Abstract
We describe the algorithm used to select the emission line galaxy (ELG) sample at z ∼ 0.85 for the extended Baryon Oscillation Spectroscopic Survey of the Sloan Digital Sky Survey IV, using ...photometric data from the DECam Legacy Survey. Our selection is based on a selection box in the g − r versus r − z colour–colour space and a cut on the g-band magnitude, to favour galaxies in the desired redshift range with strong
${{\rm O}\,\small {II}}$
emission. It provides a target density of 200 deg−2 on the North Galactic Cap and of 240 deg−2 on the South Galactic Cap (SGC), where we use a larger selection box because of deeper imaging. We demonstrate that this selection passes the extended Baryon Oscillation Spectroscopic Survey requirements in terms of homogeneity. About 50 000 ELGs have been observed since the observations have started in 2016, September. These roughly match the expected redshift distribution, though the measured efficiency is slightly lower than expected. The efficiency can be increased by enlarging the redshift range and with incoming pipeline improvement. The cosmological forecast based on these first data predict
$\sigma _{D_V}/D_V = 0.023$
, in agreement with previous forecasts. Lastly, we present the stellar population properties of the ELG SGC sample. Once observations are completed, this sample will be suited to provide a cosmological analysis at z ∼ 0.85, and will pave the way for the next decade of massive spectroscopic cosmological surveys, which heavily rely on ELGs. The target catalogue over the SGC will be released along with DR14.
We demonstrate that dwarf galaxies (10 super(7) < M sub(stellar) < 10 super(9) M sub(middot in circle), -12 < M sub(r) > -18) with no active star formation are extremely rare (<0.06%) in the field. ...We examine the relative number of quenched versus star-forming dwarf galaxies, defining quenched galaxies as having no Halpha emission (EW sub(H)alpha < 2 A) and a strong 4000 A break. The fraction of quenched dwarf galaxies decreases rapidly with increasing distance from a massive host, leveling off for distances beyond 1.5 Mpc. We define galaxies beyond 1.5 Mpc of a massive host galaxy to be in the field. We demonstrate that there is a stellar mass threshold of M sub(stellar) < 1.0 x 10 super(9) M sub(middot in circle) below which quenched galaxies do not exist in the field. The majority of quenched dwarf galaxies (often classified as dwarf elliptical galaxies) are within 2 virial radii of a massive galaxy, and only a few percent of quenched dwarf galaxies exist beyond 4 virial radii.
We investigate the cosmological implications of the latest growth of structure measurement from the Baryon Oscillation Spectroscopic Survey (BOSS) CMASS Data Release 11 with particular focus on the ...sum of the neutrino masses, ∑m
ν. We examine the robustness of the cosmological constraints from the baryon acoustic oscillation (BAO) scale, the Alcock–Paczynski effect and redshift-space distortions (D
V/r
s, F
AP, fσ8) of Beutler et al., when introducing a neutrino mass in the power spectrum template. We then discuss how the neutrino mass relaxes discrepancies between the cosmic microwave background (CMB) and other low-redshift measurements within Λ cold dark matter. Combining our cosmological constraints with 9-year Wilkinson Microwave Anisotropy Probe (WMAP9) yields ∑m
ν = 0.36 ± 0.14 eV (68 per cent c.l.), which represents a 2.6σ preference for non-zero neutrino mass. The significance can be increased to 3.3σ when including weak lensing results and other BAO constraints, yielding ∑m
ν = 0.35 ± 0.10 eV (68 per cent c.l.). However, combining CMASS with Planck data reduces the preference for neutrino mass to ∼2σ. When removing the CMB lensing effect in the Planck temperature power spectrum (by marginalizing over A
L), we see shifts of ∼1σ in σ8 and Ωm, which have a significant effect on the neutrino mass constraints. In the case of CMASS plus Planck without the A
L lensing signal, we find a preference for a neutrino mass of ∑m
ν = 0.34 ± 0.14 eV (68 per cent c.l.), in excellent agreement with the WMAP9+CMASS value. The constraint can be tightened to 3.4σ yielding ∑m
ν = 0.36 ± 0.10 eV (68 per cent c.l.) when weak lensing data and other BAO constraints are included.
The level of population structure and the extent of linkage disequilibrium (LD) can have large impacts on the power, resolution, and design of genome-wide association studies (GWAS) in plants. Until ...recently, the topics of LD and population structure have not been explored in oat due to the lack of a high-throughput, high-density marker system. The objectives of this research were to survey the level of population structure and the extent of LD in oat germplasm and determine their implications for GWAS. In total, 1,205 lines and 402 diversity array technology (DArT) markers were used to explore population structure. Principal component analysis and model-based cluster analysis of these data indicated that, for the lines used in this study, relatively weak population structure exists. To explore LD decay, map distances of 2,225 linked DArT marker pairs were compared with LD (estimated as r ²). Results showed that LD between linked markers decayed rapidly to r ² = 0.2 for marker pairs with a map distance of 1.0 centi-Morgan (cM). For GWAS, we suggest a minimum of one marker every cM, but higher densities of markers should increase marker-QTL association and therefore detection power. Additionally, it was found that LD was relatively consistent across the majority of germplasm clusters. These findings suggest that GWAS in oat can include germplasm with diverse origins and backgrounds. The results from this research demonstrate the feasibility of GWAS and related analyses in oat.
We examine the dependence of the mass-to-light (M/L) ratio of large-scale structure on cosmological parameters, in models that are constrained to match observations of the projected galaxy ...correlation function w sub(p) (r sub(p)) and the galaxy luminosity function. For a sequence of cosmological models with a fixed, observationally motivated power spectrum shape and increasing normalization s sub(8), we find parameters of the galaxy halo occupation distribution (HOD) that reproduce w sub(p)(r sub(p)) measurements as a function of luminosity from the Sloan Digital Sky Survey (SDSS). From these HOD models we calculate the r-band conditional luminosity function (L\M sub(h)), and from this the mean M/L ratio as a function of halo mass M sub(h). We also use (L\M sub(h)) to populate halos of N-body simulations with galaxies and thereby compute M/L in a range of large-scale environments, including cluster infall regions. For all cosmological models, the M/L ratio in high-mass halos or high-density regions is approximately independent of halo mass or smoothing scale. However, the "plateau" value of M/L depends on s sub(8) in addition to the obvious proportionality with the matter density parameter sub(m), and it represents the universal value (M/L) = sub(m)r sub(crit)/r sub(lum) only for models in which the galaxy correlation function is approximately unbiased, i.e., with s sub(8) - s sub(8g). Our results for cluster mass halos follow the trend (M/L) sub(cl) = 577 ( sub(m)/0.3)(s sub(8)/0.9) super(1.7) h M sub(z)/L sub(z). Combined with the mean M/L ratio for CNOC galaxy clusters, this relation implies (s sub(8)/0.9)( sub(m)/0.3) super(0.6) = 0.75 c 0.06. M/L estimates for SDSS clusters and the virial regions of clusters in the CAIRNS survey imply a similar value of s sub(8) sub(m) super(0.6), while the CAIRNS estimates for cluster infall regions imply a lower value. These results are inconsistent with parameter values sub(m) - 0.3, s sub(8) - 0.9 favored by recent joint analyses of cosmic microwave background measurements and other large-scale structure data, although they agree with values inferred from the van den Bosch et al. analysis of the 2dF Galaxy Redshift Survey. We discuss possible resolutions of this discrepancy, none of which seems entirely satisfactory. In appendices we present an improved formula for halo bias factors calibrated on our 360 super(3) N-body simulations and an improved analytic technique for calculating the galaxy correlation function from a given cosmological model and HOD.
The study aimed to identify sources of campylobacter in 10 housed broiler flocks from three United Kingdom poultry companies. Samples from (i) the breeder flocks, which supplied the broilers, (ii) ...cleaned and disinfected houses prior to chick placement, (iii) the chickens, and (iv) the environments inside and outside the broiler houses during rearing were examined. Samples were collected at frequent intervals and examined for Campylobacter spp. Characterization of the isolates using multilocus sequence typing (MLST), serotyping, phage typing, and flaA restriction fragment length polymorphism typing was performed. Seven flocks became colonized during the growing period. Campylobacter spp. were detected in the environment surrounding the broiler house, prior to as well as during flock colonization, for six of these flocks. On two occasions, isolates detected in a puddle just prior to the birds being placed were indistinguishable from those colonizing the birds. Once flocks were colonized, indistinguishable strains of campylobacter were found in the feed and water and in the air of the broiler house. Campylobacter spp. were also detected in the air up to 30 m downstream of the broiler house, which raises the issue of the role of airborne transmission in the spread of campylobacter. At any time during rearing, broiler flocks were colonized by only one or two types determined by MLST but these changed, with some strains superseding others. In conclusion, the study provided strong evidence for the environment as a source of campylobacters colonizing housed broiler flocks. It also demonstrated colonization by successive campylobacter types determined by MLST during the life of a flock.
We investigate the use of the halo mass-gap statistic-defined as the logarithmic difference in mass between the host halo and its most massive satellite subhalo-as a probe of halo age and ...concentration. A cosmological N-body simulation is used to study N ~ 25,000 group/cluster-sized halos in the mass range 10 super(12.5) < M sub(halo)/M sub(middot in circle) < 10 super(14.5). In agreement with previous work, we find that halo mass-gap is related to halo formation time and concentration. On average, older and more highly concentrated halos have larger halo mass-gaps, and this trend is stronger than the mass-concentration relation over a similar dynamic range. However, there is a large amount of scatter owing to the transitory nature of the satellite subhalo population, which limits the use of the halo mass-gap statistic on an object-by-object basis. For example, we find that 20% of very large halo mass-gap systems (akin to "fossil groups") are young and have likely experienced a recent merger between a massive satellite subhalo and the central subhalo. We relate halo mass-gap to the observable stellar mass-gap via abundance matching. Using a galaxy group catalog constructed from the Sloan Digital Sky Survey Data Release 7, we find that the star formation and structural properties of galaxies at fixed mass show no trend with stellar mass-gap. This is despite a variation in halo age of approximately 2.5 Gyr over approximately 1.2 dex in stellar mass-gap. Thus, we find no evidence to suggest that the halo formation history significantly affects galaxy properties.
We show how redshift-space distortions of the galaxy correlation function or power spectrum can constrain the matter density parameter Ωm and the linear matter fluctuation amplitude σ8. We improve on ...previous treatments by adopting a fully non-linear description of galaxy clustering and bias, which allows us to achieve the accuracy demanded by larger galaxy redshift surveys and to break parameter degeneracies by combining large-scale and small-scale distortions. Given an observationally motivated choice of the initial power spectrum shape, we consider different combinations of Ωm and σ8 and find parameters of the galaxy halo occupation distribution (HOD) that yield nearly identical galaxy correlation functions in real space. We use these HOD parameters to populate the dark matter haloes of large N-body simulations, from which we measure redshift-space distortions on small and large scales. We include a velocity bias parameter αv that allows the velocity dispersions of satellite galaxies in haloes to be systematically higher or lower than those of dark matter. Large-scale distortions are determined by the parameter combination β≡Ω0.6m/bg, where bg is the bias factor defined by the ratio of galaxy and matter correlation functions, in agreement with the linear theory prediction of parameter degeneracy. However, linear theory does not accurately describe the distortions themselves on scales accessible to our simulations. We provide fitting formulas to estimate β from measurements of the redshift-space correlation function or power spectrum, and we show that these formulas are significantly more accurate than those in the existing literature. On small scales, the ‘FOG’ distortions at projected separations ∼0.1 h−1 Mpc depend on Ωmα2v but are independent of σ8, while at intermediate separations they depend on σ8 as well. One can thus use measurements of redshift-space distortions over a wide range of scales to separately determine Ωm, σ8, and αv.
We present an analytic model for the galaxy two-point correlation function in redshift space. The cosmological parameters of the model are the matter density Ωm, power spectrum normalization σ8, and ...velocity bias of galaxies αv, circumventing the linear theory distortion parameter β and eliminating nuisance parameters for non-linearities. The model is constructed within the framework of the halo occupation distribution (HOD), which quantifies galaxy bias on linear and non-linear scales. We model one-halo pairwise velocities by assuming that satellite galaxy velocities follow a Gaussian distribution with dispersion proportional to the virial dispersion of the host halo. Two-halo velocity statistics are a combination of virial motions and host halo motions. The velocity distribution function (DF) of halo pairs is a complex function with skewness and kurtosis that vary substantially with scale. Using a series of collisionless N-body simulations, we demonstrate that the shape of the velocity DF is determined primarily by the distribution of local densities around a halo pair, and at fixed density the velocity DF is close to Gaussian and nearly independent of halo mass. We calibrate a model for the conditional probability function of densities around halo pairs on these simulations. With this model, the full shape of the halo velocity DF can be accurately calculated as a function of halo mass, radial separation, angle and cosmology. The HOD approach to redshift-space distortions utilizes clustering data from linear to non-linear scales to break the standard degeneracies inherent in previous models of redshift-space clustering. The parameters of the occupation function are well constrained by real-space clustering alone, separating constraints on bias and cosmology. We demonstrate the ability of the model to separately constrain Ωm, σ8 and αv in models that are constructed to have the same value of β at large scales as well as the same finger-of-god distortions at small scales.
Summary Background Uncertainties persist about the magnitude of associations of diabetes mellitus and fasting glucose concentration with risk of coronary heart disease and major stroke subtypes. We ...aimed to quantify these associations for a wide range of circumstances. Methods We undertook a meta-analysis of individual records of diabetes, fasting blood glucose concentration, and other risk factors in people without initial vascular disease from studies in the Emerging Risk Factors Collaboration. We combined within-study regressions that were adjusted for age, sex, smoking, systolic blood pressure, and body-mass index to calculate hazard ratios (HRs) for vascular disease. Findings Analyses included data for 698 782 people (52 765 non-fatal or fatal vascular outcomes; 8·49 million person-years at risk) from 102 prospective studies. Adjusted HRs with diabetes were: 2·00 (95% CI 1·83–2·19) for coronary heart disease; 2·27 (1·95–2·65) for ischaemic stroke; 1·56 (1·19–2·05) for haemorrhagic stroke; 1·84 (1·59–2·13) for unclassified stroke; and 1·73 (1·51–1·98) for the aggregate of other vascular deaths. HRs did not change appreciably after further adjustment for lipid, inflammatory, or renal markers. HRs for coronary heart disease were higher in women than in men, at 40–59 years than at 70 years and older, and with fatal than with non-fatal disease. At an adult population-wide prevalence of 10%, diabetes was estimated to account for 11% (10–12%) of vascular deaths. Fasting blood glucose concentration was non-linearly related to vascular risk, with no significant associations between 3·90 mmol/L and 5·59 mmol/L. Compared with fasting blood glucose concentrations of 3·90–5·59 mmol/L, HRs for coronary heart disease were: 1·07 (0·97–1·18) for lower than 3·90 mmol/L; 1·11 (1·04–1·18) for 5·60–6·09 mmol/L; and 1·17 (1·08–1·26) for 6·10–6·99 mmol/L. In people without a history of diabetes, information about fasting blood glucose concentration or impaired fasting glucose status did not significantly improve metrics of vascular disease prediction when added to information about several conventional risk factors. Interpretation Diabetes confers about a two-fold excess risk for a wide range of vascular diseases, independently from other conventional risk factors. In people without diabetes, fasting blood glucose concentration is modestly and non-linearly associated with risk of vascular disease. Funding British Heart Foundation, UK Medical Research Council, and Pfizer.
PDF
