2,286 research outputs found
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
Theoretical study of the charge transport through C60-based single-molecule junctions
We present a theoretical study of the conductance and thermopower of
single-molecule junctions based on C60 and C60-terminated molecules. We first
analyze the transport properties of gold-C60-gold junctions and show that these
junctions can be highly conductive (with conductances above 0.1G0, where G0 is
the quantum of conductance). Moreover, we find that the thermopower in these
junctions is negative due to the fact that the LUMO dominates the charge
transport, and its magnitude can reach several tens of micro-V/K, depending on
the contact geometry. On the other hand, we study the suitability of C60 as an
anchoring group in single-molecule junctions. For this purpose, we analyze the
transport through several dumbbell derivatives using C60 as anchors, and we
compare the results with those obtained with thiol and amine groups. Our
results show that the conductance of C60-terminated molecules is rather
sensitive to the binding geometry. Moreover, the conductance of the molecules
is typically reduced by the presence of the C60 anchors, which in turn makes
the junctions more sensitive to the functionalization of the molecular core
with appropriate side groups.Comment: 9 pages, 7 figure
WMAP 3yr data with the CCA: anomalous emission and impact of component separation on the CMB power spectrum
The Correlated Component Analysis (CCA) allows us to estimate how the
different diffuse emissions mix in CMB experiments, exploiting also
complementary information from other surveys. It is especially useful to deal
with possible additional components. An application of CCA to WMAP maps
assuming that only the canonical Galactic emissions are present, highlights the
widespread presence of a spectrally flat "synchrotron" component, largely
uncorrelated with the synchrotron template, suggesting that an additional
foreground is indeed required. We have tested various spectral shapes for such
component, namely a power law as expected if it is flat synchrotron, and two
spectral shapes that may fit the spinning dust emission: a parabola in the logS
- log(frequency) plane, and a grey body. Quality tests applied to the
reconstructed CMB maps clearly disfavour two of the models. The CMB power
spectra, estimated from CMB maps reconstructed exploiting the three surviving
foreground models, are generally consistent with the WMAP ones, although at
least one of them gives a significantly higher quadrupole moment than found by
the WMAP team. Taking foreground modeling uncertainties into account, we find
that the mean quadrupole amplitude for the three "good" models is less than 1
sigma below the expectation from the standard LambdaCDM model. Also the other
reported deviations from model predictions are found not to be statistically
significant, except for the excess power at l~40. We confirm the evidence for a
marked North-South asymmetry in the large scale (l < 20) CMB anisotropies. We
also present a first, albeit preliminary, all-sky map of the "anomalous"
component.Comment: 14 pages, 17 figures, submitted to MNRAS, references adde
The Planck Surveyor mission: astrophysical prospects
Although the Planck Surveyor mission is optimized to map the cosmic microwave
background anisotropies, it will also provide extremely valuable information on
astrophysical phenomena. We review our present understanding of Galactic and
extragalactic foregrounds relevant to the mission and discuss on one side,
Planck's impact on the study of their properties and, on the other side, to
what extent foreground contamination may affect Planck's ability to accurately
determine cosmological parameters. Planck's multifrequency surveys will be
unique in their coverage of large areas of the sky (actually, of the full sky);
this will extend by two or more orders of magnitude the flux density interval
over which mm/sub-mm counts of extragalactic sources can be determined by
instruments already available (like SCUBA) or planned for the next decade (like
the LSA-MMA or the space mission FIRST), which go much deeper but over very
limited areas. Planck will thus provide essential complementary information on
the epoch-dependent luminosity functions. Bright radio sources will be studied
over a poorly explored frequency range where spectral signatures, essential to
understand the physical processes that are going on, show up. The
Sunyaev-Zeldovich effect, with its extremely rich information content, will be
observed in the direction of a large number of rich clusters of Galaxies.
Thanks again to its all sky coverage, Planck will provide unique information on
the structure and on the emission properties of the interstellar medium in the
Galaxy. At the same time, the foregrounds are unlikely to substantially limit
Planck's ability to measure the cosmological signals. Even measurements of
polarization of the primordial Cosmic Microwave background fluctuations appear
to be feasible.Comment: 20 pages, Latex (use aipproc2.sty, aipproc2.cls, epsfig.sty), 10
PostScript figures; invited review talk, Proc. of the Conference: "3 K
Cosmology", Roma, Italy, 5-10 October 1998, AIP Conference Proc, in press
Note: Figures 6 and 7 have been replaced by new and correct version
Extragalactic Source Counts and Contributions to the Anisotropies of the Cosmic Microwave Background. Predictions for the Planck Surveyor mission
We present predictions for the counts of extragalactic sources, the
contributions to fluctuations and their spatial power spectrum in each channel
foreseen for the Planck Surveyor (formerly COBRAS/SAMBA) mission. The
contribution to fluctuations due to clustering of both radio and far--IR
sources is found to be generally small in comparison with the Poisson term;
however the relative importance of the clustering contribution increases and
may eventually become dominant if sources are identified and subtracted down to
faint flux limits. The central Planck frequency bands are expected to be
``clean'': at high galactic latitude (|b|>20), where the reduced galactic noise
does not prevent the detection of the extragalactic signal, only a tiny
fraction of pixels is found to be contaminated by discrete extragalactic
sources. Moreover, removal of contaminating signals is eased by the substantial
difference between their power spectrum and that of primordial fluctuations.Comment: 10 pages, Latex, mn.sty, 8 figures included, MNRAS, in the press.
Minor changes in the text. Sections 3.1 and 3.2 have been expanded. Source
counts in Table 2 have been slightly changed. Figure 1,2,7 and 8 have been
replaced by new version
Integration of cranial base and face in growing subject
Background: many papers investigate the role of the cranial base in facial development, but the results are not in agreement. This can be due to a difference between the central and lateral parts of the cranial base. The aim of the present study is to evaluate the relationship between the central and the lateral cranial base and the facial skeleton in pre-pubertal peak subjects and at the end of growth. Material/Methods: a total sample of 52 latero-lateral cranial teleradiographs were analyzed. To test the correlation between structures, the "Partial Least Square" analysis was performed. Geometric morphometric analysis were applied and partial least square analysis was used to test correlation. Integration was studied removing the effect of allometry. Results: facial skeleton has no significant relation with central cranial base. Facial skeleton has significant relationships with the lateral portion of the cranial base. This relationship is higher in the post-peak phase of growth. Conclusion: the Integration between facial structures and cranial base is significant. The Spatial orientation and shape of the facial structures are both influenced by cranial base. This is mainly due to the lateral portion of cranial base
A snapshot of knowledge about oral cancer in italy: A 505 person survey
Objectives: Patients’ knowledge about oral squamous cell carcinoma (OSCC) plays an important role in primary prevention, early diagnosis, and prognosis and survival rate. The aim of this study was to assess OSCC awareness attitudes among general population in order to provide information for educational interventions. Methods: A survey delivered as a web-based questionnaire was submitted to 505 subjects (aged from 18 to 76 years) in Italy, and the answers collected were statistically analyzed. Information was collected about existence, incidence, features of lesions, risk factors of oral cancer, and self-inspection habits, together with details about professional reference figures and preventive behaviors. Results: Chi-square tests of independence with adjusted standardized residuals highlighted correlations between population features (age, gender, educational attainment, provenance, medical relationship, or previous diagnoses of oral cancer in family) and knowledge about oral cancer. Conclusions: Knowledge about OSCC among the Italian population is limited, and it might be advisable to implement nudging and sensitive customized campaigns in order to promote awareness and therefore improve the prognosis of this disease
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
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