66 research outputs found
THE COMPLEX CIRCUMNUCLEAR ENVIRONMENT of the BROAD-LINE RADIO GALAXY 3C 390.3 REVEALED by CHANDRA HETG
We present the first high spectral resolution X-ray observation of the broad-line radio galaxy 3C 390.3 obtained with the high-energy transmission grating spectrometer on board the Chandra X-ray Observatory. The spectrum shows complex emission and absorption features in both the soft X-rays and Fe K band. We detect emission and absorption lines in the energy range E = 700–1000 eV associated with ionized Fe L transitions (Fe XVII–XX). An emission line at the energy of E sime 6.4 keV consistent with the Fe Kα is also observed. Our best-fit model requires at least three different components: (i) a hot emission component likely associated with the hot interstellar medium in this elliptical galaxy with temperature kT = 0.5 ± 0.1 keV; (ii) a warm absorber with ionization parameter logξ = 2.3 ± 0.5 erg s−1 cm, column density logN H = 20.7 ± 0.1 cm−2, and outflow velocity v out < 150 km s−1; and (iii) a lowly ionized reflection component in the Fe K band likely associated with the optical broad-line region or the outer accretion disk. These evidences suggest the possibility that we are looking directly down the ionization cone of this active galaxy and that the central X-ray source only photoionizes along the unobscured cone. This is overall consistent with the angle-dependent unified picture of active galactic nuclei
Feeding and Feedback in the Powerful Radio Galaxy 3C 120
We present the spectral analysis of a 200~ks observation of the broad-line
radio galaxy 3C~120 performed with the high energy transmission grating (HETG)
spectrometer on board the \emph{Chandra} X-ray Observatory. We find (i) a
neutral absorption component intrinsic to the source with column density of
~cm, (ii) no evidence for a warm absorber
with an upper limit on the column density of just ~cm assuming the typical ionization parameter
log2.5~erg~s~cm, the warm absorber may instead be replaced
by (iii) a hot emitting gas with temperature ~keV observed as
soft X-ray emission from ionized Fe L-shell lines which may originate from a
kpc scale shocked bubble inflated by the AGN wind or jet with a shock velocity
of about 1,000~km~s determined by the emission line width, (iv) a
neutral Fe K line and accompanying emission lines indicative of a
Compton-thick cold reflector with low reflection fraction ,
suggesting a large opening angle of the torus, (v) a highly ionized Fe~XXV
emission feature indicative of photoionized gas with ionization parameter
log~erg~s~cm and a column density of
~cm localized within 2~pc from the X-ray
source, and (vi) possible signatures for a highly ionized disk wind. Together
with previous evidence for intense molecular line emission, these results
indicate that 3C~120 is likely a late state merger undergoing strong AGN
feedback.Comment: Accepted for publication in Ap
X-ray Absorption and Reflection in Active Galactic Nuclei
X-ray spectroscopy offers an opportunity to study the complex mixture of
emitting and absorbing components in the circumnuclear regions of active
galactic nuclei, and to learn about the accretion process that fuels AGN and
the feedback of material to their host galaxies. We describe the spectral
signatures that may be studied and review the X-ray spectra and spectral
variability of active galaxies, concentrating on progress from recent Chandra,
XMM-Newton and Suzaku data for local type 1 AGN. We describe the evidence for
absorption covering a wide range of column densities, ionization and dynamics,
and discuss the growing evidence for partial-covering absorption from data at
energies > 10 keV. Such absorption can also explain the observed X-ray spectral
curvature and variability in AGN at lower energies and is likely an important
factor in shaping the observed properties of this class of source.
Consideration of self-consistent models for local AGN indicates that X-ray
spectra likely comprise a combination of absorption and reflection effects from
material originating within a few light days of the black hole as well as on
larger scales. It is likely that AGN X-ray spectra may be strongly affected by
the presence of disk-wind outflows that are expected in systems with high
accretion rates, and we describe models that attempt to predict the effects of
radiative transfer through such winds, and discuss the prospects for new data
to test and address these ideas.Comment: Accepted for publication in the Astronomy and Astrophysics Review. 58
pages, 9 figures. V2 has fixed an error in footnote
Black hole spin: theory and observation
In the standard paradigm, astrophysical black holes can be described solely
by their mass and angular momentum - commonly referred to as `spin' - resulting
from the process of their birth and subsequent growth via accretion. Whilst the
mass has a standard Newtonian interpretation, the spin does not, with the
effect of non-zero spin leaving an indelible imprint on the space-time closest
to the black hole. As a consequence of relativistic frame-dragging, particle
orbits are affected both in terms of stability and precession, which impacts on
the emission characteristics of accreting black holes both stellar mass in
black hole binaries (BHBs) and supermassive in active galactic nuclei (AGN).
Over the last 30 years, techniques have been developed that take into account
these changes to estimate the spin which can then be used to understand the
birth and growth of black holes and potentially the powering of powerful jets.
In this chapter we provide a broad overview of both the theoretical effects of
spin, the means by which it can be estimated and the results of ongoing
campaigns.Comment: 55 pages, 5 figures. Published in: "Astrophysics of Black Holes -
From fundamental aspects to latest developments", Ed. Cosimo Bambi, Springer:
Astrophysics and Space Science Library. Additional corrections mad
Past, Present, and Future X-Ray and Gamma-Ray Missions
X- and -ray astronomy began in the early sixties of the last century with balloons flights, sounding rocket experiment and satellites. Long before space satellite detected X- and -rays emitted by cosmic sources, scientists had known that the Universe should be producing these photons. In this chapter we provided an overview of past and present missions that has made the X- and -ray astronomy an integral part of astronomical research, and prospects of future developments
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