Active Galactic Nuclei Power Research Articles

Characterizing the luminosity components of luminous infrared galaxies in multi-wavelength from the X-ray to the far-infrared

We characterize luminosity components of Ultra/Luminous Infrared Galaxies (U/LIRGs) in multi-wavelength from the X-ray to far-infrared. A set of 63 AGN U/LIRGs was selected where these galaxies are powered by a central active galactic nucleus (AGN). Utilizing the X-CIGALE code, SEDs for these galaxies are carried out where their SEDs are fitted with observations. Accordingly, the physical parameters such as the stellar mass, the dust-to-gas mass ratio, and the star formation rate are calculated. The total luminosity and its decomposed components (stellar, AGN, X-ray) are also calculated. We characterized these luminosities in relative to the intrinsic luminosity and in relative to each other. As a function of the stellar mass, these luminosities reveal an increase with different correlation coefficients, showing a strong correlation. In correlation with the intrinsic AGN power, the stellar, AGN, and X-ray luminosities are strongly correlates in their variation to the intrinsic AGN luminosity, showing stronger correlations of AGN, and X-ray luminosities than those of the stellar one. In relationships between various luminosity components, both the stellar and X-ray luminosities reveal strong correlations with the AGN luminosity. On the other hand, the X-ray luminosity varies strongly with the stellar luminosity and moderately with IR luminosity. Compared to obscured AGN galaxies, both the stellar and AGN luminosities similarly vary with increasing the intrinsic power of the active nucleus but for obscured AGN they are faster in their variation than that of U/LIRG. These correlations may offer valuable insights to understand the physical properties and their relationships through the evolution of U/LIRGs.

Forecasting the BAO measurements of the CSST galaxy and AGN spectroscopic surveys

ABSTRACT The spectroscopic survey of the China’s Space Survey Telescope (CSST) is expected to obtain a huge number of slitless spectra, including more than one hundred million galaxy spectra and millions of active galactic nuclei (AGNs) spectra. By making use of these spectra, we can measure the Baryon Acoustic Oscillation (BAO) signals over large redshift ranges with excellent precisions. In this work, we predict the CSST measurements of the post-reconstruction galaxy power spectra at $0\lt z\lt 1.2$ and pre-reconstruction AGN power spectra at $0\lt z\lt 4$, and derive the BAO signals at different redshift bins by constraining the BAO scaling parameters using the Markov Chain Monte Carlo method. Our result shows that the CSST spectroscopic survey can provide accurate BAO measurements with precisions higher than 1 and 3 per cent for the galaxy and AGN surveys, respectively. By comparing with current measurements in the same range at low redshifts, this can improve the precisions by a factor of $2\sim 3$, and similar precisions can be obtained in the pessimistic case. We also investigate the constraints on the cosmological parameters using the measured BAO data by the CSST, and obtain stringent constraint results for the energy density of dark matter, Hubble constant, and equation of state of dark energy.

Active Galactic Nucleus Properties of ∼1 Million Member Galaxies of Galaxy Groups and Clusters at z < 1.4 Based on the Subaru Hyper Suprime-Cam Survey

Herein, we present the statistical properties of active galactic nuclei (AGNs) for approximately 1 million member galaxies of galaxy groups and clusters with 0.1 < cluster redshift (z cl) < 1.4 selected using the Subaru Hyper Suprime-Cam, the so-called CAMIRA clusters. In this research, we focused on the AGN power fraction (f AGN), which is defined as the proportion of the contribution of AGNs to the total infrared (IR) luminosity, L IR (AGN)/L IR, and examined how f AGN depends on (i) z cl and (ii) the distance from the cluster center. We compiled multiwavelength data using the ultraviolet–mid-IR range. Moreover, we performed spectral energy distribution fits to determine f AGN using the CIGALE code with the SKIRTOR AGN model. We found that (i) the value of f AGN in the CAMIRA clusters is positively correlated with z cl, with the correlation slope being steeper than that for field galaxies, and (ii) f AGN exhibits a high value at the cluster outskirts. These results indicate that the emergence of the AGN population depends on the redshift and environment and that galaxy groups and clusters at high redshifts are important in AGN evolution. Additionally, we demonstrated that cluster–cluster mergers may enhance AGN activity at the outskirts of particularly massive galaxy clusters. Our findings are consistent with a related study on the CAMIRA clusters that was based on the AGN number fraction.

The X-ray variability of active galactic nuclei: Power spectrum and variance analysis of the Swift/BAT light curves

Aims. We study the X-ray power spectrum of active galactic nuclei (AGN) in order to investigate whether Seyfert I and II power spectra are similar or not and whether AGN variability depends on the mass and accretion rate of black holes as well as to compare the power spectra of AGN with the power spectra of Galactic X-ray black hole binaries. Method. We used 14–195 keV band light curves from the 157-month Swift/BAT hard X-ray survey, and we computed the mean power spectrum and excess variance of AGN in narrow black hole mass and AGN luminosity bins. We fitted a power-law model to the AGN power spectra, and we investigated whether the power spectrum parameters and the excess variance depend on the black hole mass, luminosity, and accretion rate of AGN. Results. We found the Seyfert I and Seyfert II power spectra to be identical, in agreement with AGN unification models. The mean AGN X-ray power spectrum has the same power-law like shape, with a slope of −1 in all AGN irrespective of their luminosity and black hole mass. We did not detect any flattening to a slope of zero at frequencies as low as 10−9 Hz. We detected an anti-correlation between the power spectral density function (PSD) amplitude and the accretion rate, similar to what has been seen in the past in the 2–10 keV band. This implies that the variability amplitude in AGN decreases with an increasing accretion rate. The universal AGN power spectrum is consistent with the mean 2–9 keV band Cyg X-1 power spectrum in its soft state. We detected a small difference in amplitude, but this is probably due to the difference in energy. Conclusions. The mean low-frequency AGN X-ray power spectrum is consistent with the extension of the mean 0.01–25 Hz Cyg X-1 power spectrum in its soft state to lower frequencies. We cannot prove that the mean AGN PSD is analogous to the mean Cyg X-1 PSD in its soft state, as we do not know the location of the high-frequency break in the hard X-ray AGN PSDs. However, if this is the case, then the accretion disc in AGN probably extends to the radius of the innermost circular stable orbit (as is probably the case with the black hole binaries in their soft state). The X-ray corona will then be located on top, illuminating the disc and producing the X-ray reflection and disc reverberation phenomena commonly observed in these objects. Furthermore, the agreement between the PSD amplitude in AGN and the Cyg X-1 (either in the soft or the hard state) over many decades in frequency indicates that the X-ray variability process is probably the same in all accreting objects, irrespective of the mass of the compact object. We plan to investigate this issue further in the near future.

Comparative analysis of the SFR of AGN and non-AGN galaxies, as a function of stellar mass, AGN power, cosmic time, and obscuration

This study involves a comparative analysis of the star formation rates (SFRs) of active galactic nucleus (AGN) galaxies and non-AGN galaxies and of the SFRs of type 1 and 2 AGNs. To carry out this investigation, we assembled a dataset consisting of 2677 X-ray AGNs detected by the XMM-Newton observatory and a control sample of 64 556 galaxies devoid of AGNs. We generated spectral energy distributions (SEDs) for these objects using photometric data from the DES, VHS, and AllWISE surveys, and we harnessed the CIGALE code to extract measurements for the (host) galaxy properties. Our dataset encompasses a diverse parameter space, with objects spanning a range of stellar masses from 9.5 &lt; log [M*(M⊙)] &lt; 12.0, intrinsic X-ray luminosities within 42 &lt; log[LX,2−10 keV(erg s−1)] &lt; 45.5, and redshifts between 0.3 &lt; z &lt; 2.5. To compare SFRs, we calculated the SFRnorm parameter, which signifies the ratio of the SFR of an AGN galaxy to the SFR of non-AGN galaxies sharing similar M* and redshift. Our analysis reveals that systems hosting an AGN tend to exhibit elevated SFRs compared to non-AGN galaxies, particularly beyond a certain threshold in LX. Notably, this threshold increases as we move toward more massive galaxies. Additionally, for AGN systems with the same LX, the magnitude of the SFRnorm decreases as we consider more massive galaxies. This suggests that in galaxies with an AGN, the increase in SFR as a function of stellar mass is not as prominent as in galaxies without an AGN. This interpretation finds support in the shallower slope that we identify in the X-ray star-forming main sequence in contrast to the galaxy main sequence. Employing CIGALE’s measurements, we classified AGNs into type 1 and type 2. In our investigation, we focused on a subset of 652 type 1 AGNs and 293 type 2 AGNs within the stellar mass range of 10.5 &lt; log[M (M⊙)] &lt; 11.5. Based on our results, type 1 AGNs display higher SFRs than type 2 AGNs, at redshifts below z &lt; 1. However, at higher redshifts, the SFRs of the two AGN populations tend to be similar. At redshifts z &lt; 1, type 1 AGNs show augmented SFRs in comparison to non-AGN galaxies. In contrast, type 2 AGNs exhibit lower SFRs when compared to galaxies that do not host an AGN, at least up to log[LX,2−10 keV(erg s−1)] &lt; 45.

The Relationships between Active Galactic Nucleus Power and Molecular Gas Mass within 500 pc of the Center of Elliptical Galaxies

The physical quantity that directly controls the feedback of active galactic nuclei (AGNs) in elliptical galaxies remains to be determined. The discovery of molecular gas around the AGNs suggests that the gas is fueling the AGNs. Therefore, we analyze Atacama Large Millimeter/submillimeter Array data for the CO line (J = 1–0, 2–1, 3–2) emission and estimate the mass of molecular gas within 500 pc of the center of 12 noncentral elliptical galaxies (NCEGs) and 10 of the brightest cluster galaxies. We find that the mass (M mol ∼ 105–109 M ☉) is correlated with the jet power of their AGNs, which is represented by Pcav≈4.1×1042(Mmol/107M☉)1.3ergs−1 , although NCEGs alone do not show the correlation. We also find that M mol is correlated with the AGN continuum luminosities at ∼1.4 GHz (L 1.4) and ∼100–300 GHz (L con). Since P cav reflects galactic-scale, long-term AGN activity, while the continuum luminosities reflect local (≲500 pc), short-term AGN activity, our results suggest that AGN activity depends on the amount of gas, regardless of its timescale. On the other hand, we cannot find a clear correlation between the mass of the black holes in the AGNs (M BH) and P cav. This suggests that M mol, rather than M BH, is the main factor controlling AGN activity. We confirm that the origin of the continuum emission from the AGNs at ∼1.4–300 GHz is mostly synchrotron radiation.

The High-ionization IR Fine Structure Lines as Bolometric Indicators of the AGN Power: Study of the Complete 12 μm AGN Sample

The high-ionization mid-IR lines, excited in the narrow-line regions of active galactic nuclei (AGN), barely affected by stellar excitation and dust extinction, trace the AGN bolometric power. We used the complete 12 μm sample of Seyfert galaxies, for which 100/116 objects have reliable 2–10 keV observations. The [Ne v] and [O iv] mid-IR lines linearly correlate with several AGN bolometric indicators (intrinsic 2–10 keV and observed 14–195 keV X-ray emission, compact nuclear 12 μm emission, [O iii] λ5007 Å line emission) in terms of both flux and luminosity. No evidence of systematic differences in these correlations is found among the Seyfert populations, including types 1 and 2 and Compton-thick and Compton-thin AGN. Nevertheless, we find that a sequence of high-to-low Eddington ratios together with strong-to-weak line excitation (traced by the [O iv]/[Ne ii] line ratio) encompasses from type 1 through type 2 AGN to low-ionization nuclear emission-line region galaxies, showing intrinsic differences in these three AGN populations. A positive correlation between the black hole accretion rate (BHAR) and the star formation rate (SFR) is found, but no correlation between the specific SFR and the ratio BHAR/M BH, simply reflecting the fact that the more massive a galaxy is, the more it is forming stars and feeding its central black hole. The JWST, just beginning operations, will allow large samples of AGN to be observed in these lines in the nearby universe (z < 0.9).

Deep Herschel observations of the 2 Jy sample: assessing the non-thermal and AGN contributions to the far-IR continuum

ABSTRACT The far-IR/sub-mm wavelength range contains a wealth of diagnostic information that is important for understanding the role of active galactic nuclei (AGN) in galaxy evolution. Here we present the results of Herschel PACS and SPIRE observations of a complete sample of 46 powerful 2 Jy radio AGN at intermediate redshifts (0.05 &amp;lt; z &amp;lt; 0.7), which represent the deepest pointed observations of a major sample of radio AGN undertaken by Herschel. In order to assess the importance of non-thermal synchrotron emission at far-IR wavelengths, we also present new APEX sub-mm and ALMA mm data. We find that the overall incidence of non-thermal contamination in the PACS bands (&amp;lt;200 μm) is in the range 28–43 per cent; however, this rises to 30–72 per cent for wavelengths (&amp;gt;200 μm) sampled by the SPIRE instrument. Non-thermal contamination is strongest in objects with compact CSS/GPS or extended FRI radio morphologies, and in those with type 1 optical spectra. Considering thermal dust emission, we find strong correlations between the 100 and 160 μm monochromatic luminosities and AGN power indicators, providing further evidence that radiation from the AGN may be an important heating source for the far-IR emitting dust. Clearly, AGN contamination – whether by the direct emission from synchrotron-emitting lobes and cores, or via radiative heating of the cool dust – needs to be carefully considered when using the far-IR continuum to measure the star formation rates in the host galaxies of radio AGN.

The star formation rates of QSOs

ABSTRACT We examine the far-infrared (FIR) properties of a sample of 5391 optically selected QSOs in the 0.5 &amp;lt; z &amp;lt; 2.65 redshift range down to log [νLν, 2500(erg s−1)] &amp;gt; 44.7, using SPIRE data from Herschel-ATLAS. We split the sample in a grid of 74 luminosity–redshift bins and compute the average optical–IR spectral energy distribution (SED) in each bin. By normalizing an intrinsic active galactic nucleus (AGN) template to the AGN optical power (at 5100 Å), we decompose the total IR emission (LIR; 8–1000 µm) into an AGN (LIR, AGN) and star-forming component (LIR, SF). We find that the AGN contribution to LIR increases as a function of AGN power, manifesting as a reduction of the ‘FIR bump’ in the average QSO SEDs. We note that LIR, SF does not correlate with AGN power; the mean star formation rates (SFRs) of AGN host galaxies are a function of redshift only and they range from ∼6 M⊙ yr−1 at z ∼ 0 to a plateau of ≲ 200 M⊙ yr−1 at z ∼ 2.6. Our results indicate that the accuracy of FIR emission as a proxy for SFR decreases with increasing AGN luminosity. We show that, at any given redshift, observed trends between IR luminosity (whether monochromatic or total) and AGN power (in the optical or X-rays) can be explained by a simple model which is the sum of two components: (i) the IR emission from star formation, uncorrelated with AGN power and (ii) the IR emission from AGN, directly proportional to AGN power in the optical or X-rays.

Probing Multiphase Gas in Local Massive Elliptical Galaxies via Multiwavelength Observations

Abstract We investigate the cold and warm gas content, kinematics, and spatial distribution of six local massive elliptical galaxies to probe the origin of the multiphase gas in their atmospheres. We report new observations, including Stratospheric Observatory for Infrared Astronomy [C ii], Atacama Large Millimeter/submillimeter Array CO, Multi Unit Spectroscopic Explorer (MUSE) Hα+[N ii], and Very Large Array (VLA) radio observations. These are complemented by a large suite of multiwavelength archival data sets, including thermodynamical properties of the hot gas and radio jets, which are leveraged to investigate the role of active galactic nucleus (AGN) feeding/feedback in regulating the multiphase gas content. Our galactic sample shows a significant diversity in cool gas content, spanning filamentary and rotating structures. In our noncentral galaxies, the distribution of such gas is often concentrated, at variance with the more extended features observed in central galaxies. Misalignment between the multiphase gas and stars suggest that stellar mass loss is not the primary driver. A fraction of the cool gas might be acquired via galaxy interactions, but we do not find quantitative evidence of mergers in most of our systems. Instead, key evidence supports the origin via condensation out of the diffuse halo. Comparing with chaotic cold accretion (CCA) simulations, we find that our cool gas-free galaxies are likely in the overheated phase of the self-regulated AGN cycle, while for our galaxies with cool gas, the k-plot and AGN power correlation corroborate the phase of CCA feeding in which the condensation rain is triggering more vigorous AGN heating. The related C-ratio further shows that central/noncentral galaxies are expected to generate an extended/inner rain, consistent with our sample.

The Type II AGN-host galaxy connection

We present a study of optically selected Type II active galactic nuclei (AGN) at 0.5 &lt; z &lt; 0.9 from the VIPERS and VVDS surveys, to investigate the connection between AGN activity and the physical properties of their host galaxies. The host stellar mass is estimated through spectral energy distribution fitting with the CIGALE code, and star formation rates are derived from the [OII]λ3727 Å line luminosity. We find that 49% of the AGN host galaxies are on or above the main sequence (MS), 40% lie in the sub-MS locus, and 11% in the quiescent locus. Using the [OIII]λ5007 Å line luminosity as a proxy of the AGN power, we find that at fixed AGN power Type II AGN host galaxies show a bimodal behaviour: systems with host galaxy stellar mass &lt; 1010 M⊙ reside along the MS or in the starbursts locus (high-SF Type II AGN), while systems residing in massive host galaxies (&gt; 1010 M⊙) show a lower level of star formation (low-SF Type II AGN). At all stellar masses the offset from the MS is positively correlated with the AGN power. We interpret this correlation as evidence of co-evolution between the AGN and the host, possibly due to the availability of cold gas. In the most powerful AGN with host galaxies below the MS we find a hint, though weak, of asymmetry in the [OIII] line profile, likely due to outflowing gas, consistent with a scenario in which AGN feedback removes the available gas and halts the star formation in the most massive hosts.

Simulations of AGN-driven Galactic Outflow Morphology and Content

Abstract Using a series of 3D relativistic hydrodynamical simulations of active galactic nuclei (AGN) we investigate how AGN power, a clumpy interstellar medium (ISM) structure, and AGN jet angle with respect to the galactic disk affect the morphology and content of the resulting galactic outflow. For low-power AGN across three orders of magnitude of AGN luminosities (1041–1043 erg s−1) our simulations did not show significant changes to either the morphology or total mass of the outflow. Changing the angle of the AGN jet with respect to the galaxy did show small changes in the total outflow mass of a factor of 2–3. Jets perpendicular to the galactic disk created hot single-phase outflows, while jets close to parallel with the disk created multiphase outflows with equal parts warm and hot, and significant cold gas. Overall the final morphology of low-power AGN outflows depends primarily on how the jet impacts and interacts with large, dense clouds in the clumpy ISM. These clouds can disrupt, deflect, split, or suppress the jet, preventing it from leaving the galactic disk as a coherent structure. But for simulations with AGN luminosities &gt; 1044 erg s−1 the ISM played a minor role in determining the morphology of the outflow with an undisrupted jet leaving the disk. The final morphology of AGN outflows is different for low-power AGNs versus high-power AGNs with the final morphology of low-power AGN outflows dependent on the ISM structure within the first kiloparsec surrounding the AGN.

Relation between AGN type and host galaxy properties

We use 3213 active galactic nuclei (AGNs) from the XMM-XXL northern field to investigate the relation of AGN type with host galaxy properties. Applying a Bayesian method, we derive the hardness ratios, and through these the hydrogen column density (NH) for each source. We consider those with NH &gt; 1021.5 cm−2 as absorbed sources (type 2). We examine the star formation rate (SFR) and the stellar mass (M*) distributions for both absorbed and unabsorbed sources. Our work indicates that there is no significant link between AGN type and these host galaxy properties. Next, we investigate whether the AGN power, as represented by its X-ray luminosity (LX) correlates with any deviation of the host galaxy’s place from the so-called main sequence of galaxies, and we examine this separately for the obscured and the unobscured AGN populations. To take into account the effect of M* and redshift on SFR, we use the normalised SFR (SFRnorm). We find that the correlation between LX and SFRnorm follows approximately the same trend for both absorbed and unabsorbed sources, a result that favours the standard AGN unification models. Finally, we explore the connection between the obscuration (NH) and the SFR. We find that there is no relation between them, suggesting that obscuration is not related to the large-scale SFR in the galaxy.

The complex multi-component outflow of the Seyfert galaxy NGC 7130

Active galactic nuclei (AGN) are a key ingredient for understanding galactic evolution, as their activity is coupled to the host galaxy properties through feedback processes. AGN-driven outflows are one of the manifestations of this feedback. The laser guide star adaptive optics mode for MUSE at the VLT now permits us to study the innermost tens of parsecs of nearby AGN in the optical. We present a detailed analysis of the ionised gas in the central regions of NGC 7130, which is an archetypical composite Seyfert and nuclear starburst galaxy at a distance of 64.8 Mpc. We achieve an angular resolution of 0.​​″17, corresponding to roughly 50 pc. We performed a multi-component analysis of the main interstellar medium emission lines in the wavelength range of MUSE and identified nine kinematic components, six of which correspond to the AGN outflow. The outflow is biconic, oriented in an almost north–south direction, and has velocities of a few 100 km s−1 with respect to the disc of NGC 7130. The lobe length is at least 3″(∼900 pc). We decomposed the approaching side of the outflow into a broad and a narrow component with typical velocity dispersions below and above ∼200 km s−1, respectively. The blueshifted narrow nomponent has a sub-structure, in particular a collimated plume traced especially well by [O III]. The plume is aligned with the radio jet, indicating that it may be jet powered. The redshifted lobe is composed of two narrow components and a broad component. An additional redshifted component is seen outside the main north-south axis, about an arcsecond east of the nucleus. Line ratio diagnostics indicate that the outflow gas in the north–south axis is AGN powered, whereas the off-axis component has LINER properties. We hypothesise that this is because the radiation field that reaches off-axis clouds has been filtered by clumpy ionised clouds found between the central engine and the low-ionisation emitting region. If we account for all the outflow components (the blueshifted components), the ionised gas mass outflow rate is Ṁ = 1.5 ± 0.9 M⊙ yr−1 (Ṁ = 0.55 ± 0.55 M⊙ yr−1), and the kinetic power of the AGN is Ėkin = (3.4 ± 2.5) × 1041 erg s−1 (Ėkin = (8.8 ± 5.9) × 1040 erg s−1), which corresponds to Fkin = 0.15 ± 0.11% (Fkin = 0.040 ± 0.027%) of the bolometric AGN power. The broad components, those with a velocity dispersion of σ &gt; 200 km s−1, carry ∼2/3 (∼90%) of the mass outflow, and ∼90% (∼98%) of the kinetic power. The combination of high-angular-resolution integral field spectroscopy and a careful multi-component decomposition allows a uniquely detailed view of the outflow in NGC 7130, illustrating that AGN kinematics are more complex than those traditionally derived from less sophisticated data and analyses.

Ionized outflows from active galactic nuclei as the essential elements of feedback

Outflows from active galactic nuclei (AGN) are one of the fundamental mechanisms by which the central supermassive black hole interacts with its host galaxy. Detected in $\ge 50\%$ of nearby AGN, these outflows have been found to carry kinetic energy that is a significant fraction of AGN power, and thereby give negative feedback to their host galaxies. To understand the physical processes that regulate them, it is important to have a robust estimate of their physical and dynamical parameters. In this review we summarize our current understanding on the physics of the ionized outflows detected in absorption in the UV and X-ray wavelength bands. We discuss the most relevant observations and our current knowledge and uncertainties in the measurements of the outflow parameters. We also discuss their origin and acceleration mechanisms. The commissioning and concept studies of large telescope missions with high resolution spectrographs in UV/optical and X-rays along with rapid advancements in simulations offer great promise for discoveries in this field over the next decade.

A binning-free method reveals a continuous relationship between galaxies’ AGN power and offset from main sequence

ABSTRACT Studies investigating the relationship between active galactic nucleus (AGN) power and the star formation rates (SFRs) of their host galaxies often rely on averaging techniques – such as stacking – to incorporate information from non-detections. However, averages, and especially means, can be strongly affected by outliers and can therefore give a misleading indication of the ‘typical’ case. Recently, a number of studies have taken a step further by binning their sample in terms of AGN power (approximated by the 2–10 keV luminosity of the AGN), and investigating how the SFR distribution differs between these bins. These bin thresholds are often weakly motivated, and binning implicitly assumes that sources within the same bin have similar (or even identical) properties. In this paper, we investigate whether the distribution of host SFRs – relative to the locus of the star-forming main sequence (i.e. RMS) – changes continuously as a function of AGN power. We achieve this by using a hierarchical Bayesian model that completely removes the need to bin in AGN power. In doing so, we find strong evidence that the RMS distribution changes with 2–10 keV X-ray luminosity. The results suggest that higher X-ray luminosity AGNs have a tighter physical connection to the star-forming process than lower X-ray luminosity AGNs, at least within the 0.8 &amp;lt; z &amp;lt; 1.2 redshift range considered here.

Mergers trigger active galactic nuclei out to z ∼ 0.6

Aims. The fueling and feedback of active galactic nuclei (AGNs) are important for understanding the co-evolution between black holes and host galaxies. Mergers are thought to have the capability to bring gas inward and ignite nuclear activity, especially for more powerful AGNs. However, there is still significant ongoing debate on whether mergers can trigger AGNs and, if they do, whether mergers are a significant triggering mechanism. Methods. We selected a low-redshift (0.005 &lt; z &lt; 0.1) sample from the Sloan Digital Sky Survey and a high-redshift (0 &lt; z &lt; 0.6) sample from the Galaxy And Mass Assembly survey. We took advantage of the convolutional neural network technique to identify mergers. We used mid-infrared (MIR) color cut and optical emission line diagnostics to classify AGNs. We also included low excitation radio galaxies (LERGs) to investigate the connection between mergers and low accretion rate AGNs. Results. We find that AGNs are more likely to be found in mergers than non-mergers, with an AGN excess up to 1.81 ± 0.16, suggesting that mergers can trigger AGNs. We also find that the fraction of mergers in AGNs is higher than that in non-AGN controls, for both MIR and optically selected AGNs, as well as LERGs, with values between 16.40 ± 0.5% and 39.23 ± 2.10%, implying a non-negligible to potentially significant role of mergers in triggering AGNs. This merger fraction in AGNs increases as stellar mass increases, which supports the idea that mergers are more important for triggering AGNs in more massive galaxies. In terms of merger fraction as a function of AGN power we find a positive trend for MIR selected AGNs and a complex trend for optically selected AGNs, which we interpret under an evolutionary scenario proposed by previous studies. In addition, obscured MIR selected AGNs are more likely to be hosted in mergers than unobscured MIR selected AGNs.

Chaotic cold accretion in giant elliptical galaxies heated by AGN cosmic rays

ABSTRACT Black hole feedback plays a central role in shaping the circumgalactic medium (CGM) of elliptical galaxies. We systematically study the impact of plasma physics on the evolution of ellipticals by performing three-dimensional non-ideal magnetohydrodynamic simulations of the interactions of active galactic nucleus (AGN) jets with the CGM including magnetic fields, and cosmic rays (CRs) and their transport processes. We find that the physics of feedback operating on large galactic scales depends very sensitively on plasma physics operating on small scales. Specifically, we demonstrate that (i) in the purely hydrodynamical case, the AGN jets initially maintain the atmospheres in global thermal balance. However, local thermal instability generically leads to the formation of massive cold discs in the vicinity of the central black hole in disagreement with observations; (ii) including weak magnetic fields prevents the formation of the discs because local B-field amplification in the precipitating cold gas leads to strong magnetic breaking, which quickly extracts angular momentum from the accreting clouds. The magnetic fields transform the cold clouds into narrow filaments that do not fall ballistically; (iii) when plasma composition in the AGN jets is dominated by CRs, and CR transport is neglected, the atmospheres exhibit cooling catastrophes due to inefficient heat transfer from the AGN to CGM despite Coulomb/hadronic CR losses being present; (iv) including CR streaming and heating restores agreement with the observations, i.e. cooling catastrophes are prevented and massive cold central discs do not form. The AGN power is reduced as its energy is utilized efficiently.

Obscured Active Galactic Nuclei

Active galactic nuclei (AGN) are powered by the accretion of material onto a supermassive black hole (SMBH) and are among the most luminous objects in the Universe. However, the huge radiative power of most AGN cannot be seen directly, as the accretion is hidden behind gas and dust that absorb many of the characteristic observational signatures. This obscuration presents an important challenge for uncovering the complete AGN population and understanding the cosmic evolution of SMBHs. In this review, we describe a broad range of multiwavelength techniques that are currently being employed to identify obscured AGN, and we assess the reliability and completeness of each technique. We follow with a discussion of the demographics of obscured AGN activity, explore the nature and physical scales of the obscuring material, and assess the implications of obscured AGN for observational cosmology. We conclude with an outline of the prospects for future progress from both observations and theoretical models, and we highlight some of the key outstanding questions.

Dichotomy in the population of young AGN: Optical, radio, and X‐ray properties

AbstractThere are numerous examples of radio sources with various sizes which surprisingly exhibit very similar morphology. This observational fact helped to create a standard evolutionary model in which young and small radio‐loud active galactic nuclei (AGN), called gigahertz‐peaked spectrum (GPS) sources and compact steep spectrum (CSS) sources, become largescale radio objects. However, many details of this evolutionary process are still unclear. We explored evolution scenarios of radio‐loud AGN using new radio, optical and X‐ray data of so far unstudied low luminosity compact (LLC) sources and we summarize the results in this paper. Our studies show that the evolutionary track is very “individualized” although we can mention common factors affecting it. These are interaction with the ambient medium and AGN power. The second feature affects the production of the radio jets which, if they are weak, are more vulnerable for instabilities and disruption. Thus not all GPS and CSS sources will be able to develop large scale morphologies. Many will fade away being middleaged (105 yr). It seems that only radio strong, high excitation compact AGN can be progenitors of large‐scale FRII radio sources. (© 2016 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)