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Dust properties of external galaxies; NGC 891 revisited

Alton, P. B., Xilouris, E. M., Bianchi, S., Davies, Jonathan Ivor and Kylafis, N. 2000. Dust properties of external galaxies; NGC 891 revisited. Astronomy & Astrophysics 356 (3) , pp. 795-807.

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We compare [FORMULA]m SCUBA images of NGC 891 with the corresponding V-band optical depth predicted from radiation transfer simulations. These two tracers of dust show a very similar distribution along the minor axis and a reasonable agreement along the major axis. Assuming that the grains responsible for optical extinction are also the source of [FORMULA]m emission we derive a submillimeter emissivity (emission efficiency) for dust in the NGC 891 disk. This quantity is found to be a factor of 2-3 higher than the generally-accepted (but highly uncertain) values adopted for the Milky Way. It should be stated, however, that if a substantial fraction of dust in NGC 891 is clumped, the emissivity in the two galaxies may be quite similar. We use our newly-acquired emissivity to convert our [FORMULA]m images into detailed maps of dust mass and, utilizing 21cm and CO-emission data for NGC 891, derive the gas-to-dust ratio along the disk. We compute an average ratio of 260 - a value consistent with the Milky Way and external spirals within the uncertainties in deriving both the dust mass and the quantity of molecular gas. The bulk of dust in NGC 891 appears to be closely associated with the molecular gas phase although it may start to follow the distribution of atomic hydrogen at radii [FORMULA]9 kpc (i.e. [FORMULA]). Using the optical depth of the NGC 891 disk, we quantify how light emitted at high redshift is attenuated by dust residing in foreground spirals. For B-band observations of galaxies typically found in the Hubble Deep Field, the amount of light lost is expected to be small ([FORMULA] 5%). This value depends critically on the maximum radial extent of cold dust in spiral disks (which is poorly known). It may also represent a lower limit if galaxies expel dust over time into the intergalactic medium.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: ISM: dust, extinction – ISM: molecules – galaxies: spiral – galaxies: individual: NGC 891 – galaxies: ISM – infrared: galaxies
Additional Information: Pdf uploaded in accordance with publisher's policy at (accessed 16/04/2014)
Publisher: EDP Sciences
ISSN: 1432-0746
Date of First Compliant Deposit: 30 March 2016
Last Modified: 06 May 2023 20:01

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