145 research outputs found
The “Pieve di Santa Maria” in Arezzo (Italy). From the Laser Scanner Survey to the Knowledge of the Architectural Structure
The parish church of “Santa Maria” is considered one of the most important medieval buildings of Arezzo Although the church is attested from 11th century, it is between the 13th and 14th centuries that reached its current consistency, characterized by the particular façade with small columns on several levels and an imposing bell tower. Later, from the 16th to the 18th century, the church underwent profound transformations, that were almost completely erased by extensive restoration works in the second half of the 19th century.
The architectural survey of the parish church of “Santa Maria” was carried out with a phase-shift laser scanner and a digital reflex camera (Z+F 5006h). 189 scans were performed for generating the 3D model of the church: 180 of them with high density and normal quality, lasting 5-6 minutes; the remaining ones with super high density and high quality, lasting 13-14 minutes. Vectorial drawings of plans and sections were then created from the 3D model.
Thanks to laser scanner survay of the chuch, it was possible to highlight the singularity of the structure of the basilical body and the transept. The tilt of walls and columns, the variations in the thickness of the walls, the considerable deformations of some arches, the cracks and textures of the wall facing were thus shown.
The information obtained attested an architectural structure created by complex construction events that over time have affected this building. The cnstructive singularities involve the medieval genesis of the building, the transformations during the following centuries and the following restoration works.
These composite features are specific and common to every ancient building. This peculiar epistemological condition eschews from simplifications and requires deep and complex studies closely linked to the problems of conservation of the structures
Bulk Etch Rate Measurements and Calibrations of Plastic Nuclear Track Detectors
New calibrations of CR39 and Makrofol nuclear track detectors have been
obtained using 158 A GeV Pb (82+) and In (49+) ions; a new method for the bulk
etch rate determination, using both cone height and base diameter measurements
was developed. The CR39 charge resolution based on the etch-pit base area
measurement is adequate to identify nuclear fragments in the interval 7 <=
Z/beta <= 49. For CR39 the detection threshold is at REL~50 MeV cm^2/g,
corresponding to a nuclear fragment with Z/beta~7. Base cone area distributions
for Makrofol foils exposed to Pb (82+) ions have shown for the first time all
peaks due to nuclear fragments with Z > 50; the distribution of the etched cone
heights shows well separated individual peaks for Z/beta = 78 - 83 (charge
pickup). The Makrofol detection threshold is at REL 2700 MeV cm^2/g,
corresponding to a nuclear fragment with Z/beta~50.Comment: 11 pages, 5 EPS figures. Submitted to Nucl. Instr. Meth.
New MACRO results on atmospheric neutrino oscillations
The final results of the MACRO experiment on atmospheric neutrino
oscillations are presented and discussed. The data concern different event
topologies with average neutrino energies of ~3 and ~50 GeV. Multiple Coulomb
Scattering of the high energy muons in absorbers was used to estimate the
neutrino energy of each event. The angular distributions, the L/E_nu
distribution, the particle ratios and the absolute fluxes all favour nu_mu -->
nu_tau oscillations with maximal mixing and Delta m^2 =0.0023 eV^2. A
discussion is made on the Monte Carlos used for the atmospheric neutrino flux.
Some results on neutrino astrophysics are also briefly discussed.Comment: Invited Paper at the NANP03 Int. Conf., Dubna, 200
Results of the Search for Strange Quark Matter and Q-balls with the SLIM Experiment
The SLIM experiment at the Chacaltaya high altitude laboratory was sensitive
to nuclearites and Q-balls, which could be present in the cosmic radiation as
possible Dark Matter components. It was sensitive also to strangelets, i.e.
small lumps of Strange Quark Matter predicted at such altitudes by various
phenomenological models. The analysis of 427 m^2 of Nuclear Track Detectors
exposed for 4.22 years showed no candidate event. New upper limits on the flux
of downgoing nuclearites and Q-balls at the 90% C.L. were established. The null
result also restricts models for strangelets propagation through the Earth
atmosphere.Comment: 14 pages, 11 EPS figure
A Complete Skull of an Early Cretaceous Sauropod and the Evolution of Advanced Titanosaurians
Advanced titanosaurian sauropods, such as nemegtosaurids and saltasaurids, were diverse and one of the most important groups of herbivores in the terrestrial biotas of the Late Cretaceous. However, little is known about their rise and diversification prior to the Late Cretaceous. Furthermore, the evolution of their highly-modified skull anatomy has been largely hindered by the scarcity of well-preserved cranial remains. A new sauropod dinosaur from the Early Cretaceous of Brazil represents the earliest advanced titanosaurian known to date, demonstrating that the initial diversification of advanced titanosaurians was well under way at least 30 million years before their known radiation in the latest Cretaceous. The new taxon also preserves the most complete skull among titanosaurians, further revealing that their low and elongated diplodocid-like skull morphology appeared much earlier than previously thought
Euclid preparation: XXII. Selection of Quiescent Galaxies from Mock Photometry using Machine Learning
The Euclid Space Telescope will provide deep imaging at optical and
near-infrared wavelengths, along with slitless near-infrared spectroscopy,
across ~15,000 sq deg of the sky. Euclid is expected to detect ~12 billion
astronomical sources, facilitating new insights into cosmology, galaxy
evolution, and various other topics. To optimally exploit the expected very
large data set, there is the need to develop appropriate methods and software.
Here we present a novel machine-learning based methodology for selection of
quiescent galaxies using broad-band Euclid I_E, Y_E, J_E, H_E photometry, in
combination with multiwavelength photometry from other surveys. The ARIADNE
pipeline uses meta-learning to fuse decision-tree ensembles,
nearest-neighbours, and deep-learning methods into a single classifier that
yields significantly higher accuracy than any of the individual learning
methods separately. The pipeline has `sparsity-awareness', so that missing
photometry values are still informative for the classification. Our pipeline
derives photometric redshifts for galaxies selected as quiescent, aided by the
`pseudo-labelling' semi-supervised method. After application of the outlier
filter, our pipeline achieves a normalized mean absolute deviation of ~< 0.03
and a fraction of catastrophic outliers of ~< 0.02 when measured against the
COSMOS2015 photometric redshifts. We apply our classification pipeline to mock
galaxy photometry catalogues corresponding to three main scenarios: (i) Euclid
Deep Survey with ancillary ugriz, WISE, and radio data; (ii) Euclid Wide Survey
with ancillary ugriz, WISE, and radio data; (iii) Euclid Wide Survey only. Our
classification pipeline outperforms UVJ selection, in addition to the Euclid
I_E-Y_E, J_E-H_E and u-I_E,I_E-J_E colour-colour methods, with improvements in
completeness and the F1-score of up to a factor of 2. (Abridged)Comment: 37 pages (including appendices), 26 figures; accepted for publication
in Astronomy & Astrophysic
Euclid preparation. XXV. The Euclid Morphology Challenge -- Towards model-fitting photometry for billions of galaxies
The ESA Euclid mission will provide high-quality imaging for about 1.5
billion galaxies. A software pipeline to automatically process and analyse such
a huge amount of data in real time is being developed by the Science Ground
Segment of the Euclid Consortium; this pipeline will include a model-fitting
algorithm, which will provide photometric and morphological estimates of
paramount importance for the core science goals of the mission and for legacy
science. The Euclid Morphology Challenge is a comparative investigation of the
performance of five model-fitting software packages on simulated Euclid data,
aimed at providing the baseline to identify the best suited algorithm to be
implemented in the pipeline. In this paper we describe the simulated data set,
and we discuss the photometry results. A companion paper (Euclid Collaboration:
Bretonni\`ere et al. 2022) is focused on the structural and morphological
estimates. We created mock Euclid images simulating five fields of view of 0.48
deg2 each in the band of the VIS instrument, each with three realisations
of galaxy profiles (single and double S\'ersic, and 'realistic' profiles
obtained with a neural network); for one of the fields in the double S\'ersic
realisation, we also simulated images for the three near-infrared ,
and bands of the NISP-P instrument, and five Rubin/LSST optical
complementary bands (, , , , and ). To analyse the results we
created diagnostic plots and defined ad-hoc metrics. Five model-fitting
software packages (DeepLeGATo, Galapagos-2, Morfometryka, ProFit, and
SourceXtractor++) were compared, all typically providing good results. (cut)Comment: 29 pages, 33 figures. Euclid pre-launch key paper. Companion paper:
Bretonniere et al. 202
Euclid preparation. XXXI. The effect of the variations in photometric passbands on photometric-redshift accuracy
The technique of photometric redshifts has become essential for the
exploitation of multi-band extragalactic surveys. While the requirements on
photo-zs for the study of galaxy evolution mostly pertain to the precision and
to the fraction of outliers, the most stringent requirement in their use in
cosmology is on the accuracy, with a level of bias at the sub-percent level for
the Euclid cosmology mission. A separate, and challenging, calibration process
is needed to control the bias at this level of accuracy. The bias in photo-zs
has several distinct origins that may not always be easily overcome. We
identify here one source of bias linked to the spatial or time variability of
the passbands used to determine the photometric colours of galaxies. We first
quantified the effect as observed on several well-known photometric cameras,
and found in particular that, due to the properties of optical filters, the
redshifts of off-axis sources are usually overestimated. We show using simple
simulations that the detailed and complex changes in the shape can be mostly
ignored and that it is sufficient to know the mean wavelength of the passbands
of each photometric observation to correct almost exactly for this bias; the
key point is that this mean wavelength is independent of the spectral energy
distribution of the source}. We use this property to propose a correction that
can be computationally efficiently implemented in some photo-z algorithms, in
particular template-fitting. We verified that our algorithm, implemented in the
new photo-z code Phosphoros, can effectively reduce the bias in photo-zs on
real data using the CFHTLS T007 survey, with an average measured bias Delta z
over the redshift range 0.4<z<0.7 decreasing by about 0.02, specifically from
Delta z~0.04 to Delta z~0.02 around z=0.5. Our algorithm is also able to
produce corrected photometry for other applications.Comment: 19 pages, 13 figures; Accepted for publication in A&
Euclid preparation. TBD. Forecast impact of super-sample covariance on 3x2pt analysis with Euclid
Deviations from Gaussianity in the distribution of the fields probed by
large-scale structure surveys generate additional terms in the data covariance
matrix, increasing the uncertainties in the measurement of the cosmological
parameters. Super-sample covariance (SSC) is among the largest of these
non-Gaussian contributions, with the potential to significantly degrade
constraints on some of the parameters of the cosmological model under study --
especially for weak lensing cosmic shear. We compute and validate the impact of
SSC on the forecast uncertainties on the cosmological parameters for the Euclid
photometric survey, obtained with a Fisher matrix analysis, both considering
the Gaussian covariance alone and adding the SSC term -- computed through the
public code PySSC. The photometric probes are considered in isolation and
combined in the `32pt' analysis. We find the SSC impact to be
non-negligible -- halving the Figure of Merit of the dark energy parameters
(, ) in the 32pt case and substantially increasing the
uncertainties on , and for cosmic shear;
photometric galaxy clustering, on the other hand, is less affected due to the
lower probe response. The relative impact of SSC does not show significant
changes under variations of the redshift binning scheme, while it is smaller
for weak lensing when marginalising over the multiplicative shear bias nuisance
parameters, which also leads to poorer constraints on the cosmological
parameters. Finally, we explore how the use of prior information on the shear
and galaxy bias changes the SSC impact. Improving shear bias priors does not
have a significant impact, while galaxy bias must be calibrated to sub-percent
level to increase the Figure of Merit by the large amount needed to achieve the
value when SSC is not included.Comment: 22 pages, 13 figure
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