The GALEX Ultraviolet Virgo Cluster Survey (GUViCS). II. Constraints on star formation in ram-pressure stripped gas
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.
Additional Information© 2012 ESO. Article published by EDP Sciences. Received 6 July 2012; Accepted 31 July 2012. Published online 21 September 2012. We thank B. Vollmer for discussions that formed the basis of this project and for his critical comments, and the referee for detailed comments and suggestions. This work is supported in part by the French Agence Nationale de la Recherche (ANR) Grant Programme Blanc VIRAGE (ANR10-BLANC-0506-01). The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement No. 229517. This work is supported in part by the Canadian Advanced Network for Astronomical Research (CANFAR) which has been made possible by funding from CANARIE under the Network-Enabled Platforms program. This research also used the facilities of the Canadian Astronomy Data Centre operated by the National Research Council of Canada with the support of the Canadian Space Agency. This research has made use of the GOLD Mine Database, and the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. We wish to thank the GALEX Time Allocation Committee for the generous allocation of time devoted to GUViCS, and the Canada-France-Hawaii Telescope direction and staff for the support that enabled the NGVS. GALEX is a NASA Small Explorer, launched in 2003 April. We gratefully acknowledge NASA's support for the construction, operation and science analysis for the GALEX mission, developed in cooperation with the Centre National d'Etudes Spatiales of France and the Korean Ministry of Science and Technology.
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