161 research outputs found

### WiggleZ Dark Energy Survey: Cosmological neutrino mass constraint from blue high-redshift galaxies

The absolute neutrino mass scale is currently unknown, but can be constrained by cosmology. The WiggleZ high redshift, star-forming, and blue galaxy sample offers a complementary data set to previous surveys for performing these measurements, with potentially different systematics from nonlinear structure formation, redshift-space distortions, and galaxy bias. We obtain a limit of âˆ‘m_Î½<0.60â€‰â€‰eV (95% confidence) for WiggleZ+Wilkinsonâ€‰Microwaveâ€‰Anisotropyâ€‰Probe. Combining with priors on the Hubble parameter and the baryon acoustic oscillation scale gives âˆ‘m_Î½<0.29â€‰â€‰eV, which is the strongest neutrino mass constraint derived from spectroscopic galaxy redshift surveys

### C32, A Young Star Cluster in IC 1613

The Local Group irregular galaxy IC 1613 has remained an enigma for many
years because of its apparent lack of star clusters. We report the successful
search for clusters among several of the candidate objects identified many
years ago on photographic plates. We have used a single HST WFPC2 pointing and
a series of images obtained with the WIYN telescope under exceptional seeing
conditions, examining a total of 23 of the previously published candidates. All
but six of these objects were found to be either asterisms or background
galaxies. Five of the six remaining candidates possibly are small, sparse
clusters and the sixth, C32, is an obvious cluster. It is a compact, young
object, with an age of less than 10 million years and a total absolute
magnitude of M_V = -5.78+/-0.16 within a radius of 13 pc.Comment: 5 pages, 5 figures, to be published in the May 2000 issue of the PAS

### The WiggleZ Dark Energy Survey: testing the cosmological model with baryon acoustic oscillations at z = 0.6

We measure the imprint of baryon acoustic oscillations (BAOs) in the galaxy clustering pattern at the highest redshift achieved to date, z= 0.6, using the distribution of N= 132 509 emission-line galaxies in the WiggleZ Dark Energy Survey. We quantify BAOs using three statistics: the galaxy correlation function, power spectrum and the band-filtered estimator introduced by Xu et al. The results are mutually consistent, corresponding to a 4.0 per cent measurement of the cosmic distanceâ€“redshift relation at z= 0.6 [in terms of the acoustic parameter â€˜A(z)â€™ introduced by Eisenstein et al., we find A(z= 0.6) = 0.452 Â± 0.018]. Both BAOs and power spectrum shape information contribute towards these constraints. The statistical significance of the detection of the acoustic peak in the correlation function, relative to a wiggle-free model, is 3.2Ïƒ. The ratios of our distance measurements to those obtained using BAOs in the distribution of luminous red galaxies at redshifts z= 0.2 and 0.35 are consistent with a flat Î› cold dark matter model that also provides a good fit to the pattern of observed fluctuations in the cosmic microwave background radiation. The addition of the current WiggleZ data results in a â‰ˆ30 per cent improvement in the measurement accuracy of a constant equation of state, w, using BAO data alone. Based solely on geometric BAO distance ratios, accelerating expansion (w < âˆ’1/3) is required with a probability of 99.8 per cent, providing a consistency check of conclusions based on supernovae observations. Further improvements in cosmological constraints will result when the WiggleZ survey data set is complete

### The WiggleZ Dark Energy Survey: Final data release and cosmological results

This paper presents cosmological results from the final data release of the WiggleZ Dark Energy Survey. We perform full analyses of different cosmological models using the WiggleZ power spectra measured at z=0.22, 0.41, 0.60, and 0.78, combined with other cosmological data sets. The limiting factor in this analysis is the theoretical modeling of the galaxy power spectrum, including nonlinearities, galaxy bias, and redshift-space distortions. In this paper we assess several different methods for modeling the theoretical power spectrum, testing them against the Gigaparsec WiggleZ simulations (GiggleZ). We fit for a base set of six cosmological parameters, {Î©_(b)h^2,Î©_(CDM)h^2,H_0,Ï„,A_s,n_s}, and five supplementary parameters {n_(run),r,w,Î©_k,âˆ‘m_Î½}. In combination with the cosmic microwave background, our results are consistent with the Î›CDM concordance cosmology, with a measurement of the matter density of Î©m=0.29Â±0.016 and amplitude of fluctuations Ïƒ_8=0.825Â±0.017. Using WiggleZ data with cosmic microwave background and other distance and matter power spectra data, we find no evidence for any of the extension parameters being inconsistent with their Î›CDM model values. The power spectra data and theoretical modeling tools are available for use as a module for CosmoMC, which we here make publicly available at http://smp.uq.edu.au/wigglez-data. We also release the data and random catalogs used to construct the baryon acoustic oscillation correlation function

### HÎ± and UV imaging of Low Surface Brightness Galaxies and Extended UV Disks

GALEX observations have revealed UV emission extending far beyond the optical and H-alpha disks of several nearby spiral galaxies, raising the question of possible massive star deficiency, i.e., deviations from the standard 'universal' stellar initial mass function (IMF) at the upper end, in certain low density environments. We have undertaken an HÎ± imaging survey of low surface brightness galaxies observed by GALEX and with existing HI maps with the aim of investigating the variation of the HÎ±/UV ratio with the local density. Here we present preliminary results for 14 such galaxies observed with the Large Format Camera on the Palomar 200 inch telescope using custom narrow band filters

### The WiggleZ Dark Energy Survey: constraining galaxy bias and cosmic growth with three-point correlation functions

Higher order statistics are a useful and complementary tool for measuring the clustering of galaxies, containing information on the non-Gaussian evolution and morphology of large-scale structure in the Universe. In this work we present measurements of the three-point correlation function (3PCF) for 187â€‰000 galaxies in the WiggleZ spectroscopic galaxy survey. We explore the WiggleZ 3PCF scale and shape dependence at three different epochs z = 0.35, 0.55 and 0.68, the highest redshifts where these measurements have been made to date. Using N-body simulations to predict the clustering of dark matter, we constrain the linear and non-linear bias parameters of WiggleZ galaxies with respect to dark matter, and marginalize over them to obtain constraints on Ïƒ8(z), the variance of perturbations on a scale of 8 h^âˆ’1 Mpc and its evolution with redshift. These measurements of Ïƒ_8(z), which have 10â€“20 per cent accuracies, are consistent with the predictions of the Î› cold dark matter concordance cosmology and test this model in a new way

### The WiggleZ Dark Energy Survey: improved distance measurements to z = 1 with reconstruction of the baryonic acoustic feature

We present significant improvements in cosmic distance measurements from the WiggleZ Dark Energy Survey, achieved by applying the reconstruction of the baryonic acoustic feature technique. We show using both data and simulations that the reconstruction technique can often be effective despite patchiness of the survey, significant edge effects and shot-noise. We investigate three redshift bins in the redshift range 0.2 < z < 1, and in all three find improvement after reconstruction in the detection of the baryonic acoustic feature and its usage as a standard ruler. We measure model-independent distance measures D_V(r_s^(fid)/r_s) of 1716 Â± 83, 2221 Â± 101, 2516 Â± 86 Mpc (68 perâ€‰cent CL) at effective redshifts z = 0.44, 0.6, 0.73, respectively, where D_V is the volume-averaged distance, and r_s is the sound horizon at the end of the baryon drag epoch. These significantly improved 4.8, 4.5 and 3.4 per cent accuracy measurements are equivalent to those expected from surveys with up to 2.5 times the volume of WiggleZ without reconstruction applied. These measurements are fully consistent with cosmologies allowed by the analyses of the Planck Collaboration and the Sloan Digital Sky Survey. We provide the D_V(r_s^(fid)/r_s) posterior probability distributions and their covariances. When combining these measurements with temperature fluctuations measurements of Planck, the polarization of Wilkinson Microwave Anisotropy Probe 9, and the 6dF Galaxy Survey baryonic acoustic feature, we do not detect deviations from a flat Î› cold dark matter (Î›CDM) model. Assuming this model, we constrain the current expansion rate to H_0 = 67.15 Â± 0.98 km s^(âˆ’1)Mpc^(âˆ’1). Allowing the equation of state of dark energy to vary, we obtain w_(DE) = âˆ’1.080 Â± 0.135. When assuming a curved Î›CDM model we obtain a curvature value of Î©_K = âˆ’0.0043 Â± 0.0047

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