ALMA OBSERVATIONS OF A CANDIDATE MOLECULAR OUTFLOW IN AN OBSCURED QUASAR

Abstract

We present Atacama Large Millimeter/Submillimeter Array CO (1-0) and CO (3-2) observations of SDSS J135646.10 + 102609.0, an obscured quasar and ultra-luminous infrared galaxy with two merging nuclei and a known 20 kpc scale ionized outflow. The total molecular gas mass is M-mol approximate to 9(-6)(+19) x 10(8) M-circle dot, mostly distributed in a compact rotating disk at the primary nucleus (M-mol approximate to 3 x 10(8) M-circle dot) and an extended tidal arm (M-mol approximate to 5 x 10(8) M-circle dot). The tidal arm is one of the most massive molecular tidal features known; we suggest that it is due to the lower chance of shock dissociation in this elliptical/disk galaxy merger. In the spatially resolved CO (3-2) data, we find a compact (r approximate to 0.3 kpc) high-velocity (v approximate to 500 km s(-1)) redshifted feature in addition to the rotation at the N nucleus. We propose a molecular outflow as the most likely explanation for the high-velocity gas. The outflowing mass of M-mol approximate to 7 x 10(7) M-circle dot and the short dynamical time of t(dyn) approximate to 0.6 Myr yield a very high outflow rate of (M) over dot(mol) approximate to 350 M-circle dot yr(-1) and can deplete the gas in a million years. We find a low star formation rate (< 16 M-circle dot yr(-1) from the molecular content and < 21 M-circle dot yr(-1) from the far-infrared spectral energy distribution decomposition) that is inadequate to supply the kinetic luminosity of the outflow ((E) over dot approximate to 3 x 10(43) erg s(-1)). Therefore, the active galactic nucleus (AGN), with a bolometric luminosity of 10(46) erg s(-1), likely powers the outflow. The momentum boost rate of the outflow ((p) over dot/(L-bol/c) approximate to 3) is lower than typical molecular outflows associated with AGNs, which may be related to its compactness. The molecular and ionized outflows are likely two distinct bursts induced by episodic AGN activity which varies on a timescale of 10(7) yr.