10,990 research outputs found
Broad Line Radio Galaxies: Jet Contribution to the nuclear X-Ray Continuum
It is shown that, for Broad Line Radio Galaxies the strength of the
non-thermal beamed radiation, when present, is always smaller than the
accretion flow by a factor < 0.7 in the 2-10 keV band. The result has been
obtained using the procedure adopted for disentangling the Flat Spectrum Radio
Quasar 3C 273 (Grandi & Palumbo 2004). Although this implies a significantly
smaller non-thermal flux in Radio Galaxies when compared to Blazars, the jet
component, if present, could be important at very high energies and thus easily
detectable with GLAST.Comment: 12 pages including 2 figures (4 files), ApJ accepte
Competing Glauber and Kawasaki Dynamics
Using a quantum formulation of the master equation we study a kinetic Ising
model with competing stochastic processes: the Glauber dynamics with
probability and the Kawasaki dynamics with probability . Introducing
explicitely the coupling to a heat bath and the mutual static interaction of
the spins the model can be traced back exactly to a Ginzburg Landau functional
when the interaction is of long range order. The dependence of the correlation
length on the temperature and on the probability is calculated. In case
that the spins are subject to flip processes the correlation length disappears
for each finite temperature. In the exchange dominated case the system is
strongly correlated for each temperature.Comment: 9 pages, Revte
Jets and outflows in Radio Galaxies: implications for AGN feedback
One of the main debated astrophysical problems is the role of the AGN
feedback in galaxy formation. It is known that massive black holes have a
profound effect on the formation and evolution of galaxies, but how black holes
and galaxies communicate is still an unsolved problem. For Radio Galaxies,
feedback studies have mainly focused on jet/cavity systems in the most massive
and X-ray luminous galaxy clusters. The recent high-resolution detection of
warm absorbers in some Broad Line Radio Galaxies allow us to investigate the
interplay between the nuclear engine and the surrounding medium from a
different perspective. We report on the detection of warm absorbers in two
Broad Line Radio Galaxies, 3C 382 and 3C 390.3, and discuss the physical and
energetic properties of the absorbing gas. Finally, we attempt a comparison
between radio-loud and radio-quiet outflows.Comment: To be published in the proceedings of High Energy Phenomena in
Relativistic Outflows III (HEPRO III, IJMPCS). 4 pages, 2 figure
XMM-Newton unveils the type 2 nature of the BLRG 3C 445
We present an observation of XMM-Newton that unambiguously reveals the
``Seyfert 2'' nature of the Broad Line Radio Galaxy 3C 445. For the first time
the soft excess of this source has been resolved. It consists of unobscured
scattered continuum flux and emission lines, likely produced in a warm
photoionized gas near the pole of an obscuring torus. The presence of
circumnuclear (likely stratified) matter is supported by the complex
obscuration of the nuclear region. Seventy percent of the nuclear radiation
(first component) is indeed obscured by a column density ~4*10^{23} cm^{-2},
and 30 % (second component) is filtered by ~7* 10^{22} cm^{-2}. The first
component is nuclear radiation directly observed by transmission through the
thicker regions. The second one is of more uncertain nature. If the observer
has a deep view into the nucleus but near the edge of the torus, it could be
light scattered by the inner wall of the torus and/or by photoionized gas
within the Broad Line Region observed through the thinner rim of the
circumnuclear matter.Comment: MNRAS Letters, in pres
The luminosity function of cluster galaxies. II. Data reduction procedures applied to the cluster Abell 496
We initiated a large project aimed to estimate the Luminosity Function of
galaxies in clusters and to evaluate its relation to cluster morphology. With
this paper we deem necessary to outline the general procedures of the data
reduction and details of the data analysis. The cluster sample includes the
brightest southern ROSAT all-sky survey clusters with z < 0.1. These have been
observed in three colours g, r, i, and mapped up to a few core radii using a
mosaic of CCD frames. E/S0 galaxies in the cluster core are singled out both by
morphology (for the brightest galaxies), and by colour. The details of the data
reduction procedure are illustrated via the analysis of the cluster Abell 496,
which has been used as a pilot cluster for the whole program. The related
photometric catalogue consists of 2355 objects. The limiting magnitudes (the
reference Surface Brightness is given in parenthesis) in the various colours
are respectively g(25.5) = 24.14, r(25.5) = 24.46, i(25.0) = 23.75$. These
correspond to the limiting absolute magnitudes -12.28, -11.96 and -12.67
(H_0=50 km/sec/Mpc).Comment: 17 pages, 19 ps figures, aa.cl
3C 33: another case of photoionized soft X-ray emission in radio galaxies
All the observations available in the Chandra and XMM-Newton archives have
been used to investigate the X-ray spectral properties of 3C 33. In this paper
is presented a complete X-ray analysis of the nuclear emission of this narrow
line radio galaxy. The broad band spectrum of 3C 33 is complex. The hard part
resembles that of Seyfert 2 galaxies, with a heavily obscured nuclear continuum
(N_H~10^23 cm^-2) and a prominent Fe Kalpha line. This represents the nuclear
radiation directly observed in transmission through a cold circumnuclear gas.
On the other hand an unabsorbed continuum plus emission lines seem to fit well
the soft part of the spectrum (0.5-2 keV) suggesting that the jet does not
significantly contribute to the X-ray emission. We discuss the possible
collisional or photoionized origin of the gas that emits the soft X-ray lines.
Our results, strengthened by optical spectroscopy favor the photoionization
scenario.Comment: 7 pages, 5 figures, accepted for publication in A&
High-energy neutrinos from FR0 radio-galaxies?
The sources responsible for the emission of high-energy ( 100 TeV)
neutrinos detected by IceCube are still unknown. Among the possible candidates,
active galactic nuclei with relativistic jets are often examined, since the
outflowing plasma seems to offer the ideal environment to accelerate the
required parent high-energy cosmic rays. The non-detection of single point
sources or -- almost equivalently -- the absence, in the IceCube events, of
multiplets originating from the same sky position, constrains the cosmic
density and the neutrino output of these sources, pointing to a numerous
population of faint sources. Here we explore the possibility that FR0
radiogalaxies, the population of compact sources recently identified in large
radio and optical surveys and representing the bulk of radio-loud AGN
population, can represent suitable candidates for neutrino emission. Modeling
the spectral energy distribution of a FR0 radiogalaxy recently associated to a
-ray source detected by the Large Area Telescope onboard Fermi, we
derive the physical parameters of its jet, in particular the power carried by
it. We consider the possible mechanisms of neutrino production, concluding that
reactions in the jet between protons and ambient radiation is too
inefficient to sustain the required output. We propose an alternative scenario,
in which protons, accelerated in the jet, escape from it and diffuse in the
host galaxy, producing neutrinos as a result of scattering with the
interstellar gas, in strict analogy with the processes taking place in
star-forming galaxies.Comment: 5 pages, 3 figures, accepted for publication in MNRA
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