Galaxy transformation in the Virgo Cluster: Gas stripping and stellar population evolution

This study utilizes optical imaging, optical spectroscopy, HI radio maps and UV imaging to study the effects of environment on the evolution of spiral galaxies in the nearby Virgo Cluster.;Optical, HI and radio continuum observations of NGC 4402, a highly inclined HI-deficient Virgo 0.5 L* spiral galaxy, show evidence for ram pressure stripping and dense cloud ablation. Optical images show dust curving up and out of the stellar disk at the HI truncation radius. South of the main dust disk, we have discovered two linear dust filaments aligned with each other and with the skewed radio continuum halo. We interpret these dust filaments as large, dense clouds which were initially left behind as the low-density ISM was stripped, but are now being ablated by the ICM wind.;We present results from 10 spiral galaxies in Virgo that have truncated star-forming disks, with normal star formation in the inner disk and little or no star formation beyond a truncation radius. Models of observed spectra from just beyond the Ha truncation radius demonstrate that stripping was recent, within the last 500 Myr. This implies that ram pressure stripping is effective in halting star formation in the outer disks of spiral galaxies and plays a role in the morphological transformation of spiral galaxies.;The outer disk of one of our sample, NGC 4522, shows a post-star formation K+A type spectrum, consistent with star formation being truncated ∼ 100 Myr ago. From its location in the cluster, we conclude that such stripping could not have taken place in the cluster core and must have taken place near its current location, ∼ 1 Mpc from the cluster center.;The outer disk stellar populations roughly correlate with the neutral gas distributions, as measured from HI maps. Galaxies with extraplanar HI have more recently had star formation in their outer disks truncated. In the three cases where our data overlap with ram pressure simulations of Virgo galaxies, the star formation truncation times from our data agree with the time since peak pressure in the simulations. This suggests that star formation is quickly disrupted during ISM-ICM interactions.