A Water and Methanol Maser Survey of Infrared Dark Cloud Cores
Abstract
We have conducted a water and methanol maser 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 contain at least one maser, a well-known signpost of star formation. Almost all of the cores with masers show additional evidence for active star formation including (1) enhanced, slightly extended emission at 4.5 microns which might arise from shocked molecular, (2) broad line widths (delta v 10 km/s) of HCN(4-3) and CS(3-2), and the detection of SiO(2-1), a well-known shock tracer, and (3) bright, compact 24 micron emission that indicates a deeply embedded protostar. The presence of water maser emission toward a significant fraction of these active cores confirms the idea that the active IRDC cores are indeed sites of star formation, and strengthens the suggestion that IRDCs are the very earliest stages in the formation of high-mass stars and star clusters.
- Publication:
-
American Astronomical Society Meeting Abstracts #210
- Pub Date:
- May 2007
- Bibcode:
- 2007AAS...210.8702C