AGN feedback in a galaxy merger: multi-phase, galaxy-scale outflows with a fast molecular gas blob ∼6 kpc away from IRAS F08572+3915

Abstract

To understand the role that AGN feedback plays in galaxy evolution we need in-depth studies of the multi-phase structure and energetics of galaxy-wide outflows. In this work we present new, deep (∼ 50 hr) NOEMA CO(1-0) line observations of the molecular gas in the powerful outflow driven by the AGN in the ultra-luminous infrared galaxy IRAS F08572+3915. We spatially resolve the outflow, finding that its most likely configuration is a wide-angle bicone aligned with the kinematic major axis of the rotation disk. The molecular gas in the wind reaches velocities up to approximately ±1200 km s −1 and transports nearly 20% of the molecular gas mass in the system. We detect a second outflow component located ∼ 6 kpc north-west from the galaxy moving away at ∼ 900 km s −1 , which could be the result of a previous episode of AGN activity. The total mass and energetics of the outflow, which includes contributions from the ionized, neutral, warm and cold molecular gas phases is strongly dominated by the cold molecular gas. In fact, the molecular mass outflow rate is higher than the star formation rate, even if we only consider the gas in the outflow that is fast enough to escape the galaxy, which accounts for about ∼40% of the total mass of the outflow. This results in an outflow depletion time for the molecular gas in the central ∼1.5 kpc region of only ∼ 3 Myr, a factor of ∼ 2 shorter than the depletion time by star formation activity.

AGN-driven galactic outflows: comparing models to observations

“…The corresponding momentum ratio is of the order of ζ =ṗ/(L/c) ∼ 20 and the energy ratio is ǫ k =Ė k /L ∼ 0.04. The high values of the outflow energetics measured in this source have been exclusively interpreted in the framework of the wind energydriving scenario (Herrera-Camus et al 2020).…”

“…A molecular outflow was previously detected in CO observations, with an average velocity of ∼800 km s −1 (Cicone et al 2014), and the corresponding outflow energetics are reported in Fluetsch et al (2019). New high angular resolution CO observations spatially resolve the molecular outflow, which has an outflowing mass of M ∼ 3 × 10 8 M ⊙ and reaches a velocity of v ∼ 1200 km s −1 around ∼1 kpc (Herrera-Camus et al 2020). The associated mass outflowrateisṀ ∼ 350 M ⊙ yr −1 , while the outflow momentum rate and kinetic power areṗ ∼ 3 × 10 36 dyn andĖ k ∼ 2 × 10 44 erg s −1 , respectively.…”

“…The observational data point (black square) is from the latest CO observations (Herrera-Camus et al 2020), and the vertical/horizontal bars indicate previous measurements (Cicone et al 2014;Fluetsch et al 2019).…”

“…Constant luminosity case: L ∼ 4 × 10 45 erg s −1 , R 0 = 20 pc, f dg = 5 × f dg,MW (blue dotted). Luminosity decay case:L(t) = L 0 (1 + t/t d ) −δ with L 0 = 4 × 10 46 erg s −1 , t d = 10 5 yr, δ = 1, R 0 = 50 pc, f dg = 3.5 × f dg,MW (green dashed).The observational data point (black square) is from the latest CO observations(Herrera-Camus et al 2020), and the vertical/horizontal bars indicate previous measurements(Cicone et al 2014;Fluetsch et al 2019).…”

Properties of the multiphase outflows in local (ultra)luminous infrared galaxies

“…For instance, in the Seyfert galaxy IC 5063, a remarkable kinematic similarity between the ionized, neutral atomic, and the molecular phase was found (Morganti et al 2015;Oosterloo et al 2017), suggesting a link between the different phases. Similarly, HE 1353−1917 (Husemann et al 2019) and IRAS F08572+3915 (Herrera-Camus et al 2020) also display co-spatiallity between the molecular and the ionized outflow phase. In other galaxies, such as Mrk 231 (Feruglio et al 2015), the interplay between gas phases appears to be much more complex and there might have been several feedback episodes.…”