Active Galactic Nuclei Winds Research Articles

Ionised gas kinematics in MaNGA AGN

Context.Feedback from active galactic nuclei (AGNs) in general seems to play an important role in the evolution of galaxies, although the impact of AGN winds on their host galaxies is still unknown in the absence of a detailed analysis.Aims.We aim to analyse the kinematics of a sample of 170 AGN host galaxies as compared to those of a matched control sample of non-active galaxies from the MaNGA survey in order to characterise and estimate the extents of the narrow-line region (NLR) and of the kinematically disturbed region (KDR) by the AGN.Methods.We defined the observed NLR radius (rNLR, o) as the farthest distance from the nucleus within which both [O III]/Hβand [N II]/Hαratios fall in the AGN region of the BPT diagram, and the Hαequivalent width was required to be larger than 3.0 Å. The extent of the KDR (rKDR, o) is defined as the distance from the nucleus within which the AGN host galaxies show a more disturbed gas kinematics than the control galaxies.Results.The AGN [O III]λ5007 luminosity ranges from 1039to 1041erg s−1, and the kinematics derived from the [O III] line profiles reveal that, on average, the most luminous AGNs (L[O III] > 3.8 × 1040erg s−1) possess higher residual differences between the gaseous and stellar velocities and velocitie dispersions than their control galaxies in all the radial bins. Spatially resolved NLRs and KDRs were found in 55 and 46 AGN host galaxies, with corrected radii 0.2 < rKDR, c < 2.3 kpc and 0.4 < rNLR, c < 10.1 kpc and a relation between the two given by logrKDR, c = (0.53 ± 0.12) logrNLR, c + (1.07 ± 0.22), respectively. On average, the extension of the KDR corresponds to about 30% of that of the NLR. Assuming that the KDR is due to an AGN outflow, we have estimated ionised gas mass outflow rates that range between 10−5and ∼1M⊙yr−1, and kinetic powers that range from 1034to 1040erg s−1.Conclusions.Comparing the power of the AGN ionised outflows with the AGN luminosities, they are always below the 0.05LAGNmodel threshold for having an important feedback effect on their respective host galaxies. The mass outflow rates (and power) of our AGN sample correlate with their luminosities, populating the lowest AGN luminosity range of the correlations previously found for more powerful sources.

The impact of AGN outflows on the surface habitability of terrestrial planets in the Milky Way

ABSTRACTIt is well known that active galactic nuclei (AGNs) are accompanied by winds and outflows, some of which may reach weakly relativistic speeds of about 10 per cent the speed of light. Yet, in spite of their ubiquity, the impact of AGN outflows in modulating surface habitability of terrestrial planets on galactic scales, using the Milky Way as the basis for comparison, is poorly investigated and inadequately understood. In this work, we address this issue by focusing on two key mechanisms: AGN winds can heat atmospheres and drive the atmospheric escape, as well as stimulate the formation of nitrogen oxides and thence cause ozone depletion. By developing simple models, we estimate the maximal distance up to which these deleterious effects are rendered significant for Earth-like planets in the Milky Way, and thereby demonstrate that this value may extend to ≲ 1 kpc. In the case of quasars hosting larger supermassive black holes, such effects could actually influence the AGN host galaxy as a whole.

General relativistic radiation transport: implications for VLBI/EHT observations of AGN discs, winds, and jets

Abstract In 2019, the Event Horizon Telescope Collaboration (EHTC) has published the first image of a supermassive black hole (SMBH) obtained via the Very Large Baseline Interferometry (VLBI) technique. In the future, it is expected that additional and more sensitive VLBI observations will be pursued for other nearby active galactic nuclei (AGN), and it is therefore important to understand which possible features can be expected in such images. In this paper, we post-process general relativistic magneto-hydrodynamical (GR-MHD) simulations that include resistivity, thus providing a self-consistent jet formation model, including resistive mass loading of a wind launched from a disc in Keplerian rotation. The ray-tracing is done using the General Relativistic Ray-Tracing code grtrans assuming synchrotron emission. We study the appearance of the black hole environment including the accretion disc, winds and jets under a large range of condition, varying black hole mass, accretion rate, spin, inclination angle, disc parameters, and observed frequency. When we adopt M87-like parameters, we show that we can reproduce a ring-like feature (similar as observed by the EHT) for some of our simulations. The latter suggests that such Keplerian disc models thus could be consistent with the observed results. Depending on their masses, accretion rates, spin, and the sensitivity of the observation, we note that other SMBHs may show additional features like winds and jets in the observations.

The Galaxy Activity, Torus, and Outflow Survey (GATOS)

We present the first results of the Galaxy Activity, Torus, and Outflow Survey (GATOS), a project aimed at understanding the properties of the dusty molecular tori and their connection to the host galaxy in nearby Seyfert galaxies. Our project expands the range of active galactic nuclei (AGN) luminosities and Eddington ratios covered by previous surveys of Seyferts conducted by the Atacama Large Millimeter Array (ALMA), allowing us to study the gas feeding and feedback cycle in a combined sample of 19 Seyferts. We used ALMA to obtain new images of the emission of molecular gas and dust using the CO(3–2) and HCO+(4–3) lines as well as their underlying continuum emission at 870 μm with high spatial resolutions (0.1″ ∼ 7 − 13 pc) in the circumnuclear disks (CND) of ten nearby (D < 28 Mpc) Seyfert galaxies selected from an ultra-hard X-ray survey. Our new ALMA observations detect 870 μm continuum and CO line emission from spatially resolved disks located around the AGN in all the sources. The bulk of the 870 μm continuum flux can be accounted for by thermal emission from dust in the majority of the targets. For most of the sources, the disks show a preponderant orientation perpendicular to the AGN wind axes, as expected for dusty molecular tori. The median diameters and molecular gas masses of the tori are ∼42 pc and ∼6 × 105 M⊙, respectively. We also detected the emission of the 4–3 line of HCO+in four GATOS targets. The order of magnitude differences found in the CO/HCO+ratios within our combined sample point to a very different density radial stratification inside the dusty molecular tori of these Seyferts. We find a positive correlation between the line-of-sight gas column densities responsible for the absorption of X-rays and the molecular gas column densities derived from CO toward the AGN in our sources. Furthermore, the median values of both column densities are similar. This suggests that the neutral gas line-of-sight column densities of the dusty molecular tori imaged by ALMA significantly contribute to the obscuration of X-rays. The radial distributions of molecular gas in the CND of our combined sample show signs of nuclear-scale molecular gas deficits. We also detect molecular outflows in the sources that show the most extreme nuclear-scale gas deficits in our sample. These observations find for the first time supporting evidence that the imprint of AGN feedback is more extreme in higher luminosity and/or higher Eddington ratio Seyfert galaxies.

AGN jets and winds in polarized light: the case of Mrk 231

ABSTRACT We present the results of a multifrequency, multiscale radio polarimetric study with the Very Large Array (VLA) of the Seyfert 1 galaxy and BALQSO, Mrk 231. We detect complex total and polarized intensity features in the source. Overall, the images indicate the presence of a broad, one-sided, curved outflow towards the south which consists of a weakly collimated jet with poloidal inferred magnetic fields, inside a broader magnetized ‘wind’ or ‘sheath’ component with toroidal inferred magnetic fields. The model of a kpc-scale weakly collimated jet/lobe in Mrk 231 is strengthened by its C-shaped morphology, steep spectral index throughout, complexities in the magnetic field structures, and the presence of self-similar structures observed on the 10-parsec-scale in the literature. The ‘wind’ may comprise both nuclear starburst (close to the core) and active galactic nuclei winds, where the latter maybe the primary contributor. Moving away from the core, the ‘wind’ component may also comprise the outer layers (or ‘sheath’) of a broadened jet. The inferred value of the (weakly collimated) jet production efficiency, ηjet ∼ 0.01, is consistent with the estimates in the literature. The composite jet and wind outflow in Mrk 231 appears to be low-power and matter-dominated, and oriented at a small angle to our line of sight.

UV line-driven disc wind as the origin of UltraFast Outflows in AGN

ABSTRACT UltraFast Outflows (UFOs) are observed in some active galactic nuclei (AGN), with blueshifted and highly ionized Fe-K absorption features. AGN typically have an ultraviolet (UV-) bright accretion flow, so UV line driving is an obvious candidate for launching these winds. However this mechanism requires material with UV opacity, in apparent conflict with the observed high-ionization state of the wind. In this paper, we synthesize the X-ray energy spectra resulting from different lines of sight through a state of the art radiation hydrodynamics UV line-driven disc wind simulation. We demonstrate that there are some lines of sight that only intercept highly ionized and fast outflowing material. The cooler material required for the UV line driving acceleration is out of the line of sight, close to the disc, shielded from the X-rays by a failed wind. We fit these simulated wind spectra to data from the archetypal UFO source PG 1211+143 and show that they broadly reproduce the depth and velocity of the iron absorption lines seen. This directly demonstrates that UV line driving is a viable mechanism to launch even the fastest UFOs. We simulate microcalorimeter observations of this wind and show that their high-energy resolution can resolve the detailed structure in the wind and recover the wind energetics when combined with models that correctly estimate the line formation radius of the wind. New data from microcalorimeters will pave the way for physical predictions of AGN wind feedback in cosmological simulations.

Unravelling the physics of multiphase AGN winds through emission line tracers

ABSTRACT Observations of emission lines in active galactic nuclei (AGNs) often find fast (∼1000 km s−1) outflows extending to kiloparsec scales, seen in ionized, neutral atomic and molecular gas. In this work we present radiative transfer calculations of emission lines in hydrodynamic simulations of AGN outflows driven by a hot wind bubble, including non-equilibrium chemistry, to explore how these lines trace the physical properties of the multiphase outflow. We find that the hot bubble compresses the line-emitting gas, resulting in higher pressures than in the ambient interstellar medium or that would be produced by the AGN radiation pressure. This implies that observed emission line ratios such as [O iv]$_{25 \, \rm {\mu m}}$ / [Ne ii]$_{12 \, \rm {\mu m}}$, [Ne v]$_{14 \, \rm {\mu m}}$ / [Ne ii]$_{12 \, \rm {\mu m}}$, and [N iii]$_{57 \, \rm {\mu m}}$ / [N ii]$_{122 \, \rm {\mu m}}$ constrain the presence of the bubble and hence the outflow driving mechanism. However, the line-emitting gas is under-pressurized compared to the hot bubble itself, and much of the line emission arises from gas that is out of pressure, thermal and/or chemical equilibrium. Our results thus suggest that assuming equilibrium conditions, as commonly done in AGN line emission models, is not justified if a hot wind bubble is present. We also find that ≳50 per cent of the mass outflow rate, momentum flux, and kinetic energy flux of the outflow are traced by lines such as [N ii]$_{122 \, \rm {\mu m}}$ and [Ne iii]$_{15 \, \rm {\mu m}}$ (produced in the 10$^{4} \, \rm {K}$ phase) and [C ii]$_{158 \, \rm {\mu m}}$ (produced in the transition from 10$^{4} \, \rm {K}$ to 100 K).

Physics of ULIRGs with MUSE and ALMA: The PUMA project

Context. Ultraluminous infrared galaxies (ULIRGs) are characterised by extreme starburst (SB) and active galactic nucleus (AGN) activity, and are therefore ideal laboratories for studying the outflow phenomena and their feedback effects. We have recently started a project called Physics of ULIRGs with MUSE and ALMA (PUMA), which is a survey of 25 nearby (z < 0.165) ULIRGs observed with the integral field spectrograph MUSE and the interferometer ALMA. This sample includes systems with both AGN and SB nuclear activity in the pre- and post-coalescence phases of major mergers. Aims. The main goals of the project are (i) to study the prevalence of (ionised, neutral, and molecular) outflows as a function of the galaxy properties, (ii) to constrain the driving mechanisms of the outflows (e.g. distinguish between SB and AGN winds), and (iii) to identify and characterise feedback effects on the host galaxy. In this first paper, we present details on the sample selection, MUSE observations, and data reduction, and derive first high-level data products. Methods. MUSE data cubes were analysed to study the dynamical status of each of the 21 ULIRGs observed so far, taking the stellar kinematics and the morphological properties inferred from MUSE narrow-band images into account. We also located the ULIRG nuclei, taking advantage of near-infrared (HST) and millimeter (ALMA) data, and studied their optical spectra to infer (i) the ionisation state through standard optical line ratio diagnostics, and (ii) outflows in both atomic ionised ([O III], Hα) and neutral (Na ID) gas. Results. We show that the morphological and stellar kinematic classifications are consistent: post-coalescence systems are more likely associated with ordered motions, while interacting (binary) systems are dominated by non-ordered and streaming motions. We also find broad and asymmetric [O III] and Na ID profiles in almost all nuclear spectra, with line widths in the range [300 − 2000] km s−1, possibly associated with AGN- and SB-driven winds. This result reinforces previous findings that indicated that outflows are ubiquitous during the pre- and post-coalescence phases of major mergers.

Speed limits for radiation-driven SMBH winds

Context.Ultra-fast outflows (UFOs) have become an established feature in analyses of the X-ray spectra of active galactic nuclei (AGN). According to the standard picture, they are launched at accretion disc scales with relativistic velocities, up to 0.3−0.4 times the speed of light. Their high kinetic power is enough to induce an efficient feedback on a galactic scale, possibly contributing to the co-evolution between the central supermassive black hole (SMBH) and the host galaxy. It is, therefore, of paramount importance to gain a full understanding of UFO physics and, in particular, of the forces driving their acceleration and the relation to the accretion flow from which they originate.Aims.In this paper, we investigate the impact of special relativity effects on the radiative pressure exerted onto the outflow. The radiation received by the wind decreases for increasing outflow velocity,v, implying that the standard Eddington limit argument has to be corrected according tov. Due to the limited ability of the radiation to counteract the black hole gravitational attraction, we expect to find lower typical velocities with respect to the non-relativistic scenario.Methods.We integrated the relativistic-corrected outflow equation of motion for a realistic set of starting conditions. We concentrated on a range of ionisations, column densities, and launching radii consistent with those typically estimated for UFOs. We explore a one-dimensional, spherical geometry and a three-dimensional setting with a rotating, thin accretion disc.Results.We find that the inclusion of special relativity effects leads to sizeable differences in the wind dynamics and thatvis reduced up to 50% with respect to the non-relativistic treatment. We compare our results with a sample of UFOs from the literature and we find that the relativistic-corrected velocities are systematically lower than the reported ones, indicating the need for an additional mechanism, such as magnetic driving, to explain the highest velocity components. Finally, we note that these conclusions, derived for AGN winds, are generally applicable.

Location and energetics of the ultra-fast outflow in PG 1448+273

Context. Ultra-fast outflows (UFOs) are the most powerful disk-driven winds in active galactic nuclei (AGNs). Theoretical and observational evidence shows that UFOs play a key role in the AGN feedback mechanism. The mechanical power of the strongest UFOs may be enough to propagate the feedback to the host galaxies and ultimately shape the AGN-galaxy coevolution. It is therefore of paramount importance to fully characterize UFOs, their location, and energetics. Aims. We study two XMM-Newton archival observations of the narrow-line Seyfert 1 galaxy PG 1448+273. We concentrate on the latest observation, whose spectrum is characterized by a strong absorption feature in the Fe K band. This feature represents the spectral imprint of a UFO, as confirmed by other independent analyses. We study this feature in detail with a novel modeling tool. Methods. In order to constrain the physical properties of the UFO, we implemented the novel model called wind in the ionized nuclear environment (WINE) to fit the photoionized emission and absorption lines from a disk wind in X-ray spectra. WINE is a photoionization model that allows us to self-consistently calculate absorption and emission profiles. It also takes special relativistic effects into account. Results. Our detection of the UFO in PG 1448+273 is very robust. The outflowing material is highly ionized, logξ = 5.53−0.05+0.04 erg s−1 cm, has a high column density, NH = 4.5−1.1+0.8 × 1023 cm−2, is ejected with a maximum velocity v0 = 0.24−0.06+0.08 c (90% confidence level errors), and attains an average velocity vavg = 0.152 c. WINE succeeds remarkably well to constrain a launching radius of r0 = 77−19+31 rS from the black hole. We also derive a lower limit on both the opening angle of the wind (θ > 72°) and the covering factor (Cf > 0.69). We find a mass outflow rate Ṁout = 0.65−0.33+0.44 M⊙ yr−1 = 2.0−1.0+1.3 Ṁacc and a high instantaneous outflow kinetic power Ėout = 4.4−3.6+4.4 × 1044 erg s−1 = 24% Lbol = 18% LEdd (1σ errors). We find that a major error contribution on the energetics is due to r0, stressing the importance of an accurate determination through proper spectral modeling, as done with WINE. Finally, using 20 Swift (UVOT and XRT) observations together with the simultaneous Optical Monitor data from XMM-Newton, we also find that αox varied strongly, with a maximum excursion of Δαox = −0.7, after the UFO was detected, leading to a remarkable X-ray weakness. This may indicate a starving of the inner accretion disk due to the removal of matter through the wind, and it may have repercussions for the larger population of observed X-ray weak quasars.

Multiphase feedback processes in the Sy2 galaxy NGC 5643

We study the multiphase feedback processes in the central ∼3 kpc of the barred Seyfert 2 galaxy NGC 5643. We used observations of the cold molecular gas (ALMA CO(2−1) transition) and ionized gas (MUSE IFU optical emission lines). We studied different regions along the outflow zone, which extends out to ∼2.3 kpc in the same direction (east-west) as the radio jet, as well as nuclear and circumnuclear regions in the host galaxy disk. The CO(2−1) line profiles of regions in the outflow and spiral arms show two or more different velocity components: one associated with the host galaxy rotation, and the others with out- or inflowing material. In the outflow region, the [O III]λ5007 Å emission lines have two or more components: the narrow component traces rotation of the gas in the disk, and the others are related to the ionized outflow. The deprojected outflowing velocities of the cold molecular gas (median Vcentral ∼ 189 km s−1) are generally lower than those of the outflowing ionized gas, which reach deprojected velocities of up to 750 km s−1 close to the active galactic nucleus (AGN), and their spatial profiles follow those of the ionized phase. This suggests that the outflowing molecular gas in the galaxy disk is being entrained by the AGN wind. We derive molecular and ionized outflow masses of ∼5.2 × 107 M⊙ (αCOGalactic) and 8.5 × 104 M⊙ and molecular and ionized outflow mass rates of ∼51 M⊙ yr−1 (αCOGalactic) and 0.14 M⊙ yr−1, respectively. This means that the molecular phase dominates the outflow mass and outflow mass rate, while the kinetic power and momentum of the outflow are similar in both phases. However, the wind momentum loads (Ṗout/ṖAGN) for the molecular and ionized outflow phases are ∼27−5 (αCOGalactic and αCOULIRGs) and < 1, which suggests that the molecular phase is not momentum conserving, but the ionized phase most certainly is. The molecular gas content (Meast ∼ 1.5 × 107 M⊙; αCOGalactic) of the eastern spiral arm is approximately 50−70% of the content of the western one. We interpret this as destruction or clearing of the molecular gas produced by the AGN wind impacting in the eastern side of the host galaxy (negative feedback process). The increase in molecular phase momentum implies that part of the kinetic energy from the AGN wind is transmitted to the molecular outflow. This suggests that in Seyfert-like AGN such as NGC 5643, the radiative or quasar and the kinetic or radio AGN feedback modes coexist and may shape the host galaxies even at kiloparsec scales through both positive and (mild) negative feedback.

Active galactic nucleus feedback in an elliptical galaxy with the most updated AGN physics: Parameter explorations

ABSTRACT In a previous work, we have proposed a sub-grid model of active galactic nucleus (AGN) feedback by taking into account the state-of-the-art AGN physics, and used that model to study the effect of AGN feedback on the evolution of an isolated elliptical galaxy by performing 2D high-resolution (i.e. the Bondi radius is well resolved) simulations. In that work, typical values of model parameters were adopted. In this work, we extend that study by exploring the effects of uncertainties of parameter values. Such a study is also useful for us to understand the respective roles of various components of the model. These parameters include the mass flux and velocity of AGN wind and radiative efficiency in both the hot and cold feedback modes, and the initial black hole (BH) mass. We find that the velocity of AGN wind in the hot mode is the most important quantity to control the typical accretion rate and luminosity of AGN, and the mass growth of the BH. The effect of the wind on star formation is less sensitive. Within the limited parameter range explored in this work, a stronger AGN wind suppresses star formation within ∼100 pc but enhances star formation beyond this radius, while the star formation integrated over the evolution time and the whole galaxy roughly remain unchanged. AGN radiation suppresses the BH accretion in a mild way, but dust is not considered here. Finally, a smaller initial BH mass results in a more violent evolution of the BH accretion rate. The corresponding AGN spends more time in the high-luminosity state and the percentage of BH mass growth is higher. Our results indicate the robustness of AGN feedback in keeping the galaxy quenched.

The Impact of Outflows Driven by Active Galactic Nuclei on Metals in and around Galaxies

Abstract Metals in the hot gaseous halos of galaxies encode the history of star formation as well as the feedback processes that eject metals from the galaxies. X-ray observations suggest that massive galaxies have extended distributions of metals in their gas halos. We present predictions for the metal properties of massive galaxies and their gaseous halos from recent high-resolution zoom-in simulations that include mechanical and radiation-driven feedback from active galactic nuclei (AGN). In these simulations, AGN launch high-velocity outflows, mimicking observed broad absorption line winds. By comparing two sets of simulations with and without AGN feedback, we show that our prescription for AGN feedback is capable of driving winds and enriching halo gas “inside-out” by spreading centrally enriched metals to the outskirts of galaxies, into the halo and beyond. The metal (iron) profiles of halos simulated with AGN feedback have a flatter slope than those without AGN feedback, consistent with recent X-ray observations. The predicted gas iron abundance of group scale galaxies simulated with AGN feedback is Z Fe = 0.23 Z Fe,⊙ at 0.5r 500, which is 2.5 times higher than that in simulations without AGN feedback. In these simulations, AGN winds are also important for the metal enrichment of the intergalactic medium, as the vast majority of metals ejected from the galaxy by AGN-driven winds end up beyond the halo virial radius.

Searching for molecular gas inflows and outflows in the nuclear regions of five Seyfert galaxies

Active galactic nucleus (AGN) driven outflows are believed to play an important role in regulating the growth of galaxies, mostly via negative feedback. However, their effects on their hosts are far from clear, especially for low- and moderate-luminosity Seyferts. To investigate this issue, we obtained cold molecular gas observations, traced by the CO(2-1) transition, using the NOEMA interferometer of five nearby (distances between 19 and 58 Mpc) Seyfert galaxies. The resolution of ∼0.3–0.8 (∼30–100 pc) and field of view of NOEMA allowed us to study the CO(2-1) morphology and kinematics in the nuclear regions (∼100 pc) and up to radial distances of ∼900 pc. We detected CO(2-1) emission in all five galaxies with disky or circumnuclear ring-like morphologies. We derived cold molecular gas masses on nuclear (∼100 pc) and circumnuclear (∼650 pc) scales in the range from 106 to 107 M⊙ and from 107 to 108 M⊙, respectively. In all of our galaxies, the bulk of this gas is rotating in the plane of the galaxy. However, noncircular motions are also present. In NGC 4253, NGC 4388, and NGC 7465, we can ascribe the streaming motions to the presence of a large-scale bar. In Mrk 1066 and NGC 4388, the noncircular motions in the nuclear regions are explained as outflowing material due to the interaction of the AGN wind with molecular gas in the galaxy disk. We conclude that for an unambiguous and precise interpretation of the kinematics of the cold molecular gas, we need detailed knowledge of the host galaxy (i.e., presence of bars, interactions, etc.), and also of the ionized gas kinematics and ionization cone geometry.

A hadronic emission model for black hole-disc impacts in the blazar OJ 287

ABSTRACTA supermassive black hole (SMBH) binary in the core of the blazar OJ 287 has been invoked in previous works to explain its observed optical flare quasi-periodicity. Following this picture, we investigate a hadronic origin for the X-ray and γ-ray counterparts of the November 2015 major optical flare of this source. An impact outflow must result after the lighter SMBH (the secondary) crosses the accretion disc of the heavier one (the primary). We then consider acceleration of cosmic ray (CR) protons in the shock driven by the impact outflow as it expands and collides with the active galactic nucleus (AGN) wind of the primary SMBH. We show that the emission of these CRs can reproduce the X-ray and γ-ray flare data self-consistently with the optical component of the 2015 November major flare. The derived emission models are consistent with a magnetic field B ∼ 5 G in the emission region and a power-law index of q ∼ 2.2 for the energy distribution of the emitting CRs. The mechanical luminosity of the AGN wind represents $\lesssim 50{{\ \rm per\ cent}}$ of the mass accretion power of the primary SMBH in all the derived emission profiles.

The Role of Infrared Radiation Pressure in Shaping Dusty Winds in AGNs

Abstract The detection of dusty winds dominating the infrared emission of active galactic nuclei (AGNs) on parsec scales has revealed the limitations of traditional radiative transfer models based on a toroidal distribution of dusty gas. A new, more complex, dynamical structure is emerging and the physical origin of such dusty winds has to be critically assessed. We present a semi-analytical model to test the hypothesis of radiatively accelerated dusty winds launched by the AGN and by the heated dust itself. The model consists of an AGN and an infrared radiating dusty disk, the latter being the primary mass reservoir for the outflow. We calculate the trajectories of dusty gas clumps in this environment, accounting for both gravity and the AGN radiation as well as the re-radiation by the hot, dusty gas clouds themselves. We find that the morphology consists of a disk of material that orbits with sub-Keplerian velocities and a hyperboloid polar wind launched at the inner edge of the dusty disk. This is consistent with high-angular resolution infrared and sub-mm observations of some local Seyfert AGN. The strength of the wind and its orientation depend on the Eddington ratio and the column density of the dusty clumps, which is in agreement with proposed radiation regulated obscuration models developed for the X-ray obscuring material around AGNs.

The Megamaser Cosmology Project − XII. VLBI imaging of H2O maser emission in three active galaxies and the effect of AGN winds on disc dynamics

ABSTRACT We present very long baseline interferometry (VLBI) images and kinematics of water maser emission in three active galaxies: NGC 5728, Mrk 1, and IRAS 08452–0011. IRAS 08452–0011, at a distance of ∼200 Mpc, is a triple-peaked H2O megamaser, consistent with a Keplerian rotating disc, indicating a black hole mass of (3.3$\pm 0.2)\times 10^{7}\, \mathrm{ M}_{\odot }$. NGC 5728 and Mrk 1 display double-peaked spectra, and VLBI imaging reveals complicated gas kinematics that do not allow for a robust determination of black hole mass. We show evidence that the masers in NGC 5728 are in a wind while the Mrk 1 maser system has both disc and outflow components. We also find that disturbed morphology and kinematics are a ubiquitous feature of all double-peaked maser systems, implying that these maser sources may reside in environments where active galactic nucleus (AGN) winds are prominent at ∼1 pc scale and have significant impact on the masing gas. Such AGNs tend to have black hole masses $M_{\rm BH}\, \lt$ 8 × 106 M⊙ and Eddington ratios $\lambda _{\rm Edd}\, \gtrsim$ 0.1, while the triple-peaked megamasers show an opposite trend.

Powering galactic superwinds with small-scale AGN winds

ABSTRACT We present a new implementation for active galactic nucleus (AGN) feedback through small-scale, ultrafast winds in the moving-mesh hydrodynamic code arepo. The wind is injected by prescribing mass, momentum, and energy fluxes across a spherical boundary centred on a supermassive black hole according to available constraints for accretion disc winds. After sweeping-up a mass equal to their own, small-scale winds thermalize, powering energy-driven outflows with dynamics, structure, and cooling properties in excellent agreement with those of analytic wind solutions. Momentum-driven solutions do not easily occur, because the Compton cooling radius is usually much smaller than the free-expansion radius of the small-scale winds. Through various convergence tests, we demonstrate that our implementation yields wind solutions, which are well converged down to the typical resolution achieved in cosmological simulations. We test our model in hydrodynamic simulations of isolated Milky Way – mass galaxies. Above a critical AGN luminosity, initially spherical, small-scale winds power bipolar, energy-driven superwinds that break out of the galactic nucleus, flowing at speeds $\gt 1000 \rm \, km \, s^{-1}$ out to $\sim 10 \, \rm kpc$. These energy-driven outflows result in moderate, but long-term, reduction in star formation, which becomes more pronounced for higher AGN luminosities and faster small-scale winds. Suppression of star formation proceeds through a rapid mode that involves the removal of the highest density, nuclear gas, and through a slower mode that effectively halts halo gas accretion. Our new implementation makes it possible to model AGN-driven winds in a physically meaningful and validated way in simulations of galaxy evolution, the interstellar medium and black hole accretion flows.

The impact of AGN wind feedback in simulations of isolated galaxies with a multiphase ISM

ABSTRACT Accreting black holes can drive fast and energetic nuclear winds that may be an important feedback mechanism associated with active galactic nuclei (AGN). In this paper, we implement a scheme for capturing feedback from these fast nuclear winds and examine their impact in simulations of isolated disc galaxies. Stellar feedback is modelled using the Feedback In Realistic Environments (fire) physics and produces a realistic multiphase interstellar medium (ISM). We find that AGN winds drive the formation of a low-density, high-temperature central gas cavity that is broadly consistent with analytic model expectations. The effects of AGN feedback on the host galaxy are a strong function of the wind kinetic power and momentum. Low- and moderate-luminosity AGN do not have a significant effect on their host galaxy: the AGN winds inefficiently couple to the ambient ISM and instead a significant fraction of their energy vents in the polar direction. For such massive black holes, accretion near the Eddington limit can have a dramatic impact on the host galaxy ISM: if AGN wind feedback acts for ≳20–30 Myr, the inner ∼1–10 kpc of the ISM is disrupted and the global galaxy star formation rate is significantly reduced. We quantify the properties of the resulting galaxy-scale outflows and find that the radial momentum in the outflow is boosted by a factor of ∼2–3 relative to that initially supplied in the AGN wind for strong feedback scenarios, decreasing below unity for less energetic winds. In contrast to observations, however, the outflows are primarily hot, with very little atomic or molecular gas. We conjecture that merging galaxies and high-redshift galaxies, which have more turbulent and thicker discs and very different nuclear gas geometries, may be even more disrupted by AGN winds than found in our simulations.

Simulating the Fermi Bubbles as Forward Shocks Driven by AGN Jets

Abstract The Fermi bubbles are two giant bubbles in gamma-rays lying above and below the Galactic Center (GC). Despite numerous studies on the bubbles, their origin and emission mechanism remain elusive. Here we use a suite of hydrodynamic simulations to study the scenario where the cosmic rays (CRs) in the bubbles are mainly accelerated at the forward shocks driven by a pair of opposing jets from Sgr A*. We find that an active galactic nucleus (AGN) jet event that happened 5–6 Myr ago can naturally reproduce the bilobular morphology of the bubbles, and the postshock gas temperature in the bubbles is heated to ∼0.4 keV, consistent with recent X-ray observations. The forward shocks compress the hot halo gas, and at low latitudes, the compressed gas shows an X-shaped structure, naturally explaining the biconical X-ray structure in the ROSAT 1.5 keV map in both morphology and X-ray surface brightness. CR acceleration is most efficient in the head regions of the bubbles during the first 2 Myr. The opposing jets release a total energy of ∼1055 erg with an Eddington ratio of ∼10−3, which falls well in the range of the hot accretion flow mode for black holes. Our simulations further show that the forward shocks driven by spherical winds at the GC typically produce bubbles with much wider bases than observed and could not reproduce the biconical X-ray structure at low latitudes. This suggests that starburst or AGN winds are unlikely the origin of the bubbles in the shock scenario.