44 research outputs found
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
Making it not too obvious: the effect of ambient light feedback on space heating energy consumption
Supernova remnants: the X-ray perspective
Supernova remnants are beautiful astronomical objects that are also of high
scientific interest, because they provide insights into supernova explosion
mechanisms, and because they are the likely sources of Galactic cosmic rays.
X-ray observations are an important means to study these objects.And in
particular the advances made in X-ray imaging spectroscopy over the last two
decades has greatly increased our knowledge about supernova remnants. It has
made it possible to map the products of fresh nucleosynthesis, and resulted in
the identification of regions near shock fronts that emit X-ray synchrotron
radiation.
In this text all the relevant aspects of X-ray emission from supernova
remnants are reviewed and put into the context of supernova explosion
properties and the physics and evolution of supernova remnants. The first half
of this review has a more tutorial style and discusses the basics of supernova
remnant physics and thermal and non-thermal X-ray emission. The second half
offers a review of the recent advances.The topics addressed there are core
collapse and thermonuclear supernova remnants, SN 1987A, mature supernova
remnants, mixed-morphology remnants, including a discussion of the recent
finding of overionization in some of them, and finally X-ray synchrotron
radiation and its consequences for particle acceleration and magnetic fields.Comment: Published in Astronomy and Astrophysics Reviews. This version has 2
column-layout. 78 pages, 42 figures. This replaced version has some minor
language edits and several references have been correcte
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
Cytogenetics of Bisexual/Unisexual Species of Poecilia. VI. Additional Nucleolus Organizer Region Chromosomal Clones of Poecilia Formosa (Amazon Molly) From Texas, With a Survey of Chromosomal Clones Detected in the Amazon Molly
This study reports the results of different staining techniques on the chromosomes of two Poecilia formosa lineages, providing evidence of two additional nucleolus organizer region (NOR) chromosomal clones in this gynogenetic fish. A comparative analysis of chromosomal clones detected in the Amazon molly, along with their frequency and distribution in different collecting sites, is also presented, and clonal heterogeneity resulting from chromosome changes is discussed
Cytogenetics of bisexual/unisexual species of Poecilia. VI. Additional nucleolus organizer region chromosomal clones of Poecilia formosa (Amazon molly) from Texas, with a survey of chromosomal clones detected in the Amazon molly
Cytophotometric and autoradiographic evidence for functional apomixis in a gynogenetic fish, Poecilia formosa and its related, triploid unisexuals
Study of the unbound nucleus N-11 by elastic resonance scattering
Resonances in the unbound nucleus N-11 have been studied, using the resonance scattering reaction C-10+p. The data give evidence for three states above the C-10+p threshold with energies 1.30, 2.04, and 3.72 MeV. These states can be interpreted, in a potential-model analysis, as the ground state and the first two excited states with spin-parity 1/2(+), 1/2(-), and 5/2(+) arising from the shell-model orbitals 1s(1/2), Op(1/2), and Od(5/2). A narrow state superposed on a broad structure found at higher energy could be interpreted as the mirror state of the 3/2(-) in Be-11 shifted down in energy. This shift would suggest a large radius of the potential
Study of the unbound nucleus N-11 by elastic resonance scattering
Resonances in the unbound nucleus N-11 have been studied, using the resonance scattering reaction C-10+p. The data give evidence for three states above the C-10+p threshold with energies 1.30, 2.04, and 3.72 MeV. These states can be interpreted, in a potential-model analysis, as the ground state and the first two excited states with spin-parity 1/2(+), 1/2(-), and 5/2(+) arising from the shell-model orbitals 1s(1/2), Op(1/2), and Od(5/2). A narrow state superposed on a broad structure found at higher energy could be interpreted as the mirror state of the 3/2(-) in Be-11 shifted down in energy. This shift would suggest a large radius of the potential