146 research outputs found
Unification of Radio Galaxies and Their Accretion/Jet Properties
We investigate the relation between black hole mass, M_bh, and jet power,
Q_jet, for a sample of BL Lacs and radio quasars. We find that BL Lacs are
separated from radio quasars by the FR I/II dividing line in M_bh-Q_jet plane,
which strongly supports the unification scheme of FR I/BL Lac and FR II/radio
quasar. The Eddington ratio distribution of BL Lacs and radio quasars exhibits
a bimodal nature with a rough division at L_bol/L_Edd~0.01, which imply that
they may have different accretion modes. We calculate the jet power extracted
from advection dominated accretion flow (ADAF), and find that it require
dimensionless angular momentum of black hole j~0.9-0.99 to reproduce the
dividing line between FR I/II or BL Lac/radio quasar if dimensionless accretion
rate mdot=0.01 is adopted, which is required by above bimodal distribution of
Eddington ratios. Our results suggest that black holes in radio galaxies are
rapidly spinning.Comment: To appear JAA in Jun
GLAST: Understanding the High Energy Gamma-Ray Sky
We discuss the ability of the GLAST Large Area Telescope (LAT) to identify,
resolve, and study the high energy gamma-ray sky. Compared to previous
instruments the telescope will have greatly improved sensitivity and ability to
localize gamma-ray point sources. The ability to resolve the location and
identity of EGRET unidentified sources is described. We summarize the current
knowledge of the high energy gamma-ray sky and discuss the astrophysics of
known and some prospective classes of gamma-ray emitters. In addition, we also
describe the potential of GLAST to resolve old puzzles and to discover new
classes of sources.Comment: To appear in Cosmic Gamma Ray Sources, Kluwer ASSL Series, Edited by
K.S. Cheng and G.E. Romer
SUPER: II. Spatially resolved ionised gas kinematics and scaling relations in z 2 ⌠AGN host galaxies
Aims. The SINFONI survey for Unveiling the Physics and Effect of Radiative feedback (SUPER) aims to trace and characterise
ionised gas outflows and their impact on star formation in a statistical sample of X-ray selected active galactic nuclei (AGN) at z ⌠2.
We present the first SINFONI results for a sample of 21 Type 1 AGN spanning a wide range in bolometric luminosity (log Lbol = 45.4â
47.9 erg sâ1
). The main aims of this paper are to determine the extension of the ionised gas, characterise the occurrence of AGN-driven
outflows, and link the properties of such outflows with those of the AGN.
Methods. We used adaptive optics-assisted SINFONI observations to trace ionised gas in the extended narrow line region using the
[O iii] λ5007 line. We classified a target as hosting an outflow if its non-parametric velocity of the [O iii] line, w80, was larger than
600 km sâ1
. We studied the presence of extended emission using dedicated point-spread function (PSF) observations, after modelling
the PSF from the Balmer lines originating from the broad line region.
Results. We detect outflows in all the Type 1 AGN sample based on the w80 value from the integrated spectrum, which is in the
range âŒ650â2700 km sâ1
. There is a clear positive correlation between w80 and the AGN bolometric luminosity (>99% correlation
probability), and the black hole mass (98% correlation probability). A comparison of the PSF and the [O iii] radial profile shows
that the [O iii] emission is spatially resolved for âŒ35% of the Type 1 sample and the outflows show an extension up to âŒ6 kpc. The
relation between maximum velocity and the bolometric luminosity is consistent with model predictions for shocks from an AGNdriven outflow. The escape fraction of the outflowing gas increases with the AGN luminosity, although for most galaxies, this fraction
is less than 10%
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
I.Toward an unbiased study of ionized outflows in z similar to 2 active galactic nuclei: survey overview and sample characterization
Theoretical models of galaxy formation suggest that the presence of an active galactic nucleus (AGN) is required to regulate the growth of its host galaxy through feedback mechanisms, produced by, for example, AGN-driven outflows. Although many observational studies have revealed that such outflows are common both at low and high redshift, a comprehensive picture is still missing. In particular, the peak epoch of galaxy assembly (1â< âzâ< â3) has been poorly explored so far, and current observations in this redshift range are mostly limited to targets with high chances to be in an outflowing phase. This paper introduces SUPER (a SINFONI Survey for Unveiling the Physics and Effect of Radiative feedback), an ongoing ESOâs VLT/SINFONI Large Programme. SUPER will perform the first systematic investigation of ionized outflows in a sizeable and blindly-selected sample of 39 X-ray AGN at zââŒâ2, which reaches high spatial resolutions (âŒ2 kpc) thanks to the adaptive optics-assisted IFS observations. The outflow morphology and star formation in the host galaxy will be mapped through the broad component of [OâŻIII]λ5007 and the narrow component of Hα emission lines. The main aim of our survey is to infer the impact of outflows on the on-going star formation and to link the outflow properties to a number of AGN and host galaxy properties. We describe here the survey characteristics and goals, as well as the selection of the target sample. Moreover, we present a full characterization of its multi-wavelength properties: we measure, via spectral energy distribution fitting of UV-to-FIR photometry, stellar masses (4â
Ăâ
10^{9} -2 x 10^{11} M_{â}), star formation rates (25â
ââ
680âM_{â} yr^{-1}) and AGN bolometric luminosities (2â
Ăâ
10^{44} - 8 x 10^{47} erg s^{-1}), along with obscuring column densities (up to 2â
Ăâ
10^{24} cm^{-2}) and luminosities in the hard 2â
ââ
10 keV band (2â
Ăâ
10^{43} - 6 x 10^{45} erg s^{-1}) derived through X-ray spectral analysis. Finally, we classify our AGN as jetted or non-jetted according to their radio and FIR emission
Longer and less overlapping food webs in anthropogenically disturbed marine ecosystems: confirmations from the past
The human exploitation of marine resources is characterised by the preferential removal of the largest species. Although this is expected to modify the structure of food webs, we have a relatively poor understanding of the potential consequences of such alteration. Here, we take advantage of a collection of ancient consumer tissues, using stable isotope analysis and SIBER to assess changes in the structure of coastal marine food webs in the South-western Atlantic through the second half of the Holocene as a result of the sequential exploitation of marine resources by hunter-gatherers, western sealers and modern fishermen. Samples were collected from shell middens and museums. Shells of both modern and archaeological intertidal herbivorous molluscs were used to reconstruct changes in the stable isotopic baseline, while modern and archaeological bones of the South American sea lion Otaria flavescens, South American fur seal Arctocephalus australis and Magellanic penguin Spheniscus magellanicus were used to analyse changes in the structure of the community of top predators. We found that ancient food webs were shorter, more redundant and more overlapping than current ones, both in northern-central Patagonia and southern Patagonia. These surprising results may be best explained by the huge impact of western sealing on pinnipeds during the fur trade period, rather than the impact of fishing on fish populations. As a consequence, the populations of pinnipeds at the end of the sealing period were likely well below the ecosystem's carrying capacity, which resulted in a release of intraspecific competition and a shift towards larger and higher trophic level prey. This in turn led to longer and less overlapping food webs
Genome-wide analyses reveal a potential role for the MAPT, MOBP, and APOE loci in sporadic frontotemporal dementia
Frontotemporal dementia (FTD) is the second most common cause of early-onset dementia after Alzheimer disease (AD). Efforts in the field mainly focus on familial forms of disease (fFTDs), while studies of the genetic etiology of sporadic FTD (sFTD) have been less common. In the current work, we analyzed 4,685 sFTD cases and 15,308 controls looking for common genetic determinants for sFTD. We found a cluster of variants at the MAPT (rs199443; p = 2.5 Ă 10â12, OR = 1.27) and APOE (rs6857; p = 1.31 Ă 10â12, OR = 1.27) loci and a candidate locus on chromosome 3 (rs1009966; p = 2.41 Ă 10â8, OR = 1.16) in the intergenic region between RPSA and MOBP, contributing to increased risk for sFTD through effects on expression and/or splicing in brain cortex of functionally relevant in-cis genes at the MAPT and RPSA-MOBP loci. The association with the MAPT (H1c clade) and RPSA-MOBP loci may suggest common genetic pleiotropy across FTD and progressive supranuclear palsy (PSP) (MAPT and RPSA-MOBP loci) and across FTD, AD, Parkinson disease (PD), and cortico-basal degeneration (CBD) (MAPT locus). Our data also suggest population specificity of the risk signals, with MAPT and APOE loci associations mainly driven by Central/Nordic and Mediterranean Europeans, respectively. This study lays the foundations for future work aimed at further characterizing population-specific features of potential FTD-discriminant APOE haplotype(s) and the functional involvement and contribution of the MAPT H1c haplotype and RPSA-MOBP loci to pathogenesis of sporadic forms of FTD in brain cortex
Prevalence of oral manifestations in soft tissues during early childhood in Brazilian children
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