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Hα Distances to High Velocity Clouds

Published online by Cambridge University Press:  26 May 2016

Joss Bland-Hawthorn  and
Mary Putman
Joss Bland-Hawthorn
Affiliation:
Anglo-Australian Observatory, PO Box 296, Epping, NSW 2121, Australia
Mary Putman
Affiliation:
Center for Astrophysics & Space Astronomy, Univ. of Colorado, Boulder, CO 80309-0389, USA; Hubble Fellow

Abstract

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Several observing teams have now obtained deep Hα spectroscopy towards high-velocity clouds (HVCs) which vary in structure from compact (CHVCs) to the Magellanic Stream. Our team has observed clouds which range from being bright (~640 mR) to having upper limits on the order of 30 to 70 mR. The Hα measurements can be interpreted as a distance constraint if we adopt a halo ionization model based on fesc ≈ 6% of the ionizing photons escaping normal to the Galactic disk (fesc ≈ 1 − 2% when averaged over solid angle). The results suggest that many HVCs and CHVCs are within a ~40 kpc radius from the Galaxy and are not members of the Local Group at megaparsec distances. We refer the reader to Putman et al. (2003) for the full version of the paper presented here.

Type
Part 1. Census
Information
Symposium - International Astronomical Union , Volume 217: Recycling Intergalactic and Interslettar Matter , 2004 , pp. 12 - 19
Copyright
Copyright © Astronomical Society of the Pacific 2004 

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