We present ACS, NICMOS, and Keck AO-assisted photometry of 20 Type Ia supernovae (SNe Ia) from the HST Cluster Supernova Survey. The SNe Ia were discovered over the redshift interval 0.623 < z < 1.415. Fourteen of these SNe Ia pass our strict selection cuts and are used in combination with the world's sample of SNe Ia to derive the best current constraints on dark energy. Ten of our new SNe Ia are beyond redshift z = 1, thereby nearly doubling the statistical weight of HST-discovered SNe Ia beyond this redshift. Our detailed analysis corrects for the recently identified correlation between SN Ia luminosity and host galaxy mass and corrects the NICMOS zeropoint at the count rates appropriate for very distant SNe Ia. Adding these supernovae improves the best combined constraint on dark energy density, ρ DE (z), at redshifts 1.0 < z < 1.6 by 18% (including systematic errors). For a flat ΛCDM universe, we find Ω Λ = 0.729 +0.014 −0.014 (68% CL including systematic errors). For a flat wCDM model, we measure a constant dark energy equation-of-state parameter w = −1.013 +0.068 −0.073 (68% CL). Curvature is constrained to ∼ 0.7% in the owCDM model and to ∼ 2% in a model in which dark energy is allowed to vary with parameters w 0 and w a . Tightening further the constraints on the time evolution of dark energy will require several improvements, including high-quality multi-passband photometry of a sample of several dozen z > 1 SNe Ia. We describe how such a sample could be efficiently obtained by targeting cluster fields with WFC3 on HST.The updated supernova Union2.1 compilation of 580 SNe is available at http://supernova.lbl.gov/Union ⋆ is less than the mass threshold. We begin by noting that.We can then integrate this probability over all true host masses less than the threshold:⋆ )P (m true ⋆ ) up to a normalization constant found by requiring the integral to be unity when integrating over all possible true masses. P (m true ⋆ ) is estimated from the observed distribution for each type of survey. The SNLS (Sullivan et al. 2010) and SDSS (Lampeitl et al. 2010) host masses were assumed to be representative of untargeted surveys, while the mass distribution in Kelly et al. (2010) was assumed typical of nearby targeted surveys. As these distributions are approximately log-normal, we use this model for P (m true ⋆) using the mean and RMS from the log of the host masses from these surveys (with the average measurement errors subtracted in quadrature), giving log 10 P (m true ⋆ ) = N (µ = 9.88, σ 2 = 0.92 2 ) for untargeted surveys and log 10 P (m true ⋆ ) = N (10.75, 0.66 2 ) for targeted surveys. When host mass measurements are available, P (m obs ⋆ |m true ⋆ ) is also modeled as a log-normal; when no measurement is available, a flat distribution is used.For a supernova from an untargeted survey with no host mass measurement (including supernovae presented in this paper which are not in a cluster), P (m trueis the integral of P (m true ⋆ ) up to the threshold mass: 0.55. Similarly, nearby supernovae from targeted surveys w...

We present measurements of the baryon acoustic peak at redshifts z = 0.44, 0.6 and 0.73 in the galaxy correlation function of the final data set of the WiggleZ Dark Energy Survey. We combine our correlation function with lower redshift measurements from the 6-degree Field Galaxy Survey and Sloan Digital Sky Survey, producing a stacked survey correlation function in which the statistical significance of the detection of the baryon acoustic peak is 4.9σ relative to a zero-baryon model with no peak. We fit cosmological models to this combined baryon acoustic oscillation (BAO) data set comprising six distance-redshift data points, and compare the results with similar cosmological fits to the latest compilation of supernovae (SNe) and cosmic microwave background (CMB) data. The BAO and SNe data sets produce consistent measurements of the equation-of-state w of dark energy, when separately combined with the CMB, providing a powerful check for systematic errors in either of these distance probes. Combining all data sets we determine w = −1.03 ± 0.08 for a flat universe, consistent with a cosmological constant model. Assuming dark energy is a cosmological constant and varying the spatial curvature, we find k = −0.004 ± 0.006.

Numerous methods for finding clusters at moderate to high redshifts have been proposed in recent years, at wavelengths ranging from radio to X-rays. In this paper we describe a new method for detecting clusters in two-band optical/near-IR imaging data. The method relies upon the observation that all rich clusters, at all redshifts observed so far, appear to have a red sequence of early-type galaxies. The emerging picture is that all rich clusters contain a core population of passively evolving elliptical galaxies which are coeval and formed at high redshifts. The proposed search method exploits this strong empirical fact by using the red sequence as a direct indicator of overdensity. The fundamental advantage of this approach is that with appropriate filters, cluster elliptical galaxies at a given redshift are redder than all normal galaxies at lower redshifts. A simple color cut thus virtually eliminates all foreground contamination, even at significant redshifts. In this paper, one of a series of two, we describe the underlying assumptions and basic techniques of the method in detail, and contrast the method with those used by other authors. We provide a brief demonstration of the effectiveness of the technique using a real photometric sample with redshift data, and from this conclude that the method offers a powerful yet simple way of identify galaxy clusters. We find that the method can reliably detect structures to masses as small as groups with velocity dispersions of only ∼ 300 km s −1 , with redshifts for all detected structures estimated to an accuray of ∼10%.

The systematic errors in the virial mass-to-light ratio, M v /L, of galaxy clusters as an estimator of the field M/L value are assessed. We overlay 14 clusters in redshift space to create an ensemble cluster which averages over substructure and asymmetries. The combined sample, including background, contains about 1150 galaxies, extending to a projected radius of about twice r 200 . The radius r 200 , defined as where the mean interior density is 200 times the critical density, is expected to contain the bulk of the virialized cluster mass. The dynamically derivedoverestimate is attributed to not taking into account the surface pressure term in the virial equation. Under the assumption that the velocity anisotropy parameter is in the range 0 ≤ β ≤ 2 / 3 , the galaxy distribution accurately traces the mass profile beyond about the central 0.3r 200 . There are no color or luminosity gradients in the galaxy population beyond 2r 200 , but there is 0.11 ± 0.05 mag fading in the r band luminosities between the field and cluster galaxies. We correct the cluster virial mass-to-light ratio, M v /L = 289 ± 50h M ⊙ / L ⊙ (calculated assuming q 0 = 0.1), for the biases in M v and mean luminosity to estimate the field M/L = 213 ± 59h M ⊙ / L ⊙ . With our self-consistently derived field luminosity density, j/ρ c = 1136 ± 138h M ⊙ / L ⊙ (at z ≃ 1 / 3 ), the corrected M/L indicates Ω 0 = 0.19 ± 0.06 ± 0.04 (formal 1σ random error and estimated potential systematic errors) for those components of the mass field in rich clusters.

To re-examine the rich cluster $\Omega$ value the CNOC Cluster Survey has observed 16 high X-ray luminosity clusters in the redshift range 0.17 to 0.55, obtaining approximately 2600 velocities in their fields. Directly adding all the K and evolution corrected $r$ band light to $M_r(0)=-18.5$, about $0.2L_\ast$, and correcting for the light below the limit, the average mass-to-light ratio of the clusters is $283\pm27h\msun/\lsun$ and the average mass per galaxy is $3.5\pm0.4\times10^{12}h^{-1}\msun$. The clusters are consistent with having a universal $M_v/L$ value (within the errors of about 20\%) independent of their velocity dispersion, mean color of their galaxies, blue galaxy content, redshift, or mean interior density. Using field galaxies within the same data set, with the same corrections, we find that the closure mass-to-light, $\rho_c/j$, is $1160\pm130h\msun/\lsun$ and the closure mass per galaxy, $\rho_c/\phi(>0.2L_\ast)$, is $13.2\pm1.9\times10^{12}h^{-1}\msun$. Under the assumptions that the galaxies are distributed like the mass and that the galaxy luminosities and numbers are statistically conserved, which these data indirectly support, $\Omega_0=0.20\pm0.04\pm0.09$ where the errors are, respectively, the $1\sigma$ internal and an estimate of the $1\sigma$ systematic error resulting from the luminosity normalization.Comment: 34 page Latex document (no figures) requiring AAS macros. Postscript document (or uufile) availble at http://manaslu.astro.utoronto.ca/~carlberg/cnoc/general.htm

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We evaluate the effects of environment and stellar mass on galaxy properties at 0.85 < z < 1.20 using a 3.6µm-selected spectroscopic sample of 797 cluster and field galaxies drawn from the GCLASS survey. We confirm that for galaxies with LogM * /M ⊙ > 9.3 the well-known correlations between environment and properties such as star-forming fraction (f SF ), SFR, SSFR, D n (4000), and color are already in place at z ∼ 1. We separate the effects of environment and stellar mass on galaxies by comparing the properties of star-forming and quiescent galaxies at fixed environment, and fixed stellar mass. The SSFR of star-forming galaxies at fixed environment is correlated with stellar mass; however, at fixed stellar mass it is independent of environment. The same trend exists for the D n (4000) measures of both the star-forming and quiescent galaxies and shows that their properties are determined primarily by their stellar mass, not by their environment. Instead, it appears that environment's primary role is to control the fraction of star forming galaxies. Using the spectra we identify candidate poststarburst galaxies and find that those with 9.3 < LogM * /M ⊙ < 10.7 are 3.1 ± 1.1 times more common in high-density regions compared to low-density regions. The clear association of poststarbursts with high-density regions as well as the lack of a correlation between the SSFRs and D n (4000)s of starforming galaxies with their environment strongly suggests that at z ∼ 1 the environmental-quenching timescale must be rapid. Lastly, we construct a simple quenching model which demonstrates that the lack of a correlation between the D n (4000) of quiescent galaxies and their environment results naturally if self quenching dominates over environmental quenching at z > 1, or if the evolution of the self-quenching rate mirrors the evolution of the environmental-quenching rate at z > 1, regardless of which dominates.

We present the results of a study of weak lensing by galaxies based on 45.5 deg 2 of R C band imaging data from the Red-Sequence Cluster Survey (RCS). We define a sample of lenses with 19.5 < R C < 21, and a sample of background galaxies with 21.5 < R C < 24.We present the first weak lensing detection of the flattening of galaxy dark matter halos. We use a simple model in which the ellipticity of the halo is f times the observed ellipticity of the lens. We find a best fit value of f = 0.77 +0.18 −0.21 , suggesting that the dark matter halos are somewhat rounder than the light distribution. The fact that we detect a significant flattening implies that the halos are well aligned with the light distribution. Given the average ellipticity of the lenses, this implies a halo ellipticity of e halo = 0.33 +0.07 −0.09 , in fair agreement with results from numerical simulations of CDM. We note that this result is formally a lower limit to the flattening, since the measurements imply a larger flattening if the halos are not aligned with the light distribution. Alternative theories of gravity (without dark matter) predict an isotropic lensing signal, which is excluded with 99.5% confidence. Hence, our results provide strong support for the existence of dark matter.We also study the average mass profile around the lenses, using a maximum likelihood analysis. We consider two models for the halo mass profile: a truncated isothermal sphere (TIS) and an NFW profile. We adopt observationally motivated scaling relations between the lens luminosity and the velocity dispersion and the extent of the halo. The TIS model yields a best fit velocity dispersion of σ = 136±5±3 km/s (all errors are 68% confidence limits; the first error bar indicates the statistical uncertainty, whereas the second error bar indicates the systematic error) and a truncation radius s = 185 +30 −28 h −1 kpc for a galaxy with a fiducial luminosity of L B = 10 10 h −2 L B⊙ (under the assumption that the luminosity does not evolve with redshift). Alternatively, the best fit NFW model yields a mass M 200 = (8.4 ± 0.7 ± 0.4) × 10 11 h −1 M ⊙ and a scale radius r s = 16.2 +3.6 −2.9 h −1 kpc. This value for the scale radius is in excellent agreement with predictions from numerical simulations for a halo of this mass.