The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic survey that will eventually cover approximately one-quarter of the celestial sphere and collect spectra of %10 6 galaxies, 100,000 quasars, 30,000 stars, and 30,000 serendipity targets. In 2001 June, the SDSS released to the general astronomical community its early data release, roughly 462 deg 2 of imaging data including almost 14 million detected objects and 54,008 follow-up spectra. The imaging data were collected in drift-scan mode in five bandpasses (u, g, r, i, and z); our 95% completeness limits for stars are 22.0, 22.2, 22.2, 21.3, and 20.5, respectively. The photometric calibration is reproducible to 5%, 3%, 3%, 3%, and 5%, respectively. The spectra are flux-and wavelength-calibrated, with 4096 pixels from 3800 to 9200 Å at R % 1800. We present the means by which these data are distributed to the astronomical community, descriptions of the hardware used to obtain the data, the software used for processing the data, the measured quantities for each observed object, and an overview of the properties of this data set.

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 a systematic analysis of 43 nearby galaxy groups (kT 500 = 0.7 − 2.7 keV or M 500 = 10 13 − 10 14 h −1 M ⊙ , 0.012 < z < 0.12), based on Chandra archival data. With robust background subtraction and modeling, we trace gas properties to at least r 2500 for all 43 groups. For 11 groups, gas properties can be robustly derived to r 500 . For an additional 12 groups, we derive gas properties to at least r 1000 and estimate properties at r 500 from extrapolation. We show that in spite of the large variation in temperature profiles inside 0.15 r 500 , the temperature profiles of these groups are similar at > 0.15 r 500 and are consistent with a "universal temperature profile." We present the K − T relations at six characteristic radii (30 kpc, 0.15 r 500 , r 2500 , r 1500 , r 1000 and r 500 ), for 43 groups from this work and 14 clusters from the Vikhlinin et al. (2008) sample. Despite large scatter in the entropy values at 30 kpc and 0.15 r 500 , the intrinsic scatter at r 2500 is much smaller and remains the same (∼ 10%) to r 500 . The entropy excess at r 500 is confirmed, in both groups and clusters, but the magnitude is smaller than previous ROSAT and ASCA results. We also present scaling relations for the gas fraction. It appears that the average gas fraction between r 2500 and r 500 has no temperature dependence, ∼ 0.12 for 1 -10 keV systems. The group gas fractions within r 2500 are generally low and have large scatter. This work shows that the difference of groups from hotter clusters stems from the difficulty of compressing group gas inside of r 2500 . The large scatter of the group gas fraction within r 2500 causes large scatter in the group entropy around the center and may be responsible for the large scatter of the group luminosities. Nevertheless, the groups appear more regular and more like clusters beyond r 2500 , from the results on gas fraction and entropy. Therefore, mass proxies can be extended into low mass systems. The M 500 − T 500 and M 500 − Y X,500 relations derived in this work are indeed well behaved down to at least 2 ×10 13 h −1 M ⊙ .

The Cluster Lensing And Supernova survey with Hubble (CLASH) is a 524-orbit multi-cycle treasury program to use the gravitational lensing properties of 25 galaxy clusters to accurately constrain their mass distributions. The survey, described in detail in this paper, will definitively establish the degree of concentration of dark matter in the cluster cores, a key prediction of structure formation models. The CLASH cluster sample is larger and less biased than current samples of space-based imaging studies of clusters to similar depth, as we have minimized lensing-based selection that favors systems with overly dense cores. Specifically, twenty CLASH clusters are solely X-ray selected. The X-ray selected clusters are massive (kT > 5 keV) and, in most cases, dynamically relaxed. Five additional clusters are included for their lensing strength (θ Ein > 35 at z s = 2) to optimize the likelihood of finding highly magnified high-z (z > 7) galaxies. A total of 16 broadband filters, spanning the near-UV to near-IR, are employed for each 20-orbit campaign on each cluster. These data are used to measure precise (σ z ∼ 0.02(1+z)) photometric redshifts for newly discovered arcs. Observations of each cluster are spread over 8 epochs to enable a search for Type Ia supernovae at z > 1 to improve constraints on the time dependence of the dark energy equation of state and the evolution of supernovae. We present newly re-derived X-ray luminosities, temperatures, and Fe abundances for the CLASH clusters as well as a representative source list for MACS1149.6+2223 (z = 0.544).

We present radial entropy profiles of the intracluster medium (ICM) for a collection of 239 clusters taken from the Chandra X-ray Observatory's Data Archive. Entropy is of great interest because it controls ICM global properties and records the thermal history of a cluster. Entropy is therefore a useful quantity for studying the effects of feedback on the cluster environment and investigating any breakdown of cluster self-similarity. We find that most ICM entropy profiles are well-fit by a model which is a power-law at large radii and approaches a constant value at small radii: K(r) = K 0 + K 100 (r/100 kpc) α , where K 0 quantifies the typical excess of core entropy above the best fitting power-law found at larger radii. We also show that the K 0 distributions of both the full archival sample and the primary HIFLUGCS sample of Reiprich (2001) are bimodal with a distinct gap between K 0 ≈ 30 − 50 keV cm 2 and population peaks at K 0 ∼ 15 keV cm 2 and K 0 ∼ 150 keV cm 2 . The effects of PSF smearing and angular resolution on best-fit K 0 values are investigated using mock Chandra observations and degraded entropy profiles, respectively. We find that neither of these effects is sufficient to explain the entropy-profile flattening we measure at small radii. The influence of profile curvature and number of radial bins on best-fit K 0 is also considered, and we find no indication K 0 is significantly impacted by either. For completeness, we include previously unpublished optical spectroscopy of Hα and [N II] emission lines discussed in Cavagnolo et al. (2008a). All data and results associated with this work are publicly available via the project web site.Abell 119 (z = 0.0442): This is a highly diffuse cluster without a prominent cool core. The large core region and slowly varying surface brightness made deprojection highly unstable. We have excluded a small source at the very center of the BCG. The exclusion region for the source is ≈ 2.2 ′′ in radius which at the redshift of the cluster is ∼ 2 kpc. This cluster required a double β-model.Abell 160 (z = 0.0447): The highly asymmetric, low surface brightness of this cluster resulted in a noisy surface brightness profile that could not be deprojected. This cluster required a double β-model. The BCG hosts a compact X-ray source. The exclusion region for the compact source has a radius of ∼ 5 ′′ or ∼ 4.3 kpc. The BCG for this cluster is not coincident with the X-ray centroid and hence is not at the zero-point of our radial analysis.Abell 193 (z = 0.0485): This cluster has an azimuthally symmetric and a very diffuse ICM centered on a BCG which is interacting with a companion galaxy. In Fig. 1 one can see that the central three bins of this cluster's surface brightness profile are highly discrepant from the best-fit β-model. This is a result of the BCG being coincident with a bright, compact X-ray source. As we have concluded in 3.5, compact X-ray sources are excluded from our analysis as they are not the focus of our study here. Hence we have used the best-fit β-model in d...