Hα Morphologies and Environmental Effects in Virgo Cluster Spiral Galaxies

Abstract

We describe the various Hα morphologies of Virgo Cluster and isolated spiral galaxies, and associate the Hα morphologies with the types of environmental interactions which have altered the cluster galaxies. The spatial distributions of Hα and R-band emission are used to divide the star formation morphologies of the 52 Virgo Cluster spirals into several categories: normal (37%), anemic (6%), enhanced (6%), and (spatially) truncated (52%). Truncated galaxies are further subdivided based on their inner star formation rates into truncated/normal (37%), truncated/compact (6%), truncated/anemic (8%), and truncated/enhanced (2%). The fraction of anemic galaxies is relatively small (6-13%) in both environments, suggesting that starvation is not a major factor in the reduced star formation rates of Virgo spirals. The majority of Virgo spiral galaxies have their Hα disks truncated (52%), whereas truncated Hα disks are rarer in isolated galaxies (12%). Most of the Hα-truncated galaxies have relatively undisturbed stellar disks and normal-to-slightly enhanced inner disk star formation rates, suggesting that ICM-ISM stripping is the main mechanism causing the reduced star formation rates of Virgo spirals. Several of the truncated galaxies are peculiar, with enhanced central star formation rates, disturbed stellar disks, and bar-like distributions of luminous HII complexes inside the central 1 kpc, but no star formation beyond, suggesting recent tidal interactions or minor mergers have also influenced their morphology. Two highly-inclined Hα-truncated spirals have numerous extraplanar HII regions, and are likely in an active phase of ICM-ISM stripping. Several spirals have one-sided Hα enhancements at the outer edge of their truncated Hα disks, suggesting modest and local enhancements in their star formation rates due to ICM-ISM interactions. Low-velocity tidal interactions and perhaps outer cluster HI accretion seem to be the triggers for enhanced global star formation in four Virgo galaxies. These results indicate that most Virgo spiral galaxies experience ICM-ISM stripping, many experience significant tidal effects, and many experience both.

H i observations of galaxies in the southern filament of the Virgo Cluster with the Square Kilometre Array Pathfinder KAT-7 and the Westerbork Synthesis Radio Telescope

“…The VIVA sample consists of 53 late-type galaxies, mostly selected to cover a range of star formation properties based on Koopmann & Kenney's (2004) classification, and both in high-and low-density environments. The galaxies span the angular distances of 1 • to 12 • from M87 (out to ∼1.6 Abell radii of the cluster).…”

“…The arguments for tidal interaction are mainly based on the optical morphology of the galaxy, classified as a chaotic early spiral in the Uppsala General Catalogue (UGC, Nilson 1973), a peculiar Sa by and an uncertain barred Sa by de Vaucouleurs et al (1991). The H α morphology of the galaxy has been described as truncated/compact by Koopmann & Kenney (2004) and optical observations reveal that it has a heavily disturbed stellar disc, and shows a strong H α emission confined to its central kiloparsecs (Kenney et al 1996;Cortés et al 2006).…”

TheHerschelVirgo Cluster Survey

“…In the following we considered for NGC 4189 the average distance of 32 Mpc for the sub-group to which NGC 4189 belongs, determined using the Tully-Fisher relation in H-band (Gavazzi et al 1999). The HI disk is more extended than the optical disk, showing a symmetric warp (Chung et al 2009a) with enhanced emission in the South-East regions, in correspondence to a ridge of Hα emission (Koopmann & Kenney 2004).…”

OMEGA – OSIRIS Mapping of Emission-line Galaxies in A901/2 – I. Survey description, data analysis, and star formation and AGN activity in the highest density regions

“…However, the average star formation rate (SFR) in star-forming (SF) galaxies remains roughly constant with environment, and it is only the fraction of starforming galaxies that changes (Balogh et al 2004, Verdugo et al 2008, Poggianti et al 2008, Bamford et al 2008. The extent of ongoing star formation within a galaxy has also been shown to correlate with environment (Koopmann & Kenney 2004, Moss & Whittle 2000, Bamford et al 2007, implying a truncation of the star formation taking place first in the outer parts of the infalling galaxies. In fact, the last episode of star formation in cluster disc galaxies is seen to be concentrated towards the central regions (Rodríguez Del Pino et al 2014, Johnston et al 2014.…”