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Date and Time of the Query: 2019-06-19 T12:14:28 PDT
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For refcode 2015A&A...576A..33H:
Retrieve 61 NED objects in this reference.
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Copyright by European Southern Observatory (ESO). Reproduced by permission
2015A&A...576A..33H Cool dust heating and temperature mixing in nearby star-forming galaxies Hunt, L. K.; Draine, B. T.; Bianchi, S.; Gordon, K. D.; Aniano, G.; Calzetti, D.; Dale, D. A.; Helou, G.; Hinz, J. L.; Kennicutt, R. C.; Roussel, H.; Wilson, C. D.; Bolatto, A.; Boquien, M.; Croxall, K. V.; Galametz, M.; Gil de Paz, A.; Koda, J.; Munoz-Mateos, J. C.; Sandstrom, K. M.; Sauvage, M.; Vigroux, L.; Zibetti, S. Abstract. Physical conditions of the interstellar medium in galaxies are closely linked to the ambient radiation field and the heating of dust grains. In order to characterize dust properties in galaxies over a wide range of physical conditions, we present here the radial surface brightness profiles of the entire sample of 61 galaxies from Key Insights into Nearby Galaxies: Far-Infrared Survey with Herschel (KINGFISH). The main goal of our work is the characterization of the grain emissivities, dust temperatures, and interstellar radiation fields (ISRFs) responsible for heating the dust. We first fit the radial profiles with exponential functions in order to compare stellar and cool-dust disk scalelengths, as measured by 3.6 micron and 250 micron surface brightnesses. Our results show thatthe stellar and dust scalelengths are comparable, with a mean ratio of 1.04, although several galaxies show dust-to-stellar scalelength ratios of 1.5 or more. We then fit the far-infrared spectral energy distribution (SED) in each annular region with single-temperature modified blackbodies using both variable (MBBV) and fixed (MBBF) emissivity indices beta, as well as with physically motivated dust models. The KINGFISH profiles are well suited to examining trends of dust temperature T_dust_ and beta because they span a factor of ~200 in the ISRF intensity heating the bulk of the dust mass, U_min_. Results from fitting the profile SEDs suggest that, on average, T_dust_, dust optical depth tau_dust_, and U_min_ decrease with radius. The emissivity index beta also decreases with radius in some galaxies, but in others is increasing, or rising in the inner regions and falling in the outer ones. Despite the fixed grain emissivity (average beta ~ 2.1) of the physically-motivated models, they are well able to accommodate flat spectral slopes with beta <~ 1. An analysis of the wavelength variations of dust emissivities in both the data and the models shows that flatter slopes (beta <~ 1.5) are associated with cooler temperatures, contrary to what would be expected from the usual T_dust_ - beta degeneracy. This trend is related to variations in U_min_ since beta and U_min_ are very closely linked over the entire range in U_min_ sampled by the KINGFISH galaxies: low U_min_ is associated with flat beta <~ 1. Both these results strongly suggest that the low apparent beta values (flat slopes) in MBBV fits are caused by temperature mixing along the line of sight, rather than by intrinsic variations in grain properties. Finally, a comparison of dust models and the data show a slight ~10% excess at 500 micron for low metallicity (12 + log (O/H) <~ 8) and low far-infrared surface brightness (Sigma_500_). Based on Herschel observations. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendices are available in electronic form at http://www.aanda.orgData are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/576/A33 Key words: galaxies: ISM, dust, extinction, galaxies: star formation
Retrieve 61 NED objects in this reference.
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