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

Abstract

Galactic outflows are known to consist of several gas phases, however, the connection between these phases has been investigated little and only in a few objects. In this paper, we analyse MUSE/VLT data of 26 local (U)LIRGs and study their ionized and neutral atomic phases. We also include objects from the literature to obtain a sample of 31 galaxies with spatially resolved multi-phase outflow information. We find that the ionized phase of the outflows has on average an electron density three times higher than the disc (ne, disc ∼ 145 cm−3 versus ne, outflow ∼ 500 cm−3), suggesting that cloud compression in the outflow is more important than cloud dissipation. We find that the difference in extinction between outflow and disc correlates with the outflow gas mass. Together with the analysis of the outflow velocities, this suggests that at least some of the outflows are associated with the ejection of dusty clouds from the disc. This may support models where radiation pressure on dust contributes to driving galactic outflows. The presence of dust in outflows is relevant for potential formation of molecules inside them. We combine our data with millimetre data to investigate the molecular phase. We find that the molecular phase accounts for more than 60 ${{\ \rm per\ cent}}$ of the total mass outflow rate in most objects and this fraction is higher in AGN-dominated systems. The neutral atomic phase contributes of the order of 10 ${{\ \rm per\ cent}}$, while the ionized phase is negligible. The ionized-to-molecular mass outflow rate declines slightly with AGN luminosity, although with a large scatter.

Quasar Feedback Survey: Multi-phase outflows, turbulence and evidence for feedback caused by low power radio jets inclined into the galaxy disk

“…This has also been observed by other studies (e.g. ; see Fluetsch et al 2021;Davies et al 2020;Mingozzi et al 2019). However, we urge caution in interpreting the absolute values of the electron densities inferred using this approach.…”

“…We also observe that this turbulent gas has a three times higher electron density than the rest of the galaxy disk (see Figure 5). Such high electron densities within outflowing components have also been seen in previous studies (e.g, Villar Martín et al 2014;Perna et al 2017;Mingozzi et al 2019;Davies et al 2020;Fluetsch et al 2021). A possible explanation for this could be due to the compression of the gas expelled in the outflow (e.g., Bourne et al 2015;Decataldo et al 2019).…”

“…One way that AGN are known to be capable of interacting with their host galaxy's multi-phase interstellar medium (ISM) is through driving galaxy-wide (≥ 0.1 -10 kpc) energetic outflows and turbulences (e.g., Nesvadba et al 2011;Liu et al 2013;Cicone et al 2018;Veilleux et al 2020;Davies et al 2020;Fluetsch et al 2021;Venturi et al 2021;Roy et al 2021). Theoretically, these outflows may be driven by radiation pressure, jets or AGN-driven winds and could occur over scales from the accretion disc (≤ 10 −2 pc) through to galaxy-wide scales, where they could affect the properties of the gas in the ISM and beyond (Ishibashi et al 2018;Mukherjee et al 2018b;Costa et al 2018Costa et al , 2020Morganti et al 2021).…”

Quantifying Feedback from Narrow Line Region Outflows in Nearby Active Galaxies. IV. The Effects of Different Density Estimates on the Ionized Gas Masses and Outflow Rates

“…Significant effort is being devoted to understanding the physics of AGN-driven outflows and measuring their energetic impact (e.g., Fischer et al 2018;Baron & Netzer 2019a, 2019bFörster Schreiber et al 2019;Mingozzi et al 2019;Davies et al 2020b;Wylezalek et al 2020;Avery et al 2021;Fluetsch et al 2021;Lamperti et al 2021;Luo et al 2021;Negus et al 2021;Ruschel-Dutra et al 2021;Speranza et al 2021;Vayner et al 2021;Bianchin et al 2022;Deconto-Machado et al 2022;Kakkad et al 2022). However, outflows are inhomogeneous, with a large range of densities and geometries, such that the derived gas masses and outflow rates depend strongly on how the gas densities are estimated.…”

Blandford-Znajek jets in galaxy formation simulations: exploring the diversity of outflows produced by spin-driven AGN jets in Seyfert galaxies

“…Observations of AGN-driven outflows that examine the mass outflow rates and energetics are available for a wide variety of systems (see e.g. Ruschel-Dutra et al 2021;Fluetsch et al 2021;Santoro et al 2020;Davies et al 2020;Baron & Netzer 2019;Shimizu et al 2019;Fiore et al 2017), including some in which jets are believed to be responsible for driving the outflow (Oosterloo et al 2017;Morganti et al 2015).…”