54796299
Galaxy-Mass Correlations on 10 Mpc Scales in the Deep Lens Survey
We examine the projected correlation of galaxies with mass from small scales (<few hundred kpc), where individual dark matter halos dominate, out to 15 Mpc, where correlated large-scale structure dominates. We investigate these profiles as a function of galaxy luminosity and redshift. Selecting 0.8 million galaxies in the Deep Lens Survey, we use photometric redshifts and stacked weak gravitational lensing shear tomography out to radial scales of 1° from the centers of foreground galaxies. We detect correlated mass density from multiple halos and large-scale structure at radii larger than the virial radius and find the first observational evidence for growth in the galaxy-mass correlation on 10 Mpc scales with decreasing redshift and fixed range of luminosity. For a fixed range of redshift, we find a scaling of projected halo mass with rest-frame luminosity similar to previous studies at lower redshift. We control systematic errors in shape measurement and photometric redshift, enforce volume completeness through absolute magnitude cuts, and explore residual sample selection effects via simulations.
16712090
The DRaGONS Survey: A Search for High Redshift Radio Galaxies And Heavily Obscured AGNs
We present the first results from the Distant Radio Galaxies Optically Non-detected in the SDSS (DRaGONS) Survey. Using a novel selection technique for identifying high redshift radio galaxy (HzRG) candidates, a large sample of bright (S_{1.4GHz} > 100mJy) radio sources from the FIRST survey having no optical counterpart in the SDSS is compiled. K-band imaging with the FLAMINGOS instrument on the 4-meter telescope at Kitt Peak for 96 such candidates allows preliminary identification of HzRG candidates through the well-known K-z relation. Of the initial candidates, we identify 70 with magnitudes brighter than K \approx 19.5, and compute limiting magnitudes for the remainder. Assigning redshifts based on the K-z Hubble diagram gives a mean redshift for our sample of z=2.5 and a median redshift of z=2.0. This selection is also sensitive to a previously unseen population of anomalously red radio galaxies (r-K > 6.5-7), which may indicate significant obscuration at moderate redshifts. These obscured objects can be used to test the completeness of QSO surveys to the effects of reddenning. More than ten percent of our sample falls into this category, which may represent a sizable radio loud population missing from current optically selected AGN samples. We additionally identify 479 bright Extremely Red Objects (EROs) in the fields surrounding our HzRG candidates, to a magnitude of K=17.5, within a non-contiguous area of 2.38 square degrees. This constitutes a small overdensity of EROs surrounding the radio galaxy candidates over random fields, and we see possible evidence for a physical association of the EROs with the radio galaxies. However, examining the clustering of all K < 19.0 galaxies around the radio targets reveals no evidence of a global galaxy excess.
119259169
Recovering redshift distributions with cross-correlations: pushing the boundaries
Determining accurate redshift distributions for very large samples of objects has become increasingly important in cosmology. We investigate the impact of extending cross-correlation based redshift distribution recovery methods to include small scale clustering information. The major concern in such work is the ability to disentangle the amplitude of the underlying redshift distribution from the influence of evolving galaxy bias. Using multiple simulations covering a variety of galaxy bias evolution scenarios, we demonstrate reliable redshift recoveries using linear clustering assumptions well into the non-linear regime for redshift distributions of narrow redshift width. Including information from intermediate physical scales balances the increased information available from clustering and the residual bias incurred from relaxing of linear constraints. We discuss how breaking a broad sample into tomographic bins can improve estimates of the redshift distribution, and present a simple bias removal technique using clustering information from the spectroscopic sample alone.
119232505
Cosmic shear results from the deep lens survey - I: Joint constraints on omega_m and sigma_8 with a two-dimensional analysis
We present a cosmic shear study from the Deep Lens Survey (DLS), a deep BVRz multi-band imaging survey of five 4 deg2 fields with two National Optical Astronomy Observatory (NOAO) 4 m telescopes at Kitt Peak and Cerro Tololo. For both telescopes, the change of the point-spread-function (PSF) shape across the focal plane is complicated, and the exposure-to-exposure variation of this position-dependent PSF change is significant. We overcome this challenge by modeling the PSF separately for individual exposures and CCDs with principal component analysis (PCA). We find that stacking these PSFs reproduces the final PSF pattern on the mosaic image with high fidelity, and the method successfully separates PSF-induced systematics from gravitational lensing effects. We calibrate our shears and estimate the errors, utilizing an image simulator, which generates sheared ground-based galaxy images from deep Hubble Space Telescope archival data with a realistic atmospheric turbulence model. For cosmological parameter constraints, we marginalize over shear calibration error, photometric redshift uncertainty, and the Hubble constant. We use cosmology-dependent covariances for the Markov Chain Monte Carlo analysis and find that the role of this varying covariance is critical in our parameter estimation. Our current non-tomographic analysis alone constrains the Ω M -σ8 likelihood contour tightly, providing a joint constraint of Ω M = 0.262 ± 0.051 and σ8 = 0.868 ± 0.071. We expect that a future DLS weak-lensing tomographic study will further tighten these constraints because explicit treatment of the redshift dependence of cosmic shear more efficiently breaks the Ω M -σ8 degeneracy. Combining the current results with the Wilkinson Microwave Anisotropy Probe 7 year (WMAP7) likelihood data, we obtain Ω M = 0.278 ± 0.018 and σ8 = 0.815 ± 0.020.
118578896
CHARACTERIZING AND PROPAGATING MODELING UNCERTAINTIES IN PHOTOMETRICALLY-DERIVED REDSHIFT DISTRIBUTIONS
The uncertainty in the redshift distributions of galaxies has a significant potential impact on the cosmological parameter values inferred from multi-band imaging surveys. The accuracy of the photometric redshifts measured in these surveys depends not only on the quality of the flux data, but also on a number of modeling assumptions that enter into both the training set and spectral energy distribution (SED) fitting methods of photometric redshift estimation. In this work we focus on the latter, considering two types of modeling uncertainties: uncertainties in the SED template set and uncertainties in the magnitude and type priors used in a Bayesian photometric redshift estimation method. We find that SED template selection effects dominate over magnitude prior errors. We introduce a method for parameterizing the resulting ignorance of the redshift distributions, and for propagating these uncertainties to uncertainties in cosmological parameters.
119184968
Clustering-based redshift estimation: comparison to spectroscopic redshifts
We investigate the potential and accuracy of clustering-based redshift estimation using the method proposed by M\'enard et al. (2013). This technique enables the inference of redshift distributions from measurements of the spatial clustering of arbitrary sources, using a set of reference objects for which redshifts are known. We apply it to a sample of spectroscopic galaxies from the Sloan Digital Sky Survey and show that, after carefully controlling the sampling efficiency over the sky, we can estimate redshift distributions with high accuracy. Probing the full colour space of the SDSS galaxies, we show that we can recover the corresponding mean redshifts with an accuracy ranging from $\delta$z=0.001 to 0.01. We indicate that this mapping can be used to infer the redshift probability distribution of a single galaxy. We show how the lack of information on the galaxy bias limits the accuracy of the inference and show comparisons between clustering redshifts and photometric redshifts for this dataset. This analysis demonstrates, using real data, that clustering-based redshift inference provides a powerful data-driven technique to explore the redshift distribution of arbitrary datasets, without any prior knowledge on the spectral energy distribution of the sources.
12062893
The Phoenix Deep Survey: Extremely Red Galaxies and Cluster Candidates
We present the results of a study of a sample of 375 extremely red galaxies (ERGs) in the Phoenix Deep Survey, 273 of which constitute a subsample which is 80% complete to Ks = 18.5 over an area of 1160 arcmin2. The angular correlation function for ERGs is estimated, and the association of ERGs with faint radio sources explored. We find tentative evidence that ERGs and faint radio sources are associated at z 0.5. A new overdensity-mapping algorithm has been used to characterize the ERG distribution, and identify a number of cluster candidates, including a likely cluster containing ERGs at 0.5 4 criterion is more efficient than R – Ks > 5 at selecting dusty star-forming galaxies, rather than passively evolving ERGs.
41115389
Pair creation: Back reactions and damping
We solve the quantum Vlasov equation for fermions and bosons, incorporating spontaneous pair creation in the presence of back reactions and collisions. Pair creation is initiated by an external impulse field and the source term is non-Markovian. A simultaneous solution of Maxwell's equation in the presence of feedback yields an internal current and electric field that exhibit plasma oscillations with a period {tau}{sub pl}. Allowing for collisions, these oscillations are damped on a time scale {tau}{sub r} determined by the collision frequency. Plasma oscillations cannot affect the early stages of the formation of a quark-gluon plasma unless {tau}{sub r}>>{tau}{sub pl} and {tau}{sub pl}{approx}1/{lambda}{sub QCD}{approx}1 fm/c. (c) 1999 The American Physical Society.
17661148
Pair creation and an x-ray free electron laser.
Using a quantum kinetic equation we study the possibility that focused beams at proposed x-ray free electron laser facilities can initiate spontaneous electron-positron pair production from the QED vacuum. Under conditions reckoned achievable at planned facilities, repeated cycles of particle creation and annihilation will take place in tune with the laser frequency. The peak particle number density is insensitive to this frequency, and one can anticipate the production of a few hundred particle pairs per laser period.
119092008
Temperature, chemical potential and the {rho}-meson
Models of QCD must confront nonperturbative phenomena such as confinement, dynamical chiral symmetry breaking (DCSB) and the formation of bound states. In addition, a unified approach should describe the deconfinement and chiral symmetry restoring phase transition exhibited by strongly-interacting matter under extreme conditions of temperature and density. Nonperturbative Dyson-Schwinger equation (DSE) models provide insight into a wide range of zero temperature hadronic phenomena; e.g., non-hadronic electroweak interactions of light- and heavy-mesons, and diverse meson-meson and meson-nucleon form factors. This is the foundation for their application at nonzero-(T, {mu}). Herein the authors describe the calculation of the reconfinement and chiral symmetry restoring phase boundary, and the medium dependence of {rho}-meson properties. They also introduce an extension to describe the time-evolution in the plasma of the quark's scalar and vector self energies based on a Vlasov equation.
7794133
Deconfinement at finite chemical potential.
Abstract In a confining, renormalisable, Dyson-Schwinger equation model of two-flavour QCD we explore the chemical-potential dependence of the dressed-quark propagator, which provides a means of determining the behaviour of the chiral and deconfinement order parameters, and low-energy pion observables. We find coincident, first order deconfinement and chiral symmetry restoration transitions at μ c =375 MeV. f π is insensitive to μ until μ≈μ 0 :=0.7 μ c when it begins to increase rapidly. m π is weakly dependent on μ , decreasing slowly with μ and reaching a minimum 6% less than its μ =0 value at μ = μ 0 . In a two-flavour free-quark gas at μ = μ c the baryon number density would be approximately 3 ρ 0 , where ρ 0 =0.16 fm −3 ; while in such a gas at μ 0 the density is ρ 0 .