Jeffrey D. P. Kenney and Rebecca A. Koopmann 1999 The Astronomical Journal 117 181 doi:10.1086/300683
Jeffrey D. P. Kenney1 and Rebecca A. Koopmann1,2
Show affiliationsThe Virgo Cluster galaxy NGC 4522 is one of the best spiral candidates for intracluster medium–interstellar medium (ICM-ISM) stripping in action. Optical broadband and Hα images from the WIYN telescope of the highly inclined galaxy reveal a relatively undisturbed stellar disk and a peculiar distribution of Hα emission. Ten percent of the Hα emission arises from extraplanar H II regions which appear to lie within filamentary structures ≥3 kpc long above one side of the disk. The filaments emerge from the outer edge of a disk of bright Hα emission which is abruptly truncated beyond 0.35R25. Together the truncated Hα disk and extraplanar Hα filaments are reminiscent of a bow shock morphology, which strongly suggests that ISM of NGC 4522 is being stripped by the gas pressure of the ICM. The galaxy has a line-of-sight velocity of
1300 km s-1 with respect to the mean Virgo Cluster velocity and thus is expected to experience a strong interaction with the intracluster gas. The existence of H II regions apparently located above the disk plane suggests that star formation is occurring in the stripped gas, and that newly formed stars will enter the galaxy halo and/or intracluster space. The absence of H II regions in the disk beyond 0.35R25 and the existence of H II regions in the stripped gas suggest that even molecular gas has been effectively removed from the disk of the galaxy.
galaxies: clusters: general; galaxies: clusters: individual (Virgo); galaxies: evolution; galaxies: interactions; galaxies: ISM; galaxies: peculiar; galaxies: structure
Issue 1 (1999 January)
Received 1998 June 26, accepted for publication 1998 September 15
Jeffrey D. P. Kenney and Rebecca A. Koopmann 1999 The Astronomical Journal 117 181
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