G305.136 0.068: A massive and dense cold core in an early stage of evolutionReport as inadecuate

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We report molecular line observations, made with ASTE and SEST, and dust continuum observations at 0.87 mm,made with APEX, toward the cold dust core G305.136+0.068. The molecular observations show that the core isisolated and roughly circularly symmetric and imply that it has a mass of 1.1 × 103 M. A simultaneous modelfitting of the spectra observed in four transitions of CS, using a non-LTE radiative transfer code, indicates thatthe core is centrally condensed, with the density decreasing with radius as r−1.8, and that the turbulent velocityincreases toward the center. The dust observations also indicate that the core is highly centrally condensed and thatthe average column density is 1.1 g cm−2, a value slightly above the theoretical threshold required for the formationof high-mass stars. A fit to the spectral energy distribution of the emission from the core indicates a dust temperatureof 17 ± 2 K, confirming that the core is cold. Spitzer images show that the core is seen in silhouette from 3.6 to24.0μm and that it is surrounded by an envelope of emission, presumably tracing an externally excited photodissociatedregion. We found two embedded sources within a region of 20 centered at the peak of the core, one ofwhich is young, has a luminosity of 66L, and is accreting mass with a high accretion rate of ∼1 × 10−4 M yr−1.We suggest that this object corresponds to the seed of a high-mass protostar still in the process of formation. Thepresent observations support the hypothesis that G305.136+0.068 is a massive and dense cold core in an early stageof evolution, in which the formation of a high-mass star has just started.Nota general

Artículo de publicación ISI

Author: Garay Brignardello, Guido; - Mardones Pérez, Diego; - Guzmán Fernández, Andrés; - Servajean Bergoeing, Elise; - Pineda, Jaime

Source: http://repositorio.uchile.cl/


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