VLA IMAGING OF VIRGO SPIRALS IN ATOMIC GAS (VIVA). I. THE ATLAS AND THE H I PROPERTIES

Abstract

We present the results of a new VLA H i Imaging survey of Virgo galaxies, the VLA Imaging survey of Virgo galaxies in Atomic gas (VIVA). The survey includes high-resolution H i data of 53 carefully selected late type galaxies (48 spirals and five irregular systems). The goal is to study environmental effects on H i gas properties of cluster galaxies to understand which physical mechanisms affect galaxy evolution in different density regions, and to establish how far out the impact of the cluster reaches. As a dynamically young cluster, Virgo contains examples of galaxies experiencing a variety of environmental effects. Its nearness allows us to study each galaxy in great detail. We have selected Virgo galaxies with a range of star formation properties in low to high density regions (at projected distances from M87, d87 = 0.3–3.3 Mpc). Contrary to previous studies, more than half of the galaxies in the sample (∼60%) are fainter than 12 mag in BT. Overall, the selected galaxies represent the late type Virgo galaxies (S0/a to Sd/Irr) down to mp ≲ 14.6 fairly well in morphological type, systemic velocity, subcluster membership, H i mass, and deficiency. The H i observations were done in C short (CS) configuration of the VLA radio telescope, with a typical spatial resolution of 15'' and a column density sensitivity of ≈3–5 × 1019 cm−2 in 3σ per 10 km s−1 channel. The survey was supplemented with data of comparable quality from the NRAO archive, taken in CS or C configuration. In this paper, we present H i channel maps, total intensity maps, velocity fields, velocity dispersions, global/radial profiles, position–velocity diagrams and overlays of H i/1.4 GHz continuum maps on the optical images. We also present H i properties such as total flux (SH i), H i mass (MH i), linewidths (W20 and W50), velocity (VH i), deficiency (defH i), and size (DeffH i and DisoH i), and describe the H i morphology and kinematics of individual galaxies in detail. The survey has revealed details of H i features that were never seen before. In this paper, we briefly discuss differences in typical H i morphology for galaxies in regions of different galaxy densities. We confirm that galaxies near the cluster core (d87 ≲ 0.5 Mpc) have H i disks that are smaller compared to their stellar disks (DH i/D25 < 0.5). Most of these galaxies in the core also show gas displaced from the disk, which is either currently being stripped or falling back after a stripping event. At intermediate distances (d87 ∼ 1 Mpc) from the center, we find a remarkable number of galaxies with long one-sided H i tails pointing away from M87. In a previous letter, we argue that these galaxies are recent arrivals, falling into the Virgo core for the first time. In the outskirts, we find many gas-rich galaxies, with gas disks extending far beyond their optical disks. Interestingly, we also find some galaxies with H i disks that are smaller compared to their stellar disks at large clustercentric distances.