997 research outputs found
The Weak Lensing Signal and the Clustering of BOSS Galaxies I: Measurements
A joint analysis of the clustering of galaxies and their weak gravitational
lensing signal is well-suited to simultaneously constrain the galaxy-halo
connection as well as the cosmological parameters by breaking the degeneracy
between galaxy bias and the amplitude of clustering signal. In a series of two
papers, we perform such an analysis at the highest redshift () in
the literature using CMASS galaxies in the Sloan Digital Sky Survey-III Baryon
Oscillation Spectroscopic Survey Eleventh Data Release (SDSS-III/BOSS DR11)
catalog spanning 8300~deg. In this paper, we present details of the
clustering and weak lensing measurements of these galaxies. We define a
subsample of 400,916 CMASS galaxies based on their redshifts and stellar mass
estimates so that the galaxies constitute an approximately volume-limited and
similar population over the redshift range . We obtain a
signal-to-noise ratio for the galaxy clustering measurement. We
also explore the redshift and stellar mass dependence of the clustering signal.
For the weak lensing measurement, we use existing deeper imaging data from the
CFHTLS with publicly available shape and photometric redshift catalogs from
CFHTLenS, but only in a 105~deg area which overlaps with BOSS. This
restricts the lensing measurement to only 5,084 CMASS galaxies. After careful
systematic tests, we find a highly significant detection of the CMASS weak
lensing signal, with total . These measurements form the basis of
the halo occupation distribution and cosmology analysis presented in More et
al. (Paper II).Comment: 15 pages, 13 figures. Accepted for publication in the Astrophysical
Journa
Synthesis, Stability, and Crystal Structure of an Azulenium Cation Containing an Adamantyl Group
This is the pre-peer reviewed version of the following article: EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. 2008(31):5301-5307 (2008), which has been published in final form at doi:10.1002/ejoc.200800700.ArticleEUROPEAN JOURNAL OF ORGANIC CHEMISTRY. 2008(31):5301-5307 (2008)journal articl
Suppression of Tc in the (Y0.9Ca0.1)Ba2Cu4-xFexO8 system
In this paper, the effects produced by the iron substitutions in the
(Y0.9Ca0.1)Ba2Cu4-xFexO8 system on the superconducting and structural
properties are studied. The Rietveld fit of the crystal structure and Mossbauer
spectroscopy results of (Y0.9Ca0.1)Ba2Cu4-xFexO8 samples indicate that, the
iron atoms occupy the Cu(1) sites of the (Cu-O)2 double chain in fivefold
coordination at low iron concentrations. Besides at high iron concentrations
the iron atoms occupy the Cu(1) sites of single Cu-O chainss and Cu(2) sites in
the CuO2 planes of the (Y0.9Ca0.1)Ba2Cu4-xFexO8 phase with structural defects.
Simultaneouly, as iron concentration increases, a faster decrease of Tc is
observed in this material comapred with the YBa2Cu3-xFexO7-y system. According
to the charge transfer model proposed for YBa2Cu4O8 under pressure, the
decrease in the Cu(1)-O(4) bond length in parallel to the increase in the
Cu(2)-O(4) bond length may affect the charge transfer mechanism leading to the
suppression of Tc.Comment: submitted to Journal of Physics: Condensed Matter on 12 October 2001,
8 figures, 2 tables, 9 page
Spin Dynamics near the Superconductor-to-Insulator Transition in Impurity-Doped YBa2Cu4O8
We studied low-frequency spin dynamics near the impurity-induced
superconductor-to-insulator transition for underdoped high-Tc superconductor
YBa2(Cu1-xMx)4O8 (M=Ni, Zn) using the Cu nuclear quadrupole resonance (NQR)
spin-echo technique. We observed remarkable suppression of the normal-state
pseudo spin-gap and a loss of Cu NQR spectrum intensity at low temperatures
around the critical impurity concentration.Comment: 6 pages, 4 figures. To be published in J. Phys. Soc. Jpn. Vol.70,
No.7 (2001
Exchange anisotropy, disorder and frustration in diluted, predominantly ferromagnetic, Heisenberg spin systems
Motivated by the recent suggestion of anisotropic effective exchange
interactions between Mn spins in GaMnAs (arising as a result of
spin-orbit coupling), we study their effects in diluted Heisenberg spin
systems. We perform Monte Carlo simulations on several phenomenological model
spin Hamiltonians, and investigate the extent to which frustration induced by
anisotropic exchanges can reduce the low temperature magnetization in these
models and the interplay of this effect with disorder in the exchange. In a
model with low coordination number and purely ferromagnetic (FM) exchanges, we
find that the low temperature magnetization is gradually reduced as exchange
anisotropy is turned on. However, as the connectivity of the model is
increased, the effect of small-to-moderate anisotropy is suppressed, and the
magnetization regains its maximum saturation value at low temperatures unless
the distribution of exchanges is very wide. To obtain significant suppression
of the low temperature magnetization in a model with high connectivity, as is
found for long-range interactions, we find it necessary to have both
ferromagnetic and antiferromagnetic (AFM) exchanges (e.g. as in the RKKY
interaction). This implies that disorder in the sign of the exchange
interaction is much more effective in suppressing magnetization at low
temperatures than exchange anisotropy.Comment: 9 pages, 8 figure
Ownership-dependent mating tactics of minor males of the beetle Librodor japonicus (Nitidulidae) with intra-sexual dimorphism of mandibles
Intra-sexual dimorphism is found in the weapons of many male beetles. Different behavioral tactics to access females between major and minor males, which adopt fighting and alternative tactics, respectively, are thought to maintain the male dimorphism. In these species major males have enlarged weapons that they use in fights with rival males. Minor males also have small weapons in some of these species, and it is unclear why these males possess weapons. We examined the hypothesis that minor males might adopt a fighting tactic when their status was relatively high in comparison with that of other males (e.g., ownership of a territory). We observed the behavioral tactics of major and minor males of the beetle Librodor japonicus, whose males have a dimorphism of their mandibles. Major males fought for resources, whereas minor males adopted two status-dependent tactics, fighting and sneaking, to access females, depending on their ownership of a sap site. We suggest that ownership status-dependent mating tactics in minor males may maintain the intra-sexual dimorphism in this beetle.</p
Joint Survey Processing I: Compact oddballs in the COSMOS field -- low-luminosity Quasars at z > 6?
The faint-end slope of the quasar luminosity function at z~6 and its implication on the role of quasars in reionizing the intergalactic medium at early times has been an outstanding problem for some time. The identification of faint high-redshift quasars with luminosities of 25mag, with ~30% of sources having their flux contaminated by foreground objects when the seeing resolution is ~0.7". We mitigate these issues by performing a pixel-level joint processing of ground and space-based data from Subaru/HSC and HST/ACS. We create a deconfused catalog over the 1.64 deg² of the COSMOS field, after accounting for spatial varying PSFs and astrometric differences between the two datasets. We identify twelve low-luminosity (M_(UV) ~ -21 mag) z>6 quasar candidates through (i) their red color measured between ACS/F814W and HSC/i-band and (ii) their compactness in the space-based data. We estimate that late-type stars could contribute up to 50% to our sample. Our constraints on the faint end of the quasar luminosity function at z~6.4 suggests a negligibly small contribution to reionization compared to the star-forming galaxy population. The confirmation of our candidates and the evolution of number density with redshift could provide better insights into how supermassive galaxies grew in the first billion years of cosmic time
Ni-substituted sites and the effect on Cu electron spin dynamics of YBa2Cu{3-x}NixO{7-\delta}
We report Cu nuclear quadrupole resonance experiment on magnetic impurity
Ni-substituted YBaCuNiO. The distribution of
Ni-substituted sites and its effect on the Cu electron spin dynamics are
investigated. Two samples with the same Ni concentration =0.10 and nearly
the same oxygen content but different 's were prepared: One is an
as-synthesized sample (7-=6.93) in air (), and the
other is a quenched one (7-=6.92) in a reduced oxygen atmosphere
(). The plane-site Cu(2) nuclear spin-lattice
relaxation for the quenched sample was faster than that for the as-synthesized
sample, in contrast to the Cu(1) relaxation that was faster for the
as-synthesized sample. This indicates that the density of plane-site Ni(2) is
higher in the quenched sample, contrary to the chain-site Ni(1) density which
is lower in the quenched sample. From the analysis in terms of the Ni-induced
nuclear spin-lattice relaxation, we suggest that the primary origin of
suppression of is associated with nonmagnetic depairing effect of the
plane-site Ni(2).Comment: 7 pages, 5 figure
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