Abstracts of Talks
(as of 01 August 2013)
ALL TALKS HAVE A (MAXIMUM) LENGTH OF 30 MINUTES, DISCUSSION INCLUDED (SHORTER IS O.K.).
The abstracts are sorted in alphabetical order of the first author. If the presenting author is not the first author, the name
is underlined.
Viscous time lags between starburst and AGN activity
Marvin Blank (1), Wolfgang J. Duschl (1,2)
1 Astrophysik Kiel, Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel;
2 Steward Observatory, The University of Arizona, Tucson, AZ, USA
Recent observations indicate a time lag of order of some 100 Myr between starburst and AGN activity in galaxies.
Dynamical time lags have been invoked to explain this. We extend this approach by introducing a viscous time lag the
gas additionally needs to flow through the AGN's accretion disc before it reaches the central black hole. Our calculations
reproduce the observed time lags and are in agreement with the observed correlation between black hole mass and
stellar velocity dispersion.
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Extended LINER-like Emission in the NuGA source NGC 5850
Marcus Bremer - University of Cologne; Julia Scharwächter - Observatoire de Paris; Andreas Eckart -
University of Cologne; Monica Valencia-S. - University of Cologne; Jens Zuther - University of Cologne;
Francoise Combes - Observatoire de Paris; Santiago Garcia-Burillo - Observatorio Astronómico Nacional
(OAN) - Observatorio de Madrid
The role of low ionization nuclear emission region (LINER) galaxies within the picture of active galactic nuclei (AGN) has
been controversial. It is still not clear whether they host an AGN in a low accretion mode, or they are not active at all but
dominated by alternative ionization mechanisms, namely shocks, winds/outflows or photoionization by a post asymptotic
giant branch (p-AGB) stellar population. The detection of extended LINER-like mission was often taken as evidence for
ionization by stellar components but this is not undisputed either.
Using optical integral field spectroscopy (FOV: 21”x19”), we find in the central ~4 kpc of NGC 5850 (z = 0.0085)
extended LINER-like emission. I will show that this emission is not dominated by an AGN but mainly produced by
distributed ionization sources, either post-AGB stars or slow shocks. Further, I present the peculiar kinematics of this
double-barred early-type spiral galaxy which are likely caused by lopsided gas distribution.
A very brief report on the results of my current project will be given as well.
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Thermal disk spectra at high accretion rates
M. Bursa - Astronomical Institute, Academy of Sciences, Prage, Czech Republic
One of the outcomes of x-ray continuum spin measurements is that it gives us the applicability limits of the standard thin
disk model. High luminosity disks cannot be fitted by this model as the observed spectra are significantly softer than the
one predicted by the model. The talk will make a short overview of the present state of the subject and outline how high
luminosity disks may fit into the picture.
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A low-luminosity type-1 QSO sample - Near-infrared study of nearby AGN host
galaxies -
Gerold Busch (1), Jens Zuther (1), Monica Valencia-S (1), Lydia Moser (1), Andreas Eckart(1,2), Julia
Scharwaechte (3), Dimitri A. Gadotti (4), and Lutz Wisotzki (5)
1 I. Physikalisches Institut, Universität zu Köln; 2 Max-Planck-Institut für Radioastronomie; 3 Observatoire
de Paris, LERMA; 4 European Southern Observatory, Chile; 5 Leibniz-Institut für Astrophysik Potsdam
The properties of the host galaxies of quasi-stellar objects are essential for the understanding of the suspected
coevolution of central supermassive black holes and their host galaxies. The low-luminosity type-1 QSO (LLQSO)
sample contains the 99 nearest type-1 QSOs (redshift z<=0.06) from the Hamburg/ESO survey for bright UV-excess
QSOs. These objects are ideal targets because of their higher space density compared to QSOs with higher luminosity at
same distance and their smaller cosmological distance allowing for detailed structural analysis.
We have observed 20 galaxies from the LLQSO sample in the near-infrared and performed aperture photometry and
bulge-disk-bar-AGN decomposition with the BUDDA code. The parametric models are used to study the morphology of
the host galaxy and estimate stellar masses.
We find the low-luminosity QSOs to establish a "bridge" between the local Seyfert population and more distant, more
powerful QSOs. However, the observed active galaxies seem not to follow the M(BH)-L(bulge) relations of inactive
galaxies.
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Multiple accretion events as a trigger for Sagittarius A* activity
B. Czerny, D. Kunneriath, V. Karas and T. K. Das - Astronopmical Institute, Academy of Sciences, Prage,
Czech Republic
Gas clouds are present in the Galactic centre, where they orbit around the supermassive black hole. Collisions between
these clumps reduce their angular momentum, and as a result some of the clumps are set on a plunging trajectory.
Constraints can be imposed on the nature of past accretion events based on the currently observed X-ray reflection from
the molecular clouds surrounding the Galactic centre. We discuss accretion of clouds in the context of enhanced activity
of Sagittarius A* during the past few hundred years. We put forward a scenario according to which gas clouds bring
material close to the horizon of the black hole on about 0.1 parsec scale.
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X-ray polarization and strong gravity
Michal Dovciak - Astronomical Institute, Academy of Sciences, Prage, Czech Republic
The polarization properties of the light coming from regions close to the black hole are influenced by fast velocities of the
emitting matter and strong gravitation. Individual relativistic effects as Doppler shift, gravitational redshift, aberration, light
bending and rotation of the polarization vector along the light ray, manifest themselves through the total amplification of
the intensity (transfer function), total energy shift and change of the polarization angle. The importance of these three
functions on the observed polarization properties of the innermost accretion disc will be shown in two cases - the
Comptonized thermal disc emission and disc reflection of the radiation from the point source on the rotational axis.
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To be or not to be: The sub-Eddington limit for AGN accretion
Wolfgang J. Duschl (1,2), Tommy Breslein (1)
1 Astrophysik Kiel, Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel
2 Steward Observatory, The University of Arizona, Tucson, AZ, USA
Recently, for the most luminous AGN evidence was found for a luminosity limit below the Eddington luminosity. The
physical meaning of this so-called sub-Eddington limit, however, is still an issue of debate. We present new models of the
evolution of AGN black holes and their accretion disks and demonstrate that the so-called sub-Eddington limit is caused
by the evolutionary time scales rather than by a new physical mechanism.
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The Galactic Center as a Paradigm for Low Luminosity Nuclei?
The K-band identification of the DSO/G2 source from VLT and Keck data
Andreas Eckart et al. - I. Physikalisches Institut, Universität zu Köln
The super-massive 4 million solar mass black hole (SMBH) SgrA* shows flare emission from the millimeter to the X-ray
domain. The nucleus of the Milky Way has properties (stellar cluster, young stars, molecular gas and an accreting SMBH)
that resemble those of currently higher luminous Low Luminosity Active Galactic Nuclei. A detailed analysis of the
infrared light curves shows that the flares are probably generated in a single-state process forming a power-law
distribution of the flux density. Near-infrared polarimetry shows signatures of strong gravity that are statistically significant
against randomly polarized red noise. Details of the emission mechanism are discussed in a synchrotron/self-Compton
model. SgrA* also allows to study the interaction of the SMBH with the immediate interstellar and gaseous environment
of the central stellar cluster. Through infrared imaging of the central few arcseconds it is possible to study both inflow and
outflow phenomena linked to the SgrA* black hole.
In this context we also discuss the newly found dusty object that approaches SgrA* and present a comparison between
recent Keck and VLT K-band data that clearly supports its detection as a ~19m K'-band continuum source.
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The F-GAMMA program: AGN variability and the detection of significant radio/gamma-
ray correlations
L. Fuhrmann, E. Angelakis, J. A. Zensus, T. P. Krichbaum, I. Nestoras, N. Marchili, V. Karamanavis, I.
Myserlis, C. Fromm (MPIfR), H. Ungerechts, A. Sievers (IRAM), S. Larsson (Stockholm University), J. Chiang
(SLAC), V. Pavlidou (Univ. of Crete)
Variability studies furnish important clues about the size, structure, physics and dynamics of the emitting regions making
AGN/blazar monitoring programs of uttermost importance in providing the necessary constraints for understanding the
variability and energy production in these sources. The launch of the Fermi Gamma-ray Space telescope (Fermi-GST) in
June 2008 and its `all-sky monitor' capabilities has introduced a new era in the field of AGN physics providing for the first
time gamma-ray light curves resolved at a variety of time scales for a large number of AGN. In order to fully exploit these
opportunities, the complementary 'F-GAMMA program' was initiated in 2007. This long-term program is monitoring
contemporaneously the variability and spectral evolution of about 60 Fermi bright sources at frequencies between 2.6
and 345 GHz using the Effelsberg 100-m, IRAM 30-m and APEX 12-m telescopes including polarization at several
bands. After a short overview of the program, I will review interesting results emerging from the first 6 years of F-GAMMA
monitoring including variability and spectral characteristics of the sample, shock-in-jet modeling and the detection of
significant radio/gamma-ray correlations.
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APEX/sub-mm observations of the Galactic Center
Macarena Garcia Marin - I.Physikalisches Instutut, University of Cologne, Germany
We present APEX/sub-mm observations of the Galactic Center designed to study SgrA*, the radiative counterpart of the
4x106 Msun black hole located at the center of the Milky Way. SgrA* exhibits strong variability from the radio to the X-ray
domain, and these observations will help to characterize its energy flow and model its variable emission. The special star
forming conditions of the region, and events such as infalling stars are likely to play a role in the black hole variability.
This and other mechanisms responsible for the observed emission will be discussed.
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X-ray flaring activity of Sgr A*
Nicolas Grosso - Observatoire Astronomique de Strasbourg; 11 rue de l'Universite; 67000 Strasbourg,France
Thanks to the current generation of X-ray satellites, flaring activity is observed from Sgr A* which was thought to be a
dormant supermassive black hole. I will present an overview of its X-ray properties observed during the last decade.
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The dusty heart of AGN revealed by IR interferometry
Sebastian Hönig - University of California, Santa Barbara, CA, USA; Astrophysik Kiel, Institut für
Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel
Recently, for the most luminous AGN evidence was found for a luminosity limit below the Eddington luminosity. The
physical meaning of this so-called sub-Eddington limit, however, is still an issue of debate. We present new models of the
evolution of AGN black holes and their accretion disks and demonstrate that the so-called sub-Eddington limit is caused
by the evolutionary time scales rather than by a new physical mechanism.
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The Seyfert 1.5 galaxy NGC 4151 in the Infrared
Christof Iserlohe - I. Physikalisches Institut, Universität zu Köln
We present H- and K-band data from the inner arcsecond of the Seyfert 1.5 galaxy NGC 4151 obtained with the adaptive
optics assisted near-infrared imaging field spectrograph OSIRIS at the Keck Observatory. The angular resolution is about
a few parsecs on-site and thus competes easily with optical images taken previously with the Hubble Space Telescope.
We present the morphology and dynamics of the narrow line region (NLR) as traced by emission of [FeII] lambda1.644
mum and compare the observed dynamics with models that propose simple ejection or acceleration in a hollow bi-conical
outflow, the interplay between plasma ejected from the nucleus (as traced by 21 cm continuum radio data) and hot H2
gas and [FeII] and characterize the detected nuclear HeI lambda 2.058 mum absorption feature as a narrow absorption
line (NAL) phenomenon.
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Star Formation in the vicinity of Sgr A*
Behrang Jalali, Andreas Eckart et al. - I. Physikalisches Institut, Universität zu Köln
Formation of stars close to black holes at the center of galaxies is often considered not plausible. It is assumed that the
strong gravitational field of a massive black hole disrupts the parent molecular cloud and prevents star formation.
Surprisingly, young stars (less than 1 Myr to a few Myr) have been observed across various distances (0.1 to 0.5 pc)
close to the Milky Way's central black hole, Sgr A*. The observed young stars are in different configurations such as
warped disks as well as in some distinct smaller groups.
In this work we focus particularly on small young stellar groups such as IRS 13N, 0.1 pc away from Sgr A*, that is
suggested to contain about five embedded massive young stellar objects (< 1 Myr). We perform hydrodynamical
simulations to follow the evolution of molecular clumps orbiting around Sgr A*, to reproduce and constrain conditions of
such young stellar groups.
In our simulations, supposing a clump evolves in a highly eccentric orbit, strong shear from the black hole perpendicular
to the clump's orbit (in two-dimensions) causes gas densities to increase to values required for star formation, more
significantly than in the case of isolated clump with the same initial conditions. There are more numerous and more
massive protostars in a highly eccentric orbiting clump, with respect to isolated model.
I will present details of our modeling and results, including some animations and statistical properties of protostars such
as initial mass function, formed stellar groups and SFE depending on the orbit of parent clump. Furthermore, based on
our modeling we speculate about possible origin of the observed G2/DSO gas cloud moving towards Sgr A*.
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Dusty tori and organised magnetic fields around black holes
V. Karas - Astronopmical Institute, Academy of Sciences, Prage, Czech Republic
Close to a supermassive black hole, electromagnetic and gravitational forces act together to produce equilibrium
configurations of fluid accretion discs and tori. Farther out, dust particles can exist. These are thought to be embedded in
rarefied plasmas, where they can acquire a (small) electric charge by effects of irradiation and charge separation in the
magnetic field. We will describe a new approach to construct such equilibria and discuss their properties in the context of
accreting black holes.
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Modeling the variable near-infrared emission from SgrA* with an orbiting hotspot
orbiting
Grischa Karssen (1), Michal Bursa (2), Andreas Eckart (1,3), Monica Valencia-S. (1), Michal Dovciak (2), and
Vladimir Karas (2)
1. I.Physikalisches Institut, Universitaet zu Koeln; 2. Astronomical Institute, Czech Academy of Sciences; 3.
Max-Planck-Institut fuer Radioastronomie
The near-infrared (NIR) emission of Sagittarius A* (Sgr A*), the source associated with the supermassive black hole at
the center of our galaxy, is polarized and highly variable. Correlations between intensity and polarimetric parameters of
the observed light curves compared with the predicted ones for different configurations, allow us to extract information
about the geometry of the radiating region. We assume that the flux variation in the light curves is produced by
overdense regions orbiting close to the marginal stable orbit, and use numerical simulations to trace the emission from
the disk to the observer in a Kerr spacetime. Here I present a report on the progress of the numerical code. In particular, I
compare the predicted polarization signatures from hot spots when an optically thick or an optically thin accretion disk is
considered.
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eMerlin and Subaru observations of NGC3718
Kostas Markakis, A. Eckart, J. Zuther, S. Nishiyama et al. - I. Physikalisches Institut, Universität zu Köln
NGC3718 is a highly inclined elliptical system with a warped atomic and molecular gas disk. It is often also referred to as
the northern Centaurus A yet it has no prominent radio jet. We gathered high angular resolution imaging data using the
eMERLIN interferometer at 18cm wavelength and the adaptive optics system at the Subaru telescope in the near-infrared
JHK bands. We report on properties of the NGC3718 nucleus that can be derived from these observations.
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'Galactic centers near and far: interferometric observations of 3 galaxies of the low
luminosity QSO Sample and of the Galactic Center (Sgr A*)'
Lydia Moser (1) , M. Krips (2), A. Eckart (1) et al.
1 I. Physikalisches Institut, Universität zu Köln; 2 IRAM, Grenoble, France
In my talk I will give you a short insight into my recent work which can be divided into two research topics related to black
holes, i.e. active galactic nuclei (AGN) and the Galactic Center.
In the first part of my talk I present interferometric observations of three barred galaxies from our low luminosity QSO
(LLQSOs) sample with the Submillimeter Array (SMA) in the CO line emission. Two of them can be classified as luminous
infrared galaxies (LIRGs) indicating high star formation activity and we find all three galaxies to be rich in molecular gas.
The region of CO emission is very compact, i.e. FWHM < 1.7 kpc, and only in one case the molecular gas also extends
along the galactic bar. From the two galaxies with a compact CO emission region, one shows signatures of an inflow. In
terms of redshift and activity level and luminosities our sample (nearby) can be found in the region between the NUGA
sample (local) and the PG QSO sample (less nearby).
The second part deals with the minispiral and the circumnuclear disk in the galactic center in the light of different
molecules and continuum bands. The maps result from observation at ~ 100 GHz, 230 GHz and 345 GHz obtained with
the Combined Array for Research in Millimeter-wave Astronomy (CARMA), the Submillimeter Array (SMA) and - for the
first time - with the Atacama Large Millimeter Array (ALMA). They trace molecular and ionized gas in the presence of
different physical conditions in the violent environment close to the supermassive black hole Sgr A*.
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X-ray observations of AGN
Delphine Porquet - Observatoire Astronomique de Strasbourg; 11 rue de l'Universite; 67000
Strasbourg,France
I will present an overview of recent X-ray observations of radio-quiet AGN over a wide range of luminosities. I will show
how the X-ray spectral properties of AGN allow us to probe the matter from the inner part of the accretion disc to the
outer molecular torus, as well as the spin of the supermassive black hole itself.
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High resolution observations of SDSS~J080800.99+483807.7 in the optical and radio
domain;
A possible example of jet-triggered star formation
Y. E. Rashed (1,2), J. Zuther (1), A. Eckart (1,3), G. Busch (1), M. Valencia-S. (1), M. Vitale (1,3), S. Britzen (3),
T. Muxlow (4)
(1) I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany; (2) Department
of Astronomy, Faculty of Science, University of Baghdad, 10071 Baghdad - Aljadirya, Iraq; (3) Max-Planck
Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany; (4) MERLIN/VLBI National Facility,
Jodrell Bank Observatory, University of Manchester, Macclesfield, Cheshire SK11 9DL, UK
SDSS J080800.99+483807.7 has been serendipitously discovered in MERLIN 18 cm observations to be a double-lobed
radio galaxy. As an optically faint source, basic information like redshift, linear size, and structure has been incomplete
until now. Double lobe radio galaxies are ideally suited to investigate the interaction of the individual components of the
radio structure with the intergalactic medium and the interstellar medium of the host galaxy. The optical counterpart in the
Sloan Digital Sky Survey is very faint. Therefore, no redshift information was available until now.
Aims. The goal of this work is to derive the main physical properties of SDSS J080800.99+483807.7 and study the
possible interaction between the radio jets and the interstellar medium of the host galaxy.
Methods. To achieve this goal, we used optical spectroscopy and radio interferometry. The radio data were obtained with
MERLIN at 18 cm and the optical data with the Multi-Object Double Spectrograph (MODS) at the Large Binocular
Telescope (LBT).
Results. The redshift of the galaxy is z = 0.2805 +/- 0.0003, resulting in a linear size of the observed radio structure of >
26.3 kpc. The optical line emission, infrared and radio continuum emission suggest a high star-formation activity. In
addition, we estimated the mass of the central black hole to be log MBH/Msun > 6.9.
Conclusions. The optical spectrum (MODS) as well as the optical images (SDSS) suggest that SDSS
J080800.99+483807.7 is an elliptical host galaxy. In combination with the overall radio structure we argue that the star
formation could be the result of the back-flow along the jet and the ISM of the host.
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NIR triggered phase referencing of the Galactic Center radio source SgrA* at 43 GHz
C. Rauch (1), A. Eckart (1,2), T. P. Krichbaum (1), K. Muzic (3) , E. Ros (2) , B. Shahzamanian (2) , and J. A.
Zensus (1)
(1) Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany; (2) I. Physikalisches
Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany; (3) European Southern Observatory,
Alonso de Córdova 3107, Casilla 19, Santiago, 19001, Chile
The compact radio source Sagittarius A* (Sgr A*) is commonly assumed to be associated with the super-massive black
hole (SMBH) of ~ 4.0 x106 Msun at a solar distance of ~ 8.0 kpc in the center of the Milky Way. Because of being about
one hundred times closer than the second nearest active galactic nucleus (M31) and having the largest projected
Schwarzschild radius on the sky this SMBH is the most interesting target to study the physics of these objects.
Sgr A* shows spontaneous flares at radio and millimeter wavelengths. These intensity outbursts appear on timescales
ranging from 1-2 hours (main-flares) down to 7-10 minutes (sub-flares). The currently most accepted models trying to
explain these flux variations are magnetic turbulence and adiabatic expansion. The best properties to investigate the
nature of this effect are the position, the morphology and the full width at half max (FWHM) Gaussian size of the compact
radio source Sgr A*.
Relativistic Magnetohydrodynamics simulations predict a constant size and shape of its emission region. If adiabatic
expansion would be causing the flares, a change of the morphology and/or FWHM would be observed. In case of an
orbiting or asymmetrically located (with respect to the emission center) expanding feature, a position wander will be
detectable. The closure phases would also be different from zero due the increased asymmetry of the source. A
correlation between NIR/X-ray and mm-flares together with a change in source morphology or size would provide strong
evidence for the adiabatic expansion model.
We present a 7 mm VLBI observing campaign, triggered for the first time by an observed VLT NIR flare of Sgr A* which
offers the possibility to discriminate between these models.
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Faint Point Sources and a Bowshock in the Central Parsec: An Infrared View
Nadeen Sabha - I. Physikalisches Institut, Universität zu Köln
We analyze highly resolved mid-infrared data of the Galactic Center. The N-band (8.6 mum & 13.04 mum) data were
obtained using the instrument VISIR on ESO's Very Large Telescope. They cover five GC targets; the central stellar
cluster, the Arches, Quintuplet cluster and regions in the Arched Filaments and Sickle. We study faint point sources within
these regions to obtain information on star formation, disk candidates, massive young stellar objects, accreting
intermediate massive black holes and stellar remnants. In addition, we investigate the alignment of a few dusty comet-
like objects inside the central parsec.
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Infrared polarized Light from SgrA*
Shahzamanian, Banafsheh et al. - 1. Physikalisches Institut, Universität zu Köln
In this presentation I will provide an overview of polarized near-infrared (NIR) observations of Sagittarius A* (SgrA*)
which is associated with the super massive black hole at the center of the Milky Way. The observations have been
carried out using NACO adaptive optics instrument at the VLT(ESO) and CIAO NIR camera on the Subaru telescope
(from 2004 to 2012). I will present several polarized flares that have been observed during these observations and the
statistical properties of NIR polarization of SgrA*. Linear polarization at 2.2 micron and its variations can help us to
constrain the physical conditions of the accretion process around this SMBH.
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Studying extremal energy shifts from accretion rings
Vjaceslav Sochora - Astronomical Institute of the Academy of Sciences of the Czech Republic
The X-ray emission from inner regions of an accretion disk around black holes provides wealth of information about
matter in extreme conditions. A spectral profile of radiation from a narrow circular ring has a characteristic double-horn
profile. Red and blue peaks of the profile are close to the extremal values of the energy shift. We describe a useful
approach to calculate the extremal energy shifts in the regime of strong gravity. We discuss if the radial structure of the
disk emission could be reconstructed using extremal energy shifts of the individual rings. For this purpose, we simulate
artificial data from a bright active galactic nucleus and show that the required sensitivity and energy resolution can be
reached with the proposed LOFT mission.
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Many reasons why Narrow Line Seyfert 1s are not a special class of Active Galactic
Nuclei
Monica Valencia-S. - I. Physikalisches Institut Universitaet zu Koeln
Due to their apparently extreme optical to X-ray properties, Narrow Line Seyfert 1s (NLSy1s) have been considered a
special class of active galactic nuclei (AGN). Here, we summarize observational results from different groups, to
conclude that none of the characteristics that are typically used to define the NLSy1s as a distinct group - from the,
nowadays called, Broad Line Seyfert 1s (BLSy1s) - is unique, nor ubiquitous of these particular sources, but shared by
the whole Type 1 AGN. I argue that selection biases might be responsible for the reported differences between NLSy1
and BLSy1 sources.
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Galaxy evolution across optical emission-line diagnostic diagrams.
M. Vitale(1,2), L. Fuhrmann(2), M. Garcia-Marin(1), J. Zuther(1), A. Eckart(1,2) and A. Hopkins(3)
1: I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany; 2: Max-Planck
Instutut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany; 3: Australian Astronomical
Observatory, P.O. Box 915, North Ryde, NSW 1670, Australia
Optical emission-line diagnostic diagrams have been proven as a useful tool to select AGN from large spectroscopic
surveys like the SDSS. A cross-correlation of the SDSS with the FIRST radio survey at 20cm allows us to study radio-
emitters with observed optical counterparts.
The triggering of radio AGN activity has been found to be a strong function of host galaxy properties and it is possibly
lineked to different stages of massive galaxy formation. Our work aims to a better understanding of the interplay between
optical and radio emission. In particular, we make use of Effelsberg 2.8 and 6cm data to calculate spectral indexes and
polarization degrees of the brightest sources of FIRST (~150 galaxies). We study the differences between star-forming
galaxies, composite galaxies, Seyferts and LINERs, looking for a galaxy evolutionary sequence accross the optical
emission-line diagnostic diagrams.
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GRAVITY, the 2nd Generation Interferometer for Galactic Center Observations
Senol Yazici et al. - I. Physikalisches Institut, Universität zu Köln
GRAVITY, the 2nd generation Very Large Telescope Interferometer (VLTI), is currently in the Integration Phase and will
be on sky early 2015. Providing an astrometric accuracy of ~10 µas its aiming to probe the space-time around SgrA*
down to a few RS. University of Cologne is contributing the Spectrometers in the Beam Combiner Instrument (BCI). I will
talk about the current status of the project.
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Models of the Gaseous-Dust Cloud G2 near the Galactic Center
Michal Zajacek, Vladimir Karas - Affiliation: Astronopmical Institute, Academy of Sciences, Prage, Czech
Republic
We will present models of a recently discovered cloud of gas and dust moving on a highly elliptical orbit near the central
black hole. We compare the scenarios with and without a star embedded in the cloud from a dynamical point of view.
Moreover, we discuss the effect of hydrodynamic drag acting on the dust component.
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