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The Extreme Outer Regions of Disk Galaxies: Star Formation and Metal Abundances

Published online by Cambridge University Press:  12 April 2016

Annette Ferguson ,
Rosemary Wyse  and
Jay Gallagher
Annette Ferguson
Affiliation:
Institute of Astronomy, Univ. of Cambridge, Cambridge, UKCB3 0HA
Rosemary Wyse
Affiliation:
Dept. of Physics & Astronomy, JHU, Baltimore, MD, USA21218
Jay Gallagher
Affiliation:
Dept. of Astronomy, University of Wisconsin, Madison, WI, USA53706

Abstract

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The extreme outer regions of disk galaxies, lying at or beyond the classical optical radius defined by R25, present an opportunity to study star formation and chemical evolution under unique physical conditions, possibly reminscent of those which existed during the early stages of disk evolution. We present here some of the first results from a large study to measure star formation rates and metallicities in the extreme outer limits of a sample of nearby spiral galaxies. Despite their low gas column densities, massive star formation is often observed in these outer parts, but at an azimuthally–averaged rate much lower than that seen in the inner disk. Gas-phase O/H abundances of roughly 10% solar characterize the gas at 1.5–2 R25. The implications of our results for star formation ‘laws’ and models of disk evolution are discussed.

Type
Properties of Low Surface Brightness galaxies
Information
International Astronomical Union Colloquium , Volume 171: The Low Surface Brightness Universe , 1999 , pp. 196 - 203
Copyright
Copyright © Astronomical Society of the Pacific 1999

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