Document Type

Article

Publication Date

3-2013

Department

Physics and Astronomy

Abstract

Our aim is to explore the relation between gas, atomic and molecular, and dust in spiral galaxies. Gas surface densities are from atomic hydrogen and CO line emission maps. To estimate the dust content, we use the disk opacity as inferred from the number of distant galaxies identified in twelve HST/WFPC2 fields of ten nearby spiral galaxies. The observed number of distant galaxies is calibrated for source confusion and crowding with artificial galaxy counts and here we verify our results with sub-mm surface brightnesses from archival Herschel-SPIRE data. We find that the opacity of the spiral disk does not correlate well with the surface density of atomic (H I) or molecular hydrogen (H2) alone implying that dust is not only associated with the molecular clouds but also the diffuse atomic disk in these galaxies. Our result is a typical dust-to-gas ratio of 0.04, with some evidence that this ratio declines with galactocentric radius, consistent with recent Herschel results. We discuss the possible causes of this high dust-to-gas ratio; an over-estimate of the dust surface-density, an under-estimate of the molecular hydrogen density from CO maps or a combination of both. We note that while our value of the mean dust-to-gas ratio is high, it is consistent with the metallicity at the measured radii if one assumes the Pilyugin & Thuan (2005) calibration of gas metallicity.

Comments

This is the pre-peer reviewed version of the following article:

Holwerda, B. W., et al. "The Opacity of Spiral Galaxy Disks: IX. Dust and Gas Surface Densities." 2013. Astronomiche Nachrichten 334(3): 268-281.

which has been published in final form at https://doi.org/10.1002/asna.201211713

This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

Original Publication Information

Holwerda, B. W., et al. "The Opacity of Spiral Galaxy Disks: IX. Dust and Gas Surface Densities." 2013. Astronomiche Nachrichten 334(3): 268-281.

DOI

10.1002/asna.201211713

Share

COinS