Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2012
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21944413a&link_type=abstract
American Astronomical Society, AAS Meeting #219, #444.13
Astronomy and Astrophysics
Astronomy
Scientific paper
Physical models for interstellar dust are presented for NGC 628 and NGC 6946, two well-resolved spiral galaxies observed by the IRAC and MIPS cameras on Spitzer Space Telescope, and the PACS and SPIRE cameras on Herschel Space Observatory, by the KINGFISH project. With wavelength coverage from 3.6µm to 500µm, the dust models are strongly constrained. For each pixel in each galaxy we estimate (1) the mass surface density of dust, (2) the fraction of the dust mass contributed by PAHs, (3) the distribution of intensities of starlight heating the dust grains, and (4) the IR luminosity originating in regions with high starlight intensity. The angular resolution of Herschel resolves the large scale dust structures within the galaxies. We obtain total dust masses for each galaxy by summing the dust mass over the individual map pixels. These dust masses are consistent with the masses inferred from a model fit to the global photometry. The overall dust to H mass ratio is estimated to be 0.010 ± 002 for NGC 628, and 0.012 ± 0.003 for NGC 6946, consistent with what is expected for near-solar metallicities. We do not find any evidence for significant masses of cold dust (T < 12K). Discrepancies between the PACS and MIPS photometry in low surface brightness areas result in large uncertainties when the modeling is done at PACS resolutions, in which case SPIRE, MIPS70µm and MIPS160µm data cannot be used, therefore we do not recommend attempting to model dust in the outer parts of the galaxies at the angular resolution of PACS. We show that, contrary to some claims, the spectral energy distribution fits are significantly improved if the starlight distribution includes a "delta function” component.
Aniano Porcile Gonzalo J.
Draine Bruce T.
KINGFISH ..
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