The Stellar Population of Stripped Cluster Spiral NGC 4522: A Local Analog to K+A Galaxies?

We present observations of the stripped Virgo Cluster spiral galaxy NGC 4522, a clear, nearby example of a galaxy currently undergoing interstellar medium-intracluster medium (ISM-ICM) stripping. Utilizing SparsePak integral field spectroscopy on the Wisconsin-Indiana-Yale-NOAO (WIYN) 3.5 m telescope and Galaxy Evolution Explorer (GALEX) UV photometry, we present an analysis of the outer disk (r > 3 kpc) stellar population of this galaxy, beyond the H I and Hα truncation radius. We find that the star formation in the gas-stripped outer disk ceased very recently, ~100 Myr ago, in agreement with previous claims that this galaxy is currently being stripped. At the time of this stripping, data and models suggest that the galaxy experienced a modest starburst. The stripping is occurring in a region of the cluster well outside the cluster core, likely because this galaxy is experiencing extreme conditions from a dynamic ICM due to an ongoing subcluster merger. The outer disk has a spectrum of a K+A galaxy, traditionally observed in high-redshift cluster galaxies. In the case of NGC 4522, a K+A spectrum is formed by simple stripping of the interstellar gas by the hot intracluster medium. These data show K+A spectra can be created by cluster processes and that these processes likely extend beyond the cluster core.

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