2000/01/13 by S. Molinari, Sergio Molinari, Molinari, Sergio +9
Physics and Astronomy · #Astro and Planetary Science #Astrophysics (astro-ph) #Astrophysics and Star Formation Studies #FOS: Physical sciences #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0001231
14 pages, 6 figures, to be published on Astronomy and Astrophysics
arxiv created 2000/01/13 · openalex publication_date 2000/01/13 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The James Clerk Maxwell Telescope has been used to obtain submillimeter and\nmillimeter continuum photometry of a sample of 30 IRAS sources previously\nstudied in molecular lines and centimeter radio continuum. All the sources have\nIRAS colours typical of very young stellar objects (YSOs) and are associated\nwith dense gas. In spite of their high luminosities (L>10000 solar units), only\nten of these sources are also associated with a radio counterpart. In 17 cases\nwe could identify a clear peak of millimeter emission associated with the IRAS\nsource, while in 9 sources the millimeter emission was extended or faint and a\nclear peak could not be identified; upper limits were found in 4 cases only.\n Using simple greybody fitting model to the observed SED, we derive global\nproperties of the circumstellar dust. The dust temperature varies from 24 K to\n45 K, while the exponent of the dust emissivity vs frequency power-law spans a\nrange 1.56<beta<2.38, characteristic of silicate dust; total circumstellar\nmasses range up to more than 500 solar masses.\n We find that for sources with comparable luminosities, the total column\ndensities derived from the dust masses do not distinguish between sources with\nand without radio counterpart. We interpret this result as an indication that\ndust does not play a dominant role in inhibiting the formation of the HII\nregion. We examine several scenarios for their origin in terms of newborn ZAMS\nstars and although most of these fail to explain the observations, we cannot\nexclude that these sources are young stars already on the ZAMS with modest\nresidual accretion that quenches the expansion of the HII region. Finally, we\nconsider the possibility that the IRAS sources are high-mass pre-ZAMS (or\npre-H-burning) objects deriving most of the emitted luminosity from accretion.\n