The GALEX Ultraviolet Virgo Cluster Survey (GUViCS)

II. Constraints on star formation in ram-pressure stripped gas^⋆

¹ Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
e-mail: samuel.boissier@oamp.fr
² Laboratoire AIM Paris-Saclay, CEA/IRFU/SAp, CNRS/INSU, Université Paris Diderot, 91191 Gif-sur-Yvette Cedex, France
³ European Southern Observatory, Karl Schwarzschild Str. 2, 85748 Garching bei München, Germany
⁴ GEPI, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France
⁵ INAF – Osservatorio Astronomico di Trieste – via Tiepolo 11, 34143 Trieste, Italy
⁶ Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, BC, V9E 2E7, Canada
⁷ Canada-France-Hawaii Telescope Corporation, Kamuela, HI 96743, USA
⁸ Université Paris Denis Diderot, 75205 Paris Cedex 13, France
⁹ IPAC – California Institute of Technology, Pasadena, CA 91125, USA

Received: 6 July 2012
Accepted: 31 July 2012

Abstract

Context. Several galaxies in the Virgo cluster are known to have large H i gas tails related to a recent ram-pressure stripping event. The Virgo cluster has been extensively observed at 1539 Å in the far-ultraviolet for the GALEX Ultraviolet Virgo Cluster Survey (GUViCS), and in the optical for the Next Generation Virgo Survey (NGVS), allowing a study of the stellar emission potentially associated with the gas tails of 8 cluster members. On the theoretical side, models of ram-pressure stripping events have started to include the physics of star formation.

Aims. We aim to provide quantitative constraints on the amount of star formation taking place in the ram-pressure stripped gas, mainly on the basis of the far-UV emission found in the GUViCS images in relation with the gas content of the tails.

Methods. We have performed three comparisons of the young stars emission with the gas column density: visual, pixel-by-pixel, and global. We have compared our results to other observational and theoretical studies.

Results. We find that the level of star formation taking place in the gas stripped from galaxies by ram-pressure is low with respect to the available amount of gas. Star formation is lower by at least a factor 10 compared to the predictions of the Schmidt Law as determined in regular spiral galaxy disks. It is also lower than measured in dwarfs galaxies and the outer regions of spirals, and than predicted by some numerical simulations. We provide constraints on the star formation efficiency in the ram-pressure stripped gas tails, and compare these with current models.