Mon. Not. R. Astron. Soc., 484, 305-331 (2019/March-3)
On the diagnostic power of FIR/sub-mm SED fitting in massive galactic molecular clumps.
PITTS R.L., BARNES P.J. and VAROSI F.
Abstract (from CDS):
We used far-infrared (FIR) and sub-millimetre continuum data from Herschel and the Atacama Pathfinder EXperiment (APEX) to fit pixel-by-pixel modified Planck spectral energy distributions to prestellar and protostellar clumps in the Census of High- and Medium-mass Protostars (CHaMP) (280° < l < 300°, -4° < b < +2°). We present maps of dust temperature (Td) and H2 column density (NH2) for molecular clumps in the Carina Nebula complex (Regions 9 through 11), and surrounding RCW 64 (Region 26). We compare the column densities of CO and H2 to chart regional variations in their correspondence, and derive maps of the CO abundance. We find that the CO abundance varies by an order of magnitude or more across each region, averaging a few x 10–5 CO per H2, and that the CO abundance distribution across each clump is correlated in both form and magnitude with environmental conditions, especially Td. This demonstrates that no single CO abundance suffices to convert from NCO to NH2, even within a single molecular cloud. We also find that L/M traces Td almost exclusively, and therefore is not an independent star formation tracer, but minima in Td almost universally coincide with maxima in NH2, implying that cooling and density enhancement must be simultaneous steps in prestellar clump evolution. Finally, based on generalized histogram column density probability distribution functions (N-PDFs) of clump-scale (1-5 pc) and cloud-scale (>=10 pc) samples, we could only obtain dual lognormal and power-law fits to ∼10 per cent of the clumps. The physical parameters derived from these fits approach theoretical expectations, but have largely unknown uncertainties, so we advise treating the results of N-PDF fitting with caution.
© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
stars: formation - ISM: abundances - dust, extinction - ISM: individual objects: Carina Nebula - infrared: ISM - submillimetre: ISM
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