ALMA Observations of the Interaction of a Radio Jet with Molecular Gas in Minkowski's Object

Abstract

Abstract We use the Atacama Large Millimeter Array (ALMA) to detect and image CO (1-0) emission from Minkowski’s Object, a dwarf galaxy in the cluster Abell 194 that is interacting with a radio jet from a nearby elliptical galaxy. The ALMA observations, which are the first to detect molecular gas in Minkowski’s Object, also image the high-frequency continuum emission from the radio jet, allowing us to study the interaction in detail. We estimate the range in the mass of molecular gas in Minkowski’s Object assuming two different values of the ratio of the molecular gas mass to the CO luminosity, . For the Milky Way value of we obtain a molecular gas mass of , 6% of the H I gas mass. We also use the prescription of Narayanan et al. (2012) to estimate an , in which case we obtain , 36% of the H I mass. The observations are consistent with previous claims of star formation being induced in Minkowski’s Object via the passage of the radio jet, and it therefore being a rare local example of positive feedback from an active galactic nucleus. In particular, we find highly efficient star formation, with gas depletion timescales year (for assumed values of and , respectively) in the upstream regions of Minkowski’s Object that were struck first by the jet, and less efficient star formation downstream. We discuss the implications of this observation for models of jet-induced star formation and radio-mode feedback in massive galaxies.