2012/07/17 by G. Aniano, B. T. Draine, D. Calzetti +28 · 2 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Black-body radiation #Cosmic dust #Cosmology and Gravitation Theories #Dust lane #Extinction (optical mineralogy) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Luminosity #Spiral galaxy #Starlight #Surface brightness #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.1088/0004-637x/756/2/138
To be published in Apj, September 2012. See the full version at http://www.astro.princeton.edu/~ganiano/Papers/
arxiv created 2012/07/17 · openalex publication_date 2012/08/23 · arxiv updated 2015/06/05 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We characterize the dust in NGC 628 and NGC 6946, two nearby spiral galaxies in the KINGFISH sample. With data from 3.6 μm to 500 μm, dust models are strongly constrained. Using the Draine & Li dust model (amorphous silicate and carbonaceous grains), for each pixel in each galaxy we estimate (1) dust mass surface density, (2) dust mass fraction contributed by polycyclic aromatic hydrocarbons, (3) distribution of starlight intensities heating the dust, (4) total infrared (IR) luminosity emitted by the dust, and (5) IR luminosity originating in regions with high starlight intensity. We obtain maps for the dust properties, which trace the spiral structure of the galaxies. The dust models successfully reproduce the observed global and resolved spectral energy distributions (SEDs). The overall dust/H mass ratio is estimated to be 0.0082 ± 0.0017 for NGC 628, and 0.0063 ± 0.0009 for NGC 6946, consistent with what is expected for galaxies of near-solar metallicity. Our derived dust masses are larger (by up to a factor of three) than estimates based on single-temperature modified blackbody fits. We show that the SED fits are significantly improved if the starlight intensity distribution includes a (single intensity) "delta function" component. We find no evidence for significant masses of cold dust ( T ≲ 12 K). Discrepancies between PACS and MIPS photometry in both low and high surface brightness areas result in large uncertainties when the modeling is done at PACS resolutions, in which case SPIRE, MIPS70, and MIPS160 data cannot be used. We recommend against attempting to model dust at the angular resolution of PACS.