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Resolved 200µm images of nearby galaxies - evidence for an extended distribution of cold dust

Alton, P. B., Trewhella, M., Davies, Jonathan Ivor, Evans, R., Bianchi, S., Gear, W., Thronson, H., Valentijn, E. and Witt, A. 1998. Resolved 200µm images of nearby galaxies - evidence for an extended distribution of cold dust. Astronomy and Astrophysics 335 (3) , pp. 807-822.

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We present resolved 200µm images for 8 nearby galaxies observed with the Infrared Space Observatory (ISO). By comparing the200µ m observations with IRAS 60µ m and 100µ m data, we find that cold dust becomes more dominant at larger radii. We infer a grain temperature of 18-21 K for this cold component i.e. about 10 K lower than the warm dust detected by IRAS in external spirals. This value is close to theoretical predictions in the literature based on heating by the general interstellar radiation field. A comparison of the200µ m images with complementary B-band data also shows that the cold dust is radially more extensive than the stars. The gas-to-dust ratio of external spirals, derived using IRAS fluxes, has been claimed to be about an order of magnitude higher than the value infered for the Galaxy. By analysing the200µ m data for our sample, we derive a mean gas-to-dust ratio of which is close to the value in the solar neighborhood (150-300). It is likely that IRAS may have `overlooked' the vast majority of grains residing in spiral disks.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: ISM: dust, extinction – galaxies: ISM – infrared: galaxies
Publisher: Springer
ISSN: 0004-6361
Last Modified: 04 Jun 2017 04:24

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