Footprints of hierarchical thermal fragmentation in the star forming cluster NGC 2264

To fully understand how molecular clouds survive long enough to sustain multiple star forming epochs it is essential to know in detail their star forming histories. NGC2264 is one of the classical star forming regions, first studied by Walker in 1965 who discovered its pre-main sequence (PMS) population. We re-visit the region with the Spitzer Space telescope to study in detail its PMS sources in terms of circumstellar disk evolution and age spread. Our analysis of the spatial distribution of the sources indicate that there were two distinct star forming epochs in NGC2264. I will briefly discuss the correlation between the spatial distribution and the age spread of distinct populations within NGC2264.

The latest star forming event has spawned a cluster of protostars in NGC2264 (Spokes cluster) that retains a characteristic length scale (20"+-5") similar to the Jeans length for that region (27"). We found a micro-cluster within the Spokes cluster with a smaller characteristic length scale and explore the scenario of a secondary thermal fragmentation within the region. During this talk, I will present sensitive high angular resolution (~1") 230GHz continuum interferometric observations of this micro-cluster using the Submillimeter Array, in Hawai'i. We detected seven very compact millimeter sources clustered in a 20"x 20" region, four of which are associated with infrared emission. The seven new millimeter sources have ~0.1 solar masses and sizes of about 700AU. We interpret these 1.3mm sources as compact circumstellar disks+inner dense protostellar envelopes. The mean distance between these sources is ~7" which corresponds to the Jeans length for the micro-cluster. Our analysis seem to indicate that the dominant fragmentation process for this region within NGC2264 is thermal and not turbulent.

 

Date: 
23/07/2007 - 14:00
Speaker: 
Paula Teixeira
Filiation: 
Harvard-Smithsonian Center for Astrophysics (CfA)


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