Astronomy and Astrophysics – Astronomy
Scientific paper
May 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008aas...212.0609c&link_type=abstract
American Astronomical Society, AAS Meeting #212, #6.09; Bulletin of the American Astronomical Society, Vol. 40, p.197
Astronomy and Astrophysics
Astronomy
Scientific paper
We have conducted an ammonia (1,1) and (2,2) survey toward compact millimeter cores within Infrared Dark Clouds (IRDCs). IRDCs were discovered by the ISO and MSX infrared surveys as extinction features in the mid-infrared. We examined 38 of the highest extinction IRDCs in the millimeter continuum and found 189 compact cores, 140 of which are cold, compact and unassociated with 8 micron emission. Each IRDC invariably contains at least one cold, compact core, and many contain several. These cold, compact cores have sizes and masses of 0.5 pc and 120 Msun. Roughly 35 percent of these cores show evidence for active star formation including (1) enhanced, slightly extended, shock-excited 4.5 micron emission, (2) bright, compact 24 micron emission that indicates a deeply embedded protostar, and (3) water and methanol maser emission. We have created an automated algorithm which separates active, star-forming cores from quiescent, starless cores based on these IR signatures. We test our IR identification of the star formation activity within IRDC cores by examining the ammonia rotation temperatures of active and quiescent cores derived from our ammonia survey. We find that active cores have higher ammonia rotation temperatures than quiescent cores. The lower rotation temperatures of the quiescent cores support the idea that the quiescent cores are in a prestellar state, while the higher rotation temperatures of the active cores show that the active cores are currently forming stars, and are in a later evolutionary stage than quiescent cores. This finding supports the idea that IRDCs harbor cores in the very earliest stages of high-mass star and cluster formation.
Chambers Edward Thomas
Jackson James M.
Rathborne Jill M.
Simon Robert
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