Forming stars in a dual AGN host: molecular and ionized gas in the nearby, luminous infrared merger, Mrk 266

Abstract

We present star formation rates based on cold and ionized gas measurements of Mrk 266 (NGC 5256), a system composed of two colliding gas-rich galaxies, each hosting an active galactic nucleus. Using ¹²CO (1-0) observations with the Combined Array for Research in Millimeter-Wave Astronomy (CARMA), we find a total H₂ mass in the central region of 1.1 ± 0.3 × 10¹⁰ M_⊙ which leads to a possible future star formation rate of 25 ± 10 M_⊙ yr^-1. With the Fourier Transform Spectrograph (SITELLE) on the Canada-France-Hawaii Telescope, we measure an integrated H α luminosity and estimate a present-day star formation rate of 15 ± 2 M_⊙ yr^-1 in the core of the system (avoiding the two active nuclei). These results confirm that Mrk 266 is an intermediate stage merger with a relatively high recent star formation rate and enough molecular gas to sustain it for a few hundred million years. Inflowing gas associated with the merger may have triggered both the starburst episode and two active galactic nuclei but the two galaxy components differ: the region around the south-western nucleus appears to be more active than the north-east nucleus, which seems relatively quiet. We speculate that this difference may originate in the properties of the interstellar medium in the two systems.