474 research outputs found
Dark Matter Search with Direction Sensitive Scintillator
A direction sensitive dark matter detector using organic crystals is being
developed. It exploits the anisotropic scintillation efficiency of organic
crystals with respect to the direction of nuclear recoils relative to
crystallographic axes. A variation of about 7% was observed in the
scintillation efficiency of carbon recoils in a stilbene crystal for recoil
energies of 30 keV to 1 MeV. We have performed a pilot experiment at Kamioka to
prove the feasibility of this method.Comment: 6 Pages, 4 figures, To appear in the proceedings of the 5th Workshop
on "Neutrino Oscillations and their Origin" (NOON2004
Identification of K-rich fragments in chondritic breccias using Imaging Plate (IP): an application to the planetary materials.
第2回極域科学シンポジウム/第34回南極隕石シンポジウム 11月17日(木) 国立国語研究所 2階講
Adaptive Optics Rest-Frame V-band Imaging of Lyman Break Galaxies at z~3: High-surface Density Disk-like Galaxies ?
In order to reveal the rest-frame V-band morphology of galaxies at z~3, we
conducted AO-assisted K-band imaging observations of z~3 LBGs with Mv*-0.5 to
Mv*+3.0 mag. LBGs brighter than Mv* have larger rHL (0.40") than the fainter
LBGs (0.23") on average, and there is no bright LBGs with a small rHL. The LBGs
brighter than Mv* have red rest-frame U-V colors (average of 0.2 mag) and most
of the fainter LBGs show blue rest-frame U-V colors (average of -0.4 mag). The
K-band peaks of some of the LBGs brighter than K=22.0 mag show significant
shift from those in the optical images. The images of all but one of the LBGs
with K<21.5 mag are fitted well with Sersic profile with n index less than 2,
similar to disk galaxies in the local universe. Assuming that the LBGs have a
disk-shape, we compared their size-luminosity and size-stellar mass relation
with those of z=0 and z=1 disk galaxies. The LBGs are brighter than z=0 and z=1
disk galaxies at the same effective radius. The rest-frame V-band surface
brightness of the LBGs are 2.2-2.9 mag and 1.2-1.9 mag brighter than the disk
galaxies at z=0 and z=1, respectively. The size-stellar mass relation of the
LBGs shows that the effective radii of the LBGs do not depend on their stellar
mass. For the LBGs brighter than Mv*, the average surface stellar mass density
is 3-6 times larger than those of the z=0 and z=1 disk galaxies. We also
examine the profiles of the serendipitously observed DRGs. They are also fitted
with the Sersic profiles with n<2. The implications of the dominance of n<2
population among galaxies at z~3 and the presence of the high surface stellar
mass density disk systems are discussed.Comment: Accepted for publication in Astrophysical Journal Supplement. 38
pages, 26 postscript figures. Original version with high resolution figures
is available from http://www.naoj.org/staff/akiyama/papers/LBG_AO.pd
First results from dark matter search experiment with LiF bolometer at Kamioka Underground Laboratory
Tokyo group has performed first underground dark matter search experiment in
2001 through 2002 at Kamioka Observatory(2700m.w.e). The detector is eight LiF
bolometers with total mass 168g aiming for the direct detection of WIMPs via
spin-dependent interaction. With a total exposure of 4.1 kg days, we derived
the limits in the a_p-a_n (WIMP-nucleon couplings) plane and excluded a large
part of the parameter space allowed by the UKDMC experiment.Comment: 15 pages, 5 figure
The Resolved Near-Infrared Extragalactic Background
We present a current best estimate of the integrated near-infrared (NIR)
extragalactic background light (EBL) attributable to resolved galaxies in J, H,
and Ks. Our results in units of nW m-2 sr-1 are 11.7+5.6 -2.6 in J, 11.5+4.5
-1.5 in H and 10.0+2.8 -0.8 in Ks. We derive these new limits by combining our
deep wide-field NIR photometry from five widely separated fields with other
studies from the literature to create a galaxy counts sample that is highly
complete and has good counting statistics out to JHKs ~ 27-28. As part of this
effort we present new ultradeep Ks-band galaxy counts from 22 hours of
observations with the Multi Object Infrared Camera and Spectrograph (MOIRCS)
instrument on the Subaru Telescope. We use this MOIRCS Ks-band mosaic to
estimate the total missing flux from sources beyond our detection limits. Our
new limits to the NIR EBL are in basic agreement with, but 10 - 20% higher than
previous estimates, bringing them into better agreement with estimates of the
total NIR EBL (resolved + unresolved sources) obtained from TeV gamma-ray
opacity measurements and recent direct measurements of the total NIR EBL. We
examine field to field variations in our photometry to show that the integrated
light from galaxies is isotropic to within uncertainties, consistent with the
expected large-scale isotropy of the EBL. Our data also allow for a robust
estimate of the NIR light from Galactic stars, which we find to be 14.7 +/- 2.4
in J, 10.1 +/- 1.9 in H and 7.6 +/- 1.8 in Ks in units of nW m-2 sr-1.Comment: Accepted to Ap
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