Active Galactic Nucleus and Extended Starbursts in a Mid-stage Merger VV114

D. Iono, T. Saito, M. S. Yun, R. Kawabe, D. Espada, Y. Hagiwara, M. Imanishi, T. Izumi, K. Kohno, K. Motohara, K. Nakanishi, H. Sugai, K. Tateuchi, Y. Tamura, J. Ueda, Y. Yoshii

Published 2013-05-20Version 1

High resolution (0.4 arcsec) Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 0 observations of HCO+(4-3) and HCN(4-3) toward a mid-stage infrared bright merger VV114 have revealed compact nuclear (<200 pc) and extended (3 - 4 kpc) dense gas distribution across the eastern part of the galaxy pair. We find a significant enhancement of HCN(4-3) emission in an unresolved compact and broad (290km/s) component found in the eastern nucleus of VV114, and we suggest dense gas associated with the surrounding material around an Active Galactic Nucleus (AGN), with a mass upper limit of < 4 x 10^8 Msun. The extended dense gas is distributed along a filamentary structure with resolved dense gas concentrations (230pc; 10^6 Msun) separated by a mean projected distance of 600 pc, many of which are generally consistent with the location of star formation traced in Pa alpha emission. Radiative transfer calculations suggest moderately dense (10^5 - 10^6 cm^-3) gas averaged over the entire emission region. These new ALMA observations demonstrate the strength of the dense gas tracers in identifying both the AGN and star formation activity in a galaxy merger, even in the most dust enshrouded environments in the local universe.