Black Hole Feedback Research Articles

First results from the TNG50 simulation: galactic outflows driven by supernovae and black hole feedback

Abstract We present the new TNG50 cosmological, magnetohydrodynamical simulation – the third and final volume of the IllustrisTNG project. This simulation occupies a unique combination of large volume and high resolution, with a 50 Mpc box sampled by 21603 gas cells (baryon mass of 8 × 104 M⊙). The median spatial resolution of star-forming interstellar medium gas is ∼100−140 pc. This resolution approaches or exceeds that of modern ‘zoom’ simulations of individual massive galaxies, while the volume contains ∼20 000 resolved galaxies with $M_\star \gtrsim 10^7$ M⊙. Herein we show first results from TNG50, focusing on galactic outflows driven by supernovae as well as supermassive black hole feedback. We find that the outflow mass loading is a non-monotonic function of galaxy stellar mass, turning over and rising rapidly above 1010.5 M⊙ due to the action of the central black hole (BH). The outflow velocity increases with stellar mass, and at fixed mass it is faster at higher redshift. The TNG model can produce high-velocity, multiphase outflows that include cool, dense components. These outflows reach speeds in excess of 3000 km s−1 out to 20 kpc with an ejective, BH-driven origin. Critically, we show how the relative simplicity of model inputs (and scalings) at the injection scale produces complex behaviour at galactic and halo scales. For example, despite isotropic wind launching, outflows exhibit natural collimation and an emergent bipolarity. Furthermore, galaxies above the star-forming main sequence drive faster outflows, although this correlation inverts at high mass with the onset of quenching, whereby low-luminosity, slowly accreting, massive BHs drive the strongest outflows.

Not So Heavy Metals: Black Hole Feedback Enriches the Circumgalactic Medium

Abstract We examine the effects of supermassive black hole (SMBH) feedback on the circumgalactic medium (CGM) using a cosmological hydrodynamic simulation (Romulus25) and a set of four zoom-in “genetically modified” Milky-Way–mass galaxies sampling different evolutionary paths. By tracing the distribution of metals in the CGM, we show that O vi is a sensitive indicator of SMBH feedback. First, we calculate the column densities of O vi in simulated Milky-Way–mass galaxies and compare them with observations from the COS-Halos Survey. Our simulations show column densities of O vi in the CGM consistent with those of COS-Halos star-forming and quenched galaxies. These results contrast with those from previous simulation studies which typically underproduce CGM column densities of O vi. We determine that a galaxy’s star formation history and assembly record have little effect on the amount of O vi in its CGM. Instead, column densities of O vi are closely tied to galaxy halo mass and BH growth history. The set of zoom-in, genetically modified Milky-Way–mass galaxies indicates that the SMBH drives highly metal-enriched material out into its host galaxy’s halo, which in turn elevates the column densities of O vi in the CGM.

Classification of Broad Absorption Line Quasars with a Convolutional Neural Network

Abstract Quasars that exhibit blueshifted, broad absorption lines (BAL QSOs) are an important probe of black hole feedback on galaxy evolution. Yet the presence of BALs is also a complication for large spectroscopic surveys that use quasars as cosmological probes because the BAL features can affect redshift measurements and contaminate information about the matter distribution in the Lyα forest. We present a new BAL QSO catalog for quasars in the Sloan Digital Sky Survey (SDSS) Data Release 14 (DR14). As the SDSS DR14 quasar catalog has over 500,000 quasars, we have developed an automated BAL classifier with a Convolutional Neural Network (CNN). We trained our CNN classifier on the C iv λ 1549 region of a sample of quasars with reliable human classifications, and compared the results to both a dedicated test sample and visual classifications from the earlier SDSS DR12 quasar catalog. Our CNN classifier correctly classifies over 98% of the BAL quasars in the DR12 catalog, which demonstrates comparable reliability to human classification. The disagreements are generally for quasars with lower signal-to-noise ratio spectra and/or weaker BAL features. Our new catalog includes the probability that each quasar is a BAL, the strength, blueshifts and velocity widths of the troughs, and similar information for any Si iv λ 1398 BAL troughs that may be present. We find significant BAL features in 16.8% of all quasars with 1.57 < z < 5.56 in the SDSS DR14 quasar catalog.

Radio jets from AGNs in dwarf galaxies in the COSMOS survey: mechanical feedback out to redshift ∼3.4

AbstractDwarf galaxies are thought to host the remnants of the early Universe seed black holes (BHs) and to be dominated by supernova feedback. However, recent studies suggest that BH feedback could also strongly impact their growth. We report the discovery of 35 dwarf galaxies hosting radio active galactic nucleus (AGN) out to redshift ∼3.4, which constitutes the highest redshift sample of AGNs in dwarf galaxies. The galaxies are drawn from the VLA-COSMOS 3 GHz Large Project and all are star forming. After removing the contribution from star formation to the radio emission, we find a range of AGN radio luminosities of $L^\mathrm{AGN}_\mathrm{1.4\, GHz} \sim 10^{37}$–1040 erg s−1. The bolometric luminosities derived from the fit of their spectral energy distribution are ≳1042 erg s−1, in agreement with the presence of AGNs in these dwarf galaxies. The 3 GHz radio emission of most of the sources is compact and the jet powers range from Qjet ∼ 1042 to 1044 erg s−1. These values, as well as the finding of jet efficiencies ≥10 per cent in more than 50 per cent of the sample, indicate that dwarf galaxies can host radio jets as powerful as those of massive radio galaxies whose jet mechanical feedback can strongly affect the formation of stars in the host galaxy. We conclude that AGN feedback can also have a very strong impact on dwarf galaxies, either triggering or hampering star formation and possibly the material available for BH growth. This implies that those low-mass AGNs hosted in dwarf galaxies might not be the untouched relics of the early seed BHs, which has important implications for seed BH formation models.

NIHAO – XXII. Introducing black hole formation, accretion, and feedback into the NIHAO simulation suite

ABSTRACT We introduce algorithms for black hole physics, i.e. black hole formation, accretion, and feedback, into the Numerical Investigation of a Hundred Astrophysical Objects (NIHAO) project of galaxy simulations. This enables us to study high mass, elliptical galaxies, where feedback from the central black hole is generally thought to have a significant effect on their evolution. We furthermore extend the NIHAO suite by 45 simulations that encompass z = 0 halo masses from 1 × 1012 to $4 \times 10^{13}\, \mathrm{M}_{\odot }$, and resimulate five galaxies from the original NIHAO sample with black hole physics, which have z = 0 halo masses from 8 × 1011 to $3 \times 10^{12}\, \mathrm{M}_{\odot }$. Now NIHAO contains 144 different galaxies and thus has the largest sample of zoom-in simulations of galaxies, spanning z = 0 halo masses from 9 × 108 to $4 \times 10^{13}\, \mathrm{M}_{\odot }$. In this paper we focus on testing the algorithms and calibrating their free parameters against the stellar mass versus halo mass relation and the black hole mass versus stellar mass relation. We also investigate the scatter of these relations, which we find is a decreasing function with time and thus in agreement with observations. For our fiducial choice of parameters we successfully quench star formation in objects above a z = 0 halo mass of $10^{12}\, \mathrm{M}_{\odot }$, thus transforming them into red and dead galaxies.

Intermediate-mass black hole growth and feedback in dwarf galaxies at high redshifts

Abstract Intermediate-mass black holes (IMBHs; masses between $100\rm{\, and \,}10^{6} \, \mathrm{M}_{\odot }$) historically comprise of an elusive population compared to stellar-mass and supermassive black holes (BHs). Recently, IMBHs have started to be observed at the centres of low-mass galaxies. We perform cosmological hydrodynamical simulations of $(2 \, h^{-1} ~ {\rm Mpc})^3$ comoving boxes and investigate the growth and feedback of central IMBHs in dwarf galaxies (DGs). The earliest BHs appear at z ∼ 18–25 and grow thereafter by accreting gas and by merger with other BHs. We find that, starting from $10^{2} \, \mathrm{M}_{\odot }$, it is possible to build up IMBHs of a few$\times 10^{5}\!-\!10^{6} \, \mathrm{M}_{\odot }$ by z = 5, when the BHs are seeded in haloes less massive than $4 \times 10^{7} \, \mathrm{M}_{\odot }$. The BH accretion rates increase with time and reach $\dot{M}_{\rm BH} = (0.2\!-\!0.8) \dot{M}_{\rm Edd}$ for the massive IMBHs by z = 4. The star formation rate density (SFRD) evolution of the DGs (stellar mass $10^{5}\!-\!10^{8} \, \mathrm{M}_{\odot }$) has a peak plateau between z = 4 and 6. Star formation is quenched between z = 9 and 4. The SFRD is reduced by factors up to 3 when the BHs have grown to a few times $10^5 \, \mathrm{M}_{\odot }$. Even in the presence of stronger supernova (SN)-driven mass ejection, the BHs continue to grow up to z ∼ 6, sustained by gas inflows driven by galaxy mergers and interactions in a cosmological environment. Our conclusions, based on numerical simulation results, support the scenario that early feedback from IMBHs in gas-rich DGs at z = 5–8 can potentially solve several anomalies in the DG mass range within the concordance Λ cold dark matter (ΛCDM) cosmological scenario (Silk 2017). Our results suggest that IMBHs at DG centres grow faster than their host galaxies in the early Universe, and the resulting BH feedback turns the DGs and the BHs dormant.

A 10,000-solar-mass black hole in the nucleus of a bulgeless dwarf galaxy

The motions of gas and stars in the nuclei of nearby large galaxies have demonstrated that massive black holes are common and that their masses strongly correlate with the stellar velocity dispersion $\sigma_{\star}$ of the bulge. This correlation suggests that massive black holes and galaxies influence each other's growth. Dynamical measurements are less reliable when the sphere of influence is unresolved, thus it remains unknown whether this correlation exists in galaxies much smaller than the Milky Way, as well as what fraction of these galaxies have central black holes. Light echoes from photoionized clouds around accreting black holes, in combination with the velocity of these clouds, yield a direct mass measurement that circumvents this difficulty. Here we report an exceptionally low reverberation delay of $83\pm14$ minutes between variability in the accretion disk and high velocity H$\alpha$ emission from the nucleus of the bulgeless dwarf galaxy NGC~4395. Combined with the H$\alpha$ line-of-sight velocity dispersion $\sigma_{\rm line}=426\pm1$~km~s$^{-1}$, this lag determines a mass of about 10,000~$M_{\odot}$ for the black hole. This mass is among the smallest central black hole masses reported, near the low end of expected masses for heavy "seeds", and the best direct mass measurement for a galaxy of this size. Despite the lack of a bulge, NGC~4395 is consistent with the $M_{\rm BH} - \sigma_{\star}$ relation when $\sigma_{\star}$ is measured from the central region. This indicates that the relation need not originate from hierarchical galaxy assembly nor from black hole feedback.

A rapidly changing jet orientation in the stellar-mass black-hole system V404 Cygni.

Powerful relativistic jets are one of the main ways in which accreting black holes provide kinetic feedback to their surroundings. Jets launched from or redirected by the accretion flow that powers them are expected to be affected by the dynamics of the flow, which for accreting stellar-mass black holes has shown evidence for precession1 due to frame-dragging effects that occur when the black-hole spin axis is misaligned with the orbital plane of its companion star2. Recently, theoretical simulations have suggested that the jets can exert an additional torque on the accretion flow3, although the interplay between the dynamics of the accretion flow and the launching of the jets is not yet understood. Here we report a rapidly changing jet orientation-on a time scale of minutes to hours-in the black-hole X-ray binary V404 Cygni, detected with very-long-baseline interferometry during the peak of its 2015 outburst. We show that this changing jet orientation can be modelled as the Lense-Thirring precession of a vertically extended slim disk that arises from the super-Eddington accretion rate4. Our findings suggest that the dynamics of the precessing inner accretion disk could play a role in either directly launching or redirecting the jets within the inner few hundred gravitational radii. Similar dynamics should be expected in any strongly accreting black hole whose spin is misaligned with the inflowing gas, both affecting the observational characteristics of the jets and distributing the black-hole feedback more uniformly over the surrounding environment5,6.

Simba: Cosmological simulations with black hole growth and feedback

We introduce the Simba simulations, the next generation of the Mufasa cosmological galaxy formation simulations run with Gizmo's meshless finite mass hydrodynamics. Simba includes updates to Mufasa's sub-resolution star formation and feedback prescriptions, and introduces black hole growth via the torque-limited accretion model of Angl\'es-Alc\'azar et al. (2017) from cold gas and Bondi accretion from hot gas, along with black hole feedback via kinetic bipolar outflows and X-ray energy. Ejection velocities are taken to be ~10^3 km/s at high Eddington ratios, increasing to ~8000 km/s at Eddington ratios below 2%, with a constant momentum input of 20L/c. Simba further includes an on-the-fly dust production, growth, and destruction model. Our Simba run with (100 Mpc/h)^3 and 1024^3 gas elements reproduces numerous observables, including galaxy stellar mass functions at z=0-6, the stellar mass--star formation rate main sequence, HI and H2 fractions, the mass-metallicity relation at z=0 and z=2, star-forming galaxy sizes, hot gas fractions in massive halos, and z=0 galaxy dust properties. However, Simba also yields an insufficiently sharp truncation of the z=0 mass function, and too-large sizes for low-mass quenched galaxies. We show that Simba's jet feedback is primarily responsible for quenching massive galaxies.

Dwarf galaxies might not be the birth sites of supermassive black holes

Intermediate-mass black holes (BHs) in local dwarf galaxies are considered the relics of the early seed BHs. However, their growth might have been impacted by galaxy mergers and BH feedback so that they cannot be treated as tracers of the early seed BH population.

The impact of black hole seeding in cosmological simulations

Most cosmological simulations of galaxy evolution include active galactic nucleus (AGN) feedback, typically seeding black holes with masses of $\geq 10^5\, h^{-1}\, \rm{M}_{\odot}$ when the dark matter halo exceeds a given threshold mass. Taylor & Kobayashi (2014) introduced a new model, which seeds black holes at $10^3\, h^{-1}\, \rm{M}_{\odot}$ based on gas properties alone, and motivated by the channel of black hole formation due to the collapse of the most massive first stars in the Universe. We compare the black hole mass when the dark matter halo mass is $10^{10}\, h^{-1}\, \rm{M}_{\odot}$ between the different seeding methods. We find that seeding based upon gas properties gives a distribution of black hole masses with $\langle \log M_{\rm{BH}} {/ \rm{M}_{\odot}} \rangle = (5.18 \pm 0.54)$ when dark matter halo mass is $10^{10}\, h^{-1}\, \rm{M}_{\odot}$, consistent with the {seeding criteria} used in other simulations. However, the evolution of individual galaxies can be strongly affected by the different seeding mechanisms. We also find that the mean value of the distribution of black hole masses at a given halo mass evolves over time, with higher masses at higher redshifts, indicative of downsizing. Our results can inform more physically motivated black hole and AGN feedback models in cosmological simulations and semi-analytic models.

A Role for Turbulence in Circumgalactic Precipitation

Abstract The cooling time, t cool, of the hot ambient medium pervading a massive galaxy does not drop much below 10 times the freefall time t ff at any radius. Theoretical models have accounted for this finding by hypothesizing that cold clouds start to condense out of the ambient medium when t cool/t ff ≲ 10 and fuel a strong black hole feedback response, but they have not yet provided a simple explanation for the critical t cool/t ff ratio. This paper explores a heuristic model for condensation linking the critical ratio to turbulent driving of gravity wave oscillations. In the linear regime, internal gravity waves are thermally unstable in a thermally balanced medium. Buoyancy oscillations in a balanced medium with t cool/t ff ≫ 1 therefore grow until they saturate without condensing at an amplitude depending on t cool/t ff. However, in a medium with 10 ≲ t cool/t ff ≲ 20, turbulence with a velocity dispersion roughly half the galaxy’s stellar velocity dispersion can drive those oscillations into condensation. Intriguingly, this is indeed the gas-phase velocity dispersion observed among multiphase galaxy cluster cores. It is therefore possible that both the critical t cool/t ff ratio for condensation of ambient gas and the level of turbulence in that gas are determined by coupling between condensation, feedback, and turbulence. Such a system can converge to a well-regulated equilibrium state, if the fraction of feedback energy going into turbulence is subdominant.

Zooming in on supermassive black holes: how resolving their gas cloud host renders their accretion episodic

Born in rapidly evolving mini-halos during the first billion years of the Universe, super- massive black holes (SMBH) feed from gas flows spanning many orders of magnitude, from the cosmic web in which they are embedded to their event horizon. As such, accretion onto SMBHs constitutes a formidable challenge to tackle numerically, and currently requires the use of sub-grid models to handle the flow on small, unresolved scales. In this paper, we study the impact of resolution on the accretion pattern of SMBHs initially inserted at the heart of dense galactic gas clouds, using a custom super-Lagrangian refinement scheme to resolve the black hole (BH) gravitational zone of influence. We find that once the self-gravitating gas cloud host is sufficiently well re- solved, accretion onto the BH is driven by the cloud internal structure, independently of the BH seed mass, provided dynamical friction is present during the early stages of cloud collapse. For a pristine gas mix of hydrogen and helium, a slim disc develops around the BH on sub-parsec scales, turning the otherwise chaotic BH accretion duty cycle into an episodic one, with potentially important consequences for BH feedback. In the presence of such a nuclear disc, BH mass growth predominantly occurs when infalling dense clumps trigger disc instabilities, fuelling intense albeit short-lived gas accretion episodes.

The Role of Black Hole Feedback on Size and Structural Evolution in Massive Galaxies

Abstract We use cosmological hydrodynamical simulations to investigate the role of feedback from accreting black holes in the evolution of the size, compactness, stellar core density, and specific star formation of massive galaxies with stellar masses of . We perform two sets of cosmological zoom-in simulations of 30 halos to z = 0: (1) without black holes and active galactic nucleus (AGN) feedback and (2) with AGN feedback arising from winds and X-ray radiation. We find that AGN feedback can alter the stellar density distribution, reduce the core density within the central 1 kpc by 0.3 dex from z = 1, and enhance the size growth of massive galaxies. We also find that galaxies simulated with AGN feedback evolve along tracks similar to those characterized by observations of specific star formation rate versus compactness. We confirm that AGN feedback plays an important role in transforming galaxies from blue compact galaxies into red extended galaxies in two ways: (1) it effectively quenches the star formation, transforming blue compact galaxies into compact quiescent galaxies, and (2) it also removes and prevents new accretion of cold gas, shutting down in situ star formation and causing subsequent mergers to be gas-poor or mixed. Gas-poor minor mergers then build up an extended stellar envelope. AGN feedback also puffs up the central region through fast AGN-driven winds as well as the slow expulsion of gas while the black hole is quiescent. Without AGN feedback, large amounts of gas accumulate in the central region, triggering star formation and leading to overly massive blue galaxies with dense stellar cores.

Deviations from hydrostatic equilibrium in the circumgalactic medium: spinning hot haloes and accelerating flows

Hydrostatic equilibrium (HSE), where the thermal pressure gradient balances the force of gravity, is tested across a range of simulated EAGLE haloes from Milky Way L* haloes (M200|$\approx$| 1012M⊙) to cluster scales. Clusters (M200|$\approx$|1014M⊙) reproduce previous results with thermal pressure responsible for |$\sim$|90 per cent of the support against gravity, but this fraction drops for group-sized haloes (M200|$\approx$| 1013M⊙) and is even lower (40–70 per cent) for L* haloes between 0.1 and 0.3R200. Energy from feedback grows relative to the binding energy of a halo towards lower mass resulting in greater deviations from HSE. Tangential motions comprise the largest deviation from HSE in L* haloes indicating that the hot circumgalactic medium (CGM) has significant subcentrifugal rotation and angular momentum spin parameters 2−3 × higher than the dark matter spin parameters. Thermal feedback can buoyantly rise to the outer CGM of M200 ≲ 1012M⊙ haloes, both moving baryons beyond R200 and feeding uncorrelated tangential motions. The resulting hot halo density and rotation profiles show promising agreement with X-ray observations of the inner Milky Way halo, and we discuss future observational prospects to detect spinning hot haloes around other galaxies. Acceleration and radial streaming motions also comprise significant deviations from HSE, especially net outward accelerations seen in L* and group haloes indicating active feedback. Black hole feedback acts in a preventative manner during the later growth of group haloes, applying significant accelerations via shocks that do not feed tangential motions. We argue that HSE is a poor assumption for the CGM, especially in the inner regions, and rotating baryonic hot haloes are a critical consideration for analytic models of the CGM.

The Effect of AGNs on the Global H i Content of Isolated Low-mass Galaxies

Abstract We investigate the global neutral hydrogen (H i) content of isolated galaxies selected from the SDSS spectroscopic survey with optical evidence of Active Galactic Nuclei (AGNs). Our sample includes galaxies with unresolved H i observations from the ALFALFA 70% data release combined with deeper H i observations of low-mass galaxies with . We examine the H i masses of this sample using the distance from the star-forming sequence on the [O iii]/Hβ and [N ii]/Hα Baldwin Phillips Terlevich (BPT) diagram as a measurement of AGN activity. In agreement with previous studies, we find that, for galaxies with , AGN activity does not correlate with the global H i content. However, for galaxies with , we identify a set of objects at large distances from the BPT star-forming sequence and lower than expected H i masses. This gas-depleted sample is red in both g − r and NUV − r colors and compact without distinguishable signs of star formation. This is surprising because the vast majority of isolated galaxies in this stellar mass regime are both star-forming and gas-rich. These galaxies are greater than 1.5 Mpc from any massive galaxy, ruling out environmental processes as a source of the gas depletion. We suggest that either black hole feedback or shocks from extremely bursty star formation cause the emission lines and have destroyed or otherwise consumed the cold gas.

Powering of Hα Filaments by Cosmic Rays

Abstract Cluster cool cores possess networks of line-emitting filaments. These filaments are thought to originate via uplift of cold gas from cluster centers by buoyant active galactic nuclei (AGNs) bubbles, or via local thermal instability in the hot intracluster medium (ICM). Therefore, the filaments are either the signatures of AGN feedback or feeding of supermassive black holes. Despite being characterized by very short cooling times, the filaments are significant Hα emitters, which suggests that some process continuously powers these structures. Many cool cores host diffuse radio mini halos and AGN injecting radio plasma, suggesting that cosmic rays (CRs) and magnetic fields are present in the ICM. We argue that the excitation of Alfvén waves by CR streaming, and the replenishment of CR energy via accretion onto the filaments of high-plasma-β ICM characterized by low CR pressure support, can provide the adequate amount of heating to power and sustain the emission from these filaments. This mechanism does not require the CRs to penetrate the filaments, even if the filaments are magnetically isolated from the ambient ICM, and it may operate irrespectively of whether the filaments are dredged up from the center or form in situ in the ICM. This picture is qualitatively consistent with non-thermal line ratios seen in the cold filaments. Future X-ray observations of the iron line complex with XARM, Lynx, or Athena could help to test this model by providing constraints on the amount of CRs in the hot plasma that is cooling and accreting onto the filaments.

Intermediate-Mass Black Hole Feedback in Dwarf Galaxies: a View from Cosmological Simulations

AbstractBlack holes are usually observed to be of stellar-mass or supermassive. By natural extension, there should be a population of Intermediate-Mass Black Holes (IMBHs: with mass between 100 to 106M⊙) in the Universe; which has started to been observed. An exciting claim has been made recently by Silk (2017): that early feedback by IMBHs in gas-rich dwarf galaxies at z = 5–8, can potentially solve multiple dwarf galaxy problems within the Λ-cold-dark-matter cosmology. We are performing Cosmological Hydrodynamical Simulations of (2Mpc)3 volumes, starting from z = 100, to test the case for IMBHs in Dwarf Galaxies. Black holes of mass 1000M⊙ are seeded inside halos when they reach a mass of 107M⊙. The black holes grow by accretion of gas from their surroundings and by merger with other black holes, and consequently eject feedback energy. We analyze the simulation output in post-processing to study the growth of the first IMBHs, and their impact on star-formation. Our conclusions, based on numerical simulation results, support the phenomenological ideas made by Silk (2017). IMBHs at the centers of dwarf galaxies can be a strong source of feedback to quench star-formation and generate outflows. At the same time, these IMBHs form the missing link between stellar-mass and supermassive BHs.

The abundance, distribution, and physical nature of highly ionized oxygen O vi, O vii, and O viii in IllustrisTNG

We explore the abundance, spatial distribution, and physical properties of the OVI, OVII, and OVIII ions of oxygen in circumgalactic and intergalactic media (the CGM, IGM, and WHIM). We use the TNG100 and TNG300 large volume cosmological magneto-hydrodynamical simulations. Modeling the ionization states of simulated oxygen, we find good agreement with observations of the low-redshift OVI column density distribution function (CDDF), and present its evolution for all three ions from z=0 to z=4. Producing mock quasar absorption line spectral surveys, we show that the IllustrisTNG simulations are fully consistent with constraints on the OVI content of the CGM from COS-Halos and other low redshift observations, producing columns as high as observed. We measure the total amount of mass and average column densities of each ion using hundreds of thousands of simulated galaxies spanning 10^11 < Mhalo/Msun < 10^15 corresponding to 10^9 < M*/Msun < 10^12 in stellar mass. Stacked radial profiles of OVI are computed in 3D number density and 2D projected column, decomposing into the 1-halo and 2-halo terms. Relating halo OVI to properties of the central galaxy, we find a correlation between the (g-r) color of a galaxy and the total amount of OVI in its CGM. In comparison to the COS-Halos finding, this leads to a dichotomy of columns around star-forming versus passive galaxies at fixed stellar (or halo) mass. We demonstrate that this correlation is a direct result of blackhole feedback associated with quenching and represents a causal consequence of galactic-scale baryonic feedback impacting the physical state of the circumgalactic medium.

Particle content, radio-galaxy morphology, and jet power: all radio-loud AGN are not equal

Ongoing and future radio surveys aim to trace the evolution of black hole growth and feedback from active galactic nuclei (AGN) throughout cosmic time; however, there remain major uncertainties in translating radio luminosity functions into a reliable assessment of the energy input as a function of galaxy and/or dark matter halo mass. A crucial and long-standing problem is the composition of the radio-lobe plasma that traces AGN jet activity. In this paper, we carry out a systematic comparison of the plasma conditions in Fanaroff & Riley class I and II radio galaxies to demonstrate conclusively that their internal composition is systematically different. This difference is best explained by the presence of an energetically dominant proton population in the FRI, but not the FRII radio galaxies. We show that, as expected from this systematic difference in particle content, radio morphology also affects the jet-power/radio-luminosity relationship, with FRII radio galaxies having a significantly lower ratio of jet power to radio luminosity than the FRI cluster radio sources used to derive jet-power scaling relations via X-ray cavity measurements. Finally we also demonstrate conclusively that lobe composition is unconnected to accretion mode (optical excitation class): the internal conditions of low- and high-excitation FRII radio lobes are indistinguishable. We conclude that inferences of population-wide AGN impact require careful assessment of the contribution of different jet sub-classes, particularly given the increased diversity of jet evolutionary states expected to be present in deep, low-frequency radio surveys such as the LOFAR Two-Metre Sky Survey.