149 research outputs found
Cluster luminosity function and n^th ranked magnitude as a distance indicator
We define here a standard candle to determine the distance of clusters of
galaxies and to investigate their peculiar velocities by using the n^{th} rank
galaxy (magnitude m). We address the question of the universality of the
luminosity function for a sample of 28 rich clusters of galaxies () in order to model the influence on of cluster richness. This
luminosity function is found to be universal and the fit of a Schechter profile
gives and in the range
[-21,-17]. The uncorrected distance indicator is more efficient for the
first ranks n. With n=5, we have a dispersion of 0.61 magnitude for the
(m,5log(cz)) relation. When we correct for the richness effect and subtract
the background galaxies we reduce the uncertainty to 0.21 magnitude with n=15.
Simulations show that a large part of this dispersion originates from the
intrinsic scatter of the standard candle itself. These provide upper bounds on
the amplitude of cluster radial peculiar motions. At a confidence
level of 90%, the dispersion is 0.13 magnitude and is limited to
1200 km/s for our sample of clusters.Comment: 9 pages, 7 postscript figures, LateX A&A, accepted in A&
Influence of the ice growth rate on the incorporation of gaseous HCl
International audienceIce crystals were grown in the laboratory at -15°C, at different growth rates and in the presence of a partial pressure of HCl of 1.63×10-3 Pa, to test whether the ice growth rate influences the amount of HCl taken up, XHCl, as predicted by the ice growth mechanism of Domine and Thibert (1996). The plot of HCl concentration in ice as a function of growth rate has the aspect predicted by that mechanism: XHCl decreases with increasing growth rate, from a value that depends on thermodynamic equilibrium to a value that depends only on kinetic factors. The height of the growth steps of the ice crystals is determined to be about 1.5 nm from these experiments. We discuss that the application of these laboratory experiments to cloud ice crystals and to snow metamorphism is not quantitatively possible at this stage, because the physical variables that determine crystal growth in nature, and in particular the step height, are not known. Qualitative applications are attempted for HCl and HNO3 incorporation in cloud ice and snowpack crystals
Influence of the ice growth rate on the incorporation of gaseous HCl
Ice crystals were grown in the laboratory at −15°C, at different growth rates and in the presence of a partial pressure of HCl of 1.63×10-3 Pa, to test whether the ice growth rate influences the amount of HCl taken up, XHCl, as predicted by the ice growth mechanism of Domine and Thibert (1996). The plot of HCl concentration in ice as a function of growth rate has the aspect predicted by that mechanism: XHCl decreases with increasing growth rate, from a value that depends on thermodynamic equilibrium to a value that depends only on kinetic factors. The height of the growth steps of the ice crystals is determined to be about 150 nm from these experiments. We discuss that the application of these laboratory experiments to cloud ice crystals and to snow metamorphism is not quantitatively possible at this stage, because the physical variables that determine crystal growth in nature, and in particular the step height, are not known. Qualitative applications are attempted for HCl and HNO3 incorporation in cloud ice and snowpack crystals
Affine interval exchange maps with a wandering interval
For almost all interval exchange maps T_0, with combinatorics of genus g>=2,
we construct affine interval exchange maps T which are semi-conjugate to T_0
and have a wandering interval.Comment: 43 pages, 1 figur
A Study of Nine High-Redshift Clusters of Galaxies: IV. Photometry and Sp ectra of Clusters 1324+3011 and 1604+4321
New photometric and spectroscopic observations of galaxies in the directions
of three distant clusters are presented as part of our on-going high-redshift
cluster survey. The clusters are CL1324+3011 at z = 0.76, CL1604+4304 at z =
0.90, and CL1604+4321 at z = 0.92. The observed x-ray luminosities in these
clusters are at least a factor of 3 smaller than those observed in clusters
with similar velocity dispersions at z <= 0.4. These clusters contain a
significant population of elliptical-like galaxies, although these galaxies are
not nearly as dominant as in massive clusters at z <= 0.5. We also find a large
population of blue cluster members. Defining an active galaxy as one in which
the rest equivalent width of [OII] is greater than 15 Angstroms, the fraction
of active cluster galaxies, within the central 1.0 Mpc, is 45%. In the field
population, we find that 65% of the galaxies with redshifts between z = 0.40
and z = 0.85 are active, while the fraction is 79% for field galaxies at z >
0.85. The star formation rate normalized by the rest AB B-band magnitude, SFRN,
increases as the redshift increases at a given evolving luminosity. At a given
redshift, however, SFRN decreases linearly with increasing luminosity
indicating a remarkable insensitivity of the star formation rate to the
intrinsic luminosity of the galaxy over the range -18 >= ABB >= -22. Cluster
galaxies in the central 1 Mpc regions exhibit depressed star formation rates.
We are able to measure significant evolution in the B-band luminosity function
over the range 0.1 <= z <= 1. The characteristic luminosity increases by a
factor of 3 with increasing redshift over this range.Comment: 64 pages, 18 figures, accepted for publication in the Astronomical
Journal on May 25, 2001. Scheduled to appear in Sept 2001 issu
Generalized quasiperiodic Rauzy tilings
We present a geometrical description of new canonical -dimensional
codimension one quasiperiodic tilings based on generalized Fibonacci sequences.
These tilings are made up of rhombi in 2d and rhombohedra in 3d as the usual
Penrose and icosahedral tilings. Thanks to a natural indexing of the sites
according to their local environment, we easily write down, for any
approximant, the sites coordinates, the connectivity matrix and we compute the
structure factor.Comment: 11 pages, 3 EPS figures, final version with minor change
Observational Mass-to-Light Ratio of Galaxy Systems: from Poor Groups to Rich Clusters
We study the mass-to-light ratio of galaxy systems from poor groups to rich
clusters, and present for the first time a large database for useful
comparisons with theoretical predictions. We extend a previous work, where B_j
band luminosities and optical virial masses were analyzed for a sample of 89
clusters. Here we also consider a sample of 52 more clusters, 36 poor clusters,
7 rich groups, and two catalogs, of about 500 groups each, recently identified
in the Nearby Optical Galaxy sample by using two different algorithms. We
obtain the blue luminosity and virial mass for all systems considered. We
devote a large effort to establishing the homogeneity of the resulting values,
as well as to considering comparable physical regions, i.e. those included
within the virial radius. By analyzing a fiducial, combined sample of 294
systems we find that the mass increases faster than the luminosity: the linear
fit gives M\propto L_B^{1.34 \pm 0.03}, with a tendency for a steeper increase
in the low--mass range. In agreement with the previous work, our present
results are superior owing to the much higher statistical significance and the
wider dynamical range covered (about 10^{12}-10^{15} M_solar). We present a
comparison between our results and the theoretical predictions on the relation
between M/L_B and halo mass, obtained by combining cosmological numerical
simulations and semianalytic modeling of galaxy formation.Comment: 25 pages, 12 eps figures, accepted for publication in Ap
Geometric representation of interval exchange maps over algebraic number fields
We consider the restriction of interval exchange transformations to algebraic
number fields, which leads to maps on lattices. We characterize
renormalizability arithmetically, and study its relationships with a
geometrical quantity that we call the drift vector. We exhibit some examples of
renormalizable interval exchange maps with zero and non-zero drift vector, and
carry out some investigations of their properties. In particular, we look for
evidence of the finite decomposition property: each lattice is the union of
finitely many orbits.Comment: 34 pages, 8 postscript figure
One Net Fits All: A unifying semantics of Dynamic Fault Trees using GSPNs
Dynamic Fault Trees (DFTs) are a prominent model in reliability engineering.
They are strictly more expressive than static fault trees, but this comes at a
price: their interpretation is non-trivial and leaves quite some freedom. This
paper presents a GSPN semantics for DFTs. This semantics is rather simple and
compositional. The key feature is that this GSPN semantics unifies all existing
DFT semantics from the literature. All semantic variants can be obtained by
choosing appropriate priorities and treatment of non-determinism.Comment: Accepted at Petri Nets 201
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