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

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.

Inspiraling halo accretion mapped in Ly α emission around a z ∼ 3 quasar

“…In particular, given the expected softer UV radiation from star-forming galaxies with respect to a quasar, photoionization from these objects could explain the observed level of SB Lyα , together with the non-detections in He ii and C iv with more reasonable densities (∼ 1 cm −3 ). In addition, part of the cool CGM in quasar haloes and emitting in Lyα could be gas stripped from infalling satellites (e.g., Arrigoni Battaia et al 2012). Such gas has been predicted to emit preferentially through collisional excitation in low-redshift systems, though definite conclusions on this have not been reached (e.g., Tonnesen & Bryan 2011).…”