2,134 research outputs found
Dust in active nuclei. II. Powder or gravel?
In a companion paper, Maiolino et al. (2000) presented various observational
evidences for "anomalous" dust properties in the circumnuclear region of AGNs
and, in particular, the reduced E(B-V)/N_H and Av/N_H ratios, the absence of
the silicate absorption feature in mid-IR spectra of Sy2s and the absence of
the carbon dip in UV spectra of reddened Sy1s. In this paper we discuss various
explanations for these facts.
The observational constraints favor a scenario where coagulation, catalyzed
by the high densities in the circumnuclear region, yields to the formation of
large grains. The resulting extinction curve is featureless, flatter than
Galactic and the E(B-V)/N_H and Av/N_H ratios are significantly reduced. These
results should warn about an unappropriate use of the standard Galactic
extinction curve and Av/N_H ratio when dealing with the extreme gas conditions
typical of the circumnuclear clouds of AGNs.
We also investigated alternative scenarios for the observed anomalous
properties of dust in AGNs. Some of these scenarios might explain some of the
observed properties for a few objects, but they generally fail to account for
all of the observational constraints obtained for the large sample of AGNs
studied in these works.Comment: 13 pages, 7 figures, accepted for publication in A&
Seyfert Activity and Nuclear Star Formation in the Circinus Galaxy
We present high angular resolution (0".15-0".5) near infrared images and
spectroscopy of the Circinus galaxy, the closest Seyfert 2 galaxy known. The
data reveal a non-stellar nuclear source at 2.2 microns. The coronal line
region and the hot molecular gas emission extend for 20-50 pc in the ionization
cone. The data do not show evidence for a point-like concentration of dark
mass; we set an upper limit of 4*10^6 Mo to the mass of a putative black hole.
We find evidence for a young nuclear stellar population, with typical ages
between 4*10^7 and 1.5*10^8 yrs. The luminosity of the starburst inside a few
hundred pc is comparable to the intrinsic luminosity of the Seyfert nucleus,
and the two of them together account for most of the observed bolometric
luminosity of the galaxy. Within the central 12 pc the starburst has an age of
about 7*10^7 yrs and radiates about 2% of the luminosity of the active nucleus.
We discuss the implications of these results for models that have been proposed
for the starburst-AGN connection.Comment: 44 pages, Latex (including 11 Figures), Color Figures 1, 2 and 4 are
available at http://www.arcetri.astro.it/~maiolino/ , ApJ in pres
Infrared 3D Observations of Nearby Active Galaxies
We present multi-wavelength imaging observations of three nearby and famous
active galaxies obtained with NICMOS, ISOCAM and the MPE near-IR integral field
spectrometer. The data reveal a variety of features and properties that are
missed in optical studies and in traditional IR monodimensional spectroscopy.Comment: 6 pages, to appear in "Imaging the Universe in Three Dimensions:
Astrophysics with Advanced Multi-Wavelength Imaging Devices", eds. W. van
Breugel and J. Bland-Hawthorn, needs pasp3D.st
Nuclear star formation in the quasar PG1126-041 from adaptive optics assisted spectroscopy
We present adaptive optics assisted spectroscopy of three quasars obtained
with NACO at VLT. The high angular resolution achieved with the adaptive optics
(~0.08"), joined to the diagnostic power of near-IR spectroscopy, allow us to
investigate the properties of the innermost 100 pc of these quasars. In the
quasar with the best adaptive optics correction, PG1126-041, we spatially
resolve the Pa-alpha emission within the nuclear 100 pc. The comparison with
higher excitation lines suggests that the narrow Pa-alpha emission is due to
nuclear star formation. The inferred intensity of the nuclear star formation
(13 M(sun)/yr) may account for most of the far-IR luminosity observed in this
quasar.Comment: 4 pages, 4 figures. Accepted for publication in A&
Relationship between NOX4 level and angiotensin II signaling in Gitelman's syndrome. Implications with hypertension
Recent evidence showed that endogenous nicotinamide adenine dinucleotide phosphate-oxidase 4 (NOX4) may exert a protective role on the cardiovascular system inducing vasodilation, reduction of blood pressure, and anti-proliferative actions. However, the functional significance of NOX4 in the cardiovascular system in humans remains elusive. Mononuclear cell levels of NOX4 were assessed by immunoblotting in 14 Gitelman's patients (GS), a unique human model of endogenous Ang II signaling antagonism and activation of anti-atherosclerotic and anti-remodeling defenses, and compared to 11 untreated essential hypertensive patients as well as to 11 healthy normotensive subjects. The association between NOX4 and its effector heme oxygenase (HO-1) (sandwich immunoassay) was also evaluated. NOX4 protein levels were decreased in hypertensive patients as compared to both GS and healthy subjects (1.06±0.31 AU vs. 1.76±0.54, P=0.002 and vs. 1.61±0.54, P=0.018, respectively). NOX4 protein level did not differ between GS and healthy subjects. HO-1 levels were increased in GS patients as compared to both hypertensive patients and healthy subjects (8.65±3.08 ng/ml vs 3.70±1.19, P<0.0001, and vs 5.49±1.04, P=0.008, respectively. NOX4 levels correlate with HO-1 levels only in GS (r(2)=0.63; P=0.001), (r(2)=0.088; P=ns, in hypertensive patients and r(2)=0.082; P=ns, in healthy subjects). Our findings show that NOX4 and its effector HO-1 are reduced in hypertensive patients compared to GS patients, a human model opposite to hypertension. Although the functional significance of NOX4 needs further clarification, our preliminary data in a unique human model of anti-atherosclerotic and anti-remodeling defenses activation, highlight the potentially protective role of NOX4 in the human cardiovascular system
Mapping metals at high redshift with far-infrared lines
Cosmic metal enrichment is one of the key physical processes regulating
galaxy formation and the evolution of the intergalactic medium (IGM). However,
determining the metal content of the most distant galaxies has proven so far
almost impossible; also, absorption line experiments at become
increasingly difficult because of instrumental limitations and the paucity of
background quasars. With the advent of ALMA, far-infrared emission lines
provide a novel tool to study early metal enrichment. Among these, the [CII]
line at 157.74 m is the most luminous line emitted by the interstellar
medium of galaxies. It can also resonant scatter CMB photons inducing
characteristic intensity fluctuations () near the peak of the
CMB spectrum, thus allowing to probe the low-density IGM. We compute both [CII]
galaxy emission and metal-induced CMB fluctuations at by using
Adaptive Mesh Refinement cosmological hydrodynamical simulations and produce
mock observations to be directly compared with ALMA BAND6 data ( GHz). The [CII] line flux is correlated with as
. Such
relation is in very good agreement with recent ALMA observations (e.g. Maiolino
et al. 2015; Capak et al. 2015) of galaxies. We predict that a
() galaxy can be detected at in
(2000) hours, respectively. CMB resonant scattering can produce Jy/beam emission/absorptions features that are very challenging to be
detected with current facilities. The best strategy to detect these signals
consists in the stacking of deep ALMA observations pointing fields with known
galaxies. This would allow to simultaneously detect both
[CII] emission from galactic reionization sources and CMB fluctuations produced
by metals.Comment: 13 pages, 6 figure
- …