1,370 research outputs found
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&
Super-massive Black Hole Demography: the Match between the Local and Accreted Mass Functions
We have performed a detailed analysis of the local super-massive black-hole
(SMBH) mass function based on both kinematic and photometric data and derived
an accurate analytical fit in the range 10^6 <= (M_BH/M_sun) <= 5*10^9. We find
a total SMBH mass density of (4.2+/-1.1)*10^5 M_sun/Mpc^3, about 25% of which
is contributed by SMBHs residing in bulges of late type galaxies. Exploiting
up-to-date luminosity functions of hard X-ray and optically selected AGNs, we
have studied the accretion history of the SMBH population. If most of the
accretion happens at constant \dot{M_BH}/M_BH the local SMBH mass function is
fully accounted for by mass accreted by X-ray selected AGNs, with bolometric
corrections indicated by current observations and a standard mass-to-light
conversion efficiency \epsilon ~10%. The analysis of the accretion history
highlights that the most massive BHs accreted their mass faster and at higher
redshifts (z>1.5), while the lower mass BHs responsible for most of the hard
X-ray background have mostly grown at z<1.5. The accreted mass function matches
the local SMBH mass function if \epsilon ~0.09(+0.04,-0.03) and the Eddington
ratio \lambda=L/L_Edd \~0.3(+0.3,-0.1) (68% confidence errors). The visibility
time, during which AGNs are luminous enough to be detected by the currently
available X-ray surveys, ranges from ~0.1 Gyr for present day BH masses
M_BH(z=0) ~10^6 M_sun to ~0.3 Gyr for M_BH(z=0) >= 10^9 M_sun. The mass
accreted during luminous phases is >= 25-30% even if we assume extreme values
of \epsilon (\epsilon \~0.3-0.4). An unlikely fine tuning of the parameters
would be required to account for the local SMBH mass function accomodating a
dominant contribution from 'dark' BH growth (due, e.g., to BH coalescence).Comment: 12 pages, 14 figures, accepted for publication in MNRAS, minor
changes following referee's comment
Are z>2 Herschel galaxies proto-spheroids?
We present a backward approach for the interpretation of the evolution of the
near-infrared and the far-infrared luminosity functions across the redshift
range 0<z<3. In our method, late-type galaxies are treated by means of a
parametric phenomenological method based on PEP/HerMES data up to z~4, whereas
spheroids are described by means of a physically motivated backward model. The
spectral evolution of spheroids is modelled by means of a single-mass model,
associated to a present-day elliptical with K-band luminosity comparable to the
break of the local early-type luminosity function. The formation of
proto-spheroids is assumed to occurr across the redshift range 1< z < 5. The
key parameter is represented by the redshift z_0.5 at which half
proto-spheroids are already formed. A statistical study indicates for this
parameter values between z_0.5=1.5 and z_0.5=3. We assume as fiducial value
z_0.5~2, and show that this assumption allows us to describe accourately the
redshift distributions and the source counts. By assuming z_0.5 ~ 2 at the
far-IR flux limit of the PEP-COSMOS survey, the PEP-selected sources observed
at z>2 can be explained as progenitors of local spheroids caught during their
formation. We also test the effects of mass downsizing by dividing the
spheroids into three populations of different present-day stellar masses. The
results obtained in this case confirm the validity of our approach, i.e. that
the bulk of proto-spheroids can be modelled by means of a single model which
describes the evolution of galaxies at the break of the present-day early type
K-band LF.Comment: Accepted for publication in ApJ; 26 pages; 13 figure
Current-voltage scaling of a Josephson-junction array at irrational frustration
Numerical simulations of the current-voltage characteristics of an ordered
two-dimensional Josephson junction array at an irrational flux quantum per
plaquette are presented. The results are consistent with an scaling analysis
which assumes a zero temperature vortex glass transition. The thermal
correlation length exponent characterizing this transition is found to be
significantly different from the corresponding value for vortex-glass models in
disordered two-dimensional superconductors. This leads to a current scale where
nonlinearities appear in the current-voltage characteristics decreasing with
temperature roughly as in contrast with the behavior expected
for disordered models.Comment: RevTex 3.0, 12 pages with Latex figures, to appear in Phys. Rev. B
54, Rapid. Com
Endocrine and metabolic evaluation of classic Klinefelter syndrome and high-grade aneuploidies of sexual chromosomes with male phenotype: are they different clinical conditions?
Klinefelter syndrome (KS) is the most common sex chromosome aneuploidy in males. As well as classic KS, less frequent higher-grade aneuploidies (HGAs) are also possible. While KS and HGAs both involve testicular dysgenesis with hypergonadotropic hypogonadism, they differ in many clinical features. The aim of this study was to investigate the endocrinal and metabolic differences between KS and HGAs.Objective: Klinefelter syndrome (KS) is the most common sex chromosome aneuploidy in males. As well as classic KS, less frequent higher-grade aneuploidies (HGAs) are also possible. While KS and HGAs both involve testicular dysgenesis with hypergonadotropic hypogonadism, they differ in many clinical features. The aim of this study was to investigate the endocrinal and metabolic differences between KS and HGAs. Design: Cross-sectional, case-control study. Methods: 88 patients with KS, 24 with an HGA and 60 healthy controls. Given the known age-related differences all subjects were divided by age into subgroups 1, 2 and 3. Pituitary, thyroid, gonadal and adrenal functions were investigated in all subjects. Metabolic aspects were only evaluated in subjects in subgroups 2 and 3. Results: FT4 and FT3 levels were significantly higher in HGA than in KS patients in subgroups 1 and 2; in subgroup 3, FT4 was significantly higher in controls than in patients. Thyroglobulin was significantly higher in HGA patients in subgroup 1 than in KS patients and controls. Hypergonadotropic hypogonadism was confirmed in both KS and HGA patients, but was more precocious in the latter, as demonstrated by the earlier increase in gonadotropins and the decrease in testosterone, DHEA-S and inhibin B. Prolactin was significantly higher in HGA patients, starting from subgroup 2. Total and LDL cholesterol were significantly higher in HGA patients than in KS patients and controls, while HDL cholesterol was higher in controls than in patients. Conclusions: KS and HGAs should be considered as two distinct conditions
Numerical Studies of the Two Dimensional XY Model with Symmetry Breaking Fields
We present results of numerical studies of the two dimensional XY model with
four and eight fold symmetry breaking fields. This model has recently been
shown to describe hydrogen induced reconstruction on the W(100) surface. Based
on mean-field and renormalization group arguments,we first show how the
interplay between the anisotropy fields can give rise to different phase
transitions in the model. When the fields are compatible with each other there
is a continuous phase transition when the fourth order field is varied from
negative to positive values. This transition becomes discontinuous at low
temperatures. These two regimes are separated by a multicritical point. In the
case of competing four and eight fold fields, the first order transition at low
temperatures opens up into two Ising transitions. We then use numerical methods
to accurately locate the position of the multicritical point, and to verify the
nature of the transitions. The different techniques used include Monte Carlo
histogram methods combined with finite size scaling analysis, the real space
Monte Carlo Renormalization Group method, and the Monte Carlo Transfer Matrix
method. Our numerical results are in good agreement with the theoretical
arguments.Comment: 29 pages, HU-TFT-94-36, to appear in Phys. Rev. B, Vol 50, November
1, 1994. A LaTeX file with no figure
Dust Emission from Active Galactic Nuclei
Unified schemes of active galactic nuclei (AGN) require an obscuring dusty
torus around the central source, giving rise to Seyfert 1 line spectrum for
pole-on viewing and Seyfert 2 characteristics in edge-on sources. Although the
observed IR is in broad agreement with this scheme, the behavior of the 10
micron silicate feature and the width of the far-IR emission peak remained
serious problems in all previous modeling efforts. We show that these problems
find a natural explanation if the dust is contained in about 5-10 clouds along
radial rays through the torus. The spectral energy distributions (SED) of both
type 1 and type 2 sources are properly reproduced from different viewpoints of
the same object if the visual optical depth of each cloud is larger than about
60 and the clouds' mean free path increases roughly in proportion to radial
distance.Comment: 11 pages, submitted to ApJ Letter
A Physical Model for Co-evolution of QSOs and of their Spheroidal Hosts
At variance with most semi-analytic models, in the Anti-hierarchical Baryon
Collapse scenario (Granato et al. 2001, 2004) the main driver of the galaxy
formation and evolution is not the merging sequence but are baryon processes.
This approach emphasizes, still in the framework of the hierarchical clustering
paradigm for dark matter halos, feedback processes from supernova explosions
and from active nuclei, that tie together star formation in spheroidal galaxies
and the growth of black holes at their centers. We review some recent results
showing the remarkably successful predictive power of this scenario, which
allows us to account for the evolution with cosmic time of a broad variety of
properties of galaxies and active nuclei, which proved to be very challenging
for competing models.Comment: Invited talk at the Specola Vaticana Workshop on "AGN and Galaxy
Evolution", Castel Gandolfo, 3-6 October 2005, 10 pages, 2 figure
From First Galaxies to QSOs: feeding the baby monsters
We present a physical model for the coevolution of massive spheroidal
galaxies and active nuclei at their centers. Supernova heating is increasingly
effective in slowing down the star formation and in driving gas outflows in
smaller and smaller dark matter halos. Thus the more massive protogalaxies
virializing at early times are the sites of faster star formation. The
correspondingly higher radiation drag causes a faster angular momentum loss by
the gas and induces a larger accretion rate onto the central black hole. In
turn, the kinetic energy of the outflows powered by the active nuclei can
unbind the residual gas in a time shorter for larger halos. The model accounts
for a broad variety of dynamical, photometric and metallicity properties of
early-type galaxies, for the M_BH -- \sigma relation and for the local
supermassive black-hole mass function.Comment: 6 pages, contributed paper to Proceedings of the Conference on
"Growing Black Holes" held in Garching, Germany, on June 21-25, 2004, edited
by A. Merloni, S. Nayakshin and R. Sunyaev, Springer-Verlag series of "ESO
Astrophysics Symposia
Affinity and selectivity of plant proteins for red wine components relevant to color and aroma traits
The effects of fining with various plant proteins were assessed on Aglianico red wine, using both the young wine and wine aged for twelve and twenty-four months, and including wine unfined or fined with gelatin as controls. Color traits and fining efficiency were considered, along with the content of various types of phenolics and of aroma-related compounds of either varietal or fermentative origin. All agents had comparable fining efficiency, although with distinct kinetics, and had similar effects on wine color. Individual plant proteins and enzymatic hydrolyzates differed in their ability to interact with some anthocyanins, with specific proanthocyanidins complexes, and with some aroma components of fermentative origin. Changes in varietal aroma components upon fining were very limited or absent. Effects of all the fining agents tested in this study on the anthocyanidin components were most noticeable in young red wine, and decreased markedly with increasing wine ageing
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