3,214 research outputs found
A radial mass profile analysis of the lensing cluster MS2137-23
We reanalyze the strong lens modeling of the cluster of galaxies MS2137-23
using a new data set obtained with the ESO VLT. We found the photometric
redshifts of the two main arc systems are both at z=1.6. After subtraction of
the central cD star light of the HST image we found that only one object lying
underneath has the expected properties of the fifth image associated to the
tangential arc. We improve the previous lens modelings of the central dark
matter distribution of the cluster, using an isothermal model with a core (IS)
and the NFW-like model with a cusp. Without the fifth image, the arc properties
together with the shear map profile are equally well fit by the and by an IS
and a sub-class of generalized-NFW mass profiles having inner slope power index
in the range 0.7<alpha<1.2. Adding new constrains provided by the fifth image
favors IS profiles that better predict the fifth image properties. A model
including cluster galaxy perturbations or the the stellar mass distribution
does not change our conclusions but imposes the M/L_I of the cD stellar
component is below 10 at a 99% confidence level.
Using our new detailed lensing model together with Chandra X-ray data and the
cD stellar component we finally discuss intrinsic properties of the
gravitational potential. Whereas X-ray and dark matter have a similar shape at
various radius, the cD stellar isophotes are twisted by 13 deg. The sub-
arc-second azimuthal shift we observe between the radial arc position and the
predictions of elliptical models correspond to what is expected from a mass
distribution twist. This shift may result from a projection effect of the cD
and the cluster halos, thus revealing the triaxiality of the system.Comment: Final version accepted in A&
Test of Information Theory on the Boltzmann Equation
We examine information theory using the steady-state Boltzmann equation. In a
nonequilibrium steady-state system under steady heat conduction, the
thermodynamic quantities from information theory are calculated and compared
with those from the steady-state Boltzmann equation. We have found that
information theory is inconsistent with the steady-state Boltzmann equation.Comment: 12 page
More Schooling, More Children: Compulsory Schooling Reforms and Fertility in Europe
We study the relationship between education and fertility, exploiting compulsory schooling reforms in Europe as source of exogenous variation in education. Using data from 8 European countries, we assess the causal effect of education on the number of biological kids and the incidence of childlessness. We find that more education causes a substantial decrease in childlessness and an increase in the average number of children per woman. Our findings are robust to a number of falsification checks and we can provide complementary empirical evidence on the mechanisms leading to these surprising results.
Properties of high-z galaxies as seen through lensing clusters
We discuss the first results obtained on the study of a sample of high-z
galaxies (2 < z < 7), using the gravitational amplification effect in the core
of lensing clusters. Sources are located close to the critical lines in
clusters with well constrained mass distributions, and selected through
photometric redshifts, computed on a large wavelength domain, and lens
inversion techniques.Comment: 5 pages, 3 figures, Conference Proceedings of the "Clustering at High
Redshift" Conference, June 29 to July 2, 1999, Marseille (France
MOND and Cosmology
I review various ideas on MOND cosmology and structure formation beginning
with non-relativistic models in analogy with Newtonian cosmology. I discuss
relativistic MOND cosmology in the context of Bekenstein's theory and propose
an alternative biscalar effective theory of MOND in which the acceleration
parameter is identified with the cosmic time derivative of a matter coupling
scalar field. Cosmic CDM appears in this theory as scalar field oscillations of
the auxiliary "coupling strength" field.Comment: 8 pages, LaTeX, 2 figures, to appear in proceedings of IAP05 in
Paris: Mass Profiles and Shapes of Cosmological Structures, G. Mamon, F.
Combes, C. Deffayet and B. Fort (eds), (EDP-Sciences 2005
Methods for heat transfer and temperature field analysis of the insulated diesel phase 2 progress report
This report describes work done during Phase 2 of a 3 year program aimed at developing a comprehensive heat transfer and thermal analysis methodology for design analysis of insulated diesel engines. The overall program addresses all the key heat transfer issues: (1) spatially and time-resolved convective and radiative in-cylinder heat transfer, (2) steady-state conduction in the overall structure, and (3) cyclical and load/speed temperature transients in the engine structure. During Phase 2, radiation heat transfer model was developed, which accounts for soot formation and burn up. A methodology was developed for carrying out the multi-dimensional finite-element heat conduction calculations within the framework of thermodynamic cycle codes. Studies were carried out using the integrated methodology to address key issues in low heat rejection engines. A wide ranging design analysis matrix was covered, including a variety of insulation strategies, recovery devices and base engine configurations. A single cylinder Cummins engine was installed at Purdue University, and it was brought to a full operational status. The development of instrumentation was continued, concentrating on radiation heat flux detector, total heat flux probe, and accurate pressure-crank angle data acquisition
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