The multi-phase winds of Markarian 231: from the hot, nuclear, ultra-fast wind to the galaxy-scale, molecular outflow

Abstract

We present the best sensitivity and angular resolution maps of the molecular disk and outflow of Mrk 231, as traced by CO observations obtained with IRAM/PdBI, and we analyze archival Chandra and NuSTAR observations. We constrain the physical properties of both the molecular disk and outflow, the presence of a highly-ionized ultra-fast nuclear wind, and their connection. The molecular outflow has a size of ~1 kpc, and extends in all directions around the nucleus, being more prominent along the south-west to north-east direction, suggesting a wide-angle biconical geometry. The maximum projected velocity of the outflow is nearly constant out to ~1 kpc, thus implying that the density of the outflowing material decreases from the nucleus outwards as $r^{-2}$. This suggests that either a large part of the gas leaves the flow during its expansion or that the bulk of the outflow has not yet reached out to ~1 kpc, thus implying a limit on its age of ~1 Myr. We find ${\dot{M}}_{OF}=[500-1000]M_{\odot }y{r}^{-1}$ and ${\dot{E}}_{kin,OF}=[7-10]\times 10^{43}$ erg s${}^{-1}$. Remarkably, our analysis of the X-ray data reveals a nuclear ultra-fast outflow (UFO) with velocity -20000 km s${}^{-1}$, ${\dot{M}}_{UFO}=[0.3-2.1]M_{\odot }y{r}^{-1}$, and momentum load ${\dot{P}}_{UFO}/{\dot{P}}_{rad}=[0.2-1.6]$.We find ${\dot{E}}_{kin,UFO}\sim {\dot{E}}_{kin,OF}$ as predicted for outflows undergoing an energy conserving expansion. This suggests that most of the UFO kinetic energy is transferred to mechanical energy of the kpc-scale outflow, strongly supporting that the energy released during accretion of matter onto super-massive black holes is the ultimate driver of giant massive outflows. We estimate a momentum boost ${\dot{P}}_{OF}/{\dot{P}}_{UFO}\approx [30-60]$. The ratios ${\dot{E}}_{kin,UFO}/L_{bol,AGN}=[1-5]\%$ and ${\dot{E}}_{kin,OF}/L_{bol,AGN}=[1-3]\%$ agree with the requirements of the most popular models of AGN feedback.

16 pages, 17 figures. Accepted for publication in A&A