Extraplanar Dust in Spiral Galaxies: Observations and Implications
Abstract
Recent optical and submillimeter observations have begun to probe the existence of dust grains in the halos of spiral galaxies. I review our own work in this area which employs high-resolution optical images of edge-on spiral galaxies to trace high-z dust in absorption against the background stellar light of the galaxies. We have found that a substantial fraction of such galaxies (>50%) show extensive webs of dust-bearing clouds to heights z>2 kpc. Extraplanar dust in galaxies is statistically correlated with extraplanar diffuse ionized gas, though there is no evidence for a direct, physical relationship between these two phases of the high-z interstellar medium. The dense high-z clouds individually have masses estimated to be >10^5} to 10^6 solar masses. The detailed properties of the observed dust structures suggest the clouds seen in our images may represent the dense phase of a multiphase ISM at high-z. Such dense clouds can have an important effect on the observed light distribution in spiral galaxies. I discuss the effects such high-z dust can have on quantitative measures of the vertical structure of stars and ionized gas in edge-on systems.
Cite
@article{arxiv.astro-ph/9910092,
title = {Extraplanar Dust in Spiral Galaxies: Observations and Implications},
author = {J. Christopher Howk},
journal= {arXiv preprint arXiv:astro-ph/9910092},
year = {2009}
}
Comments
To appear in "Toward a New Millennium in Galaxy Morphology," eds. D.L. Block, I. Puerari, A. Stockton, & D. Ferreira (Kluwer, Dordrecht). 8 pages; 3 embedded figures. Version with high-resolution figures available at http://fuse.pha.jhu.edu/~howk/Papers/papers.html