  The whole of the Taurus region (a total area of 52 sq. deg.) has been
observed by the Herschel SPIRE and PACS instruments at wavelengths of 70, 160,
250, 350 and 500 {\mu}m as part of the Herschel Gould Belt Survey. In this
paper we present the first results from the part of the Taurus region that
includes the Barnard 18 and L1536 clouds. A new source-finding routine, the
Cardiff Source-finding AlgoRithm (CSAR), is introduced, which is loosely based
on CLUMPFIND, but that also generates a structure tree, or dendrogram, which
can be used to interpret hierarchical clump structure in a complex region.
Sources were extracted from the data using the hierarchical version of CSAR and
plotted on a mass-size diagram. We found a hierarchy of objects with sizes in
the range 0.024-2.7 pc. Previous studies showed that gravitationally bound
prestellar cores and unbound starless clumps appeared in different places on
the mass-size diagram. However, it was unclear whether this was due to a lack
of instrumental dynamic range or whether they were actually two distinct
populations. The excellent sensitivity of Herschel shows that our sources fill
the gap in the mass-size plane between starless and pre-stellar cores, and
gives the first clear supporting observational evidence for the theory that
unbound clumps and (gravitationally bound) prestellar cores are all part of the
same population, and hence presumably part of the same evolutionary sequence
(c.f. Simpson et al. 2011).
