173 research outputs found
Deep R-band counts of z~3 Lyman break galaxy candidates with the LBT
Aims. We present a deep multiwavelength imaging survey (UGR) in 3 different
fields, Q0933, Q1623, and COSMOS, for a total area of ~1500arcmin^2. The data
were obtained with the Large Binocular Camera on the Large Binocular Telescope.
Methods. To select our Lyman break galaxy (LBG) candidates, we adopted the well
established and widely used color-selection criterion (U-G vs. G-R). One of the
main advantages of our survey is that it has a wider dynamic color range for
U-dropout selection than in previous studies. This allows us to fully exploit
the depth of our R-band images, obtaining a robust sample with few interlopers.
In addition, for 2 of our fields we have spectroscopic redshift information
that is needed to better estimate the completeness of our sample and interloper
fraction. Results. Our limiting magnitudes reach 27.0(AB) in the R band
(5\sigma) and 28.6(AB) in the U band (1\sigma). This dataset was used to derive
LBG candidates at z~3. We obtained a catalog with a total of 12264 sources down
to the 50% completeness magnitude limit in the R band for each field. We find a
surface density of ~3 LBG candidates arcmin^2 down to R=25.5, where
completeness is >=95% for all 3 fields. This number is higher than the original
studies, but consistent with more recent samples.Comment: in press by A&A, full LBG candidates' catalog will be available in
electronic form at the CD
ASTRI SST-2M prototype and mini-array simulation chain, data reduction software, and archive in the framework of the Cherenkov Telescope Array
The Cherenkov Telescope Array (CTA) is a worldwide project aimed at building
the next-generation ground-based gamma-ray observatory. Within the CTA project,
the Italian National Institute for Astrophysics (INAF) is developing an
end-to-end prototype of the CTA Small-Size Telescopes with a dual-mirror
(SST-2M) Schwarzschild-Couder configuration. The prototype, named ASTRI SST-2M,
is located at the INAF "M.C. Fracastoro" observing station in Serra La Nave
(Mt. Etna, Sicily) and is currently in the scientific and performance
validation phase. A mini-array of (at least) nine ASTRI telescopes has been
then proposed to be deployed at the Southern CTA site, by means of a
collaborative effort carried out by institutes from Italy, Brazil, and
South-Africa. The CTA/ASTRI team is developing an end-to-end software package
for the reduction of the raw data acquired with both ASTRI SST-2M prototype and
mini-array, with the aim of actively contributing to the global ongoing
activities for the official data handling system of the CTA observatory. The
group is also undertaking a massive Monte Carlo simulation data production
using the detector Monte Carlo software adopted by the CTA consortium.
Simulated data are being used to validate the simulation chain and evaluate the
ASTRI SST-2M prototype and mini-array performance. Both activities are also
carried out in the framework of the European H2020-ASTERICS (Astronomy ESFRI
and Research Infrastructure Cluster) project. A data archiving system, for both
ASTRI SST-2M prototype and mini-array, has been also developed by the CTA/ASTRI
team, as a testbed for the scientific archive of CTA. In this contribution, we
present the main components of the ASTRI data handling systems and report the
status of their development.Comment: Proceedings of the 35th International Cosmic Ray Conference (ICRC
2017), Bexco, Busan, Korea. All CTA contributions at arXiv:1709.0348
The Blue Straggler population in the globular cluster M53 (NGC5024): a combined HST, LBT, CFHT study
We used a proper combination of multiband high-resolution and wide field
multi-wavelength observations collected at three different telescopes (HST, LBT
and CFHT) to probe Blue Straggler Star (BSS) populations in the globular
cluster M53. Almost 200 BSS have been identified over the entire cluster
extension. The radial distribution of these stars has been found to be bimodal
(similarly to that of several other clusters) with a prominent dip at ~60'' (~2
r_c) from the cluster center. This value turns out to be a factor of two
smaller than the radius of avoidance (r_avoid, the radius within which all the
stars of ~1.2 M_sun have sunk to the core because of dynamical friction effects
in an Hubble time). While in most of the clusters with a bimodal BSS radial
distribution, r_avoid has been found to be located in the region of the
observed minimum, this is the second case (after NGC6388) where this
discrepancy is noted. This evidence suggests that in a few clusters the
dynamical friction seems to be somehow less efficient than expected.
We have also used this data base to construct the radial star density profile
of the cluster: this is the most extended and accurate radial profile ever
published for this cluster, including detailed star counts in the very inner
region. The star density profile is reproduced by a standard King Model with an
extended core (~25'') and a modest value of the concentration parameter
(c=1.58). A deviation from the model is noted in the most external region of
the cluster (at r>6.5' from the center). This feature needs to be further
investigated in order to address the possible presence of a tidal tail in this
cluster.Comment: 25 pages, 9 figures, accepted for publication on Ap
An optical and HI study of the dwarf Local Group galaxy VV124=UGC4879. A gas-poor dwarf with a stellar disk?
We present a detailed study of the dwarf galaxy VV124, recently recognized as
a isolated member of the Local Group. We have obtained deep (r=26.5) wide-field
g,r photometry of individual stars with the LBT under sub-arcsec seeing
conditions. The Color-Magnitude Diagram suggests that the stellar content of
the galaxy is dominated by an old, metal-poor population, with a significant
metallicity spread. A very clean detection of the RGB tip allows us to derive
an accurate distance of D=1.3 +/- 0.1 Mpc. Combining surface photometry with
star counts, we are able to trace the surface brightness profile of VV124 out
to ~ 5' = 1.9 kpc radius (where mu_r=30 mag/arcsec^2), showing that it is much
more extended than previously believed. Moreover, the surface density map
reveals the presence of two symmetric flattened wings emanating from the
central elongated spheroid and aligned with its major axis, resembling a
stellar disk seen nearly edge-on. We also present HI observations obtained with
the WSRT, the first ever of this object. A total amount of 10^6 M_sun of HI gas
is detected in VV124. Compared to the total luminosity, this gives a value of
M_HI/L_V=0.11, which is particularly low for isolated Local Group dwarfs. The
spatial distribution of the gas does not correlate with the observed stellar
wings. The systemic velocity of the HI in the region superposed to the stellar
main body of the galaxy is V_h=-25 km/s. The velocity field shows substructures
typical of galaxies of this size but no sign of rotation. The HI spectra
indicates the presence of a two-phase interstellar medium, again typical of
many dwarf galaxies.Comment: Accepted for publication in A&A. 19 pages, 20 reduced-resolution
figures, pdflatex, A&A style. The full resolution pdf file can be be
downloaded from http://www.bo.astro.it/SGR
A low escape fraction of ionizing photons of L>L* Lyman break galaxies at z=3.3
We present an upper limit for the relative escape fraction (f_{esc}^{rel}) of
ionizing radiation at z~3.3 using a sample of 11 Lyman Break Galaxies (LBGs)
with deep imaging in the U band obtained with the Large Binocular Camera,
mounted on the prime focus of the Large Binocular Telescope. We selected 11
LBGs with secure redshift in the range 3.27<z<3.35, from 3 independent fields.
We stacked the images of our sources in the R and U band, which correspond to
an effective rest-frame wavelength of 1500\AA and 900\AA respectively,
obtaining a limit in the U band image of >=30.7(AB)mag at 1 sigma. We derive a
1 sigma upper limit of f_{esc}^{rel}~5%, which is one of the lowest values
found in the literature so far at z~3.3. Assuming that the upper limit for the
escape fraction that we derived from our sample holds for all galaxies at this
redshift, the hydrogen ionization rate that we obtain (Gamma_{-12}<0.3 s^{-1})
is not enough to keep the IGM ionized and a substantial contribution to the UV
background by faint AGNs is required. Since our sample is clearly still limited
in size, larger z~3 LBG samples, at similar or even greater depths are
necessary to confirm these results on a more firm statistical basis.Comment: 15 pages, 2 figures, 1 table, accepted for publication in Ap
Wide and deep near-UV (360nm) galaxy counts and the extragalactic background light with the Large Binocular Camera
Deep multicolour surveys are the main tool to explore the formation and
evolution of the faint galaxies which are beyond the spectroscopic limit with
the present technology. The photometric properties of these faint galaxies are
usually compared with current renditions of semianalytical models to provide
constraints on the fundamental physical processes involved in galaxy formation
and evolution, namely the mass assembly and the star formation. Galaxy counts
over large sky areas in the near-UV band are important because they are
difficult to obtain given the low efficiency of near-UV instrumentation, even
at 8m class telescopes. A large instrumental field of view helps in minimizing
the biases due to the cosmic variance. We have obtained deep images in the
360nm U band provided by the blue channel of the Large Binocular Camera at the
prime focus of the Large Binocular Telescope. We have derived over an area of
~0.4 sq. deg. the galaxy number counts down to U=27 in the Vega system
(corresponding to U=27.86 in the AB system) at a completeness level of 30%
reaching the faintest current limit for this wavelength and sky area. The shape
of the galaxy counts in the U band can be described by a double power-law, the
bright side being consistent with the shape of shallower surveys of comparable
or greater areas. The slope bends over significantly at U>23.5 ensuring the
convergence of the contribution by star forming galaxies to the EBL in the
near-UV band to a value which is more than 70% of the most recent upper limits
derived for this band. We have jointly compared our near-UV and K band counts
collected from the literature with few selected hierarchical CDM models
emphasizing critical issues in the physical description of the galaxy formation
and evolution.Comment: Accepted for publication in A&A. Uses aa.cls, 9 pages, 4 figures.
Citations update
Miglioramento della resistenza e della performance muscolare mediante trattamento con onde d’urto defocalizzate
Scopo di questo studio \ue8 la valutazione degli effetti di un trattamento con onde d\u2019urto defocalizzate sull\u2019attivit\ue0 del muscolo scheletrico in termini di resistenza e di performance.
Sono stati reclutati 60 soggetti sani, 30 maschi e 30 femmine. 40 pazienti sono stati sottoposti al protocollo di intervento, mentre 20 hanno partecipato al gruppo di controllo, senza ricevere il trattamento con onde d\u2019urto.
Al termine di un ciclo di quattro sedute di onde d\u2019urto si \ue8 osservato un aumento dell\u2019Endurance Time e una diminuzione della Frequenza Cardiaca Massimale durante il test da sforzo a carico costante su cicloergometro.
A 12 settimane dalla fine del trattamento i valori della Frequenza cardiaca Massimale non hanno subito variazioni statisticamente significative, mentre quelli dell\u2019Endurance Time hanno subito un ritorno ai valori basali.
Per quanto riguarda la performance muscolare si \ue8 visto un miglioramento significativo alla valutazione T1, subito dopo la terapia con onde d\u2019urto, e alla valutazione T2, 12 settimane dopo l\u2019ultima seduta di onde d\u2019urto, rispetto alla valutazione iniziale a T0. Non \ue8 stata evidenziata una differenza statisticamente significativa tra i valori rilevati a T1e quelli a T2.
I risultati di questo studio suggeriscono che il trattamento con onde d\u2019urto defocalizzate pu\uf2 portare a un miglioramento dell\u2019attivit\ue0 del muscolo scheletrico in termini di performance e di resistenza muscolare senza provocare alcun tipo di danno ai tessuti.
Questi risultati aprono possibilit\ue0 di applicazione di questa metodica sia in ambito clinico (per esempio per il recupero funzionale dell\u2019amiotrofia ex non usu), sia in ambito sportivo
- …