MPI für Kernphysik / Infrared Astrophysics |
|A comparative study of the spatial distribution of ultraviolet
and far-infrared fluxes from M 101
|Authors:||Popescu, Cristina C.; Tuffs, Richard J.; Madore, Barry F.; Gil de Paz, A.; Völk, Heinrich J.; Barlow, Tom; Bianchi, Luciana; Yong-Ik, Byun; Donas, Jose; Forster, Karl; Friedman, Peter G.; Heckman, Timothy M.; Jelinsky, Patrick N.; Young-Wook, Lee; Malina, Roger F.; Martin, Christopher D.; Milliard, Bruno; Morrissey, Patrick; Neff, Susan G.; Rich, Michael R.; Schiminovich, David; Siegmund, Oswald H.; Small, Todd; Szalay, Alex S.; Welsh, Barry Y.; Wyder, Ted K.|
|Research Context:||dust, extinctiongalaxies: individual (M101)galaxies: spiralinfrared: galaxiesscatteringultraviolet: galaxies|
|Date of Publication (YYYY-MM-DD):||2005-01-20|
|Title of Journal:||Astrophysical Journal Letters|
|Journal Abbrev.:||ApJ Letters|
|Issue / Number:||Nr.1, Part 2|
|Copyright:||The American Astronomical Society.|
|Abstract / Description:||The total ultraviolet (UV) flux (from 1412 to 2718 Å) of M101 is compared on a pixel-to-pixel basis with the total far-infrared (FIR) flux (from 60 to 170 μm) using the maps of the galaxy taken by the Galaxy Evolution Explorer (GALEX) in the near-UV and far-UV and by the Infrared Space Observatory (ISO) at 60, 100, and 170 μm. The main result of this investigation is the discovery of a tight dependence of the FIR/UV ratio on radius, with values monotonically decreasing from 4 in the nuclear region to nearly zero toward the edge of the optical disk. Although the tightness of this dependence is in part attributable to resolution effects, the result is consistent with the presence of a large-scale distribution of diffuse dust having a face-on optical depth that decreases with radius and that dominates over the more localized variations in opacity between the arm and interarm regions. We also find a trend for the FIR/UV ratio of taking on higher values in the regions of diffuse interarm emission than in the spiral-arm regions, at a given radius. This is interpreted quantitatively in terms of the escape probability of UV photons from spiral arms and their subsequent scattering in the interarm regions, and in terms of the larger relative contribution of optical photons to the heating of the dust in the interarm regions.|
|Free Keywords:||dust, extinctiongalaxies: individual (M101)galaxies: spiralinfrared: galaxiesscatteringultraviolet: galaxies|
|External Publication Status:||published|
|Affiliations:||MPI für Kernphysik/Group H. J. Völk/Infrared Astrophysics (R. Tuffs, H.J. Völk)|
|External Affiliations:||Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, 91101 CA.
NASA/IPAC Extragalactic Database, 770 South Wilson Avenue, Pasadena, CA 91125.
California Institute of Technology, MC 405-47, 1200 East California Boulevard, Pasadena, CA 91125.
Center for Astrophysical Sciences, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218.
Center for Space Astrophysics, Yonsei University, Seoul 120-749, Korea.
Laboratoire d'Astrophysique de Marseille, BP 8, Traverse du Siphon, 13376 Marseille Cedex 12, France.
Department of Physics and Astronomy, Johns Hopkins University, Homewood Campus, Baltimore, MD 21218.
Space Sciences Laboratory, University of California at Berkeley, 601 Campbell Hall, Berkeley, CA 94720.
Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, Greenbelt, MD 20771.
Department of Physics and Astronomy, University of California, Los Angeles, CA 90095.
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