61 research outputs found
Characterizing SL2S galaxy groups using the Einstein radius
We analyzed the Einstein radius, , in our sample of SL2S galaxy
groups, and compared it with (the distance from the arcs to the center of
the lens), using three different approaches: 1.- the velocity dispersion
obtained from weak lensing assuming a Singular Isothermal Sphere profile
(), 2.- a strong lensing analytical method ()
combined with a velocity dispersion-concentration relation derived from
numerical simulations designed to mimic our group sample, 3.- strong lensing
modeling () of eleven groups (with four new models presented in
this work) using HST and CFHT images. Finally, was analyzed as a function
of redshift to investigate possible correlations with L, N, and the
richness-to-luminosity ratio (N/L). We found a correlation between
and , but with large scatter. We estimate = (2.2 0.9)
+ (0.7 0.2), = (0.4 1.5) + (1.1
0.4), and = (0.4 1.5) + (0.9 0.3) for
each method respectively. We found a weak evidence of anti-correlation between
and , with Log = (0.580.06) - (0.040.1), suggesting
a possible evolution of the Einstein radius with , as reported previously by
other authors. Our results also show that is correlated with L and N
(more luminous and richer groups have greater ), and a possible
correlation between and the N/L ratio. Our analysis indicates that
is correlated with in our sample, making useful to
characterize properties like L and N (and possible N/L) in galaxy groups.
Additionally, we present evidence suggesting that the Einstein radius evolves
with .Comment: Accepted for publication in Astronomy & Astrophysics. Typos correcte
Dark matter-baryons separation at the lowest mass scale: the Bullet Group
We report on the X-ray observation of a strong lensing selected group, SL2S
J08544-0121, with a total mass of
which revealed a separation of kpc between the X-ray emitting
collisional gas and the collisionless galaxies and dark matter (DM), traced by
strong lensing. This source allows to put an order of magnitude estimate to the
upper limit to the interaction cross section of DM of 10 cm g. It is
the lowest mass object found to date showing a DM-baryons separation and it
reveals that the detection of bullet-like objects is not rare and confined to
mergers of massive objects opening the possibility of a statistical detection
of DM-baryons separation with future surveys.Comment: 5 pages, 3 figures. Accepted for publication in MNRAS Letters. Typos
correcte
CLASH-VLT: The mass, velocity-anisotropy, and pseudo-phase-space density profiles of the z
Low-temperature magnetic ordering and structural distortions in vanadium sesquioxide V2O3
Vanadium sesquioxide (V2O3) is an antiferromagnetic insulator below T-N approximate to 155 K. The magnetic order does not consist of only antiferromagnetic nearest-neighbor bonds, possibly excluding the interplane vanadium pairs, as one would infer from the bipartite character of the hexagonal basal plane in the high-temperature corundum structure. In fact, a magnetic structure with one ferromagnetic bond and two antiferromagnetic ones in the honeycomb plane is known experimentally to be realized, accompanied by a monoclinic distortion that makes the ferromagnetic bond inequivalent from the other two. We show here that the magnetic ordering, the accompanying monoclinic structural distortion, the magnetic anisotropy, and also the recently discovered high-pressure nonmagnetic monoclinic phase, can all be accurately described by conventional electronic structure calculations within GGA and GGA+U. Remarkably, our calculations yield that the corundum phase would be unstable to a monoclinic distortion even without magnetic ordering, thus suggesting that magnetism and lattice distortion are independent phenomena, though they reinforce each other. By means of GGA+U, we find a metal-to-insulator transition at a critical U-c. Bothmetal at U <= U-c and insulator above U-c have the same magnetic order as that actually observed below T-N, but different monoclinic distortions. Reassuringly, the distortion on the insulating side agrees with the experimental one. Our results are in line with DMFT calculations for the paramagnetic phase [A. I. Poteryaev et al., Phys. Rev. B 76, 085127 (2007)], which predict that the insulating character is driven by a correlation-enhanced crystal-field splitting between e(g)(pi) and a(1g) orbitals that pushes the latter above the chemical potential. We find that the a(1g) orbital, although almost empty in the insulating phase, is actually responsible for the unusual magnetic order as it leads to magnetic frustration whose effect is similar to a next-nearest-neighbor exchange in a Heisenberg model on a honeycomb lattice
MAGNETIC SUSCEPTIBILITIES AND POLYMERIC STRUCTURES OF COPPER(II) COMPLEXES WITH PYRAZOLE, IMIDAZOLE, AND TRIAZOLE
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