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October 13, 2004
Mass Loss by X-ray Winds in Active Galactic Nuclei
Abstract: We consider a small sample of five type-I active galactic nuclei (AGN) which were observed with Chandra/HETG resulting in high S/N X-ray spectrum. We are able to estimate the mass loss rates and kinetic luminosities associated with the highly ionized outflowing gas in those objects and study its physical properties. Our conclusions are as follows: 1) All objects show signatures for a very high ionization outflow. 2) There is a strong indication that the flows in all objects are multi-phase with little or no kinematic differences between different phases. 3) The X-ray spectrum is consistent with such flows being thermally driven from pc scales and are therefore not associated with the inner accretion disk. 4) The underlying hard X-ray spectrum yields a consistent photon index of ~1.6 for all objects emitting below their Eddington rate while an additional soft X-ray component is required for some of them. Also, there is no clear indication for a broad relativistic iron line in any object. 5) The physical properties of the flow are similar for all objects and a coherent picture emerges concerning its physical properties. 5) The mass loss rates are of the order of 0.1 solar masses per year and the kinetic luminosities are \<\<1\% of the bolometric luminosity of the AGN. We discuss the implications of our results to AGN structure and AGN interaction with the environment.
Feedback and Non-Equilibrium Evolution of the Warm-Hot Intergalactic
Medium
Abstract: After briefly reviewing our current understanding of the
radio properties of black hole X-ray binaries over different accretion regimes, I will report on
the discovery of a low surface brightness jet-blown bubble around
the 10 solar mass black hole in Cygnus X-1. It is estimated that, in order to
sustain the observed emission of the bubble, the jet of Cyg X-1 has to carry a
kinetic power that is a sizable fraction of the liberated accretion
luminosity.
The Development of the ACIS Instrumsnt on Chandra
Abstract: The ACIS instrument on Chandra began as a developmental
offshoot of the WFPC being built for HST. I will go through the various phases of the improvements to this instrument for X-ray applications and how the X-ray work benefited the optical.
Finally, I will talk about the science programs that have grown out of the GTO
program.
Whispering through whipped cream: Dissipation of weak shocks and sound
waves in a filamentary intracluster medium
Radio galaxies have long been suspected as the heat sources in Galaxy
clusters that can counterbalance catastrophic cooling. However, the
weak shocks and sound waves excited by sub-sonic inflation and buoyancy
of radio lobes are, by themselves, very inefficient in dissipating the
energy they carry. But the very presence of relativistic plasma bubbles
in the cluster gas provides a simple catalyst to tap into this energy
through the creation of a vortex field upon their interaction with the
waves. I will show how this mechanism can contribute significantly to
the heating of galaxy clusters.
Chandra and XMM observations of distant galaxy clusters
We present the results of an analysis of 67 clusters of galaxies in the
redshift range 0.1-0.9 (median=0.4). We give an overview of the sample,
which includes a diverse array of galaxy clusters and investigate some of
its statistical properties with an emphasis the scaling relations between
cluster properties. We then focus on two remarkable high redshift systems
with contrasting properties.
X-ray observations through the stages of Classical Novae
A Classical Nova explosion occurs on the surface of a white dwarf accreting
material from a main sequence companion. This material supplies the energy for
the explosion by hydrogen burning bursting out when ignition conditions
are reached. Numerical simulations of the explosion have been carried
out and important constraints for the models can be obtained from X-ray observa
tions.
The explosion itself has never been observed in X-rays and during some months
after the explosion any X-ray emission is absorbed by surrounding material ejec
ted
by the explosion. During a phase of constant bolometric luminosity the expandin
g shell
is transparent to X-rays and X-ray spectra reflect the conditions of the nuclea
r
burning and the expanding shell. A strong, broad emission peak originates from
ongoing
nuclear burning and recent Chandra high-resolution X-ray grating spectra show
absorption lines from the expanding shell. Very similar spectra have been obser
ved
from Super-Soft X-ray Sources, likely candidates for predecessors of SN Ia expl
osions.
The spectra of Classical Novae and Super-Soft X-ray Sources are awaiting to be
analysed
with sophisticated atmospheric codes like PHOENIX. In the very late phase, afte
r nuclear
burning has switched off, one can see an emission line spectrum produced in the
shell
by collisional ionisation and excitation followed by radiative decays.
I give an overview of the potential in high-resolution X-ray spectroscopy. We
can
learn about the velocity structure, the temperature conditions, evolution of op
acity,
and elemental composition. These are important ingredients to feed the numerica
l models
to understand the development in detail and to find out which conditions can ac
tually
lead to a SN Ia explosion.
Supernovae and Gamma-Ray Bursts Powered by Hot Neutrino-Cooled Coronae
Although they were discovered more than 30 years ago, short lived
gamma-ray bursts are still a mystery. All that we can be confident
about is that they involve compact objects and relativistic
plasma. Current ideas and prospects are briefly reviewed. There are,
fortunately, several new observations that could help clarify the
issues.
Neutron loaded Gamma Ray Bursts fireballs
I present here the theory of a relativistic neutron-loaded outflow in
gamma-ray bursts. The focus is on its early stages, before deceleration by
a surrounding medium. The outflow has four components: radiation,
electrons, protons and neutrons. The components interact with each other
and exchange energy as the outflow expands. The presence of neutrons
significantly changes the outflow evolution. Before the neutron-proton
decoupling, friction between the neutron and proton components increases
their temperatures by many orders of magnitude. After the decoupling, the
gradual neutron decay inside the outflow has a drag effect on the protons
and reduces their final Lorentz factor.
AGN feedback in clusters
Recent observations show a multitude of physical effects that occur when
AGN interact with the ambient ICM. An understanding of these effects is
essential for all models of feedback, which is believed to be the crucial
ingredient for the baryonic part of galaxy formation. We have performed a
series of cosmological simulations of galaxy clusters on an adaptive mesh,
which include physics that is usually neglected in these types of
simulations. In particular, we include thermal conduction and viscosity.
These effects are likely to play an important role in dissipating the
mechanical energy of the AGN, and therefore have implications for the
cooling flow problem. We also show synthetic data, showing how our
simulations would appear when observed with Chandra, including the proper
background and response functions.
Taotao Fang
Berkeley
Abstract: Numerical simulations have shown that at the present epoch a
significant fraction of baryons should be found in the warm-hot
intergalactic medium (WHIM) via UV/X-ray observations. We compute the
evolution of the WHIM by (1) including galactic superwind feedback
processes from galaxy/star formation, (2) explicitly computing major metal
species in a non-equilibrium way, and (3) significantly increasing mass
and spatial dynamic ranges in the simulation. Our simulation shows that
feedback processes and non-equilibrium calculations have dramatic impact
on the evolution and distribution of major metal species, and therefore
provide strong constraints on the current models of the IGM when compared
with observational data.
Elena Gallo
Relativistic Jets from Stellar Black Holes
Gordon Garmire
ACIS IPI, Evan Pugh Professor of Astronomy and Astrophysics,
Penn State University
Sebastian Heinz
MIT
Ben Maughan
SAO
Jan-Uwe Ness
Enrico Ramirez-Ruiz
Elena Rossi
Mateusz Ruszkowski
Colorado
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