Star-forming protoclusters associated with methanol masers

Abstract

We present a multiwavelength study of five methanol maser sites which are not directly associated with a strong ($>100$ mJy) radio continuum source: G 31.28+0.06, G 59.78+0.06, G 173.49+2.42 (S231, S233IR), G 188.95+0.89 (S252, AFGL5180) and G 192.60-0.05 (S255IR). These radio-quiet methanol maser sites are often interpreted as precursors of ultra-compact \ion{H}{ii} regions or massive protostar sites. In this work, the environment of methanol masers is probed from mid-IR to millimetre wavelengths at angular resolutions of $8^{\prime \prime }-34^{\prime \prime }$. Spectral energy distribution (SED) diagrams for each site are presented, together with mass and luminosity estimates. Each radio-quiet maser site is always associated with a massive ($>50$ M${}_{\odot }$), deeply embedded ($A_v>40$ mag) and very luminous ($>10^4$ S L${}_{\odot }$) molecular clump, with $L_{total}\propto M_{gas}^{0.75}$. These physical properties characterise massive star-forming clumps in earlier evolutionary phases than \ion{H}{ii} regions. In addition, colder gas clumps seen only at mm-wavelengths are also found near the methanol maser sites. These colderclumps may represent an even earlier phase of massive star formation. These results suggest an evolutionary sequence for massive star formation from a cold clump, seen only at mm wavelengths, evolving to a hot molecular core with a two-component SED with peaks at far-IR and mid-IR wavelengths, to an (ultra-compact) \ion{H}{ii} region. Alternatively, the cold clumps might be clusters of low-mass YSOs, in formation near the massive star-forming clusters. Finally, the values of the dust grain emissivity index ($\beta$) range between 1.6 and 1.9.

17 pages. A&A in press

References in corpus (6)

• Embedded Clusters in Molecular Clouds
• High-Mass Proto-Stellar Candidates - II : Density structure from dust continuum and CS emission
• High-Mass Proto-Stellar Candidates - I : The Sample and Initial Results
• Massive Stars: Their Environment and Formation
• The Population of the Galactic Plane as Seen by MSX
• IRAS 23385+6053: a candidate protostellar massive object

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