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We present 21-cm observations of a 10 × 2 deg 2 region in the Virgo cluster, obtained as part of the Arecibo Galaxy Environment Survey. 289 sources are detected over the full redshift range (−2000 < v hel < +20 000 km s −1 ) with 95 belonging to the cluster (v hel < 3000 km s −1 ). We combine our observations with data from the optically selected Virgo Cluster Catalogue (VCC) and the Sloan Digital Sky Survey. Most of our detections can be clearly associated with a unique optical counterpart, and 30 per cent of the cluster detections are new objects fainter than the VCC optical completeness limit. Seven detections may have no optical counterpart and we discuss the possible origins of these objects. Seven detections appear associated with early-type galaxies. We perform H I stacking on the H I-undetected galaxies listed in the VCC in this region and show that they must have significantly less gas than those actually detected in H I. Galaxies undetected in H I in the cluster appear to be really devoid of gas, in contrast to a sample of field galaxies from the Arecibo Legacy Fast ALFA (ALFALFA).The AGES V: The Virgo Cluster (I) 789 but higher inclination angles) since their flux is spread out over more channels.Follow-up observations were performed using the L-wide receiver. This uses the position-switching method, with the ON and OFF source times each of 5 min. The data were quickly reduced and additional observations taken if necessary. We use the Wideband Arecibo Pulsar Processors (WAPPs) with nine-level sampling and one polarization per board, giving us 4096 channels. We use two bandwidth settings, 50 MHz (giving a velocity resolution of 1.25 km s −1 ) and 25 MHz (0.63 km s −1 resolution). The criteria for performing follow-up observations are described in Section 2.2. Data contamination: the Milky Way and radio frequency interferenceAlthough the bandwidth observed spans over 20 000 km s −1 of redshift, in certain regions the survey is effectively blinded due to the presence of strong contaminating sources. The signal from the Milky Way is extremely strong and fills the whole sky, and LIVEDATA is unable to correctly process the signal using our standard techniques. Consequently, we are unable to obtain meaningful data over the velocity range −50 < v < +50 km s −1 . Similarly, the Punta del Este Federal Aviation Administration radar, operating at 1350 MHz, causes strong false signals over the approximate velocity range +15 400 < v < +16 000 km s −1 , as well as the intermod at approximately 7000 km s −1 . Harmonics of the radar are present throughout the cube but are much weaker and do not significantly detract from the available bandwidth. Some scans were also affected by the signal from the L3 GPS satellite, generating false signals at approximately 8500 km s −1 . The survey is not blinded within these regions affected by RFI, but sensitivity is greatly reduced. This work has made use of the SDSS.

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The removal of gas by ram pressure stripping of galaxies is treated by a purely kinematic description. The solution has two asymptotic limits: if the duration of the ram pressure pulse exceeds the period of vertical oscillations perpendicular to the galactic plane, the commonly used quasi-static criterion of Gunn & Gott is obtained which uses the maximum ram pressure that the galaxy has experienced along its orbit. For shorter pulses the outcome depends on the time-integrated ram pressure. This parameter pair fully describes the gas mass fraction that is stripped from a given galaxy. This approach closely reproduces results from SPH simulations. We show that typical galaxies follow a very tight relation in this parameter space corresponding to a pressure pulse length of about 300 Myr. Thus, the Gunn & Gott criterion provides a good description for galaxies in larger clusters. Applying the analytic description to a sample of 232 Virgo galaxies from the GoldMine database, we show that the ICM provides indeed the ram pressures needed to explain the deficiencies. We also can distinguish current and past strippers, including objects whose stripping state was unknown.

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