666 research outputs found
Measurement of the Spatial Cross-Correlation Function of Damped Lyman Alpha Systems and Lyman Break Galaxies
We present the first spectroscopic measurement of the spatial
cross-correlation function between damped Lyman alpha systems (DLAs) and Lyman
break galaxies (LBGs). We obtained deep u'BVRI images of nine QSO fields with
11 known z ~ 3 DLAs and spectroscopically confirmed 211 R < 25.5
photometrically selected z > 2 LBGs. We find strong evidence for an overdensity
of LBGs near DLAs versus random, the results of which are similar to that of
LBGs near other LBGs. A maximum likelihood cross-correlation analysis found the
best fit correlation length value of r_0 = 2.9^(+1.4)_(-1.5) h^(-1)Mpc using a
fixed value of gamma = 1.6. The implications of the DLA-LBG clustering
amplitude on the average dark matter halo mass of DLAs are discussed.Comment: 12 pages, 2 figures, accepted for publication in Astrophysical
Journal Letter
Survey for Galaxies Associated with z~3 Damped Lyman alpha Systems II: Galaxy-Absorber Correlation Functions
We use 211 galaxy spectra from our survey for Lyman break galaxies (LBGs)
associated with 11 damped Lyman alpha systems (DLAs) to measure the
three-dimensional LBG auto-correlation and DLA-LBG cross-correlation functions
with the primary goal of inferring the mass of DLAs at z~3. Conventional
binning of the data while varying both r_0 and gamma parameters of the fiducial
model of the correlation function xi(r)=(r/r_0)^{-gamma} resulted in the best
fit values and 1 sigma uncertainties of r_0=2.65+/-0.48, gamma=1.55+/-0.40 for
the LBG auto-correlation and r_0=3.32+/-1.25, gamma=1.74+/-0.36 for DLA-LBG
cross-correlation function. To circumvent shortcomings found in binning small
datasets, we perform a maximum likelihood analysis based on Poisson statistics.
The best fit values and 1 sigma confidence levels from this analysis were
found to be r_0=2.91(+1.0,-1.0), gamma=1.21(+0.6,-0.3) for the LBG
auto-correlation and r_0=2.81(+1.4,-2.0), gamma=2.11(+1.3,-1.4) for the DLA-LBG
cross-correlation function. We report a redshift spike of five LBGs with Delta
z = 0.015 of the z=2.936 DLA in the PSS0808+5215 field and find that the
DLA-LBG clustering signal survives when omitting this field from the analysis.
Using the correlation functions measurements and uncertainties, we compute the
z~3 LBG galaxy bias b_LBG to be 1.5<b_LBG<3 corresponding to an average halo
mass of 10^(9.7)<M_LBG<10^(11.6) M_odot and the z~3 DLA galaxy bias b_DLA to be
1.3<b_DLA<4 corresponding to an average halo mass of 10^(9)<M_LBG<10^(12)
M_odot. Lastly, two of the six QSOs discovered in this survey were found to lie
within Delta z = 0.0125 of two of the survey DLAs. We estimate the probability
of this occurring by chance is 1 in 940 and may indicate a possible
relationship between the distribution of QSOs and DLAs at z~3.Comment: 44 pages, 12 figures, accepted to The Astrophysical Journa
A CD11d monoclonal antibody treatment reduces tissue injury and improves neurological outcome after fluid percussion brain injury in rats
Traumatic brain injury (TBI) is an international health concern often resulting in chronic neurological abnormalities, including cognitive deficits, emotional disturbances, and motor impairments. An anti-CD11d monoclonal antibody that blocks the CD11d/CD18 integrin and vascular cell adhesion molecule (VCAM)-1 interaction following experimental spinal cord injury improves functional recovery, while reducing the intraspinal number of neutrophils and macrophages, oxidative activity, and tissue damage. Since the mechanisms of secondary injury in the brain and spinal cord are similar, we designed a study to evaluate fully the effects of anti-CD11d treatment after a moderate lateral fluid percussion TBI in the rat. Rats were treated at 2 h after TBI with either the anti-CD11d antibody or an isotype-matched control antibody 1B7, and both short (24-to 72-h) and long (4-week) recovery periods were examined. The anti-CD11d integrin treatment reduced neutrophil and macrophage levels in the injured brain, with concomitant reductions in lipid peroxidation, astrocyte activation, amyloid precursor protein accumulation, and neuronal loss. The reduced neuroinflammation seen in anti-CD11d-treated rats correlated with improved performance on a number of behavioral tests. At 24 h, the anti-CD11d group performed significantly better than the 1B7 controls on several water maze measures of spatial cognition. At 4 weeks post-injury the anti-CD11d-treated rats had better sensorimotor function as assessed by the beam task, and reduced anxiety-like behaviors, as evidenced by elevated-plus maze testing, compared to 1B7 controls. These findings suggest that neuroinflammation is associated with behavioral deficits after TBI, and that anti-CD11d antibody treatment is a viable strategy to improve neurological outcomes after TBI. © 2012, Mary Ann Liebert, Inc
The Atacama Cosmology Telescope: Two-Season ACTPol Lensing Power Spectrum
We report a measurement of the power spectrum of cosmic microwave background
(CMB) lensing from two seasons of Atacama Cosmology Telescope Polarimeter
(ACTPol) CMB data. The CMB lensing power spectrum is extracted from both
temperature and polarization data using quadratic estimators. We obtain results
that are consistent with the expectation from the best-fit Planck LCDM model
over a range of multipoles L=80-2100, with an amplitude of lensing A_lens =
1.06 +/- 0.15 (stat.) +/- 0.06 (sys.) relative to Planck. Our measurement of
the CMB lensing power spectrum gives sigma_8 Omega_m^0.25 = 0.643 +/- 0.054;
including baryon acoustic oscillation scale data, we constrain the amplitude of
density fluctuations to be sigma_8 = 0.831 +/- 0.053. We also update
constraints on the neutrino mass sum. We verify our lensing measurement with a
number of null tests and systematic checks, finding no evidence of significant
systematic errors. This measurement relies on a small fraction of the ACTPol
data already taken; more precise lensing results can therefore be expected from
the full ACTPol dataset.Comment: 17 pages, 11 figures, to be submitted to Physical Review
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Coronary atherosclerosis scoring with semiquantitative CCTA risk scores for prediction of major adverse cardiac events: Propensity score-based analysis of diabetic and non-diabetic patients.
AIMS:We aimed to compare semiquantitative coronary computed tomography angiography (CCTA) risk scores - which score presence, extent, composition, stenosis and/or location of coronary artery disease (CAD) - and their prognostic value between patients with and without diabetes mellitus (DM). Risk scores derived from general chest-pain populations are often challenging to apply in DM patients, because of numerous confounders. METHODS:Out of a combined cohort from the Leiden University Medical Center and the CONFIRM registry with 5-year follow-up data, we performed a secondary analysis in diabetic patients with suspected CAD who were clinically referred for CCTA. A total of 732 DM patients was 1:1 propensity-matched with 732 non-DM patients by age, sex and cardiovascular risk factors. A subset of 7 semiquantitative CCTA risk scores was compared between groups: 1) any stenosis ≥50%, 2) any stenosis ≥70%, 3) stenosis-severity component of the coronary artery disease-reporting and data system (CAD-RADS), 4) segment involvement score (SIS), 5) segment stenosis score (SSS), 6) CT-adapted Leaman score (CT-LeSc), and 7) Leiden CCTA risk score. Cox-regression analysis was performed to assess the association between the scores and the primary endpoint of all-cause death and non-fatal myocardial infarction. Also, area under the receiver-operating characteristics curves were compared to evaluate discriminatory ability. RESULTS:A total of 1,464 DM and non-DM patients (mean age 58 ± 12 years, 40% women) underwent CCTA and 155 (11%) events were documented after median follow-up of 5.1 years. In DM patients, the 7 semiquantitative CCTA risk scores were significantly more prevalent or higher as compared to non-DM patients (p ≤ 0.022). All scores were independently associated with the primary endpoint in both patients with and without DM (p ≤ 0.020), with non-significant interaction between the scores and diabetes (interaction p ≥ 0.109). Discriminatory ability of the Leiden CCTA risk score in DM patients was significantly better than any stenosis ≥50% and ≥70% (p = 0.003 and p = 0.007, respectively), but comparable to the CAD-RADS, SIS, SSS and CT-LeSc that also focus on the extent of CAD (p ≥ 0.265). CONCLUSION:Coronary atherosclerosis scoring with semiquantitative CCTA risk scores incorporating the total extent of CAD discriminate major adverse cardiac events well, and might be useful for risk stratification of patients with DM beyond the binary evaluation of obstructive stenosis alone
Imaging of the gravitational lens system PG 1115+080 with the Hubble Space Telescope
This paper is the first of a series presenting observations of gravitational lenses and lens candidates, taken with the Wide Field/Planetary Camera (WFPC) of the Hubble Space Telescope (HST). We have resolved the gravitational lens system PG 1115 + 080 into four point sources and a red, extended object that is presumably the lens galaxy; we present accurate relative intensities, colors, and positions of the four images, and lower accuracy intensity and position of the lens galaxy, all at the epoch 1991.2.
Comparison with earlier data shows no compelling evidence for relative intensity variations between the QSO components having so far been observed. The new data agree with earlier conclusions that the system is rather simple, and can be produced by the single observed galaxy. The absence of asymmetry in the HST images implies that the emitting region of the quasar itself has an angular radius smaller than about 10 milliarcsec (100 pc for H_0=50, q_0=0.5)
Evidence for dark energy from the cosmic microwave background alone using the Atacama Cosmology Telescope lensing measurements
For the first time, measurements of the cosmic microwave background radiation
(CMB) alone favor cosmologies with dark energy over models without dark
energy at a 3.2-sigma level. We demonstrate this by combining the CMB lensing
deflection power spectrum from the Atacama Cosmology Telescope with temperature
and polarization power spectra from the Wilkinson Microwave Anisotropy Probe.
The lensing data break the geometric degeneracy of different cosmological
models with similar CMB temperature power spectra. Our CMB-only measurement of
the dark energy density confirms other measurements from
supernovae, galaxy clusters and baryon acoustic oscillations, and demonstrates
the power of CMB lensing as a new cosmological tool.Comment: 4 pages, 3 figures; replaced with version accepted by Physical Review
Letters, added sentence on models with non-standard primordial power spectr
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