Stripped gas as fuel for newly formed H ii regions in the encounter between VCC 1249 and M 49: a unified picture from NGVS and GUViCS

¹ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
e-mail: arrigoni@mpia.de
² Dipartimento di Fisica G. Occhialini, Università di Milano- Bicocca, Piazza della Scienza 3, 20126 Milano, Italy
e-mail: giuseppe.gavazzi@mib.infn.it
³ Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064, USA
e-mail: mfumagalli@ucolick.org
⁴ Laboratoire d’Astrophysique de Marseille – LAM, Université d’Aix-Marseille & CNRS, UMR 7326, 38 rue F. Joliot-Curie, 13388 Marseille Cedex 13, France
e-mail: alessandro.boselli@oamp.fr; samuel.boissier@oamp.fr; Sebastien.heinis@oamp.fr
⁵ European Southern Observatory, Karl-Schwarzschild Strasse 2, 85748 Garching bei Muenchen, Germany
e-mail: lcortese@eso.org
⁶ Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, BC V9E 2E7, Canada
e-mail: Laura.Ferrarese@nrc-cnrc.gc.ca; patrick.cote@nrc-cnrc.gc.ca; Stephen.Gwyn@nrc-cnrc.gc.ca
⁷ CFHT corporation, 65-1238 Mamalahoa Highway, Kamuela, Hawaii 96743, USA ;
e-mail: jcc@cfht.hawaii.edu
⁸ Kavli Institute for Astronomy and Astrophysics, Peking University, 100871 Beijing, PR China ;
e-mail: peng@pku.edu.cn
⁹ Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Vicuna Mackenna 4860, 7820436 Macul, Santiago, Chile ;
e-mail: ajordan@astro.puc.cl
¹⁰ Department of Astronomy, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, USA
e-mail: mihos@case.edu
¹¹ Department of Physics & Astronomy, Youngstown State University, Youngstown, OH 44555, USA
e-mail: prdurrell@ysu.edu
¹² Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot, Dapnia/Service d’Astrophysique, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
e-mail: paduc@cea.fr
¹³ INPAC and Department of Physics, Shanghai Jiao Tong University, 800 Dongchuan Road, 200240 Shanghai, PR China
e-mail: czliu@pku.edu.cn
¹⁴ GEPI, Observatoire de Paris, Section de Meudon, 5 place J. Janssen, 92190 Meudon Cedex, France
e-mail: simona.mei@obspm.fr
¹⁵ Université Paris Denis Diderot, 75205 Paris Cedex 13, France
¹⁶ California Institute of Technology, Pasadena, CA 91125, USA

Received: 26 January 2012
Accepted: 30 April 2012

Abstract

Context. We study the peculiar interacting galaxy system of VCC 1249/M 49 located in the core of the Virgo B subcluster. Owing to a recent interaction between the dwarf galaxy VCC 1249 and the halo gas of the elliptical galaxy M 49, neutral hydrogen has been displaced from the interstellar medium of this dwarf into the Virgo intracluster medium. Observations also reveal multiple compact star-forming regions (aka H ii regions) that are embedded in this H i cloud, with a projected separation up to 13 kpc from VCC 1249 in the northwest direction.

Aims. Motivated by recent near-ultraviolet imaging from the GALEX Ultraviolet Virgo Cluster Survey (GUViCS) of the VCC 1249/M 49 system that shows significant ongoing/recent star formation in the compact regions, we aim to constrain the origin of these outlying H ii regions with a multi-wavelength approach.

Methods. Using deep optical (u,g,i,z) imaging from the Next Generation Virgo Cluster Survey (NGVS) and new Hα imaging obtained at the San Pedro Martir observatory together with Keck long-slit spectroscopy, we characterize the star formation rates, ages, and metallicity of VCC 1249 and its outlying compact regions. Moreover, we analyze the color and luminosity profile of the galaxy to investigate its recent interaction with M 49.

Results. Our new observations indicate that VCC 1249 underwent a recent interaction with M 49 in which both ram-pressure stripping and tidal interaction occured. The joint action of the two mechanisms led to the removal of the H i gas from the interstellar medium of VCC 1249, while the gravitational tides triggered the stellar tail and counter-tail of VCC 1249. Our stellar population synthesis analysis reveals that the star formation in this galaxy was truncated around 200 Myr ago and that the outlying H ii regions were born in situ  ≈10 Myr ago out of pre-enriched gas removed from the dwarf galaxy. These observations also reveal that interactions between central and satellite galaxies similar to those between VCC 1249/M 49 may be an effective way of dispersing metals into the halos of massive galaxies.