A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

III. Star formation in the stripped gas of NGC 4254^★

¹ Aix Marseille Univ, CNRS, CNES, LAM, France
e-mail: alessandro.boselli@lam.fr, samuel.boissier@lam.fr, veronique.buat@lam.fr
² Universitäts-Sternwarte München, Scheinerstrasse 1, 81679 München, Germany
³ Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
⁴ CEA/IRFU/SAP, Laboratoire AIM Paris-Saclay, CNRS/INSU, Université Paris Diderot, Observatoire de Paris, PSL Research University, 91191 Gif-sur-Yvette Cedex, France
⁵ Universidad de Antofagasta, Unidad de Astronomía, Avenida Angamos 601, Antofagasta 1270300, Chile
⁶ Universitá di Milano-Bicocca, piazza della scienza 3, 20100 Milano, Italy
⁷ INAF - Osservatorio Astronomico di Brera, via Brera 28, 20159 Milano, Italy
⁸ International Centre for Radio Astronomy Research, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Australia
⁹ NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria BC V9E 2E7, Canada
¹⁰ Department of Physiscs and Astronomy, Youngstown State University, Youngstown OH 44555, USA
¹¹ Institute for Computational Cosmology and Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
¹² Department of Astrophysics, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
¹³ Australia Telescope National Facility, CSIRO Astronomy and Space Science, PO Box 76, Epping NSW 1710, Australia
¹⁴ Astronomy Centre, Department of Physics and Astronomy, University of Sussex, Falmer, Brighton BN1 9QH, UK
¹⁵ Physics Department, University of Alabama in Huntsville, Huntsville AL 35899, USA
¹⁶ Department of Physiscs, University of the Pacific, 3601 Pacific Avenue, Stockton CA 95211, USA
¹⁷ Observatoire Astronomique de Strasbourg, UMR 7750, 11 rue de l’Université, 67000 Strasbourg, France

Received: 4 December 2017
Accepted: 7 March 2018

Abstract

During pilot observations of the Virgo Environmental Survey Tracing Galaxy Evolution (VESTIGE), a blind narrow-band Hα + [NII] imaging survey of the Virgo cluster carried out with MegaCam at the CFHT, we have observed the spiral galaxy NGC 4254 (M99). Deep Hα + [NII] narrow-band and GALEX UV images reveal the presence of 60 compact (70–500 pc radius) star-forming regions up to ≃20 kpc outside the optical disc of the galaxy. These regions are located along a tail of HI gas stripped from the disc of the galaxy after a rapid gravitational encounter with another Virgo cluster member that simulations indicate occurred 280–750 Myr ago. We have combined the VESTIGE data with multifrequency data from the UV to the far-infrared to characterise the stellar populations of these regions and study the star formation process in an extreme environment such as the tails of stripped gas embedded in the hot intracluster medium. The colour, spectral energy distribution (SED), and linear size consistently indicate that these regions are coeval and have been formed after a single burst of star formation that occurred ≲100 Myr ago. These regions might become free floating objects within the cluster potential well, and be the local analogues of compact sources produced after the interaction of gas-rich systems that occurred during the early formation of clusters.