6,861 research outputs found
A chemical evolution model for galaxy clusters
We develop a toy-model for the chemical evolution of the intracluster medium,
polluted by the galactic winds from elliptical galaxies. The model follows the
"galaxy formation history" of cluster galaxies, constrained by the observed
luminosity function.Comment: 6 pages, 10 figures, to appear in the Proceedings of the Workshop
"Chemical Enrichment of Intracluster and Intergalactic Medium", Vulcano,
Italy, 14-18 May 2001, ASP Conference Serie
Green public procurement criteria for road infrastructures: State of the art and proposal of a weighted sum multicriteria analysis to assessenvironmental impacts
In the last years, the attention to environmental issue is growing, demonstrating the interest to protect the nature and to better use the non-renewable resources. At international level, and especially in the European Community, for different trades, a wide production of voluntary documents and institutional acts proves the interest and the need for a green economy. An innovative approach may lead to the experience of Green Public Procurements (GPP), to protect the environment as a public interest and to promote technological developments. So far, the experiences of GPP are limited, not entirely positive and in the field of road infrastructures almost entirely absent. Construction and maintenance of road infrastructures is objectively more complex than purchasing goods or services. The paper proposes the integration of the weighted sum multi-criteria analysis into existing procedures. The methodology needs for environmental labels related to materials, machines and works which contribute to the final product "road". The labels are recognized at international level and consistent with procedures, conditions and criteria currently published in road tenders, therefore the approach can be followed to pursue the environmental sustainability of road infrastructures without compromising the economic attention
Tree Level Unitarity Bounds for the Minimal B-L Model
We have derived the unitarity bounds in the high energy limit for the minimal
B-L extension of the Standard Model by analysing the full class of Higgs and
would-be Goldstone boson two-to-two scatterings at tree level. Moreover, we
have investigated how these limits could vary at some lower critical value of
the energy.Comment: 20 pages, 4 figures, 2 tables; 1d figure modified, typos corrected,
bibliography augmented; published in PRD after minor adjustmen
The Z' boson of the minimal B-L model at future Linear Colliders in e+e- --> mu+mu-
We study the capabilities of future electron-positron Linear Colliders, with
centre-of-mass energy at the TeV scale, in accessing the parameter space of a
boson within the minimal model. We carry out a detailed comparison
between the discovery regions mapped over a two-dimensional configuration space
( mass and coupling) at the Large Hadron Collider and possible future
Linear Colliders for the case of di-muon production. As known in the literature
for other models, we confirm that leptonic machines, as compared to the
CERN hadronic accelerator, display an additional potential in discovering a
boson as well as in allowing one to study its properties at a level of
precision well beyond that of any of the existing colliders.Comment: 5 pages, proceeding of LC09 (Perugia), published by the Italian
Physical Society in the Nuovo Cimento C (Colloquia
Variegate galaxy cluster gas content: Mean fraction, scatter, selection effects and covariance with X-ray luminosity
We use a cluster sample selected independently of the intracluster medium
content with reliable masses to measure the mean gas mass fraction and its
scatter, the biases of the X-ray selection on gas mass fraction, and the
covariance between the X-ray luminosity and gas mass. The sample is formed by
34 galaxy clusters in the nearby () Universe, mostly with
, and with masses calculated with the
caustic technique. First, we found that integrated gas density profiles have
similar shapes, extending earlier results based on subpopulations of clusters
such as those that are relaxed or X-ray bright for their mass. Second, the
X-ray unbiased selection of our sample allows us to unveil a variegate
population of clusters; the gas mass fraction shows a scatter of
dex, possibly indicating a quite variable amount of feedback from cluster to
cluster, which is larger than is found in previous samples targeting
subpopulations of galaxy clusters, such as relaxed or X-ray bright clusters.
The similarity of the gas density profiles induces an almost scatterless
relation between X-ray luminosity, gas mass, and halo mass, and modulates
selection effects in the halo gas mass fraction: gas-rich clusters are
preferentially included in X-ray selected samples. The almost scatterless
relation also fixes the relative scatters and slopes of the and
relations and makes core-excised X-ray luminosities and gas masses
fully covariant. Therefore, cosmological or astrophysical studies involving
X-ray or SZ selected samples need to account for both selection effects and
covariance of the studied quantities with X-ray luminosity/SZ strength.Comment: A&A, in press, minor language changes from previous versio
Photonic band gaps analysis of Thue-Morse multilayers made of porous silicon
Dielectric aperiodic Thue-Morse structures up to 128 layers have
been fabricated by using porous silicon technology. The photonic band gap
properties of Thue-Morse multilayers have been theoretically investigated
by means of the transfer matrix method and the integrated density of states.
The theoretical approach has been compared and discussed with the
reflectivity measurements at variable angles for both the transverse electric
and transverse magnetic polarizations of light. The photonic band gap
regions, wide 70 nm and 90 nm, included between 0 and 30°, have been
observed for the sixth and seventh orders, respectively
Pushing the limits, episode 2: K2 observations of extragalactic RR Lyrae stars in the dwarf galaxy Leo IV
We present the first observations of extragalactic pulsating stars in the K2
ecliptic survey of the Kepler space telescope. Variability of all three RR
Lyrae stars in the dwarf spheroidal galaxy Leo IV were successfully detected,
at a brightness of Kp~21.5 mag, from data collected during Campaign 1. We
identified one modulated star and another likely Blazhko candidate with periods
of 29.8+-0.9 d and more than 80 d, respectively. EPIC 210282473 represents the
first star beyond the Magellanic Clouds for which the Blazhko period and
cycle-to-cycle variations in the modulation were unambiguously measured.The
photometric [Fe/H] indices of the stars agree with earlier results that Leo IV
is a very metal-poor galaxy. Two out of three stars blend with brighter
background galaxies in the K2 frames. We demonstrate that image subtraction can
be reliably used to extract photometry from faint confused sources that will be
crucial not only for the K2 mission but for future space photometric missions
as well.Comment: 8 pages, 6 figures, accepted for publication in the Astrophysical
Journal. Light curves can be downloaded from http://konkoly.hu/KIK/data.htm
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