Artículo de revista
Star-forming protoclusters associated with methanol masers
Fecha
2005Registro en:
A&A 429, 945–960 (2005)
DOI: 10.1051/0004-6361:20041137
Autor
Minier, V.
Burton, M. G.
Hill, T.
Pestalozzi, M. R.
Purcell, C. R.
Garay Brignardello, Guido
Walsh, A. J.
Longmore, S.
Institución
Resumen
We present a multiwavelength study of five methanol maser sites which are not directly associated with a strong
(>100 mJy) radio continuum source: G31.28+0.06, G59.78+0.06, G173.49+2.42 (S231, S233IR), G188.95+0.89 (S252,
AFGL5180) and G192.60-0.05 (S255IR). These radio-quiet methanol maser sites are often interpreted as precursors of ultracompact
H 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 −34 . 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 ),
deeply embedded (Av > 40 mag) and very luminous (>104 L ) molecular clump, with Ltotal ∝ M0.75
gas . These physical properties
characterise massive star-forming clumps in earlier evolutionary phases than H regions. In addition, colder gas clumps seen
only at mm-wavelengths are also found near the methanol maser sites. These colder clumps 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) H 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 (β) range between 1.6 and 1.9.