Luminous Seyfert Galaxy Research Articles

Low-redshift absorption in the Seyfert galaxy PG1211+143 – a distant inflow maintaining off-plane accretion or the gravitational redshift of matter orbiting the SMBH?

ABSTRACT The detection of a high-velocity (∼0.3c) inflow of highly ionized matter during an extended XMM–Newton observation of the luminous Seyfert galaxy PG1211+143 in 2014 provided the first direct evidence of a short-lived accretion event, and an explanation for the powerful winds (UFOs) now recognized as a common property of many luminous Seyfert galaxies. Although the ultra-fast inflow observed at a redshift of 0.483 was detected in only one of seven spacecraft orbits, weaker (lower column) but more persistent absorption is seen at a redshift of 0.123 in the high-exposure soft X-ray (RGS) spectra summed over all seven individual spacecraft orbits. Similar stacking of the higher energy (pn camera) spectra reveals underlying absorption at a redshift of 0.148. Interpreted, conventionally, as a Doppler redshift, the RGS observation indicates a line-of-sight inflow velocity v ∼ 0.038c and (free-fall) radial location at 1400 Rg, with the higher redshift and ionization in pn camera spectra perhaps detecting that inflow closer to the black hole. A very different explanation would be absorption in matter subject to the strong gravity close to the SMBH, an interpretation supported by the launch of a new UFO in the final spacecraft orbit.

Local models of two-temperature accretion disc coronae – I. Structure, outflows, and energetics

ABSTRACT We use local stratified shearing-box simulations to elucidate the impact of two-temperature thermodynamics on the thermal structure of coronae in radiatively efficient accretion flows. Rather than treating the coronal plasma as an isothermal fluid, we use a simple, parametrized cooling function that models the collisional transfer of energy from the ions to the rapidly cooling leptons. Two-temperature models naturally form temperature inversions, with a hot, magnetically dominated corona surrounding a cold disc. Simulations with net vertical flux (NF) magnetic fields launch powerful magnetocentrifugal winds that would enhance accretion in a global system. The outflow rates are much better converged with increasing box height than analogous isothermal simulations, suggesting that the winds into two-temperature coronae may be sufficiently strong to evaporate a thin disc and form a radiatively inefficient accretion flow under some conditions. We find evidence for multiphase structure in the corona, with broad density and temperature distributions, and we propose criteria for the formation of a multiphase corona. The fraction of cooling in the surface layers of the disc is substantially larger for NF fields compared to zero net-flux configurations, with moderate NF simulations radiating ≳30 per cent of the flow’s total luminosity above two mid-plane scale heights. Our work shows that NF fields may efficiently power the coronae of luminous Seyfert galaxies and quasars, providing compelling motivation for future studies of the heating mechanisms available to NF fields and the interplay of radiation with two-temperature thermodynamics.

AGN feedback in action in the molecular gas ring of the Seyfert galaxy NGC 7172

We present new ALMA observations of the CO(3−2) transition and associated 854 μm continuum at 0.06 − 0.3″ resolution, together with new VLT/SINFONI observations of NGC 7172. This is a luminous (bolometric luminosity of ≃1044 erg s−1) Seyfert galaxy that belongs to the Galaxy Activity, Torus, and Outflow Survey (GATOS). The ALMA CO(3−2) observations reveal the presence of a highly inclined cold molecular gas ring with an approximate radius of 3 − 4″ ≃ 540 − 720 pc, which is likely associated with an inner Lindblad resonance of a putative stellar bar. There are noncircular motions in the VLT/SINFONI [Si VI]λ1.96 μm and H2 at 2.12 μm, and ALMA CO(3−2) velocity fields. After subtracting the stellar velocity field, we detected [Si VI] blueshifted velocities of a few hundred km s−1 to the south of the active galactic nucleus (AGN) position. They trace outflowing ionized gas outside the plane of the galaxy and out to projected distances of ≃200 pc. The CO(3−2) position-velocity diagram along the kinematic minor axis displays noncircular motions with observed velocities of up to ∼150 km s−1. Assuming that these are taking place in the disk of the galaxy, the observed velocity signs imply that the molecular gas ring is not only rotating but also outflowing. We derived an integrated cold molecular gas mass outflow rate of ∼40 M⊙ yr−1 for the ring. Using the ALMA 854 μm extended emission map, we resolved a 32 pc radius torus with a gas mass of 8 × 105 M⊙. These torus properties are similar to other Seyfert galaxies in the GATOS sample. We measured a decreased cold molecular gas concentration in the nuclear-torus region relative to the circumnuclear region when compared to other less luminous Seyfert galaxies. We conclude that the effects of AGN feedback in NGC 7172, which are likely caused by the AGN wind and/or the moderate luminosity radio jet, are seen as a large-scale outflowing molecular gas ring and accompanying redistribution of molecular gas in the nuclear regions.

A high angular resolution view of the PAH emission in Seyfert galaxies using JWST/MRS data

Polycyclic aromatic hydrocarbons (PAHs) are carbon-based molecules that are ubiquitous in a variety of astrophysical objects and environments. In this work we use JWST/MIRI MRS spectroscopy of three Seyferts to compare their nuclear PAH emission with that of star-forming (SF) regions. This study represents the first of its kind to use sub-arcsecond angular resolution data of local luminous Seyferts (Lbol > 1044.46 erg s−1) with a wide wavelength coverage (4.9–28.1 μm). We present an analysis of their nuclear PAH properties by comparing the observed ratios with PAH diagnostic model grids derived from theoretical spectra. Our results show that a suite of PAH features is present in the innermost parts of luminous Seyfert galaxies (∼0.45″ at 12 μm; in the inner ∼142–245 pc). We find that the nuclear regions of active galactic nuclei (AGN) lie at different positions of the PAH diagnostic diagrams, whereas the SF regions are concentrated around the average values of SF galaxies. In particular, we find that the nuclear PAH emission mainly originates in neutral PAHs. In contrast, PAH emission originating in the SF regions favours ionised PAH grains. The observed PAH ratios in the nuclear region of the AGN-dominated galaxy NGC 6552 indicate the presence of larger PAH molecules compared with those of the SF regions. Therefore, our results provide evidence that the AGN have a significant impact on the ionisation state (and probably the size) of the PAH grains on scales of ∼142–245 pc.

Chemical abundances in Seyfert galaxies – V. The discovery of shocked emission outside the AGN ionization axis

ABSTRACT We present maps for the electron temperature in the inner kpc of three luminous Seyfert galaxies: Mrk 79, Mrk 348, and Mrk 607 obtained from Gemini Multi-Object Spectrograph-integral field unit observations at spatial resolutions of ∼110–280 pc. We study the distributions of electron temperature in active galaxies and find temperatures varying in the range from ∼8000 to $\gtrsim 30\, 000\,$K. Shocks due to gas outflows play an important role in the observed temperature distributions of Mrk 79 and Mrk 348, while standard photoionization models reproduce the derived temperature values for Mrk 607. In Mrk 79 and Mrk 348, we find direct evidence for shock ionization with overall orientation orthogonal to the ionization axis, where shocks can be easily observed as the active galactic nuclei radiation field is shielded by the nuclear dusty torus. This also indicates that even when the ionization cones are narrow, the shocks can be much wider angle.

Circumnuclear multi-phase gas around nearby AGNs investigated by ALMA

AbstractSince the advent of the Atacama Large Millimeter/submillimeter Array (ALMA), more attention has been paid on the ≲100 pc scale circumnuclear disk (CND) to reveal feeding and feedback processes of active galactic nuclei (AGNs). By using cold molecular CO and atomic C0 emission line observations, we have revealed that there are multi-component gas dynamical flows around the AGN of the Circinus galaxy, which may explain the physical origin of the AGN torus. In the luminous Seyfert galaxy NGC 7469, we found that [CI](1–0) line is extraordinary bright relative to CO lines (for example J 2−1), manifesting the physical/chemical influence of the AGN on the surrounding gas in the form of X-ray dominated region (XDR).

An ultra-fast inflow in the luminous Seyfert PG1211+143

Blueshifted absorption lines in the X-ray spectra of AGN show that ultra-fast outflows with typical velocities $v \sim 0.1c$ are a common feature of these luminous objects. Such powerful AGN winds offer an explanation of the observed M-$\sigma$ relation linking the mass of the supermassive black hole and the velocity dispersion in the galaxy's stellar bulge. An extended XMM-Newton study of the luminous Seyfert galaxy PG1211+143 recently revealed a variable multi-velocity wind. Here we report the detection of a short-lived, ultra-fast inflow during the same observation. Previous reports of inflows used single absorption lines with uncertain identifications, but this new result identifies an array of resonance absorption lines of highly ionised Fe, Ca, Ar, S and Si, sharing a common redshift when compared with a grid of realistic photoionization spectra. The redshifted absorption arises in a column of highly ionized matter close to the black hole, with a line-of-sight velocity, $v \sim 0.3c$, inconsistent with the standard picture of a plane circular accretion disc. This may represent the first direct evidence for chaotic accretion in AGN, where accretion discs are generally misaligned to the black hole spin. For sufficient inclinations, the Lense-Thirring effect can break the discs into discrete rings, which then precess, collide and shock, causing near free-fall of gas towards the black hole. The observed accretion rate for the reported infall is comparable to the hard X-ray luminosity in PG1211+143, suggesting that direct infall may be a significant contributor to inner disc accretion.

Hubble Space Telescope Observations of Extended [O iii]λ 5007 Emission in Nearby QSO2s: New Constraints on AGN Host Galaxy Interaction

Abstract We present a Hubble Space Telescope survey of extended [O iii] λ5007 emission for a sample of 12 nearby (z < 0.12), luminous Type 2 quasars (QSO2s), which we use to measure the extent and kinematics of their AGN-ionized gas. We find that the size of the observed [O iii] regions scale with luminosity in comparison to nearby, less luminous Seyfert galaxies and radially outflowing kinematics to exist in all targets. We report an average maximum outflow radius of ∼600 pc, with gas continuing to be kinematically influenced by the central active galactic nucleus (AGN) out to an average radius of ∼1130 pc. These findings question the effectiveness of AGNs being capable of clearing material from their host bulge in the nearby universe and suggest that disruption of gas by AGN activity may prevent star formation without requiring evacuation. Additionally, we find a dichotomy in our targets when comparing [O iii] radial extent and nuclear FWHM, where QSO2s with compact [O iii] morphologies typically possess broader nuclear emission lines.

LLAMA: normal star formation efficiencies of molecular gas in the centres of luminous Seyfert galaxies

Using new APEX and JCMT spectroscopy of the CO 2-1 line, we undertake a controlled study of cold molecular gas in moderately luminous Active Galactic Nuclei (AGN) and inactive galaxies from the Luminous Local AGN with Matched Analogs (LLAMA) survey. We use spatially resolved infrared photometry of the LLAMA galaxies from 2MASS, WISE, IRAS & Herschel, corrected for nuclear emission using multi-component spectral energy distribution (SED) fits, to examine the dust-reprocessed star-formation rates (SFRs), molecular gas fractions and star formation efficiencies (SFEs) over their central 1 - 3 kpc. We find that the gas fractions and central SFEs of both active and inactive galaxies are similar when controlling for host stellar mass and morphology (Hubble type). The equivalent central molecular gas depletion times are consistent with the discs of normal spiral galaxies in the local Universe. Despite energetic arguments that the AGN in LLAMA should be capable of disrupting the observable cold molecular gas in their central environments, our results indicate that nuclear radiation only couples weakly with this phase. We find a mild preference for obscured AGN to contain higher amounts of central molecular gas, which suggests a connection between AGN obscuration and the gaseous environment of the nucleus. Systems with depressed SFEs are not found among the LLAMA AGN. We speculate that the processes that sustain the collapse of molecular gas into dense pre-stellar cores may also be a prerequisite for the inflow of material on to AGN accretion disks.

On the Disappearance of a Cold Molecular Torus around the Low-luminosity Active Galactic Nucleus of NGC 1097

Abstract We used the Atacama Large Millimeter/Submillimeter Array to map the CO(3–2) and the underlying continuum emissions around the type-1 low-luminosity active galactic nucleus (LLAGN; bolometric luminosity erg s−1) of NGC 1097 at ∼10 pc resolution. These observations revealed a detailed cold gas distribution within a ∼100 pc of this LLAGN. In contrast to the luminous Seyfert galaxy NGC 1068, where a ∼7 pc cold molecular torus was recently revealed, a distinctively dense and compact torus is missing in our CO(3–2) integrated intensity map of NGC 1097. Based on the CO(3–2) flux, the gas mass of the torus of NGC 1097 would be a factor of ≳2–3 less than that found for NGC 1068 by using the same CO-to-H2 conversion factor, which implies less active nuclear star formation and/or inflows in NGC 1097. Our dynamical modeling of the CO(3–2) velocity field implies that the cold molecular gas is concentrated in a thin layer as compared to the hot gas traced by the 2.12 μm H2 emission in and around the torus. Furthermore, we suggest that NGC 1097 hosts a geometrically thinner torus than NGC 1068. Although the physical origin of the torus thickness remains unclear, our observations support a theoretical prediction that geometrically thick tori with high opacity will become deficient as AGNs evolve from luminous Seyferts to LLAGNs.

THE FAST UV VARIABILITY OF THE ACTIVE GALACTIC NUCLEUS IN FAIRALL 9

We present results from a new optical/UV/X-ray monitoring campaign of the luminous Seyfert galaxy Fairall 9 using the Swift satellite. Using the UV-Optical Telescope (UVOT) on Swift, we find correlated optical/UV variability on all time scales ranging from the sampling time (4-days) to the length of the campaign (2.5 months). In one noteworthy event, the UW2-band flux dips by 20% in 4-days, and then recovers equally quickly; this event is not seen in either the optical or the X-ray bands. We argue that this event provides further evidence that a significant fraction of the UV-emission must be driven by irradiation/reprocessing of emission from the central disk. We also use an archival XMM-Newton observation to examine shorter time scale UV/X-ray variability. We find very rapid (<10 ks) UV flares of small amplitude. We show that, unless this emission is non-thermal, we must be seeing the Wien tail from a compact (<3 light hours), hot (T > $8\times10^4$ K) region. The possible association with X-ray microflares suggests that we may be seeing the UV signatures of direct X-ray flare heating of the innermost disk.

The soft X-ray spectrum of the luminous narrow line Seyfert galaxy PG 1211+143 – evidence for a second high-velocity outflow component

An XMM-Newton observation of the luminous Seyfert galaxy PG1211+143 in 2001 revealed the first clear evidence for a highly ionised high speed wind (in a non-BAL AGN), with a velocity of v~0.09c based on the identification of blue-shifted absorption lines in both EPIC and RGS spectra. A subsequent analysis of EPIC spectra, including additional absorption lines, led to an upward revision of the wind speed to ~0.14c, while broad band modelling indicated the need for a second, partial covering absorber to account for continuum curvature and spectral variability. We show here, in a new analysis of the XMM-Newton RGS data, that this additional absorber is detected in the soft X-ray spectra, with the higher spectral resolution providing a much improved velocity constraint, with v~0.07c. Similar variability of the 0.07c and 0.14c outflow components suggest they are physically linked, and we speculate that occurs by the fast (primary) wind impacting on small clumps of higher density, slow moving matter close to the disc. We show that strong, velocity broadened soft X-ray emission features, located at the redshift of PG1211+143, indicate the extended scale of the ionised outflow.

THE BLACK HOLE SPIN AND SOFT X-RAY EXCESS OF THE LUMINOUS SEYFERT GALAXY FAIRALL 9

We present an analysis of all XMM-Newton and Suzaku X-ray spectra of the nearby luminous Seyfert galaxy Fairall 9. Confirming previous analyses, we find robust evidence for a broad iron line associated with X-ray reflection from the innermost accretion disk. By fitting a spectral model that includes a relativistically ionized reflection component, we examine the constraints on the inclination of the inner accretion disk and the black hole spin, and the complications introduced by the presence of a photoionized emission line system. Employing multi-epoch fitting, we attempt to obtain robust and concordant measures of the accretion disk parameters. We also clearly see a soft X-ray excess in Fairall 9. During certain epochs, the soft excess can be described with same disk reflection component that produces the iron line. However, there are epochs where an additional soft component is required. This can be attributed to either an additional highly-ionized, strongly blurred disk reflection component, or a new X-ray continuum component.

Origin of the antihierarchical growth of black holes

Observational studies have revealed a "downsizing" trend in black hole (BH) growth: the number densities of luminous AGN peak at higher redshifts than those of faint AGN. This would seem to imply that massive black holes formed before low mass black holes, in apparent contradiction to hierarchical clustering scenarios. We investigate whether this observed "downsizing" in BH growth is reproduced in a semi-analytic model for the formation and evolution of galaxies and black holes, set within the hierarchical paradigm for structure formation (Somerville et al. 2008; S08). In this model, black holes evolve from light seeds (\sim100M\odot) and their growth is merger-driven. The original S08 model (baseline model) reproduces the number density of AGN at intermediate redshifts and luminosities, but underproduces luminous AGN at very high redshift (z > 3) and overproduces them at low redshift (z < 1). In addition, the baseline model underproduces low-luminosity AGN at low redshift (z < 1). To solve these problems we consider several modifications to the physical processes in the model: (1) a 'heavy' black hole seeding scenario (2) a sub-Eddington accretion rate ceiling that depends on the cold gas fraction, and (3) an additional black hole accretion mode due to disk instabilities. With these three modifications, the models can explain the observed downsizing, successfully reproduce the bolometric AGN luminosity function and simultaneously reproduce galaxy and black hole properties in the local Universe. We also perform a comparison with the observed soft and hard X-ray luminosity functions of AGN, including an empirical correction for torus-level obscuration, and reach similar conclusions. Our best-fit model suggests a scenario in which disk instabilities are the main driver for moderately luminous Seyfert galaxies at low redshift, while major mergers are the main trigger for luminous AGN.

Quantifying the fast outflow in the luminous Seyfert galaxy PG1211+143

We report two new XMM-Newton observations of PG1211+143 in December 2007, again finding evidence of the fast outflow of highly ionised gas first detected in 2001. Stacking the new spectra with those from two earlier XMM-Newton observations reveals strong and broad emission lines of FeXXV and OVIII, indicating the fast outflow to be persistent and to have a large covering factor. This finding confirms a high mass rate for the ionised ouflow in PG1211+143 and provides the first direct measurement of a wide angle, sub-relativistic outflow from an AGN transporting mechanical energy with the potential to disrupt the growth of the host galaxy. We suggest PG1211+143 may be typical of an AGN in a rapid super-Eddington growth phase.

X-RAY ABSORPTION AND OPTICAL EXTINCTION IN THE PARTIALLY OBSCURED SEYFERT NUCLEUS IN MRK 1393

We present a detailed study of the X-ray and optical spectra of the luminous Seyfert galaxy Mrk 1393, which revealed variable partial obscuration of the active nucleus. The X-ray spectra obtained by XMM-Newton and Swift show moderate absorption with a column density around 3 x 10(21) cm(-2), consistent with a dust-reddening interpretation of the steep Balmer decrement seen in recent optical spectra. The X-ray flux in the 0.5-2 keV band during the XMM-Newton observation in 2005, and Swift observation in 2006 was a factor of 6 brighter than that of the ROSAT All Sky Survey in 1991. In the past four years, the broad-H alpha line brightened by a factor of 4 accompanied by a decrease in the Balmer decrement. A comparison with literature spectra reveals variations in the dust extinction on timescales of several years, suggesting that the obscuring material are very close to the active nucleus. These observations indicate that a dust-to-gas ratio as high as the Galactic value can be present in moderately thick gas in the vicinity of the central engine within a few parsecs. We suggest that the obscuring material may be debris disrupted from the dusty torus.

The Structure of Narrow-Line Region in LINERs

Low-ionization nuclear emission regions (LINERs) are present in a large fraction of local galaxies, while their connection to the more luminous active galactic nuclei (AGN) remains elusive. We analyze the narrow band images obtained by the Hubble Space Telescope (HST) in Hα+[NII] and/or [OIII] band for 23 LINERs and low luminosity Seyfert galaxies in the sample of the Palomar Optical Spectroscopic Survey of nearby galaxies in an attempt to resolve the structure of Narrow Emission Line Regions (NLRs) of these objects. In all cases, NLRs are well resolved and their morphology differs from object to object. Clumps, linear structure, spiral arms or a ring are detected in a large fraction of the objects, while there is no significant difference between Seyfert galaxies and LINERs. We find that the NLR size and the narrow line luminosity are strongly correlated for both LINERs and low luminosity Seyfert galaxies, and that the size of Hα+[NII] emission line region scales with Hα luminosity as RNLR∝LHα0.44±0.06, consistent with an extension of the NLR size-luminosity relation defined for luminous Seyfert galaxies and quasars, to two orders of magnitude lower in luminosity and to lower activity levels. Our results suggest that NLRs in LINERs are similar to those of Seyfert galaxies, and they are powered by the central active galactic nucleus.

On the X-ray, optical emission line and black hole mass properties of local Seyfert galaxies

We investigate the relation between X-ray nuclear emission, optical emission line luminosities and black hole masses for a sample of 47 Seyfert galaxies. The sample, which has been selected from the Palomar optical spectroscopic survey of nearby galaxies (Ho et al. 1997a, ApJS, 112, 315), covers a wide range of nuclear powers, from L2 10keV # 10 43 erg/s down to very low luminosities (L2 10keV # 10 38 erg/s). Best available data from Chandra, XMM-Newton and, in a few cases, ASCA observations have been considered. Thanks to the good spatial resolution available from these observations and a proper modeling of the various spectral components, it has been possible to obtain accurate nuclear X-ray luminosities not contaminated by o! -nuclear sources and/or di! use emission. X-ray luminosities have then been corrected taking into account the likely candidate Compton thick sources, which are a high fraction (>30%) among type 2 Seyferts in our sample. The main result of this study is that we confirm strong linear correlations between 2-10 keV, (OIII)! 5007, H luminosities which show the same slope as quasars and luminous Seyfert galaxies, independent of the level of nuclear activity displayed. Moreover, despite the wide range of Eddington ratios (L/LEdd) tested here (six orders of magnitude, from 0.1 down to # 10 7 ), no correlation is found between the X-ray or optical emission line luminosities and the black hole mass. Our results suggest that Seyfert nuclei in our sample are consistent with being a scaled-down version of more luminous AGN.

Low-Luminosity Active Galactic Nuclei as Analogs of Galactic Black Holes in the Low/Hard State: Evidence from X-Ray Timing of NGC 4258

We present a broadband power spectral density function (PSD) measured from extensive RXTE monitoring data of the low-luminosity active galactic nucleus (LLAGN) NGC 4258, which has an accurate, maser-determined black hole mass of (3.9 ± 0.1) × 107 M☉. We constrain the PSD break timescale to be greater than 4.5 days at >90% confidence, which appears to rule out the possibility that NGC 4258 is an analog of black hole X-ray binaries (BHXRBs) in the high/soft state. In this sense, the PSD of NGC 4258 is different from those of some more luminous Seyfert galaxies, which appear similar to the PSDs of high/soft state X-ray binaries. This result supports previous analogies between LLAGNs and X-ray binaries in the low/hard state based on spectral energy distributions, indicating that the AGN/BHXRB analogy is valid across a broad range of accretion rates.

XMM-Newtonobservations of the dwarf elliptical galaxy NGC 3226

We report on an XMM-Newton observation of the dwarf elliptical galaxy NGC 3226 performed in November 2000. The analysis of the 0.4-10 keV spectrum of its nucleus is consistent with a power law continuum (Γ ≈ 1.96) absorbed at low energies by neutral gas (with a hydrogen column density NH ≈ 3-8×10 21 cm −2 and a covering fraction greater than 85%) and by weakly ionized gas (NW ≈ 4-6 × 10 21 cm −2 with ξ ≈ 1-7 erg s −1 cm). However, the study indicates that a bremstrahlung model absorbed by neutral material is a better description reminiscent of the X-ray emission from advection-dominated accretion flows (ADAFs). The temperature of the best fit bremstrahlung model (T ≈ 10 8 K) and the absence of short and mid time-scale variability suggests that the X-ray emission originates from regions relatively far from the nucleus as in convection-dominated accretion flows (CDAFs) or in the so-called wind models. By comparing the 2-10 keV luminosity of the central object (LX = 2.58 × 10 40 erg s −1 after correction from Galactic and intrinsic absorption) with radio flux measurements, we find a mass in the range (1.7-50) × 10 7 Mfor the accreting black hole, a value comparable with an independent estimate from the dispersion of radial velocities. We argue that the dwarf elliptical galaxy NGC 3226 may harbor a sub-Eddington, super-massive black hole in a radiative inefficient state which is distinct from the near-Eddington, thermally dominated black holes presumably found in quasars and luminous Seyfert galaxies.