11,902 research outputs found
Rotation of the cluster of galaxies A2107
We present indications of rotation in the galaxy cluster A2107 by a method
that searches for the maximum gradient in the velocity field in a flat
disk-like model of a cluster. Galaxies from cumulative sub-samples containing
more and more distant members from the cluster centre, are projected onto an
axis passing through the centre and we apply a linear regression model on the
projected distances and the line-of-sight velocities . The axis with the
maximum linear correlation coefficient defines the
direction of the maximum velocity gradient, and consequently it presents the
major axis of the apparently elliptical cluster. Because the effects of
rotation are subtle, we put strong emphasis on the estimation of the
uncertainties of the results by implementing different bootstrap techniques. We
have found the rotational effects are more strongly expressed from distances
Mpc from the cluster centre. The total virial mass of the
cluster is (3.2\pm0.6)\times10^{14} {\cal M}_{\sun}, while the virial mass,
corrected for the rotation, is (2.8\pm0.5) \times 10^{14}{\cal M}_{\sun}.Comment: 7 pages, 9 figures gzipped tar file. to be published in MNRA
Improved Parameters and New Lensed Features for Q0957+561 from WFPC2 Imaging
New HST WFPC2 observations of the lensed double QSO 0957+561 will allow
improved constraints on the lens mass distribution and hence will improve the
derived value of H. We first present improved optical positions and
photometry for the known components of this lens. The optical separation
between the A and B quasar images agrees with VLBI data at the 10 mas level,
and the optical center of the primary lensing galaxy G1 coincides with the VLBI
source G' to within 10 mas. The best previous model for this lens (Grogin and
Narayan 1996) is excluded by these data and must be reevaluated.
Several new resolved features are found within 10\arcsec of G1, including an
apparent fold arc with two bright knots. Several other small galaxies are
detected, including two which may be multiple images of each other. We present
positions and crude photometry of these objects.Comment: 7 pages including 2 postscript figures, LaTeX, emulateapj style. Also
available at
http://www.astro.lsa.umich.edu:80/users/philf/www/papers/list.htm
Reduced Fine-Tuning in Supersymmetry with R-parity violation
Both electroweak precision measurements and simple supersymmetric extensions
of the standard model prefer a mass of the Higgs boson less than the
experimental lower limit of 114 GeV. We show that supersymmetric models with R
parity violation and baryon number violation have a significant range of
parameter space in which the Higgs dominantly decays to six jets. These decays
are much more weakly constrained by current LEP analyses and would allow for a
Higgs mass near that of the . In general, lighter scalar quark and other
superpartner masses are allowed and the fine-tuning typically required to
generate the measured scale of electroweak symmetry breaking is ameliorated.
The Higgs would potentially be discovered at hadron colliders via the
appearance of new displaced vertices. The lightest neutralino could be
discovered by a scan of vertex-less events LEP I data.Comment: 5 pages, 2 figures. Significant detail added to the arguments
regarding LEP limits - made more quantitative. Better figures used, plotting
more physical quantities. Typos corrected and references updated. Conclusions
unchange
Dark Matter Scaling Relations
We establish the presence of a dark matter core radius, for the first time in
a very large number of spiral galaxies of all luminosities. Contrary to common
opinion we find that the sizes of these cores and the " DM core problem" are
bigger for more massive spirals. As a result the Burkert profile provides an
excellent mass model for dark halos around disk galaxies. Moreover, we find
that the spiral dark matter core densities and core radii
lie in the same scaling relation of dwarf galaxies with core radii upto ten times more
smaller.Comment: 4 pages, 4 figures, Accepted for Publication in Apj Let
Density functional calculations of the electronic structure and magnetic properties of the hydrocarbon K3picene superconductor near the metal-insulator transition
We have investigated the electronic structures and magnetic properties of of
K3picene, which is a first hydrocarbon superconductor with high transition
temperature T_c=18K. We have shown that the metal-insulator transition (MIT) is
driven in K3picene by 5% volume enhancement with a formation of local magnetic
moment. Active bands for superconductivity near the Fermi level E_F are found
to have hybridized character of LUMO and LUMO+1 picene molecular orbitals.
Fermi surfaces of K3picene manifest neither prominent nesting feature nor
marked two-dimensional behavior. By estimating the ratio of the Coulomb
interaction U and the band width W of the active bands near E_F, U/W, we have
demonstrated that K3picene is located in the vicinity of the Mott transition.Comment: 5 pages, 5 figure
The Ellipticity and Orientation of Clusters of Galaxies from N-Body Experiments
In this study we use simulations of 128 particles to study the
ellipticity and orientation of clusters of galaxies in N-body simulations of
differing power-law initial spectra (P(k) \propto k^n ,n = +1, 0, -1, -2\Omega_0 = 0.2nD < 15 h^{-1}n-$dependent way.Comment: 22 pages, requires aaspp4.sty, flushrt.sty, and epsf.sty Revised
manuscript, accepted for publication in Ap
Diabetes mellitus: Complex interplay between metformin, AKI and lactic acidosis.
Debate exists regarding the safety of metformin and the risk of metformin-associated lactic acidosis, particularly in the setting of kidney dysfunction. Data from two studies examining the interplay between metformin, acute kidney injury, and complications including lactic acidosis suggest that metformin should be used conservatively in patients with kidney dysfunction
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