Simultaneous low- and high-mass star formation in a massive protocluster: ALMA observations of G11.92-0.61

C. J. Cyganowski, C. L. Brogan, T. R. Hunter, R. Smith, J. M. D. Kruijssen, I. A. Bonnell, Q. Zhang

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We present 1.05 mm ALMA observations of the deeply embedded high-mass protocluster G11.92−0.61, designed to search for low-mass cores within the accretion reservoir of the massive protostars. Our ALMA mosaic, which covers an extent of ∼0.7 pc at sub-arcsecond (∼1400 au) resolution, reveals a rich population of 16 new millimetre continuum sources surrounding the three previously-known millimetre cores. Most ofthe new sources are located in the outer reaches of the accretion reservoir: the median projected separation from the central, massive (proto)star MM1 is ∼0.17 pc. The derived physical properties of the new millimetre continuum sources are consistent with those of low-mass prestellar and protostellar cores in nearby star-forming regions:the median mass, radius, and density of the new sources are 1.3 M, 1600 au, and nH2 ∼107 cm−3. At least three of the low-mass cores in G11.92−0.61 drive molecular outflows, traced by high-velocity 12CO(3-2) (observed with the SMA) and/or by H2CO and CH3OH emission (observed with ALMA). This finding, combined with the known outflow/accretion activity of MM1, indicates that high- and low-mass stars are forming (accreting) simultaneously within this protocluster. Our ALMA results are consistent with the predictions of competitive-accretion-type models in which high-mass stars form along with their surrounding clusters.
Original languageEnglish
Pages (from-to)3694-3708
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Early online date8 Feb 2017
Publication statusPublished - 1 Jul 2017


  • ISM: individual objects (G11.92-0.61)
  • ISM: molecules
  • Stars: formation
  • Stars: protostars
  • Submillimetre: ISM


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