Cosmic Bulk Flow and the Local Motion from Cosmicflows-2

Full sky surveys of peculiar velocity are arguably the best way to map the large scale structure out to distances of a few times 100 Mpc/h. Using the largest and most accurate ever catalog of galaxy peculiar velocities "Cosmicflows-2", the large scale structure has been reconstructed by means of the Wiener filter and constrained realizations assuming as a Bayesian prior model the LCDM model with the WMAP inferred cosmological parameters. The present paper focuses on studying the bulk flow of the local flow field, defined as the mean velocity of top-hat spheres with radii ranging out to R=500 Mpc/h. The estimated large scale structures, in general, and the bulk flow, in particular, are determined by the tension between the observational data and the assumed prior model. A prerequisite for such an analysis is the requirement that the estimated bulk flow is consistent with the prior model. Such a consistency is found here. At R=50(150) Mpc/h the estimated bulk velocity is 250+/-21 (239+/-38) km/s. The corresponding cosmic variance at these radii is 126(60)km/s, which implies that these estimated bulk flows are dominated by the data and not by the assumed prior model. The estimated bulk velocity is dominated by the data out to R~200 Mpc/h, where the cosmic variance on the individual Supergalactic Cartesian components (of the r.m.s. values) exceeds the variance of the Constrained Realizations by at least a factor of 2. The supergalactic SGX and SGY components of the CMB dipole velocity are recovered by the Wiener filter velocity field down to a very few km/s. The SGZ component of the estimated velocity, the one that is most affected by the Zone of Avoidance, is off by 126 km/s (an almost 2 sigma discrepancy).Comment: 10 pages, accepted for MNRA

The Mid-Infrared Tully-Fisher Relation: Calibration of the SNIa Scale and Ho

This paper builds on a calibration of the SNIa absolute distance scale begun with a core of distances based on the correlation between galaxy rotation rates and optical Ic band photometry. This new work extends the calibration through the use of mid-infrared photometry acquired at 3.6 microns with Spitzer Space Telescope. The great virtue of the satellite observations is constancy of the photometry at a level better than 1% across the sky. The new calibration is based on 39 individual galaxies and 8 clusters that have been the sites of well observed SNIa. The new 3.6 micron calibration is not yet as extensively based as the Ic band calibration but is already sufficient to justify a preliminary report. Distances based on the mid-infrared photometry are 2% greater in the mean than reported at Ic band. This difference is only marginally significant. The Ic band result is confirmed with only a small adjustment. Incorporating a 1% decrease in the LMC distance, the present study indicates Ho = 75.2 +/- 3.0 km/s/Mpc.Comment: Accepted for publication in The Astrophysical Journal Letters, 6 pages, 2 figure

Goodness-of-fit analysis of the Cosmicflows-2 database of velocities

The goodness-of-fit (GoF) of the Cosmicflows-2 (CF2) database of peculiar velocities with the LCDM standard model of cosmology is presented. Standard application of the Chi^2 statistics of the full database, of its 4,838 data points, is hampered by the small scale nonlinear dynamics which is not accounted for by the (linear regime) velocity power spectrum. The bulk velocity constitutes a highly compressed representation of the data which filters out the small scales non-linear modes. Hence the statistics of the bulk flow provides an efficient tool for assessing the GoF of the data given a model. The particular approach introduced here is to use the (spherical top-hat window) bulk velocity extracted from the Wiener filter reconstruction of the 3D velocity field as a linear low pass filtered highly compressed representation of the CF2 data. An ensemble 2250 random linear realizations of the WMAP/LCDM model has been used to calculate the bulk velocity auto-covariance matrix. We find that the CF2 data is consistent with the WMAP/LCDM model to better than the 2 sigma confidence limits. This provides a further validation that the CF2 database is consistent with the standard model of cosmology.Comment: submitted to MNRAS, V2 : solved page sizing proble

The Arrowhead Mini-Supercluster of Galaxies

Superclusters of galaxies can be defined kinematically from local evaluations of the velocity shear tensor. The location where the smallest eigenvalue of the shear is positive and maximal defines the center of a basin of attraction. Velocity and density fields are reconstructed with Wiener Filter techniques. Local velocities due to the density field in a restricted region can be separated from external tidal flows, permitting the identification of boundaries separating inward flows toward a basin of attraction and outward flows. This methodology was used to define the Laniakea Supercluster that includes the Milky Way. Large adjacent structures include Perseus-Pisces, Coma, Hercules, and Shapley but current kinematic data are insufficient to capture their full domains. However there is a small region trapped between Laniakea, Perseus-Pisces, and Coma that is close enough to be reliably characterized and that satisfies the kinematic definition of a supercluster. Because of its shape, it is given the name the Arrowhead Supercluster. This entity does not contain any major clusters. A characteristic dimension is ~25 Mpc and the contained mass is only ~10^15 Msun.Comment: Accepted for publication in The Astrophysical Journal. Video can be viewed at http://irfu.cea.fr/arrowhea

Accountable Care Organizations in California: Promise and Performance

California has more accountable care organizations (ACOs) than any other state in the country, with particularly rapid growth over the past two years. This report introduces new evidence that ACOs improve the quality of care, increase patient satisfaction, and may reduce costs

Sediment management for Southern California mountains, coastal plains and shoreline

The Environmental Quality Laboratory at Caltech and the Shore Processes Laboratory at Scripps Institution of Oceanography have jointly undertaken a study of regional sediment balance problems in coastal southern California (see map in Figure 1). The overall objective in this study is to define specific alternatives in sediment management that may be implemented to alleviate a) existing sediment imbalance problems (e.g. inland debris disposal, local shoreline erosion) and b) probable future problems that have not yet manifested themselves. These alternatives will be identified through a consideration of economic, legal, and institutional issues as well as an analysis of governing physical processes and engineering constraints. The first part of this study (Phase I), which is currently under way, involves a compilation and analysis of all available data in an effort to obtain an accurate definition of the inland/coastal regional sediment balance under natural conditions, and specific quantitative effects man-made controls have on the overall natural process. During FY77, substantial progress was made at EQL and SPL in achieving the objectives of the initial Planning and Assessment Phase of the CIT/SIO Sediment Management Project. Financial support came from Los Angeles County, U.S. Geological Survey, Orange County, U.S. Army Corps of Engineers, and discretionary funding provided by a grant from the Ford Foundation. The current timetable for completion of this phase is Fall 1978. This report briefly describes the project status, including general administration, special activities, and research work as of January 1978

Bimodality of Galaxy Disk Central Surface Brightness Distribution in the Spitzer 3.6 micron band

We report on measurements of the disk central surface brightnesses (mu0) at 3.6 microns for 438 galaxies selected by distance and absolute magnitude cutoffs from the 2350+ galaxies in the Spitzer Survey of Stellar Structure in Galaxies (S4G), one of the largest and deepest homogeneous mid-infrared datasets of nearby galaxies. Our sample contains nearly 3 times more galaxies than the most recent study of the mu0 distribution. We demonstrate that there is a bimodality in the distribution of mu0. Between the low and high surface brightness galaxy regimes there is a lack of intermediate surface brightness galaxies. Caveats invoked in the literature from small number statistics to the knowledge of the environmental influences, and possible biases from low signal to noise data or corrections for galaxy inclination are investigated. Analyses show that the bimodal distribution of mu0 cannot be due to any of these biases or statistical fluctuations. It is highly probable that galaxies settle in two stable modes: a dark matter dominated mode where the dark matter dominates at all radii - this gives birth to low surface brightness galaxies - and a baryonic matter dominated mode where the baryons dominate the dark matter in the central parts - this gives rise to the high surface brightness disks. The lack of intermediate surface brightness objects suggests that galaxies avoid (staying in) a mode where dark matter and baryons are co-dominant in the central parts of galaxies.Comment: Accepted for publication in MNRAS, 9 pages, 10 figures, 1 tabl

Monte Carlo simulations of the directional-ordering transition in the two-dimensional classical and quantum compass model

A comprehensive study of the two-dimensional (2D) compass model on the square lattice is performed for classical and quantum spin degrees of freedom using Monte Carlo and quantum Monte Carlo methods. We employ state-of-the-art implementations using Metropolis, stochastic series expansion and parallel tempering techniques to obtain the critical ordering temperatures and critical exponents. In a pre-investigation we reconsider the classical compass model where we study and contrast the finite-size scaling behavior of ordinary periodic boundary conditions against annealed boundary conditions. It is shown that periodic boundary conditions suffer from extreme finite-size effects which might be caused by closed loop excitations on the torus. These excitations also appear to have severe effects on the Binder parameter. On this footing we report on a systematic Monte Carlo study of the quantum compass model. Our numerical results are at odds with recent literature on the subject which we trace back to neglecting the strong finite-size effects on periodic lattices. The critical temperatures are obtained as $T_\mathrm{c}=0.1464(2)J$ and $T_\mathrm{c}=0.055(1)J$ for the classical and quantum version, respectively, and our data support a transition in the 2D Ising universality class for both cases.Comment: 8 pages, 7 figures, differs slightly from published versio