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We present a detailed non-spherical modeling of dark matter halos on the basis of a combined analysis of the high-resolution halo simulations (12 halos with N ∼ 10 6 particles within their virial radius) and the large cosmological simulations (5 realizations with N = 512 3 particles in a 100h −1 Mpc boxsize). The density profiles of those simulated halos are well approximated by a sequence of the concentric triaxial distribution with their axis directions being fairly aligned. We characterize the triaxial model quantitatively by generalizing the universal density profile which has previously been discussed only in the framework of the spherical model. We obtain a series of practically useful fitting formulae in applying the triaxial model; the mass and redshift dependence of the axis ratio, the mean of the concentration parameter, and the probability distribution functions of the the axis ratio and the concentration parameter. These accurate fitting formulae form a complete description of the triaxial density profiles of halos in Cold Dark Matter models. Our current description of the dark halos will be particularly useful in predicting a variety of nonsphericity effects, to a reasonably reliable degree, including the weak and strong lens statistics, the orbital evolution of galactic satellites and triaxiality of galactic halos, and the non-linear clustering of dark matter. In addition, this provides a useful framework for the non-spherical modeling of the intra-cluster gas, which is crucial in discussing the gas and temperature profiles of X-ray clusters and the Hubble constant estimated via the Sunyaev -Zel'dovich effect.

We study the luminosity and color dependence of the galaxy 2-point correlation function in the Sloan Digital Sky Survey, starting from a sample of 200,000 galaxies over 2500 deg^2. We concentrate on the projected correlation function w(r_p), which is directly related to the real space \xi(r). The amplitude of w(r_p) grows continuously with luminosity, rising more steeply above the characteristic luminosity L_*. Redder galaxies exhibit a higher amplitude and steeper correlation function at all luminosities. The correlation amplitude of blue galaxies increases continuously with luminosity, but the luminosity dependence for red galaxies is less regular, with bright red galaxies more strongly clustered at large scales and faint red galaxies more strongly clustered at small scales. We interpret these results using halo occupation distribution (HOD) models assuming concordance cosmological parameters. For most samples, an HOD model with two adjustable parameters fits the w(r_p) data better than a power-law, explaining inflections at r_p ~ 1-3 Mpc/h as the transition between the 1-halo and 2-halo regimes of \xi(r). The implied minimum mass for a halo hosting a central galaxy above a luminosity threshold L grows as M_min ~ L at low luminosities and more steeply above L_*. The mass at which an average halo has one satellite galaxy brighter than L is M_1 ~ 23 M_min(L). These results imply a conditional luminosity function (at fixed halo mass) in which central galaxies lie far above a Schechter function extrapolation of the satellite population. HOD models nicely explain the joint luminosity-color dependence of w(r_p) in terms of the color fractions of central and satellite populations as a function of halo mass. The inferred HOD properties are in good qualitative agreement with theoretical predictions.Comment: 64 pages, 24 figures. Minor changes to match accepted ApJ versio

With the Sixth Data Release of the Sloan Digital Sky Survey, the imaging of the Northern Galactic Cap is now complete. The survey contains images and parameters of roughly 287 million objects over 9583 deg^2, and 1.27 million spectra of stars, galaxies, quasars and blank sky (for sky subtraction) selected over 7425 deg^2. This release includes much more extensive stellar spectroscopy than previously, and also includes detailed estimates of stellar temperatures, gravities, and metallicities. The results of improved photometric calibration are now available, with uncertainties of roughly 1% in g, r, i, and z, and 2% in u, substantially better than the uncertainties in previous data releases. The spectra in this data release have improved wavelength and flux calibration, especially in the extreme blue and extreme red, leading to the qualitatively better determination of stellar types and radial velocities. The spectrophotometric fluxes are now tied to point spread function magnitudes of stars rather than fiber magnitudes, giving a 0.35 mag change in the spectrophotometric flux scale. Systematic errors in the velocity dispersions of galaxies have been fixed, and the results of two independent codes for determining spectral classifications and redshifts are made available. (Abridged)Comment: 21 pages with 8 color figures. ApJS, in press. Minor modifications from previous versio

Hyper Suprime-Cam (HSC) is a wide-field imaging camera on the prime focus of the 8.2m Subaru telescope on the summit of Maunakea in Hawaii. A team of scientists from Japan, Taiwan and Princeton University is using HSC to carry out a 300-night multi-band imaging survey of the high-latitude sky. The survey includes three layers: the Wide layer will cover 1400 deg 2 in five broad bands (grizy), with a 5 σ point-source depth of r ≈ 26. The Deep layer covers a total of 26 deg 2 in four fields, going roughly a magnitude fainter, while the UltraDeep layer goes almost a magnitude fainter still in two pointings of HSC (a total of 3.5 deg 2). Here we describe the instrument, the science goals of the survey, and the survey strategy and data processing. This paper serves as an introduction to a special issue of the Publications of the Astronomical Society of Japan, which includes a large number of technical and scientific papers describing results from the early phases of this survey.

We perform a series of high-resolution N-body simulations designed to examine the density profiles of dark matter halos. From 12 simulated halos ranging in mass from 2x1012 to 5x1014 h-1 M middle dot in circle (represented by approximately 1 million particles within the virial radius), we find a clear systematic correlation between the halo mass and the slope of the density profile at 1% of the virial radius, in addition to the variations of the slope among halos of similar mass. More specifically, the slope is approximately -1.5, -1.3, and -1.1 for galaxy-, group-, and cluster-mass halos, respectively. While we confirm the earlier simulation results that the inner slope is steeper than the universal profile originally proposed by Navarro, Frenk, & White, this mass dependence is inconsistent with several analytical arguments attempting to link the inner slope with the primordial index of the fluctuation spectrum. Thus, we conclude that the dark matter density profiles, especially in the inner region, are not universal.

The Subaru Prime Focus Spectrograph (PFS) is a massively-multiplexed fiber-fed optical and near-infrared 3-arm spectrograph (N fiber =2400, 380≤ λ ≤ 1260nm, 1.3 degree diameter hexagonal field), offering unique opportunities in survey astronomy. Following a successful external design review the instrument is now under construction with first light anticipated in late 2017. Here we summarize the science case for this unique instrument in terms of provisional plans for a Subaru Strategic Program of ≃300 nights. We describe plans to constrain the nature of dark energy via a survey of emission line galaxies spanning a comoving volume of 9.3h −3 Gpc 3 in the redshift range 0.8 < z < 2.4. In each of 6 independent redshift bins, the cosmological distances will be measured to 3% precision via the baryonic acoustic oscillation scale, and redshift-space distortion measures will be used to constrain structure growth to 6% precision. In the near-field cosmology program, radial velocities and chemical abundances of stars in the Milky Way and M31 will be used to infer the past assembly histories of spiral galaxies and the structure of their dark matter halos. Data will be secured for 10 6 stars in the Galactic thick-disk, halo and tidal streams as faint as V ∼ 22, including stars with V < 20 to complement the goals of the Gaia mission. A medium-resolution mode with R = 5, 000 to be implemented in the red arm will allow the measurement of multiple α-element abundances and more precise velocities for Galactic stars, elucidating the detailed chemo-dynamical structure and evolution of each of the main stellar components of the Milky Way Galaxy and of its dwarf spheroidal galaxies. The M31 campaign will target red giant branch stars with 21.5< V <22.5, obtaining radial velocities and metallicities over an unprecedented area of 65 deg 2 . For the extragalactic program, our simulations suggest the wide wavelength range of PFS will be particularly powerful in probing the galaxy population and its clustering over a wide redshift range. We propose to conduct a color-selected survey of 1 < z < 2 galaxies and AGN over 16 deg 2 to J ≃23.4, yielding a fair sample of galaxies with stellar masses above ∼ 10 10 M ⊙ at z ≃ 2. A two-tiered survey of higher redshift Lyman break galaxies and Lyman alpha emitters will quantify the properties of early systems close to the reionization epoch. PFS will also provide unique spectroscopic opportunities beyond these currentlyenvisaged surveys, particularly in the era of Euclid, LSST and TMT.

Temperature and luminosity functions of X-ray clusters are computed semi-analytically, combining a simple model for the cluster gas properties with the distribution functions of halo formation epochs proposed by Lacey & Cole (1993) and . In contrast to several previous approaches which apply the Press-Schechter mass function in a straightforward manner, our method can explicitly take into account the temperature and luminosity evolution of clusters. In order to make quantitative predictions in a specific cosmological context, we adopt cold dark matter (CDM) universes.Assuming the baryon density parameter Ω B = 0.0125h −2 (h is the Hubble constant in units of 100km•sec −1 •Mpc −1 ) and the COBE normalization of matter fluctuations, temperature and luminosity functions of X-ray clusters depend sensitively on the density parameter Ω 0 . Allowing for several uncertainties in observational data as well as in our simplified assumptions, we conclude that Ω 0 ∼ 0.2 − 0.5 and h ∼ 0.7 CDM models with/without the cosmological constant reproduce simultaneously the observed temperature and luminosity functions of X-ray clusters at redshift z ∼ 0.