to 24μ bright objects. We conclude that all 70μ quiet objects have similar properties on clump scales, independently of the presence of an embedded protostar. Based on our data we speculate that the majority, if not all of these clumps may already embed faint, low-mass protostellar cores. If these clumps are to form massive stars, this must occur after the formation of these lower mass stars.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: Stars ‐ stars: formation, stars: kinematics and dynamics, stars: massive, Resolved and unresolved sources as a function of wavelength, radio lines: stars, submillimetre:stars, Physical Data and Processes, line: profiles
Publisher: Oxford University Press
ISSN: 0035-8711
Funders: STFC
Date of First Compliant Deposit: 12 June 2017
Date of Acceptance: 1 June 2017
Last Modified: 22 Sep 2017 14:47
URI: http://orca-mwe.cf.ac.uk/id/eprint/101363

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