Publication Date:
2013-11-14
Description:
We have detected bright HC 7 N J = 21 – 20 emission towards multiple locations in the Serpens South cluster-forming region using the K -Band Focal Plane Array at the Robert C. Byrd Green Bank Telescope. HC 7 N is seen primarily towards cold filamentary structures that have yet to form stars, largely avoiding the dense gas associated with small protostellar groups and the main central cluster of Serpens South. Where detected, the HC 7 N abundances are similar to those found in other nearby star-forming regions. Towards some HC 7 N ‘clumps’, we find consistent variations in the line centroids relative to NH 3 (1,1) emission, as well as systematic increases in the HC 7 N non-thermal line widths, which we argue reveal infall motions on to dense filaments within Serpens South with minimum mass accretion rates of M ~ 2–5 M Myr –1 . The relative abundance of NH 3 to HC 7 N suggests that the HC 7 N is tracing gas that has been at densities n ~ 10 4 cm –3 for time-scales t 1–2 10 5 yr. Since HC 7 N emission peaks are rarely co-located with those of either NH 3 or continuum, it is likely that Serpens South is not particularly remarkable in its abundance of HC 7 N, but instead the serendipitous mapping of HC 7 N simultaneously with NH 3 has allowed us to detect HC 7 N at low abundances in regions where it otherwise may not have been looked for. This result extends the known star-forming regions containing significant HC 7 N emission from typically quiescent regions, like the Taurus molecular cloud, to more complex, active environments.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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