Active Galactic Nuclei Luminosity Research Articles

Redshift–luminosity characterization of active galactic nucleus galaxies having obscuring dusty material using the spectral energy distribution from the X-ray to far-infrared

ABSTRACT The spectral energy distribution (SED) from the X-ray to far-IR is used to characterize active galactic nuclei (AGNs) having obscuring dusty material. A sample of 73 AGNs, with redshifts of z < 2.5, is subdivided based on the optical spectra into subgroups of type 1 and 2 AGNs and no-AGN. The x-cigale code is used to produce the SEDs of these galaxies, fitting them with their observed flux densities. Accordingly, this code provides estimates of the physical properties, including the stellar mass, dust-to-gas mass ratio, far-UV attenuation, star-formation rate, and luminosity. All these properties and luminosity components, namely stellar, AGN, X-ray, and dust luminosities, are characterized versus the redshift. With the caveat that the sample is flux-limited and thus is affected by Malmquist bias, the results show that these properties increase as a function of redshift with various variation rates for each galaxy group, except for the far-UV attenuation of type 1 AGNs, which shows a slight reduction with redshift. The stellar, AGN, and X-ray luminosities show tight correlations with the intrinsic AGN luminosity, which is, in principle, attributed to the intrinsic AGN accretion power acting as a fuelling source. This power has an impact on most other correlations versus the redshift when the intrinsic AGN luminosity increases with redshift. Owing to their different emission sources, these luminosities make different fractional contributions to the total luminosity. The stellar luminosity, where the dust luminosity is the most effective, has the highest contribution of all galaxy groups, while the AGN luminosity has the lowest.

The X-ray view of optically selected dual AGN

ABSTRACT We present a study of optically selected dual Active Galactic Nuclei (AGN) with projected separations of 3–97 kpc. Using multiwavelength (MWL) information (optical, X-ray, mid-IR), we characterized the intrinsic nuclear properties of this sample and compared them with those of isolated systems. Among the 124 X-ray-detected AGN candidates, 52 appear in pairs and 72 as single X-ray sources. Through MWL analysis, we confirmed the presence of the AGN in >80 per cent of the detected targets in pairs (42 out of 52). X-ray spectral analysis confirms the trend of increasing AGN luminosity with decreasing separation, suggesting that mergers may have contributed to triggering more luminous AGN. Through X-ray/mid-IR ratio versus X-ray colours, we estimated a fraction of Compton-thin AGN (with 1022 cm−2 < NH < 1024 cm−2) of about 80 per cent, while about 16 per cent are Compton-thick sources (with NH > 1024 cm−2). These fractions of obscured sources are larger than those found in samples of isolated AGN, confirming that pairs of AGN show higher obscuration. This trend is further confirmed by comparing the de-reddened [O iii] emission with the observed X-ray luminosity. However, the derived fraction of Compton-thick sources in this sample at the early stages of merging is lower than that reported for late-merging dual-AGN samples. Comparing NH from X-rays with that derived from E(B − V) from narrow-line regions, we found that the absorbing material is likely to be associated with the torus or broad-line regions. We also explored the X-ray detection efficiency of dual-AGN candidates, finding that, when observed properly (at on-axis positions and with long exposures), X-ray data represent a powerful way to confirm and investigate dual-AGN systems.

The impact of the AGN and the torus properties on the evolution of spiral galaxies

ABSTRACT For spiral galaxies, the active galactic nucleus (AGN) and some physical parameters that concern the host galaxy such as spiral arm radius and density can play an important role in the morphological evolution of these galaxies. Considering the gravitational effect of the central black hole as a feeding mechanism, the gas flows from spiral arms to the accretion disk. Accordingly, we constructed our approach and derived an equation for the AGN luminosity that depends on parameters such as the black hole mass and the spiral arm density. The galaxy samples were taken from a catalog of type 1 AGN from SDSS-DR7. In our model, we present the relation between the AGN luminosity and the black hole mass depending on the above physical parameters. We also investigated the relation between the black hole mass and the star formation rate for the galaxy sample. The physical properties of the torus, such as the spiral arm radius, density, the torus length, and the gas mass, and the star formation rate were explained in terms of the variation of the AGN luminosity. These properties are more effective in the evolutionary scenario of the spiral galaxy. Relative to the variation of the AGN luminosity, the evolutionary track is different based quantitatively on the star formation rate. In which the variation in the star formation rate is positively correlated with the AGN luminosity.

The Obscured Fraction of Quasars at Cosmic Noon

Statistical studies of X-ray selected active galactic nuclei (AGN) indicate that the fraction of obscured AGN increases with increasing redshift, and the results suggest that a significant part of the accretion growth occurs behind obscuring material in the early universe. We investigate the obscured fraction of highly accreting X-ray AGN at around the peak epoch of supermassive black hole growth utilizing the wide and deep X-ray and optical/IR imaging data sets. A unique sample of luminous X-ray selected AGNs above z > 2 was constructed by matching the XMM-SERVS X-ray point-source catalog with a point-spread function convolved photometric catalog covering the u*–4.5 μm bands. Photometric redshift, hydrogen column density, and 2–10 keV AGN luminosity of the X-ray selected AGN candidates were estimated. Using the sample of 306 2–10 keV detected AGN at above redshift 2, we estimate the fraction of AGN with , assuming parametric X-ray luminosity and absorption functions. The results suggest that of luminous quasars () above redshift 2 are obscured. The fraction indicates an increased contribution of obscured accretion at high redshift than that in the local universe. We discuss the implications of the increasing obscured fraction with increasing redshift based on the AGN obscuration scenarios, which describe obscuration properties in the local universe. Both the obscured and unobscured z > 2 AGN show a broad range of SEDs and morphology, which may reflect the broad variety of host galaxy properties and physical processes associated with the obscuration.

Polar Dust Emission in Quasar IR SEDs and Its Correlation with Narrow-line Regions

Polar dust has been found to play an important role in the mid-infrared emission of nearby Seyfert nuclei. If and how often polar dust exists among the quasar population is unknown due to the lack of spatially resolved observations. In this Letter, we report correlations between the prominence of active galactic nucleus (AGN) forbidden line emission (commonly associated with the narrow-line region) and the dust mid-IR energy output among the archetypal Palomar-Green quasar sample and other bright type-1 AGNs drawn from the Sloan Digital Sky Survey, Spitzer, and Wide-field Infrared Survey Explorer (WISE) archives. The AGN mid-IR color differences traced by WISE W2 (∼4.6 μm)−W3 (∼12 μm) and W2 (∼4.6 μm)−W4 (∼22 μm), and near-IR to mid-IR spectral energy distributions (SEDs) constrained with the Two Micron All Sky Survey, WISE, and Spitzer data have clear trends with the relative strength of the forbidden line regions traced by the optical [O iii] and mid-IR [O iv] emission lines. These observations indicate that, where the lines are strong, a large fraction of the AGN emission at λ ≳ 5 μm comes from dust in the forbidden line regions. We find that the widely quoted universal AGN template is a result of averaging quasar SEDs with different levels of polar dust emission above the torus output and that the typical intrinsic IR SED of compact torus dust emission alone falls with increasing wavelength past 5 μm (in νF ν ). In addition, the association of polar dust with the forbidden lines suggests an alternative to the receding torus hypothesis for the decrease in infrared output with increasing AGN luminosity.

On the Coevolution of the AGN and Star-forming Galaxy Ultraviolet Luminosity Functions at 3 < z < 9

Studies of the rest-frame ultraviolet (UV) luminosity functions (LFs) typically treat star-forming galaxies and active galactic nuclei (AGNs) separately. However, modern ground-based surveys now probe volumes large enough to discover AGNs at depths sensitive enough for fainter galaxies, bridging these two populations. Using these observations as constraints, we present a methodology to empirically jointly model the evolution of the rest-UV LFs at z = 3–9. Our critical assumptions are that both populations have LFs well described by double power laws modified to allow for a flattening at the faint-end, and that all LF parameters evolve smoothly with redshift. This methodology provides a good fit to the observations and makes predictions to volume densities not yet observed, finding that the volume density of bright (M UV = −28) AGNs rises by ∼105 from z = 9 to z = 3, while bright (M UV = −21) star-forming galaxies rise by only ∼102 across the same epoch. The observed bright-end flattening of the z = 9 LF is unlikely to be due to AGN activity, and rather is due to a shallowing of the bright-end slope, implying a reduction of feedback in bright galaxies at early times. The intrinsic ionizing emissivity is dominated by star-forming galaxies at z > 3, even after applying a notional escape fraction. We find decent agreement between our AGN LFs and predictions based on different black hole seeding models, though all models underpredict the observed abundance of bright AGNs. We show that the wide-area surveys of the upcoming Euclid and Roman observatories should be capable of discovering AGNs to z ∼ 8.

BASS XXXII: Studying the Nuclear Millimeter-wave Continuum Emission of AGNs with ALMA at Scales ≲100–200 pc

To understand the origin of nuclear (≲100 pc) millimeter-wave (mm-wave) continuum emission in active galactic nuclei (AGNs), we systematically analyzed subarcsecond resolution Band-6 (211–275 GHz) Atacama Large Millimeter/submillimeter Array data of 98 nearby AGNs (z < 0.05) from the 70 month Swift/BAT catalog. The sample, almost unbiased for obscured systems, provides the largest number of AGNs to date with high mm-wave spatial resolution sampling (∼1–200 pc), and spans broad ranges of 14–150 keV luminosity {}, black hole mass ], and Eddington ratio (). We find a significant correlation between 1.3 mm (230 GHz) and 14–150 keV luminosities. Its scatter is ≈0.36 dex, and the mm-wave emission may serve as a good proxy of the AGN luminosity, free of dust extinction up to N H ∼ 1026 cm−2. While the mm-wave emission could be self-absorbed synchrotron radiation around the X-ray corona according to past works, we also discuss different possible origins of the mm-wave emission: AGN-related dust emission, outflow-driven shocks, and a small-scale (<200 pc) jet. The dust emission is unlikely to be dominant, as the mm-wave slope is generally flatter than expected. Also, due to no increase in the mm-wave luminosity with the Eddington ratio, a radiation-driven outflow model is possibly not the common mechanism. Furthermore, we find independence of the mm-wave luminosity on indicators of the inclination angle from the polar axis of the nuclear structure, which is inconsistent with a jet model whose luminosity depends only on the angle.

Supermassive black holes at high redshift are expected to be obscured by their massive host galaxies’ interstellar medium

We combine results from deep ALMA observations of massive (M* &gt; 1010 M⊙) galaxies at different redshifts to show that the column density of their interstellar medium (ISM) rapidly increases toward early cosmic epochs. Our analysis includes objects from the ASPECS and ALPINE large programs, as well as individual observations ofz ∼ 6 quasar hosts. When accounting for non-detections and correcting for selection effects, we find that the median surface density of the ISM of the massive galaxy population evolves as ∼(1 + z)3.3. This means that the ISM column density toward the nucleus of az &gt; 3 galaxy is typically &gt; 100 times larger than locally, and it may reach values as high as Compton-thick atz ≳ 6. Remarkably, the median ISM column density is on the same order of what is measured from X-ray observations of large active galactic nucleus (AGN) samples already atz ≳ 2. We have developed a simple analytic model for the spatial distribution of ISM clouds within galaxies, and estimate the total covering factor toward active nuclei when obscuration by ISM clouds on the host scale is added to that of parsec-scale circumnuclear material (the so-called torus). The model includes clouds with a distribution of sizes, masses, and surface densities, and also allows for an evolution of the characteristic cloud surface density with redshift, Σc, * ∝ (1 + z)γ. We show that, forγ = 2, such a model successfully reproduces the increase in the obscured AGN fraction with redshift that is commonly observed in deep X-ray surveys, both when different absorption thresholds and AGN luminosities are considered. Our results suggest that 80–90% of supermassive black holes in the early Universe (z &gt; 6 − 8) are hidden to our view, primarily by the ISM in their hosts. We finally discuss the implications of our results and how they can be tested observationally with current and forthcoming facilities (e.g., VLT, E-ELT, ALMA, and JWST) and with next-generation X-ray imaging satellites. By extrapolating the observed X-ray nebulae around local AGN to the environments of supermassive black holes at high redshifts, we find ≲1″ nebulae impose stringent design constraints on the spatial resolution of any future X-ray imaging Great Observatory in the coming decades.

Dwarf AGNs from variability for the origins of seeds (DAVOS): Intermediate-mass black hole demographics from optical synoptic surveys

ABSTRACT We present a phenomenological forward Monte Carlo model for forecasting the population of active galactic nuclei (AGNs) in dwarf galaxies observable via their optical variability. Our model accounts for expected changes in the spectral energy distribution of AGNs in the intermediate-mass black hole (IMBH) mass range and uses observational constraints on optical variability as a function of black hole (BH) mass to generate mock light curves. Adopting several different models for the BH occupation function, including one for off-nuclear IMBHs, we quantify differences in the predicted local AGN mass and luminosity functions in dwarf galaxies. As a result, we are able to model the fraction of variable AGNs as a function of important galaxy host properties, such as host galaxy stellar mass, in the presence of selection effects. We find that our adopted occupation fractions for the ‘heavy’ and ‘light’ initial BH seeding scenarios can be distinguished with variability at the 2–3σ level for galaxy host stellar masses below ∼108M⊙ with data from the upcoming Vera C. Rubin Observatory. We also demonstrate the prevalence of a selection bias whereby recovered IMBH masses fall, on average, above the predicted value from the local host galaxy–BH mass scaling relation with the strength of this bias dependent on the survey sensitivity. Our methodology can be used more broadly to calibrate AGN demographic studies in synoptic surveys. Finally, we show that a targeted ∼ hourly cadence program over a few nights with the Rubin Observatory can provide strong constraints on IMBH masses given their expected rapid variability time-scales.

What powers galactic outflows: nuclear starbursts or AGN?

ABSTRACT Galactic outflows can be powered either by nuclear starbursts (SB) or active galactic nuclei (AGNs). It has been argued that extreme starbursts can power extreme outflows, without the need to invoke AGN feedback. However, contributions from past and/or hidden AGN activity cannot be ruled out. Here, we constrain the potential role of the central black hole in driving powerful outflows in starburst galaxies (with no sign of ongoing AGN activity). We examine whether the galactic outflows can be explained by AGN luminosity evolution in the framework of our AGN ‘radiative dusty feedback’ scenario. We show that the outflow energetics of starburst galaxies in the local Universe can be quantitatively reproduced by power-law and exponential luminosity decays, coupled with radiation trapping. Likewise, a combination of heavy obscuration and mild luminosity decay may account for the energetics of galactic outflows observed in dusty star-forming galaxies in the early Universe. We discuss different physical arguments for SB versus AGN outflow-driving, and conclude that the latter can have a major impact on the evolution of galaxies.

Cosmic rays and thermal instability in self-regulating cooling flows of massive galaxy clusters

One of the key physical processes that helps prevent strong cooling flows in galaxy clusters is the continued energy input from the central active galactic nucleus (AGN) of the cluster. However, it remains unclear how this energy is thermalised so that it can effectively prevent global thermal instability. One possible option is that a fraction of the AGN energy is converted into cosmic rays (CRs), which provide non-thermal pressure support, and can retain energy even as thermal energy is radiated away. By means of magneto-hydrodynamical simulations, we investigate how CR injected by the AGN jet influence cooling flows of a massive galaxy cluster. We conclude that converting a fraction of the AGN luminosity as low as 10% into CR energy prevents cooling flows on timescales of billion years, without significant changes in the structure of the multi-phase intra-cluster medium. CR-dominated jets, by contrast, lead to the formation of an extended, warm central nebula that is supported by CR pressure. We report that the presence of CRs is not able to suppress the onset of thermal instability in massive galaxy clusters, but CR-dominated jets do significantly change the continued evolution of gas as it continues to cool from isobaric to isochoric. The CR redistribution in the cluster is dominated by advection rather than diffusion or streaming, but the heating by CR streaming helps maintain gas in the hot and warm phase. Observationally, self-regulating, CR-dominated jets produce a γ-ray flux in excess of current observational limits, but low CR fractions in the jet are not ruled out.

Detailed Accretion History of the Supermassive Black Hole in NGC 5972 over the Past ≳104 yr through the Extended Emission-line Region

We present integral field spectroscopic observations of NGC 5972 obtained with the Multi-Unit Spectroscopic Explorer at the Very Large Telescope. NGC 5972 is a nearby galaxy containing both an active galactic nucleus (AGN) and an extended emission-line region (EELR) reaching out to ∼17 kpc from the nucleus. We analyze the physical conditions of the EELR using spatially resolved spectra, focusing on the radial dependence of ionization state together with the light-travel time distance to probe the variability of the AGN on ≳104 yr timescales. The kinematic analysis suggests multiple components: (a) a faint component following the rotation of the large-scale disk, (b) a component associated with the EELR suggestive of extraplanar gas connected to tidal tails, and (c) a kinematically decoupled nuclear disk. Both the kinematics and the observed tidal tails suggest a major past interaction event. Emission-line diagnostics along the EELR arms typically evidence Seyfert-like emission, implying that the EELR was primarily ionized by the AGN. We generate a set of photoionization models and fit these to different regions along the EELR. This allows us to estimate the bolometric luminosity required at different radii to excite the gas to the observed state. Our results suggest that NGC 5972 is a fading quasar, showing a steady gradual decrease in intrinsic AGN luminosity, and hence the accretion rate onto the SMBH, by a factor ∼100 over the past 5 × 104 yr.

Ionized Outflows in Nearby Quasars Are Poorly Coupled to Their Host Galaxies

We analyze Multi-Unit Spectroscopic Explorer observations of nine low-redshift (z < 0.1) Palomar-Green quasar host galaxies to investigate the spatial distribution and kinematics of the warm, ionized interstellar medium, with the goal of searching for and constraining the efficiency of active galactic nucleus (AGN) feedback. After separating the bright AGN from the starlight and nebular emission, we use pixel-wise, kpc-scale diagnostics to determine the underlying excitation mechanism of the line emission, and we measure the kinematics of the narrow-line region (NLR) to estimate the physical properties of the ionized outflows. The radial size of the NLR correlates with the AGN luminosity, reaching scales of ∼5 kpc and beyond. The geometry of the NLR is well-represented by a projected biconical structure, suggesting that the AGN radiation preferably escapes through the ionization cone. We find enhanced velocity dispersions (≳100 km s−1) traced by the Hα emission line in localized zones within the ionization cones. Interpreting these kinematic features as signatures of interaction between an AGN-driven ionized gas outflow and the host galaxy interstellar medium, we derive mass-outflow rates of ∼0.008–1.6 M ⊙ yr−1 and kinetic injection rates of ∼1039–1042 erg s−1, which yield extremely low coupling efficiencies of ≲10−3. These findings add to the growing body of recent observational evidence that AGN feedback is highly ineffective in the host galaxies of nearby AGNs.

Ionization Distributions in Outflows of Active Galaxies: Universal Trends and Prospect of Future XRISM Observations

The physics behind the ionization structure of outflows from black holes is yet to be fully understood. Using archival observations with the Chandra/HETG gratings over the past two decades, we measured an absorption measure distribution for a sample of outflows in nine active galactic nuclei (AGNs), namely the dependence of outflow column density, N H, on the ionization parameter, ξ. The slope of N H versus is found to be between 0.00 and 0.72. We find an anticorrelation between the log of total column density of the outflow and the log of AGN luminosity, and none with the black hole mass and accretion efficiency. A major improvement in the diagnostics of AGN outflows will potentially occur with the launch of the XRISM/Resolve spectrometer. We study the ability of Resolve to reveal the outflow ionization structure by constructing the absorption measure distribution from simulated Resolve spectra, utilizing its superior resolution and effective area. Resolve constrains the column density as well as HETG, but with much shorter observations.

Unexplored outflows in nearby low luminosity AGNs

Context. Multi-phase outflows play a central role in galaxy evolution shaping the properties of galaxies. Understanding outflows and their effects in low luminosity active galactic nuclei (AGNs), such as low ionisation nuclear emission line regions (LINERs), is essential. LINERs bridge the gap between normal and active galaxies, being the most numerous AGN population in the local Universe. Aims. Our goal is to analyse the kinematics and ionisation mechanisms of the multi-phase gas of NGC 1052, the prototypical LINER, in order to detect and map the ionised and neutral phases of the putative outflow. Methods. We obtained Very Large Telescope MUSE and Gran Telescopio Canarias MEGARA optical integral field spectroscopy data for NGC 1052. In addition to stellar kinematics maps, by modelling spectral lines with multiple Gaussian components, we obtained flux, kinematic, and excitation maps of both ionised and neutral gas. Results. The stars are distributed in a dynamically hot disc (V/σ ∼ 1.2), with a centrally peaked velocity dispersion map (σc = 201 ± 10 km s−1) and large observed velocity amplitudes (ΔV = 167 ± 19 km s−1). The ionised gas, probed by the primary component is detected up to ∼30″ (∼3.3 kpc) mostly in the polar direction with blue and red velocities (∣V∣ &lt; 250 km s−1). The velocity dispersion map shows a notable enhancement (σ &gt; 90 km s−1) crossing the galaxy along the major axis of rotation in the central 10″. The secondary component has a bipolar morphology, velocity dispersion larger than 150 km s−1, and velocities up to 660 km s−1. A third component is detected with MUSE (and barely with MEGARA), but it is not spatially resolved. The broad-line region (BLR) component (used to model the broad Hα emission only) has a full width at half maximum of 2427 ± 332 and 2350 ± 470 km s−1 for MUSE and MEGARA data, respectively. The maps of the NaD absorption indicate optically thick neutral gas with complex kinematics. The velocity field is consistent with a slow rotating disc (ΔV = 77 ± 12 km s−1), but the velocity dispersion map is off-centred without any counterpart in the (centrally peaked) flux map. Conclusions. We found evidence of an ionised gas outflow (secondary component) with a mass of 1.6 ± 0.6 × 105 M⊙, and mass rate of 0.4 ± 0.2 M⊙ yr−1. The outflow is propagating in a cocoon of gas with enhanced turbulence and might be triggering the onset of kiloparsec-scale buoyant bubbles (polar emission), both probed by the primary component. Taking into account the energy and kinetic power of the outflow (1.3 ± 0.9 × 1053 erg and 8.8 ± 3.5 × 1040 erg s−1, respectively) as well as its alignment with both the jet and the cocoon, and that the gas is collisionally ionised (due to gas compression), we consider that the most likely power source of the outflow is the jet, although some contribution from the AGN is possible. The hints of the presence of a neutral gas outflow are weak.

Determining active galactic nucleus luminosity histories using present-day outflow properties: a neural network-based approach

ABSTRACT Large-scale outflows driven by active galactic nuclei (AGNs) can have a profound influence on their host galaxies. The outflow properties themselves depend sensitively on the history of AGN energy injection during the lifetime of the outflow. Most observed outflows have dynamical time-scales longer than the typical AGN episode duration, i.e. they have been inflated by multiple AGN episodes. Here, we present a neural network-based approach to inferring the most likely duty cycle and other properties of AGN based on the observable properties of their massive outflows. Our model recovers the AGN parameters of simulated outflows with typical errors $\lt 25{{\ \rm per\ cent}}$. We apply the method to a sample of 59 real molecular outflows and show that a large fraction of them have been inflated by AGN shining with a rather high duty cycle δAGN &amp;gt; 0.2. This result suggests that nuclear activity in galaxies is clustered hierarchically in time, with long phases of more frequent activity composed of many short activity episodes. We predict that $\sim \! 19{{\ \rm per\ cent}}$ of galaxies should have AGN-driven outflows, but half of them are fossils – this is consistent with currently available data. We discuss the possibilities to investigate AGN luminosity histories during outflow lifetimes and suggest ways to use our software to test other physical models of AGN outflows. The source code of all of the software used here is made public.

Cold Gas Reservoirs of Low- and High-mass Central Galaxies Differ in Response to Active Galactic Nucleus Feedback

The growth of supermassive black holes, especially the associated state of active galactic nuclei (AGNs), is generally believed to be the key step in regulating star formation in massive galaxies. As the fuel of star formation, the cold gas reservoir is a direct probe of the effect of AGN feedback on their host galaxies. However, in observations, no clear connection has been found between AGN activity and the cold gas mass. In this paper, we find observational signals of the significant depletion of the total neutral hydrogen gas reservoir in optically selected Type 2 AGN-host central galaxies of stellar mass 109–1010 M ⊙. The effect of AGN feedback on the cold gas reservoir is stronger for higher star formation rates and higher AGN luminosity. But it becomes much weaker above this mass range, consistent with previous findings focusing on massive galaxies. Our result suggests that low-mass and gas-rich AGN-host central galaxies would first form dense cores before AGN feedback is triggered, removing their neutral hydrogen gas. More massive central galaxies may undergo a significantly different formation scenario by gradually building up dense cores with less effective and recurrent AGN feedback.

Dependence of Narrow-line Region Sizes on [O iii] Luminosity in Low-redshift Active Galactic Nuclei with Double-peaked Broad Balmer Emission Lines

In this paper, simple but interesting results are reported on the upper limits of narrow-line region (NLR) sizes of a small sample of 38 low-redshift (z < 0.1) active galactic nuclei (AGN) with double-peaked broad emission lines (double-peaked BLAGN), in order to check whether the NLR sizes in type-1 AGN (broad line) and type-2 AGN (narrow line) obey a similar empirical dependence on [O iii] luminosity. In order to correct the inclination effects on projected NLR sizes of type-1 AGN, the accretion disk origin is commonly applied to describe the double-peaked broad Hα line, leading to the determined inclination angles of central disk-like broad-line regions of 38 double-peaked BLAGN. Then, considering the fixed Sloan Digital Sky Survey (SDSS) fiber radius, the upper limits of the NLR sizes of the 38 double-peaked BLAGN can be estimated. Meanwhile, a strong linear correlation between continuum luminosity and [O iii] luminosity is applied to confirm that the [O iii] emissions of the 38 double-peaked BLAGN are totally covered in the SDSS fibers. Considering the reddening-corrected measured [O iii] luminosity, the upper limits of the NLR sizes of the 38 double-peaked BLAGN are within a 99.9999% confidence interval of the expected results from the empirical relation between NLR size and [O iii] luminosity in type-2 AGN. In the current understanding, there are no challenges to the unified model of AGN through the space properties of NLRs.

Infrared Spectral Energy Distribution and Variability of Active Galactic Nuclei: Clues to the Structure of Circumnuclear Material

The active galactic nucleus (AGN) phenomenon results from a supermassive black hole accreting its surrounding gaseous and dusty material. The infrared (IR) regime provides most of the information to characterize the dusty structures that bridge from the galaxy to the black hole, providing clues to the black hole growth and host galaxy evolution. Over the past several decades, with the commissioning of various ground, airborne and space IR observing facilities, our interpretations of the AGN circumnuclear structures have advanced significantly through an improved understanding of how their dust emission changes as a function of wavelength and how the heating of the dusty structures responds to variations in the energy released from the central engine. In this review, we summarize the current observational knowledge of the AGN IR broad-band spectral energy distributions (SEDs) and the IR time variability behavior covering large ranges of AGN luminosity and redshift, and discuss some first-order insights into the obscuring structures and host galaxy IR properties that can be obtained by integrating the relevant observations into a coherent picture.

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.