The Herschel view of the on-going star formation in the Vela-C molecular cloud
Publication date: 12 March 2012
Authors: T. Giannini, et al.
Journal: Astronomy & Astrophysics
Volume: 539
Page: A156
Year: 2012
Copyright: ESO
Aims: As part of the Herschel guaranteed time key programme "HOBYS", we present the PACS and SPIRE photometric survey of the star-forming region Vela-C, one of the nearest sites of low-to-high-mass star formation in the Galactic plane. Our main objectives are to take a census of the cold sources and to derive their mass distribution down to a few solar masses.
Methods: Vela-C was observed with PACS and SPIRE in parallel mode at five wavelengths between 70 micron and 500 micron over an area of about 3 square degrees. A photometric catalogue was extracted from the detections in each of the five bands, using a threshold of 5sigma over the local background. Out of this catalogue we selected a robust sub-sample of 268 sources, of which ~75 per cent are cloud clumps (diameter between 0.05 pc and 0.13 pc) and 25 per cent are cores (diameter between 0.025 pc and 0.05 pc). Their spectral energy distributions (SEDs) were fitted with a modified black body function. We classify 48 sources as protostellar, based on their detection at 70 um or at shorther wavelengths, and 218 as starless, because of non-detections at 70 micron. For two other sources, we do not provide a secure classification, but suggest they are Class 0 protostars.
Results: From the SED fitting we derived key physical parameters (i.e. mass, temperature, bolometric luminosity). Protostellar sources are in general warmer (< T > = 12.8 K) and more compact (< diameter > = 0.040 pc) than starless sources (< T > = 10.3 K, < diameter > = 0.067 pc). Both these findings can be ascribed to the presence of an internal source(s) of moderate heating, which also causes a temperature gradient and hence a more peaked intensity distribution. Moreover, the reduced dimensions of protostellar sources may indicate that they will not fragment further.
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