International Workshop jointly organized by:
ESO/Chile, FONDAP-Chile and Universidad de Chile

Physics of Active Galactic Nuclei at all Scales
at ESO/Santiago Headquarters, Chile - December 3 to 6, 2003



Review - H.Netzer


Review - D.Worrall

Precession in the Parsec-Scale Jets of AGNs
Many of the brightest and best studied quasars present superluminal features in their parsec-scale jets that differ in velocity and position angle in the plane of the sky. If the jet is precessing, the velocities and position angles of the superluminal components will reflect the jet direction at the epoch in which each feature was formed. Variations in the integrated optical light curve could also be explained as differences in the boosting factor of the undelying jet, as its angle to the line of sight changes due to precession. During the last years, this model was successfuly applied to 3C273, 3C279 and OJ287 (Abraham & Carrara 1998, ApJ 496, 172; Abraham & Romero 1999, A&A 344,61; Abraham 2000, A&A 355, 915), using all the observations available at that time. Since then, a considerable number of high quality, closely spaced observations became available for these sources. We re-analized the precessing model for these quasars, taking into account the new observational data, as well as the new cosmological constants determined by WMAP.

Observational effects of black hole binary systems in AGNs
High-resolution radio maps have shown that several radio-loud objects exhibit a complex structure: a relativistic jet formed by several superluminal components emanating from a stationary core, which is thought to harbour the central engine that powers the AGN phenomena. In some cases, jet components are observed being ejected with different apparent proper motions and directions. Sometimes, these sources also present long-term periodic variability at optical wavelengths. In this work, we select some objects that exhibit these characteristics and interpret them as due to jet precession. Assuming that precession is induced by a secondary supermassive black hole in a non-coplanar orbit in relation to the primary accretion disk, we estimated some physical parameters of the binary system, such as the separation between the black holes and limits for their masses.

Quasar Atmospheres: The next level of Unification
The canonical Black Hole/Accretion Disk/Relativistic Jet paradigm of quasars is naked. That is it has no place for the veiling gas and dust that produces the wealth of sometimes confusing atomic emission and absorption features seen in Quasar/AGN spectra throughout the X-ray and the UV/optical/near-IR bands.
I will summarize the evidence that these atomic features are strongly interconnected, sufficiently so to form a "Quasar Atmosphere". By combining constraints that come from considering the BELs, NALs, Warm Absorbers, BALs, and scattering phenomena to be different manifestations of the same quasar atmosphere I find that we build up a simple coherent unified paradigm that points strongly toward a physical basis for the quasar atmosophere.
Fundamental to this unification is the concept of a disk wind. Several teams have modelled disk winds both radiation line driven and magnetically confined, centrifugally driven winds. The quasar atmosphere paradigm usefully constrains these models and can be used to separate some of the crucial physics from the incidental effects.
A quasar wind connects the disk to the surrounding environment. As we understand quasar atmospheres more we can work both outward to study the effects of the quasar winds on the host galaxy and the larger scale environment, and back to the physics of the accretion disk that is capable of emitting such winds, so leading us toward a complete physics theory for quasars.

Electrodynamics Around Magnetized Black Holes
The present status of Wald and Ernst's procedures to study black holes immersed in external magnetic fields is reviewed and compared. Then, we present (for any value of the external magnetic field parameter) a set of analytical equations to obtain the electromagnetic fields associated with a magnetized Kerr-Newman black hole. As an application, we obtain for a weakly magnetized charged and rotating black hole its associated electromagnetic fields, total charge, four-vector potential, and magnetic flux. The fact that these results may provide a physical insight in the understanding of active galactic nuclei and jets is briefly discussed.

Resolving the inner regions of scintillating radio AGN
The compact components of quasars and BL Lacs exhibit intraday radio variability due to scintillation when observed through the ionized medium of our Galaxy. In this talk I will describe the use of this phenomenon to model the microarcsecond scale components in total and polarized flux density. This method provides an angular resolution which cannot be obtained with any other direct imaging instruments at present, and has a potential to give a unique insight into the structure and strength of magnetic fields in the most inner regions of AGN.

Blazars: separating physics from selection effects
Blazar is a term commonly used to denominate radio-loud AGN whose continuum emission spreads across all the electromagnetic spectrum, and whose Spectral Energy Distribution (SED) can be modelled by two broad components: one attributed to synchrotron emission, and the other to Inverse Compton. In recent years it has been suggested that blazars can be unified according to a single parameter, the bolometric luminosity, a claim based on the apparent correlation between radio luminosity and the frequency at which the synchrotron emission peaks. In this contribution the possibility that this correlation arises as a result of selection effects is discussed, and new data to support this idea is presented.

Is There an ADAF in AGNs with Double-Peaked Balmer Lines?
To examine the prediction that the broad-line radio galaxies (BLRGs) with double-peaked Balmer lines harbor an advection-dominated accretion flow (ADAF) in their nuclei, we investigate emission line flux ratios of the narrow-line regions (NLRs) which are photoionized by nuclear continuum radiation. We compiled data from the literature and have found that the BLRGs with the double-peaked Balmer emission exhibit larger flux ratios of both [O I]/[O III] and [O II]/[O III] than the BLRGs without the double-peaked Balmer emission. To examine whether these properties are attributed to the difference in the SED of the ionizing radiation between the BLRGs with and without the double-peaked Balmer emission, we have performed photoionization model calculations using two types of input continuum radiation; one has the strong big blue bump which is expected for standard optically thick accretion disks and the other does not exhibit a strong big blue bump as expectedm for optically thin ADAFs. We have found that the data of the BLRGs with the double-peaked Balmer lines are consistent with the models adopting the SED without a strong big blue bump, while the data of the BLRGs without the double-peaked emission lines are well described by the models adopting the SED with a strong big blue bump. This result supports the idea that the double-peaked Balmer lines arise at an outer region of an accretion disk which is illuminated by an inner, geometrically thick ADAF.

Accretion flows in Sgr A* and Low Luminosity Active Galactic Nuclei
The recent observations (Genzel et al. 2003; Ghez et al. 2003) of the best studied galactic nuclei -- that of the Milky Way -- showed that the nuclear star cluster Sgr A* contains at least two sub-parsec rings of young massive stars. Most likely these stars were formed by the gravitational instability in a massive accretion disk that existed in Sgr A$^*$ as recently as $\sim 107$ years ago. We propose that a ``tiny'' inactive remnant of the disk is still present in the center of our Galaxy. We show that the presence of such a disk may solve two major mysteries of Sgr A$^*$: why there seems to be very little accretion onto the black hole now and also what produces frequent and strong X-ray and near infra-red flares. The first problem is resolved by realization that the accretion of the hot gas observed near Sgr A* may be stopped by a catastrophic thermal conduction cooling, when the hot flow gets ``frozen'' and hence collapses onto the inactive disk. X-ray and NIR flares are emitted due to impacts by thousands of stars and possibly stellar mass black holes onto the inactive disk.  Finally, we discuss what these findings may imply for the bigger picture of accretion cycles in Low and high Luminosity AGN.

X-ray Observations of Relativistic Accretion Disks in AGN
We compare the X-ray spectra of three active galactic nuclei observed with XMM-Newton. Two of the galaxies, Mrk 766 and NGC 4051, show evidence for emission from a relativistic, photoionized accretion disk. The third galaxy, 3C 120, has a much weaker reflection spectrum in hard X-rays, but has a similar soft X-ray excess. This difference may be associated with the presence of a strong relativistic jet in 3C 120.
The relativistic emission line profiles indicate emission from the inner accretion disk, which peaks at R < 1.6 GM/c2 in the case of NGC 4051. Emission from highly ionized iron and oxygen imply an origin in the photoionized surface of the accretion disk. These emission lines allow us to constrain densities and abundances in the accretion flow, just outside the radius where it plunges into the black hole.

The Synchrotron Spectrum Of Powerful Radio Galaxies
Observational analyses of the synchrotron spectrum and spectral indices of radio galaxies can provide useful information and help develop models of the energy distribution, acceleration mechanism and transport of relativistic electrons as they are 'injected' into the diffuse lobe regions which are characteristic of radio galaxies.
A sample of powerfull radio galaxies from the 3CRR survey have been investigated in which some important source properties pertaining to the propagation and ageing of the relativistic electrons have been derived.  Most sources exhibit spectral steepening towards the outer lobe regions, with spectral changes which are basically consistent with synchrotron ageing arguments which have been used to determine the ages of sources in the sample.


Review - J.Gallimore
Review - B.Peterson
Review - B.Fosbury

Dust emission from AGN -- support for unified schemes
Unified schemes of active galactic nuclei (AGN) require an obscuring dusty torus around the central source, giving rise to Seyfert 1 line spectrum for pole-on viewing and Seyfert 2 characteristics in edge-on sources. Although the observed IR is in broad agreement with this scheme, numerous attempts to model the torus emission with continuous dust distributions could not explain some puzzling observational results. While x-ray observations reveal a large range of torus column densities, the observed IR spectral energy distributions (SEDs) show only a moderate variation. Type 2 sources display the typical 10 micron silicate feature in absorption, but it is never deep and its depth doesn't correlate with column density inferred from x-ray observations. The feature is absent altogether in type 1 sources, even though the dust is presumably the same in both types of AGN.
In this talk I show that these problems find a natural explanation if the dust is contained in about 5--10 clouds along radial rays through the torus. The spectral energy distributions (SED) of both type 1 and type 2 sources are properly reproduced from different viewpoints of the same object if the optical depth of each cloud is above ~ 60 at visual wavelengths and the clouds' mean free path increases roughly in proportion to radial distance.

Dusty and molecular environment of the AGN in NGC1068
We present an analysis of the dusty and molecular emission around the AGN in NGC1068. (1) Using a broad range of dusty torus simulations, we show that the nuclear NIR-MIR SED of NGC1068 is compatible with a broad range of models. Hence, the SED alone does not constrain the geometry of the torus, and spatially resolved information must be used for the modelling of the torus. (2) We present a model for the molecular emission observed perpendicularly to the axis of the ionizing cone: a simple configuration where the 'large scale' molecular disk is slightly tilted with respect to the central Compton absorber allows to reproduce the complex morphology of the H2 and, to a some extent CO emission.

Probing the ionization structure of the extended NLR in NGC 4151
There is growing evidence that the extended soft X-ray emission observed in nearby heavily obscured AGN are dominated by of photoionized emission lines that originate in low temperature (~40,000 K) gas in the extended Narrow Line Region (NLR). We present the results of recent XMM-Newton observations of NGC 4151 with a total exposure time of ~125ks. The RGS spectrum of NGC 4151 is extremely rich in emission lines and radiative recombination continua with no strong evidence for any underlying continuum emission. The spectrum of NGC 4151 is remarkably similar to those of NGC 1068 and Mrk 3. The spectra are modeled in terms of photoionized and photoexcited gas in the extended NLR of the source and accurately define the ionization state of the material in the ionization cones.

A remarkable case of line-locking

The spectrum of the quasar HE2347-4342 shows a remarkable z_abs ~ z_em system. More than 20 absorption lines can be identified as CIV 1548 or 1550A. Amongst them, 5 CIV 1548/1550 doublets are separated in velocities by a multiple (= 1,2,3,4) of the velocity difference between the 1548 and 1550 lines. Other sets of doublets have a similar velocity distribution. This absorption system therefore shows a clear case of line-locking. Comparison between spectra taken several years apart do not show variations in velocity or line strengths. Quasars showing line-locking in their (narrow line) z_abs ~ z_em systems are not uncommon.


Review - S.Jogee

Cid Fernandes
The Low-Luminosity End of the Starburst-AGN Connection: The role of stellar processes in gas ionization in LINERs and Transition Objects

Fuelling of the central kiloparsec: bar-induced inflow and long-term stellar mass-loss in N-body models
We present 3D N-body simulations of spiral galaxies including effects of long-term mass-loss from low and intermediate-mass stars. We estimate how this gas supply from bulge and disk stars can be important for the mass budget and dynamics of the central kiloparsec and speculate about its impact on host galaxy and AGN evolution.


Review - N.Brandt
Review - O.Almaini

The XMM Newton 2df Survey
We present the spectral analysis of the sources detected in 18 shallow (5- 10 ks) XMM fields. These fields have been coverd by the 2df spectroscopic survey and also by the SDSS survey. About 300 sources have been detected in the 0.5-8 keV band. We discuss the optical identifications and the Xray spectral properties of our sample.

The Relation of Radio Quiet Quasars to Galaxy Clusters at z < 0.3
We investigate whether radio-quiet quasars (RQQs) with $z < 0.3$ (and >predominantly of low luminosity) are located preferentially in specific >regions with respect to the centers and boundaries of neighbouring galaxy >clusters. This way of characterising the environment of RQQs differs from >previous studies, which relied on the galaxy excess statistics within small >radii around the quasars. For the detection of galaxy clusters we use a >robust, semi-parametric method based on a maximum likelihood estimate applied >to Voronoi tessellation and enhanced by a colour-cut approach, allowing >boundary determination and redshift estimates. We find that most of the RQQs >reside within 3$h^{-1}$~Mpc of the centre of a galaxy cluster with comparable >redshift and that none of them lies in the core itself. About $20\%$ of the >investigated quasars reside between two galaxy clusters, which are possibly >at an early stage of merger. Consequently, we suggest that quasars found in >rich environments are associated with cluster mergers whereas those found in >poorer environments are associated with infall towards a cluster. We discuss our findings >in the context of existing quasar formation models and suggest that at least two >formation mechanisms co-exist. Additionally, we confirm, using multiple data >sets, that low-redshift quasars follow a narrow channel of width $\sim >10h^{-1}$ Mpc around the large-scale structure (LSS) traced by galaxy >clusters, in agreement with the first report of this effect by S\"{o}chting, >Clowes \& Campusano (2002).

The Role of Gas in the Merging of Massive Black Holes in Galactic Nuclei.
Using high-resolution SPH numerical simulations, we investigate the effects of gas on the inspiral and merger of a massive black hole binary. This study is moti vated by both observational and theoretical work that indicate the presence of l arge amounts of gas in the central regions of merging galaxies. N-body simulatio ns have shown that the coalescence of a massive black hole binary eventually sta lls in a stellar background. However, our simulations suggest that the massive b lack hole binary will finally merge if it is embedded in a gaseous background. Our work thus supports scenarios of massive black hole evolution and growth wher e hierarchical merging plays an important role. The final coalescence of the bla ck holes leads to gravitational radiation emission that would be detectable up t o high redshift by LISA.

Determining the Formation Environment of SMBH Using the High-z AGN-Galaxy Cross-Correlation
Evidence for a fundamental connection between galaxy formation and the formation of supermassive black holes (SMBH) continues to grow.  At redshift three, the universe was only 2 billion years old and still in the early stages of galaxy formation.  I will describe a VLT-VIMOS survey designed to study the high-redshift SMBH-galaxy connection through two methods:  1.  measuring the spatial cross-correlation of Quasars and Lyman break galaxies and 2. determining the fraction of Lyman break galaxies whose spectra reveal lower-luminosity AGN.


Black hole mass estimations for different types of AGN
Supermassive black hole is essential for AGN activities. However, how to accurately estimate the black hole mass in AGN is still a big challenge to astronomers. In this presentation I will summarize several methods that have been frequently adopted in deriving the black hole masses for various types of AGN, compare the advantages and disadvantages of these techniques and mention some possible improvements of them. In addition, I will simply address some important issues in AGN study that are closely related to the black hole mass estimation, such as the dichotomy of radio-loud and radio-quiet AGN, the difference between broad line and narrow line AGN, the accretion disk structure of AGN and the relation between black hole and galaxy formation.

The evolution of optically faint AGN
I present results from the deep wide-field COMBO-17 survey and its HST imaging follow-up GEMS. We have mapped the AGN luminosity function and its evolution between z=1 and z=5 down to apparent magnitudes of R<24, providing a substantial sample of optically selected low-luminosity Seyfert-type AGN at high redshifts. We detect a well-defined maximum in the AGN space density around z=2, followed by a gradual downturn towards higher redshifts. There are indications that the location of the maximum actually depends on luminosity, especially when folding in results from recent high-luminosity QSO surveys. For the first time we are able to constrain the faint-end slope of the LF sufficiently well that the total UV luminosity production density can be integrated without extrapolation. As part of the GEMS project, we have secured deep HST-ACS images of some 100 AGN selected from the COMBO-17 sample, enabling us to assess the evolution of host galaxy properties with cosmics time, such as merger fraction and dominant stellar populations.


Review - C.Lidman
Review - M. Smith