A possible far-ultraviolet flux-dependent core mass function in NGC 6357
  To derive the properties of the dense cores in the galactic star-forming
complex NGC6357 and to investigate the effects of an intense far-UV radiation
field on their properties, we mapped the region at 450 and 850 micron, and in
the CO(3-2) line with the JCMT. We also made use of the Herschel Hi-GAL data at
70 and 160 micron. We used Gaussclumps to retrieve 686 compact cores embedded
in the diffuse sub-mm emission and constructed their SED from 70 to 850 micron,
from which we derived mass and temperature. The estimated mass completeness
limit is ~5Mo. We divided the observed area in an 'active' region, exposed to
the far-UV radiation from the more massive members of three star clusters (411
cores), and a 'quiescent' region, less affected by far-UV radiation (275
cores). We also attempted to select a sample of pre-stellar cores based on
cross-correlation with 70 micron emission and red WISE point sources. Most of
the cores above the mass completeness limit are likely to be gravitationally
bound. The fraction of gas in dense cores is very low, 1.4%. We found a
mass-size relation log(M/Mo) ~ (2.0-2.4) x log (D/arcsec), depending on the
precise selection of the sample. The temperature distributions in the two
sub-regions are clearly different, peaking at ~25K in the quiescent region and
at ~35K in the active region. The core mass functions are different as well, at
a 2sigma level, consistent with a Salpeter IMF in the quiescent region and
flatter than that in the active region. The dense cores lying close to the HII
regions are consistent with pre-existing cores being gradually engulfed by a
PDR and photoevaporating. We attribute the different global properties of dense
cores in the two sub-regions to the influence of the far-UV radiation field.
