2,048 research outputs found
Studying the Evolution of Multi-Wavelength Emissivities with the Vimos VLT Deep Survey
The VIMOS VLT Deep Survey is a unique I-selected spectroscopic sample to
study galaxies all the way from z=5 to z=0. We recapitulate the first results
about the evolution of the galaxy populations as a function of type,
morphology, environment and luminosity.Comment: 9 pages, 11 figures. To appear in the proceedings of the XLIst
Rencontres de Moriond, XXVIth Astrophysics Moriond Meeting: "From dark halos
to light", Eds. L.Tresse, S. Maurogordato and J. Tran Thanh Van (Editions
Frontieres
The renovation of Santa Maria di Collemaggio Basilica: the intervention on the nave’s columns
The earthquake of L’Aquila in 2009 caused the partial collapse of the S. Maria di Collemaggio Basilica. The XIII century nave’s columns showed serious cracking throughout their height. Therefore, a retrofitting intervention was planned with the purpose of protecting these valuable elements from future additional damages. The intervention designed involved the complete unloading and reloading of the columns. To avoid additional damages, it was necessary to verify that the procedure would not alter significantly the existing stress state and would not lead to the occurrence of tensile stresses greater than the materials’ tensile strength. Therefore, a 3D FE model of the colonnade and the supported wall has been realized and a construction stage non-linear analysis implemented. The geometry was modeled through the acquisition of the results of a laser scanner survey in order to reflect faithfully the Basilica’s irregularities (lack of verticality of the wall, eccentricities, different dimensions from one column to the other). Moreover, elastic-brittle constitutive laws were assigned to the model’s materials to reproduce the intrinsic non-linearity of the masonry. The analysis results in terms of stresses and displacements were attentively analyzed. Furthermore, a comparison between the numerical results and the values measured during the intervention has been executed. An acceptable deviation between the values was observed and, therefore, the reliability of the model was assured
Two-bands effect on the superconducting fluctuating diamagnetism in MgB₂
The field dependence of the magnetization above the transition temperature Tc
in MgB₂ is shown to evidence a diamagnetic contribution consistent with
superconducting fluctuations reflecting both the σ and π bands. In
particular, the upturn field Hup in the magnetization curve, related to the
incipient effect of the magnetic field in quenching the fluctuating pairs,
displays a double structure, in correspondence to two correlation lengths. The
experimental findings are satisfactorily described by the extension to the
diamagnetism of a recent theory for paraconductivity, in the framework of a
zero-dimensional model for the fluctuating superconducting droplets above Tc
The Big Brown Bear
https://digitalcommons.library.umaine.edu/mmb-vp/5536/thumbnail.jp
The Ha Luminosity Function and Star Formation Rate at z\sim 0.2
We have measured the Ha+[N II] fluxes of the I-selected Canada-France
Redshift Survey (CFRS) galaxies lying at a redshift z below 0.3, and hence
derived the Ha luminosity function. The magnitude limits of the CFRS mean that
only the galaxies with M(B) > -21 mag were observed at these redshifts. We
obtained a total Ha luminosity density of at least 10^{39.44\pm 0.04}
erg/s/Mpc^{3} at a mean z=0.2 for galaxies with rest-fame EW(Ha+[N II]) > 10
Angs. This is twice the value found in the local universe by Gallego et al.
1995. Our Ha star formation rate, derived from Madau (1997) is higher than the
UV observations at same z, implying a UV dust extinction of about 1 mag. We
found a strong correlation between the Ha luminosity and the absolute magnitude
in the B-band: M(B(AB)) = 46.7 - 1.6 log L(Ha). This work will serve as a basis
of future studies of Ha luminosity distributions measured from
optically-selected spectroscopic surveys of the distant universe, and it will
provide a better understanding of the physical processes responsible for the
observed galaxy evolution.Comment: Accepted for publication in ApJ, 14 pages, LaTeX (macro aas2pp4.sty),
6 figure
The VIMOS VLT Deep Survey. The different assembly history of passive and star-forming L_B >= L*_B galaxies in the group environment at z < 1
We use the VIMOS VLT Deep Survey to study the close environment of galaxies
in groups at 0.2 = L*_B galaxies (Me_B =
M_B + 1.1z <= -20) are identified with Me_B <= -18.25 and within a relative
distance 5h^-1 kpc <= rp <= 100h^-1 kpc and relative velocity Delta v <= 500
km/s . The richness N of a group is defined as the number of Me_B <= -18.25
galaxies belonging to that group. We split our principal sample into red,
passive galaxies with NUV - r >= 4.25 and blue, star-forming galaxies with NUV
- r < 4.25. We find that blue galaxies with a close companion are primarily
located in poor groups, while the red ones are in rich groups. The number of
close neighbours per red galaxy increases with N, with n_red being proportional
to 0.11N, while that of blue galaxies does not depend on N and is roughly
constant. In addition, these trends are found to be independent of redshift,
and only the average n_blue evolves, decreasing with cosmic time. Our results
support the following assembly history of L_B >= L*_B galaxies in the group
environment: red, massive galaxies were formed in or accreted by the dark
matter halo of the group at early times (z >= 1), therefore their number of
neighbours provides a fossil record of the stellar mass assembly of groups,
traced by their richness N. On the other hand, blue, less massive galaxies have
recently been accreted by the group potential and are still in their parent
dark matter halo, having the same number of neighbours irrespective of N. As
time goes by, these blue galaxies settle in the group potential and turn red
and/or fainter, thus becoming satellite galaxies in the group. With a toy
quenching model, we estimate an infall rate of field galaxies into the group
environment of R_infall = 0.9 - 1.5 x 10^-4 Mpc^-3 Gyr^-1 at z ~ 0.7.Comment: Astronomy and Astrophysics, in press. 11 pages, 11 figures, 4 tables.
Minor changes with respect to the first versio
Nonlinear dynamic analysis of gas turbine combustor leaf seal
The leaf seals are one of the typical sealing systems in gas turbine and jet engines. In Baker Hughes LT family gas turbines, they are used to create sealing between the combustion chamber and the first stage nozzle. The leaf seals are thin metallic plates and subjected to dynamic loads and high temperatures. They have curved contacts, and depending on the inclination, they can experience partial contact. Furthermore, when excited by dynamic loads, the leaf seal can be subject to intermittent contact, possibly triggering wear out or vibratory phenomena. Due to its flexibility and its partial seating, it exhibits a complex nonlinear dynamic behaviour, strongly variable with the operating conditions. This study presents a numerical investigation using coupled static/dynamic harmonic balance method (HBM) frequency-based solution technique. The reported solutions include nonlinear forced response and contact studies for various operating and kinematic conditions along with brief insights
Analog front-end for pixel sensors in a 3D CMOS technology for the SuperB Layer0
This work is concerned with the design of two different analog channels for hybrid and monolithic pixels readout in view of applications to the SVT at the SuperB Factory. The circuits have been designed in a 130nm CMOS, vertically integrated technology, which, among others, may provide some advantages in terms of functional density and electrical isolation between the analog and the digital sections of the front-end
Luminosity Functions of Elliptical Galaxies at z < 1.2
The luminosity functions of E/S0 galaxies are constructed in 3 different
redshift bins (0.2 < z < 0.55, 0.55 < z < 0.8, 0.8 < z < 1.2), using the data
from the Hubble Space Telescope Medium Deep Survey (HST MDS) and other HST
surveys. These independent luminosity functions show the brightening in the
luminosity of E/S0s by about 0.5~1.0 magnitude at z~1, and no sign of
significant number evolution.
This is the first direct measurement of the luminosity evolution of E/S0
galaxies, and our results support the hypothesis of a high redshift of
formation (z > 1) for elliptical galaxies, together with weak evolution of the
major merger rate at z < 1.Comment: To be published in ApJ Letters, 4 pages, AAS Latex, 4 figures, and 2
table
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