AAS 204th Meeting, June 2004
Session 62 Protoplanets, Star Formation and Debris Disks
Poster, Wednesday, June 2, 2004, 10:00am-7:00pm, Ballroom

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[62.21] IRAS 18317-0757: A Cluster of Massive Stars and Protostars

T.R. Hunter, Q. Zhang, T.K. Sridharan (Harvard-Smithsonian Center for Astrophysics)

We present multiwavelength, high-resolution continuum and molecular line images of the massive star-forming region IRAS 18317-0757. Previous submillimeter imaging resolved this luminous region (105.2 Lsolar) into a cluster of five dust cores: one associated with the ultracompact HII region G23.955+0.150, and another with a water maser. In our new 2.7mm continuum image from BIMA, only the UCHII is detected, with total flux and morphology in agreement with the free-free emission in VLA maps. For the other four objects, non-detections at 2.7mm and in the MSX mid-infrared bands are consistent with cool dust emission (13-40K) with a luminosity of 1,000-40,000Lsolar. By combining single-dish and interferometric data, we have identified over two dozen virialized C18O(1-0) cores which contain ~40% of the total molecular gas mass present. While the overall extent of the C18O and dust emission is similar, their emission peaks do not correlate well in detail. At least 11 of the 123 infrared stars identified by 2MASS are likely to be associated with the star-forming cluster. Two of these objects (both associated with the UCHII) were previously identified as O stars via infrared spectroscopy. Most of the other reddened stars have no obvious correlation with the C18O cores or the dust continuum sources. In summary, our observations indicate that considerable fragmentation of the molecular cloud has taken place during the time required to form the UCHII and for the O stars to become detectable at infrared wavelengths. Additional star formation appears to be ongoing on the periphery of the central region where up to four B-type (proto)stars have apparently formed among a substantial number of C18O cores.

The author(s) of this abstract have provided an email address for comments about the abstract: thunter@cfa.harvard.edu

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