974 research outputs found
Determination of Dark Matter Properties at High-Energy Colliders
If the cosmic dark matter consists of weakly-interacting massive particles,
these particles should be produced in reactions at the next generation of
high-energy accelerators. Measurements at these accelerators can then be used
to determine the microscopic properties of the dark matter. From this, we can
predict the cosmic density, the annihilation cross sections, and the cross
sections relevant to direct detection. In this paper, we present studies in
supersymmetry models with neutralino dark matter that give quantitative
estimates of the accuracy that can be expected. We show that these are well
matched to the requirements of anticipated astrophysical observations of dark
matter. The capabilities of the proposed International Linear Collider (ILC)
are expected to play a particularly important role in this study.Comment: 124 pages, 62 figures; corrections and new material in Section 2.6
(direct detection); misc. additional correction
High-Angular Resolution Dust Polarization Measurements: Shaped B-field Lines in the Massive Star Forming Region Orion BN/KL
We present observational results of the thermal dust continuum emission and
its linear polarization in one of the nearest massive star-forming sites Orion
BN/KL in Orion Molecular Cloud-1. The observations were carried out with the
Submillimeter Array. With an angular resolution of 1" (~2 mpc; 480 AU), we have
detected and resolved the densest cores near the BN/KL region. At a wavelength
of ~870 micron, the polarized dust emission can be used to trace the structure
of the magnetic field in this star-forming core. The dust continuum appears to
arise from a V-shaped region, with a cavity nearly coincident with the center
of the explosive outflows observed on larger scales. The position angles
(P.A.s) of the observed polarization vary significantly by a total of about 90
degree but smoothly, i.e., curl-like, across the dust ridges. Such a
polarization pattern can be explained with dust grains being magnetically
aligned instead of mechanically with outflows, since the latter mechanism would
cause the P.A.s to be parallel to the direction of the outflow, i.e.,
radial-like. The magnetic field projected in the plane of sky is therefore
derived by rotating the P.A.s of the polarization by 90 degree. We find an
azimuthally symmetric structure in the overall magnetic field morphology, with
the field directions pointing toward 2.5" west to the center of the explosive
outflows. We also find a preferred symmetry plane at a P.A. of 36 degree, which
is perpendicular to the mean magnetic field direction (120 degree) of the 0.5
pc dust ridge. Two possible interpretations of the origin of the observed
magnetic field structure are discussed.Comment: 27 pages, 7 figures; ApJ in pres
Multi-scale cluster lens mass mapping I. Strong Lensing modelling
We propose a novel technique to refine the modelling of galaxy clusters mass
distribution using gravitational lensing. The idea is to combine the strengths
of both "parametric" and "non-parametric" methods to improve the quality of the
fit. We develop a multi-scale model that allows sharper contrast in regions of
higher density where the number of constraints is generally higher. Our model
consists of (i) a multi-scale grid of radial basis functions with physically
motivated profiles and (ii) a list of galaxy-scale potentials at the location
of the cluster member galaxies. This arrangement of potentials of different
sizes allows to reach a high resolution for the model with a minimum number of
parameters. We apply our model to the well studied cluster Abell 1689. We
estimate the quality of our mass reconstruction with a Bayesian MCMC sampler.
For a selected subset of multiple images, we manage to halve the errors between
the predicted and observed image positions compared to previous studies. This
owes to the flexibility of multi-scale models at intermediate scale between
cluster and galaxy scale. The software developed for this paper is part of the
public lenstool package which can be found at www.oamp.fr/cosmology/lenstool.Comment: 15 pages, 17 figures, accepted for publication in MNRA
The molecular distribution of the IRDC G351.77-0.51
Infrared dark clouds are massive, dense clouds seen in extinction against the
IR Galactic background. Many of these objects appear to be on the verge of star
and star cluster formation. Our aim is to understand the physical properties of
IRDCs in very early evolutionary phases. We selected the filamentary IRDC
G351.77 - 0.51, which is remarkably IR quiet at 8{\mu}m. As a first step, we
observed mm dust continuum emission and rotational lines of moderate and dense
gas tracers to characterise different condensations along the IRDC and study
the velocity field of the filament. Our initial study confirms coherent
velocity distribution along the infrared dark cloud ruling out any coincidental
projection effects. Excellent correlation between MIR extinction, mm continuum
emission and gas distribution is found. Large-scale turbulence and line
profiles throughout the filament is indicative of a shock in this cloud.
Excellent correlation between line width, and MIR brightness indicates
turbulence driven by local star formation.Comment: accepted for publication in A&
First Results On Shear-Selected Clusters From the Deep Lens Survey: Optical Imaging, Spectroscopy, and X-ray Followup
We present the first sample of galaxy clusters selected on the basis of their
weak gravitational lensing shear. The shear induced by a cluster is a function
of its mass profile and its redshift relative to the background galaxies being
sheared; in contrast to more traditional methods of selecting clusters, shear
selection does not depend on the cluster's star formation history, baryon
content, or dynamical state. Because mass is the property of clusters which
provides constraints on cosmological parameters, the dependence on these other
parameters could induce potentially important biases in traditionally-selected
samples. Comparison of a shear-selected sample with optically and X-ray
selected samples is therefore of great importance. Here we present the first
step toward a new shear-selected sample: the selection of cluster candidates
from the first 8.6 deg of the 20 deg Deep Lens Survey (DLS), and
tabulation of their basic properties such as redshifts and optical and X-ray
counterparts.Comment: v2 as published in ApJ, 45 pages, 18 figures. Biggest change from v1
is addition of a figure showing the 1-point distribution of pixels in the
mass maps and control "mass maps" using the non-tangential component of
shear, demonstrating that all candidate peaks are higher than any peak seen
in the control map
- …