First results from the Herschel★ Gould Belt Survey in Taurus

Abstract

The whole of the Taurus region (a total area of 52 sq. deg.) has been\nobserved by the Herschel SPIRE and PACS instruments at wavelengths of 70, 160,\n250, 350 and 500 {\\mu}m as part of the Herschel Gould Belt Survey. In this\npaper we present the first results from the part of the Taurus region that\nincludes the Barnard 18 and L1536 clouds. A new source-finding routine, the\nCardiff Source-finding AlgoRithm (CSAR), is introduced, which is loosely based\non CLUMPFIND, but that also generates a structure tree, or dendrogram, which\ncan be used to interpret hierarchical clump structure in a complex region.\nSources were extracted from the data using the hierarchical version of CSAR and\nplotted on a mass-size diagram. We found a hierarchy of objects with sizes in\nthe range 0.024-2.7 pc. Previous studies showed that gravitationally bound\nprestellar cores and unbound starless clumps appeared in different places on\nthe mass-size diagram. However, it was unclear whether this was due to a lack\nof instrumental dynamic range or whether they were actually two distinct\npopulations. The excellent sensitivity of Herschel shows that our sources fill\nthe gap in the mass-size plane between starless and pre-stellar cores, and\ngives the first clear supporting observational evidence for the theory that\nunbound clumps and (gravitationally bound) prestellar cores are all part of the\nsame population, and hence presumably part of the same evolutionary sequence\n(c.f. Simpson et al. 2011).\n