Stripped gas as fuel for newly formed H\u2009ii regions in the encounter between VCC\u20091249 and M\u200949: a unified picture from NGVS and GUViCS

Context. We study the peculiar interacting galaxy system of VCC\u20091249/M\u200949 located in the core of the Virgo B subcluster. Owing to a recent interaction between the dwarf galaxy VCC\u20091249 and the halo gas of the elliptical galaxy M\u200949, 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\u2009ii regions) that are embedded in this H\u2009i cloud, with a projected separation up to 13\u2009kpc from VCC\u20091249 in the northwest direction. Aims. Motivated by recent near-ultraviolet imaging from the GALEX Ultraviolet Virgo Cluster Survey (GUViCS) of the VCC\u20091249/M\u200949 system that shows significant ongoing/recent star formation in the compact regions, we aim to constrain the origin of these outlying H\u2009ii 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 H\u3b1 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\u20091249 and its outlying compact regions. Moreover, we analyze the color and luminosity profile of the galaxy to investigate its recent interaction with M\u200949. Results. Our new observations indicate that VCC\u20091249 underwent a recent interaction with M\u200949 in which both ram-pressure stripping and tidal interaction occured. The joint action of the two mechanisms led to the removal of the H\u2009i gas from the interstellar medium of VCC\u20091249, while the gravitational tides triggered the stellar tail and counter-tail of VCC\u20091249. Our stellar population synthesis analysis reveals that the star formation in this galaxy was truncated around 200 Myr ago and that the outlying H\u2009ii regions were born in situ 4810\u2009Myr 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\u20091249/M\u200949 may be an effective way of dispersing metals into the halos of massive galaxies.Peer reviewed: YesNRC publication: Ye