Gaps in the cloud cover? Comparing extinction measures in spiral disks

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dc.creatorHolwerda, B. W.
dc.creatorMeyer, M.
dc.creatorRegan, M.
dc.creatorCalzetti, D.
dc.creatorGordon, K. D.
dc.creatorSmith, J. D.
dc.creatorDale, D.
dc.creatorEngelbracht, C. W.
dc.creatorJarrett, T.
dc.creatorThornley, M.
dc.creatorBot, C.
dc.creatorBuckalew, B.
dc.creatorKennicutt, R. C.
dc.creatorGonzalez, R. A.
dc.date2007-07-27
dc.date.accessioned2026-07-07T11:18:13Z
dc.date.available2026-07-07T11:18:13Z
dc.descriptionDust in galaxies can be mapped by either the FIR/sub-mm emission, the optical or infrared reddening of starlight, or the extinction of a known background source. We compare two dust extinction measurements for a set of fifteen sections in thirteen nearby galaxies, to determine the scale of the dusty ISM responsible for disk opacity: one using stellar reddening and the other a known background source. In our earlier papers, we presented extinction measurements of 29 galaxies, based on calibrated counts of distant background objects identified though foreground disks in HST/WFPC2 images. For the 13 galaxies that overlap with the Spitzer Infrared Nearby Galaxies Survey (SINGS), we now compare these results with those obtained from an I-L color map. Our goal is to determine whether or not a detected distant galaxy indicates a gap in the dusty ISM, and hence to better understand the nature and geometry of the disk extinction. We find that distant galaxies are predominantly in low-extinction sections marked by the color maps, indicating that their number depends both on the cloud cover of {\it Spitzer}-resolved dust structures --mostly the spiral arms--and a diffuse, unresolved underlying disk. We note that our infrared color map (E[I-L]) underestimates the overall dust presence in these disks severely, because it implicitly assumes the presence of a dust screen in front of the stellar distribution.
dc.description22 pages, 2 figures, 3 tables, accepted for publication in AJ
dc.identifierhttps://arxiv.org/abs/0707.4167
dc.identifierhttp://arxiv.org/abs/0707.4167
dc.identifierAstron.J.134:1655-1661,2007
dc.identifierdoi:10.1086/521824
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/193268
dc.subjectAstrophysics
dc.titleGaps in the cloud cover? Comparing extinction measures in spiral disks
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