Wolfgang J. Duschl

Theory of accretion disks--2

Preface. Protoplanetary disks S.V.W. Beckwith. Magnetospheric accretion and winds from pre-main sequence disks L. Hartmann. Forbidden line diagnostics of disk winds in YSOs R.E. Pudritz, R. Ouyed. Magnetized accretion disks and the origin of bipolar flows A. Konigl. Wind magnetospheres of protostellar accretion disks Ch. Fendt, M. Camenzind. Accretion disks in cataclysmic variable stars: Recent observational developments K. Horne. Disk instability model for SU UMa stars: SU UMa/WZ Sge connection Y. Osaki. Eccentric disk instabilities and their relation to superhump binaries S.H. Lubow. On the sequencing of long and short outbursts in dwarf novae J.K. Cannizzo. Dynamics of dwarf novae accretion discs R. Whitehurst. The viscous evolution of elliptical accretion discs D. Syer, C. Clarke. Probing the kinematics of disk winds F.V. Hessman, J. Eisloffel. Coronal winds producing the tilted and twisted shape of the accretion disk in Her X-1 S. Horn, F. Meyer. Recurrence time for dwarf nova outbursts: Dependence on mass transfer rate S. Ichikawa, Y. Osaki. Circulation, pulsation and convection in accretion disks W. Kley. Instability in a braking disk: Her X-1 in complete-off state F. Meyer, E. Meyer-Hofmeister. Temperature profiles of accretion disks in X-ray binaries S. Mineshige, F. Honma, A. Hirano, S. Kitamoto, T. Yamada, J. Fukue. An empirical approach to accretion disks in AGN S. Collin-Souffrin. Periodic X-ray variability of the Seyfert galaxy NGC 6814 M.A. Abramowicz, G. Bao, V. Karas, A. Lanza. Atmospheres and thermal continua of AGN disks G.A. Shields, H.H. Coleman. Star-disk interaction in quasars and AGNs D.N.C. Lin, P. Artymowicz, J.Wampler. How to tyransport angular momentum in the inner 150 pc of galaxies W.J. Duschl, S. von Linden, P.L. Biermann. The energy budget in the irradiation model of quasars M.-H.D. Ulrich. X-ray illumination of AGN disks H. Netzer. Pulsational instability of relativistic accretion disks and the periodic X-ray time variability of NGC 6814 F. Honma, R. Matsumoto, S. Kato. Large-scale dynamics of molecular clouds in the interstellar medium of disk galaxies S. von Linden, H. Lesch, F. Combes. A self-consistent accretion disk-coronal model for the active galacticnuclei K. Nakamura, Y. Osaki. Simulations with smoothed particles confirm stationary shocks in accretion flows onto Black Holes D. Molteni, S. Chakrabarti. A single variability model for NGC 6814 and NGC 5548 F. Wallinder. Accretion disk boundary layers R. Narayan, R. Popham. Measuring the radial extent of the disk-star boundary layer in T Tauri stars W.J. Duschl, W.M. Tscharnuter, C. Bertout, J. Bouvier. Magnetic interaction between accretion disks and supermassive Black Holes in AGN M. Camenzind. On the dynamics of warped accretion disks J.C.B. Papaloizou, D.N.C. Lin. Slim accretion discs J.P. Lasota. A two dimensional steady state configuration of a thick accretion disk E. Szuszkiewicz, J. Paploizou. Recent work on angular momentum transport in accretion discs J.E. Pringle. Tidal excitation of spiral waves in accretion discs G.J. Savonije, J.C.B. Paploizou, D.N.C. Lin. Magnetic discs A.R. King, G.A. Wynn. A magnetic turbulence model in disks S. Kato. Electron-positron pairs in accretion disks M. Kusunose, S. Mineshige. Intriguing morphologies, jets and disks in planetary nebulae M. Livio.<

Radio-loud Narrow-Line Type 1 Quasars

We present the first systematic study of (non-radio-selected) radio-loud narrow-line Seyfert 1 (NLS1) galaxies. Cross-correlation of the Catalogue of Quasars and Active Nuclei with several radio and optical catalogs led to the identification of ~11 radio-loud NLS1 candidates, including four previously known ones. This study almost triples the number of known radio-loud NLS1 galaxies if all candidates are confirmed. Most of the radio-loud NLS1 galaxies are compact, steep-spectrum sources accreting close to or above the Eddington limit. The radio-loud NLS1 galaxies of our sample are remarkable in that they occupy a previously rarely populated regime in NLS1 multiwavelength parameter space. While their [O III]/Hβ and Fe II/Hβ intensity ratios almost cover the whole range observed in NLS1 galaxies, their radio properties extend the range of radio-loud objects to those with small widths of the broad Balmer lines. Their black hole masses are generally at the upper observed end among NLS1 galaxies but are still unusually small in view of the radio loudness of the sources. Among the radio-detected NLS1 galaxies, the radio index R is distributed quite smoothly up to the critical value of R 10 and covers about 4 orders of magnitude in total. Statistics show that ~7% of the NLS1 galaxies are formally radio-loud, while only 2.5% exceed a radio index R > 100. Implications for NLS1 models are discussed. Several mechanisms are considered as explanations for the radio loudness of the NLS1 galaxies and for the lower frequency of radio-loud galaxies among NLS1 galaxies than among quasars. While properties of most sources (with two to three exceptions) generally do not favor relativistic beaming, the combination of accretion mode and spin may explain the observations.

The dusty heart of nearby active galaxies. I. High-spatial resolution mid-IR spectro-photometry of Seyfert galaxies

In a series of papers, we aim at stepping towards characterizing physical properties of the AGN dust torus by combining IR highspatial resolution observations with 3D clumpy torus models. In this first paper, we present mid-IR imaging and 8−13 μ ml owresolution spectroscopy of nine type 1 and ten type 2 AGN. The observations were carried out with the VLT/VISIR mid-IR imager and spectrograph and can be considered the largest currently available mid-infrared spectro-photometric data set of AGN at spatial resolution <100 pc. These data resolve scales at which the emission from the dust torus dominates the overall flux, and emission from the host galaxy (e.g. star-formation) is resolved out in most cases. The silicate absorption features are moderately deep and emission features, if seen at all, are shallow. The strongest silicate emission feature in our sample shows some notable shift of the central wavelength from the expected 9.7 μm (based on ISM extinction curves) to ∼10.5 μm. We compare the observed mid-IR luminosities of our objects to AGN luminosity tracers (X-ray, optical and [O iii] luminosities) and find that the mid-IR radiation is emitted quite isotropically. In two cases, IC 5063 and MCG–3–34–64, we find evidence for extended dust emission in the narrow-line region. We confirm the correlation between observed silicate feature strength and Hydrogen column density, which was recently found in Spitzer data at lower spatial resolution. In a further step, our 3D clumpy torus model has been used to interpret the data. We show that the strength of the silicate feature and the mid-IR spectral index α can be used to get reasonable constraints on the radial dust distribution of the torus and the average number of clouds N0 along an equatorial line-of-sight in clumpy torus models. The mid-IR spectral index α is almost exclusively determined by the radial dust distribution power-law index a, while the silicate feature depth mostly depends on N0 and the torus inclination. A comparison of model predictions to our type 1 and type 2 AGN reveals that average parameters of a = −1.0 ± 0. 5a ndN0 = 5 − 8 are typically seen in the presented sample, which means that the radial dust distribution is rather shallow. As a proof-of-concept of this method, we compared the model parameters derived from α and the silicate feature strength to more detailed studies of full IR SEDs and interferometry and found that the constraints on a and N0 are consistent. Finally, we may have found evidence that the radial structure of the torus changes from low to high AGN luminosities towards steeper dust distributions, and we discuss implications for the IR size-luminosity relation.

The subarcsecond mid-infrared view of local active galactic nuclei – I. The N- and Q-band imaging atlas?

We present the first subarcsecond-resolution mid-infrared (MIR) atlas of local active galactic nuclei (AGN). Our atlas contains 253 AGN with a median redshift of z = 0.016, and includes all publicly available MIR imaging performed to date with ground-based 8-m class telescopes, a total of 895 independent measurements. Of these, more than 60 per cent are published here for the first time. We detect extended nuclear emission in at least 21 per cent of the objects, while another 19 per cent appear clearly point-like, and the remaining objects cannot be constrained. Where present, elongated nuclear emission aligns with the ionization cones in Seyferts. Subarcsecond resolution allows us to isolate the AGN emission on scales of a few tens of parsecs and to obtain nuclear photometry in multiple filters for the objects. Median spectral energy distributions (SEDs) for the different optical AGN types are constructed and individual MIR 12 and 18 mu m continuum luminosities are computed. These range over more than six orders of magnitude. In comparison to the arcsecond-scale MIR emission as probed by Spitzer, the continuum emission is much lower on subarcsecond scales in many cases. The silicate feature strength is similar on both scales and generally appears in emission (absorption) in type I (II) AGN. However, the polycyclic aromatic hydrocarbon emission appears weaker or absent on subarcsecond scales. The differences of the MIR SEDs on both scales are particularly large for AGN/starburst composites and close-by (and weak) AGN. The nucleus dominates over the total emission of the galaxy only at luminosities greater than or similar to 10(44) erg s(-1). The AGN MIR atlas is well suited not only for detailed investigation of individual sources but also for statistical studies of AGN unification.

The mid IR - hard X-ray correlation in AGN and its implications for dusty torus models ,

Aims. We investigate mid-infrared and X-ray properties of the dusty torus invoked in the unification scenario for active galactic nuclei by using the relation between mid IR and hard X-ray luminosities to constrain the geometry and physical state of the dusty torus. Methods. We present new VISIR observations of 17 nearby AGN and combined these with our earlier VISIR sample of 8 Seyfert galaxies. After combining these observations with X-ray data from the literature, we studied the correlation between their mid IR and hard X-ray luminosities. Results. A statistically highly significant correlation is found between the rest frame 12.3 μm (L MIR ) and 2-10 keV (L x ) luminosities. Furthermore, with a probability of 97%, we find that Sy 1 and Sy 2 nuclei have the same distribution of L MIR over L x . Conclusions. The high resolution of our MIR imaging allows us to exclude any significant non-torus contribution to the AGN mid IR continuum, thereby implying that the similarity in the L MIR /L X ratio between Sy 1s and Sy 2s is intrinsic to AGN. We argue that this is best explained by clumpy torus models. The slope of the correlation is in good agreement with the expectations from the unified scenario and indicates little to no change in the torus geometry with luminosity. In addition, we demonstrate that the high angular resolution is crucial for AGN studies in the IR regime.

Mid-infrared properties of nearby low-luminosity AGN at high angular resolution

We present high spatial resolution mid-infrared (MIR) 12 μm continuum imaging of low-luminosity active galactic nuclei (LLAGN) obtained with VLT/VISIR. Our goal is to determine whether the nuclear MIR emission of LLAGN is consistent with the existence of a dusty obscuring torus, the key component of the unification model for AGN. Based on available hard X-ray luminosities and the previously known tight correlation between the hard X-ray and 12 μm luminosities, we selected a sample of 17 nearby LLAGN without available VISIR N-band photometry. Combined with archival VISIR data of 9 additional LLAGN with available X-ray measurements, the dataset represents the bulk of southern LLAGN currently detectable from the ground in the MIR. Of the 17 observed LLAGN, 7 are detected, while upper limits are derived for the 10 non-detections. This increases the total number of AGN detected with VLT/VISIR to more than 50. All detections except NGC 3125 appear point-like on a spatial scale of ∼0.35 �� . The detections do not significantly deviate from the known MIR-X-ray correlation but exceed it by a factor of ∼10 down to luminosities <10 41 erg/s with a narrow scatter (σ = 0.35 dex, Spearman rank ρ = 0.92). The latter is dominated by the uncertainties in the X-ray luminosity. Interestingly, a similar correlation with a comparable slope but with a normalization differing by ∼2.6 orders of magnitude has been found for local starburst galaxies. In addition, we compared the VISIR data with lower spatial resolution data from Spitzer/IRS and IRAS. By using a scaled starburst template spectral energy distribution and the polycyclic aromatic hydrocarbon (PAH) 11.3 μm emission line, we were able to restrict the maximum nuclear star-formation contamination of the VISIR photometry to 30% for 75% of the LLAGN. Exceptions are NGC 1097 and NGC 1566, which may possess unresolved strong PAH emission. Furthermore, the MIRX-ray luminosity ratio is unchanged over more than 4 orders of magnitude in accretion rate within the uncertainties. These results are consistent with the existence of the dusty torus in all observed LLAGN, although a jet or accretion disk as origin of the MIR emission cannot be excluded. Finally, because the MIR-X-ray correlation holds for all LLAGN and Seyferts, this is a very useful empirical tool for converting between the MIR and X-ray powers of these nuclei.

The subarcsecond mid-infrared view of local active galactic nuclei – II. The mid-infrared–X-ray correlation

We present an updated mid-infrared (MIR) versus X-ray correlation for the local active galactic nuclei (AGN) population based on the high angular resolution 12 and 18?m continuum fluxes from the AGN subarcsecond MIR atlas and 2–10 keV and 14–195 keV data collected from the literature. We isolate a sample of 152 objects with reliable AGN nature and multi-epoch X-ray data and minimal MIR contribution from star formation. Although the sample is not homogeneous or complete, we show that our results are unlikely to be affected by significant biases. The MIR–X-ray correlation is nearly linear and within a factor of 2 independent of the AGN type and the wavebands used. The observed scatter is <0.4 dex. A possible flattening of the correlation slope at the highest luminosities probed (?1045? erg s?1) towards low MIR luminosities for a given X-ray luminosity is indicated but not significant. Unobscured objects have, on average, an MIR–X-ray ratio that is only ?0.15?dex higher than that of obscured objects. Objects with intermediate X-ray column densities (22 < log?NH < 23) actually show the highest MIR–X-ray ratio on average. Radio-loud objects show a higher mean MIR–X-ray ratio at low luminosities while the ratio is lower than average at high luminosities. This may be explained by synchrotron emission from the jet contributing to the MIR at low luminosities and additional X-ray emission at high luminosities. True Seyfert 2 candidates do not show any deviation from the general behaviour suggesting that they possess a dusty obscurer as in other AGN. Double AGN also do not deviate. Finally, we show that the MIR–X-ray correlation can be used to investigate the AGN nature of uncertain objects. Specifically, we give equations that allow us to determine the intrinsic 2–10 keV luminosities and column densities for objects with complex X-ray properties to within 0.34 dex. These techniques are applied to the uncertain objects of the remaining AGN MIR atlas, demonstrating the usefulness of the MIR–X-ray correlation as an empirical tool.

Rosseland and Planck mean opacities for primordial matter

We present newly calculated low-temperature opacities for gas with a primordial chemical composition. In contrast to earlier calculations, which took a pure metal-free hydrogen/helium mixture, we take into account the small fractions of deuterium and lithium as resulting from standard big bang nucleosynthesis. Our opacity tables cover the density range -16 10 3 K. We find that, while the presence of deuterium does not significantly alter the opacity values, the presence of lithium gives rise to major modifications of the opacities, at some points increasing it by approximately two orders of magnitude relative to pure hydrogen/helium opacities.

Simultaneous NIR/sub-mm observation of flare emission from Sagittarius A*

Context. We report on a successful, simultaneous observation and modeling of the sub-millimeter to near-infrared flare emission of the Sgr A* counterpart associated with the super-massive (4×10 6 M⊙ ) black hole at the Galactic center. Aims. We study and model the physical processes giving rise to the variable emission of Sgr A*. Methods. Our non-relativistic modeling is based on simultaneous observations that have been carried out on 03 June, 2008. We used the NACO adaptive optics (AO) instrument at the European Southern Observatory’s Very Large Telescope and the LABOCA bolometer at the Atacama Pathfinder Experiment (APEX). We emphasize the importance of a multi-wavelength simultaneous fitting as a tool for imposing adequate constraints on the flare model ing. Results. The observations reveal strong flare activity in the 0.87 mm ( 345 GHz) sub-mm domain and in the 3.8µ/2.2µm NIR. Inspection and modeling of the light curves show that the sub-mm follows the NIR emission with a delay of 1.5±0.5 hours. We explain the flare emission delay by an adiabatic expansion of the source components. The derived physical quantities that describe the flare emission give a source component expansion speed of vexp∼ 0.005c, source sizes around one Schwarzschild radius with flux densities of a few Janskys, and spectral indices of �=0.8 to 1.8, corresponding to particle spectral indices ∼2.6 to 4.6. At the start of the flare the spectra of these components peak at frequencies of a few THz. Conclusions. These parameters suggest that the adiabatically expanding source components either have a bulk motion greater than vexp or the expanding material contributes to a corona or disk, confined to the immediate surroundings of Sgr A*.

The small dispersion of the mid IR - hard X-ray correlation in active galactic nuclei

Context. We investigate mid-infrared and X-ray properties of the dusty torus in unification scenarios for active galactic nuclei. Aims. We use the relation between mid IR and hard X-ray luminosities to constrain AGN unification scenarios. Methods. With VISIR at the VLT, we have obtained the currently highest angular resolution (