The prevalence and energetics of quasar feedback is a major unresolved problem in galaxy formation theory. In this paper, we present Gemini Integral Field Unit observations of ionized gas around 11 ...luminous, obscured, radio-quiet quasars at z ∼ 0.5 out to ∼15 kpc from the quasar; specifically, we measure the kinematics and morphology of O iii λ5007 Å emission. The round morphologies of the nebulae and the large line-of-sight velocity widths (with velocities containing 80 per cent of the emission as high as 103 km s−1) combined with relatively small velocity difference across them (from 90 to 520 km s−1) point towards wide-angle quasi-spherical outflows. We use the observed velocity widths to estimate a median outflow velocity of 760 km s−1, similar to or above the escape velocities from the host galaxies. The line-of-sight velocity dispersion declines slightly towards outer parts of the nebulae (by 3 per cent kpc−1 on average). The majority of nebulae show blueshifted excesses in their line profiles across most of their extents, signifying gas outflows. For the median outflow velocity, we find
between 4 × 1044 and 3 × 1045 erg s−1 and
between 2 × 103 and 2 × 104 M yr−1. These values are large enough for the observed quasar winds to have a significant impact on their host galaxies. The median rate of converting bolometric luminosity to kinetic energy of ionized gas clouds is ∼2 per cent. We report four new candidates for 'superbubbles' - outflows that may have broken out of the denser regions of the host galaxy.
ABSTRACT
We apply a turbulence-regulated model of star formation to calculate the star formation rate (SFR) of dense star-forming clouds in simulations of jet–interstellar medium (ISM) interactions. ...The method isolates individual clumps and accounts for the impact of virial parameter and Mach number of the clumps on the star formation activity. This improves upon other estimates of the SFR in simulations of jet–ISM interactions, which are often solely based on local gas density, neglecting the impact of turbulence. We apply this framework to the results of a suite of jet–ISM interaction simulations to study how the jet regulates the SFR both globally and on the scale of individual star-forming clouds. We find that the jet strongly affects the multiphase ISM in the galaxy, inducing turbulence and increasing the velocity dispersion within the clouds. This causes a global reduction in the SFR compared to a simulation without a jet. The shocks driven into clouds by the jet also compress the gas to higher densities, resulting in local enhancements of the SFR. However, the velocity dispersion in such clouds is also comparably high, which results in a lower SFR than would be observed in galaxies with similar gas mass surface densities and without powerful radio jets. We thus show that both local negative and positive jet feedback can occur in a single system during a single jet event, and that the SFR in the ISM varies in a complicated manner that depends on the strength of the jet–ISM coupling and the jet break-out time-scale.
Black hole feedback - the strong interaction between the energy output of supermassive black holes and their surrounding environments - is routinely invoked to explain the absence of overly luminous ...galaxies, the black hole versus bulge correlations and the similarity of black hole accretion and star formation histories. Yet direct probes of this process in action are scarce and limited to small samples of active nuclei. In this paper, we present Gemini Integral Field Unit observations of the distribution of ionized gas around luminous, obscured, radio-quiet quasars at z ∼ 0.5. We detect extended ionized gas nebulae via O iii λ5007 Å emission in every case, with a mean diameter of 28 kpc. These nebulae are nearly perfectly round, with Hβ surface brightness declining ∝R
−3.5 ± 1.0. The regular morphologies of nebulae around radio-quiet quasars are in striking contrast with lumpy or elongated O iii nebulae seen around radio galaxies at low and high redshifts. We present the uniformly measured size-luminosity relationship of O iii nebulae around Seyfert 2 galaxies and type 2 quasars spanning six orders of magnitude in luminosity and confirm the flat slope of the correlation (
). We propose a model of clumpy nebulae in which clouds that produce line emission transition from being ionization-bounded at small distances from the quasar to being matter-bounded in the outer parts of the nebula. The model - which has a declining pressure profile - qualitatively explains line ratio profiles and surface brightness profiles seen in our sample. It is striking that we see such smooth and round large-scale gas nebulosities in this sample, which are inconsistent with illuminated merger debris and which we suggest may be the signature of accretion energy from the nucleus reaching gas at large scales.
Radio emission from radio-quiet quasars may be due to star formation in the quasar host galaxy, to a jet launched by the supermassive black hole, or to relativistic particles accelerated in a ...wide-angle radiatively driven outflow. In this paper, we examine whether radio emission from radio-quiet quasars is a byproduct of star formation in their hosts. To this end, we use infrared spectroscopy and photometry from Spitzer and Herschel to estimate or place upper limits on star formation rates in hosts of ∼300 obscured and unobscured quasars at z < 1. We find that low-ionization forbidden emission lines such as Ne ii and Ne iii are likely dominated by quasar ionization and do not provide reliable star formation diagnostics in quasar hosts, while polycyclic aromatic hydrocarbon (PAH) emission features may be suppressed due to the destruction of PAH molecules by the quasar radiation field. While the bolometric luminosities of our sources are dominated by the quasars, the 160 μm fluxes are likely dominated by star formation, but they too should be used with caution. We estimate median star formation rates to be 6–29 M⊙ yr−1, with obscured quasars at the high end of this range. This star formation rate is insufficient to explain the observed radio emission from quasars by an order of magnitude, with log (L
radio, obs/L
radio, SF) = 0.6–1.3 depending on quasar type and star formation estimator. Although radio-quiet quasars in our sample lie close to the 8–1000 μm infrared/radio correlation characteristic of the star-forming galaxies, both their infrared emission and their radio emission are dominated by the quasar activity, not by the host galaxy.
Abstract
We propose that Gigahertz Peak Spectrum (GPS) and Compact Steep Spectrum (CSS) radio sources are the signposts of relativistic jet feedback in evolving galaxies. Our simulations of ...relativistic jets interacting with a warm, inhomogeneous medium, utilizing cloud densities and velocity dispersions in the range derived from optical observations, show that free–free absorption can account for the ∼ GHz peak frequencies and low-frequency power laws inferred from the radio observations. These new computational models replace a power-law model for the free–free optical depth a more fundamental model involving disrupted log-normal distributions of warm gas. One feature of our new models is that at early stages, the low-frequency spectrum is steep but progressively flattens as a result of a broader distribution of optical depths, suggesting that the steep low-frequency spectra discovered by Callingham et al. may possibly be attributed to young sources. We also investigate the inverse correlation between peak frequency and size and find that the initial location on this correlation is determined by the average density of the warm ISM. The simulated sources track this correlation initially but eventually fall below it, indicating the need for a more extended ISM than presently modelled. GPS and CSS sources can potentially provide new insights into the phenomenon of AGN feedback since their peak frequencies and spectra are indicative of the density, turbulent structure, and distribution of gas in the host galaxy.
We present 0.″3 (band 6) and 1.″5 (band 3) ALMA observations of the (sub)millimeter dust continuum emission for 25 radio galaxies at 1 < z < 5.2. Our survey reaches a rms flux density of ∼50 μJy in ...band 6 (200–250 GHz) and ∼20 μJy in band 3 (100–130 GHz). This is an order of magnitude deeper than single-dish 850 μm observations, and reaches fluxes where synchrotron and thermal dust emission are expected to be of the same order of magnitude. Combining our sensitive ALMA observations with low-resolution radio data from ATCA, higher resolution VLA data, and infrared photometry from Herschel and Spitzer, we have disentangled the synchrotron and thermal dust emission. We determine the star-formation rates and AGN infrared luminosities using our newly developed Multi-resolution and multi-object/origin spectral energy distribution fitting code (MR-MOOSE). We find that synchrotron emission contributes substantially at λ ∼ 1 mm. Through our sensitive flux limits and accounting for a contribution from synchrotron emission in the mm, we revise downward the median star-formation rate by a factor of seven compared to previous estimates based solely on Herschel and Spitzer data. The hosts of these radio-loud AGN appear predominantly below the main sequence of star-forming galaxies, indicating that the star formation in many of the host galaxies has been quenched. Future growth of the host galaxies without substantial black hole mass growth will be needed to bring these objects on the local relation between the supermassive black holes and their host galaxies. Given the mismatch in the timescales of any star formation that took place in the host galaxies and lifetime of the AGN, we hypothesize that a key role is played by star formation in depleting the gas before the action of the powerful radio jets quickly drives out the remaining gas. This positive feedback loop of efficient star formation rapidly consuming the gas coupled to the action of the radio jets in removing the residual gas is how massive galaxies are rapidly quenched.
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AGN feedback now appears as an attractive mechanism to resolve some of the outstanding problems with the “standard” cosmological models, in particular those related to massive galaxies. At low ...redshift, evidence is growing that gas cooling and star formation may be efficiently suppressed by mechanical energy input from radio sources. To directly constrain how this may influence the formation of massive galaxies near the peak in the redshift distribution of powerful quasars, $z\sim 2$, we present an analysis of the emission-line kinematics of 3 powerful radio galaxies at $z\sim 2{-}3$ (HzRGs) based on rest-frame optical integral-field spectroscopy obtained with SINFONI on the VLT. The host galaxies of powerful radio-loud AGN are among the most massive galaxies, and thus AGN feedback may have a particularly clear signature in these galaxies. We find evidence for bipolar outflows in all HzRGs, with kinetic energies that are equivalent to 0.2% of the rest-mass of the supermassive black hole. Observed total velocity offsets in the outflows are ~$800{-}1000$ km s-1 between the blueshifted and redshifted line emission, and FWHMs ~ 1000 km s-1 suggest strong turbulence. Line ratios allow to measure electron temperatures, ~104 K from OIII$\lambda\lambda\lambda$4363, 4959, 5007 at $z\sim 2$, electron densities (~500 cm-3) and extinction ($A_V\sim 1{-}4$ mag). Ionized gas masses estimated from the Hα luminosity are of order $10^{10}~M_{\odot}$, similar to the molecular gas content of HzRGs, underlining that these outflows may indicate a significant phase in the evolution of the host galaxy. The total energy release of ~1060 erg during a dynamical time of ~107 yrs corresponds to about the binding energy of a massive galaxy, similar to the prescriptions adopted in galaxy evolution models. Geometry, timescales and energy injection rates of order 10% of the kinetic energy flux of the jet suggest that the outflows are most likely driven by the radio source. The global energy density release of ~1057 erg s-1 Mpc-3 may also influence the subsequent evolution of the HzRG by enhancing the entropy and pressure in the surrounding halo and facilitating ram-pressure stripping of gas in satellite galaxies that may contribute to the subsequent mass assembly of the HzRG through low-dissipation “dry” mergers.
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ABSTRACT
Hydrodynamical simulations predict that the jets of young radio sources can inhibit star formation in their host galaxies by injecting heat and turbulence into the interstellar medium (ISM). ...To investigate jet–ISM interactions in a galaxy with a young radio source, we have carried out a multiwavelength study of the z = 0.025 Compact Steep Spectrum radio source hosted by the early-type galaxy UGC 05771. Using Keck/OSIRIS observations, we detected H2 1–0 S(1) and Fe ii emission at radii of 100s of parsecs, which traces shocked molecular and ionized gas being accelerated outwards by the jets to low velocities, creating a ‘stalling wind’. At kpc radii, we detected shocked ionized gas using observations from the CALIFA survey, covering an area much larger than the pc-scale radio source. We found that existing interferometric radio observations fail to recover a large fraction of the source’s total flux, indicating the likely existence of jet plasma on kpc scales, which is consistent with the extent of shocked gas in the host galaxy. To investigate the star formation efficiency in UGC 05771, we obtained IRAM CO observations to analyse the molecular gas properties. We found that UGC 05771 sits below the Kennicutt–Schmidt relation, although we were unable to definitively conclude if direct interactions from the jets are inhibiting star formation. This result shows that jets may be important in regulating star formation in the host galaxies of compact radio sources.
ABSTRACT The impact of winds and jet-inflated bubbles driven by active galactic nuclei (AGN) are believed to significantly affect the host galaxy’s interstellar medium (ISM) and regulate star ...formation. To explore this scenario, we perform a suite of hydrodynamic simulations to model the interaction between turbulent star-forming clouds and highly pressurized AGN-driven outflows, focusing on the effects of self-gravity. Our results demonstrate that the cloudlets fragmented by the wind can become gravitationally bound, significantly increasing their survival time. While external pressurization leads to a global collapse of the clouds in cases of weaker winds ($10^{42}\!-\!10^{43}~{\rm erg\, s^{-1}}$), higher power winds ($10^{44}\!-\!10^{45}~{\rm erg\, s^{-1}}$) disperse the gas and cause localized collapse of the cloudlets. We also demonstrate that a kinetic energy-dominated wind is more efficient in accelerating and dispersing the gas than a thermal wind with the same power. The interaction can give rise to multiphase outflows with velocities ranging from a few 100 to several 1000 ${\rm km\, s^{-1}}$. The mass outflow rates are tightly correlated with the wind power, which we explain by an ablation-based mass-loss model. Moreover, the velocity dispersion and the virial parameter of the cloud material can increase by up to one order of magnitude through the effect of the wind. Even though the wind can suppress or quench star formation for about 1 Myr during the initial interaction, a substantial number of gravitationally bound dense cloudlets manage to shield themselves from the wind’s influence and subsequently undergo rapid gravitational collapse, leading to an enhanced star formation rate.
ABSTRACT
Relativistic jets are believed to have a substantial impact on the gas dynamics and evolution of the interstellar medium (ISM) of their host galaxies. In this paper, we aim to draw a link ...between the simulations and the observable signatures of jet-ISM interactions by analyzing the emission morphology and gas kinematics resulting from jet-induced shocks in simulated disc and spherical systems. We find that the jet-induced laterally expanding forward shock of the energy bubble sweeping through the ISM causes large-scale outflows, creating shocked emission and high-velocity dispersion in the entire nuclear regions (∼2 kpcs) of their hosts. The jetted systems exhibit larger velocity widths (>800 km s−1), broader Position-Velocity maps and distorted symmetry in the disc’s projected velocities than systems without a jet. We also investigate the above quantities at different inclination angles of the observer with respect to the galaxy. Jets inclined to the gas disc of its host are found to be confined for longer times, and consequently couple more strongly with the disc gas. This results in prominent shocked emission and high-velocity widths, not only along the jet’s path, but also in the regions perpendicular to them. Strong interaction of the jet with a gas disc can also distort its morphology. However, after the jets escape their initial confinement, the jet-disc coupling is weakened, thereby lowering the shocked emission and velocity widths.
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