7,164 research outputs found
CoMaLit III. Literature Catalogs of weak Lensing Clusters of galaxies (LC^2)
The measurement of the mass of clusters of galaxies is crucial for their use
in cosmology and astrophysics. Masses can be efficiently determined with weak
lensing (WL) analyses. I compiled Literature Catalogs of weak Lensing Clusters
(LC). Cluster identifiers, coordinates, and redshifts have been
standardised. WL masses were reported to over-densities of 2500, 500, 200, and
to the virial one in the reference CDM model. Duplicate entries were
carefully handled. I produced three catalogs: LC-single, with 485 unique
groups and clusters analysed with the single-halo model; LC-substructure,
listing substructures in complex systems; LC-all, listing all the 822 WL
masses found in literature. The catalogs and future updates are publicly
available at http://pico.bo.astro.it/~sereno/CoMaLit/LC2/.Comment: 10 pages, 4 figures. v2: MNRAS in press; minor changes; updated link.
The catalogs and future updates will be hosted at
http://pico.bo.astro.it/~sereno/CoMaLit/LC2
Kinematic effect in gravitational lensing by clusters of galaxies
Gravitational lensing provides an efficient tool for the investigation of
matter structures, independent of the dynamical or hydrostatic equilibrium
properties of the deflecting system. However, it depends on the kinematic
status. In fact, either a translational motion or a coherent rotation of the
mass distribution can affect the lensing properties. Here, light deflection by
galaxy clusters in motion is considered. Even if gravitational lensing mass
measurements of galaxy clusters are regarded as very reliable estimates, the
kinematic effect should be considered. A typical peculiar motion with respect
to the Hubble flow brings about a systematic error < 0.3%, independent of the
mass of the cluster. On the other hand, the effect of the spin increases with
the total mass. For cluster masses ~ 10^{15}M_{sun}, the effect of the
gravitomagnetic term is < 0.04% on strong lensing estimates and < 0.5% in the
weak lensing analyses. The total kinematic effect on the mass estimate is then
< 1%, which is negligible in current statistical studies. In the weak lensing
regime, the rotation imprints a typical angular modulation in the tangential
shear distortion. This would allow in principle a detection of the
gravitomagnetic field and a direct measurement of the angular velocity of the
cluster but the required background source densities are well beyond current
tecnological capabilities.Comment: 6 pages; accepted for publication in MNRA
Measuring dark energy with the shear triplet statistics
The shear triplet statistics is a geometric method to measure cosmological
parameters with observations in the weak gravitational lensing regime towards
massive haloes. Here, this proposal is considered to probe the dark energy
equation of state and its time derivative in view of future wide-field galaxy
surveys. A survey with a median redshift of nearly 0.7 and a total area of
nearly 10000 square degrees would be pretty effective in determining the dark
matter cosmological density and in putting useful constraints on the dark
energy properties.Comment: 5 pages, 3 figures, accepted for publication in MNRA
Bridging fiddle and classical communities in Calgary, Canada : the Baroque & Buskin’ String Orchestra
Publisher PD
The mass-concentration relation in massive galaxy clusters at redshift ~1
Mass and concentration of clusters of galaxies are related and evolving with
redshift. We study the properties of a sample of 31 massive galaxy clusters at
high redshift, 0.8 < z < 1.5, using weak and strong lensing observations.
Concentration is a steep function of mass, c_{200} ~M_{200}^{-0.83 +-0.39},
with higher-redshift clusters being less concentrated. Mass and concentration
from the stacked analysis, M_{200}=(4.1+-0.4)x10^{14}M_Sun/h and
c_{200}=2.3+-0.2, are in line with theoretical results extrapolated from the
local universe. Clusters with signs of dynamical activity preferentially
feature high concentrations. We discuss the possibility that the whole sample
is a mix of two different kinds of haloes. Over-concentrated clusters might be
accreting haloes out of equilibrium in a transient phase of compression,
whereas less concentrated ones might be more relaxed.Comment: 10 pages, 3 figures; in press on MNRA
Hubble constant and dark energy inferred from free-form determined time delay distances
Time delays between multiple images of lensed sources can probe the geometry
of the universe. We propose a novel method based on free-form modelling of
gravitational lenses to estimate time-delay distances and, in turn,
cosmological parameters. This approach does not suffer from the degeneracy
between the steepness of the profile and the cosmological parameters. We apply
the method to 18 systems having time delay measurements and find
H_0=69+-6(stat.)+-4(syst.) km s^{-1}Mpc^{-1}. In combination with WMAP9, the
constraints on dark energy are Omega_w=0.68+-0.05 and w=-0.86+-0.17 in a flat
model with constant equation-of-state.Comment: 6 pages; accepted for publication on MNRA
Weak field limit of Reissner-Nordstrom black hole lensing
We study gravitational lensing by a Reissner-Nordstrom (RN) black hole in the
weak field limit. We obtain the basic equations for the deflection angle and
time delay and find analytical expressions for the positions and amplifications
of the primary and secondary images. Due to a net positive charge, the
separation between images increases, but no change in the total magnification
occurs.Comment: 8 pages, to appear in Phys. Rev.
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