Radio Galaxy Clustering at z~0.3

Radio galaxies are uniquely useful as probes of large-scale structure as their uniform identification with giant elliptical galaxies out to high redshift means that the evolution of their bias factor can be predicted. As the initial stage in a project to study large-scale structure with radio galaxies we have performed a small redshift survey, selecting 29 radio galaxies in the range 0.19<z<0.45 from a contiguous 40 square degree area of sky. We detect significant clustering within this sample. The amplitude of the two-point correlation function we measure is consistent with no evolution from the local (z<0.1) value. This is as expected in a model in which radio galaxy hosts form at high redshift and thereafter obey a continuity equation, although the signal:noise of the detection is too low to rule out other models. Larger surveys out to z~1 should reveal the structures of superclusters at intermediate redshifts and strongly constrain models for the evolution of large-scale structure.Comment: 7 pages, 3 figures, accepted by ApJ Letter

The finite size effect of galaxies on the cosmic virial theorem and the pairwise peculiar velocity dispersions

We discuss the effect of the finite size of galaxies on estimating small-scale relative pairwise peculiar velocity dispersions from the cosmic virial theorem (CVT). Specifically we evaluate the effect by incorporating the finite core radius $r_c$ in the two-point correlation function of mass, i.e. $\xi_\rho(r) \propto (r+r_c)^{-\gamma}$ and the effective gravitational force softening $r_s$ on small scales. We analytically obtain the lowest-order correction term for $\gamma <2$ which is in quantitative agreement with the full numerical evaluation. With a nonzero $r_s$ and/or $r_c$ the cosmic virial theorem is no longer limited to the case of $\gamma<2$. We present accurate fitting formulae for the CVT predicted pairwise velocity dispersion for the case of $\gamma>2$. Compared with the idealistic point-mass approximation ($r_s=r_c=0$), the finite size effect can significantly reduce the small-scale velocity dispersions of galaxies at scales much larger than $r_s$ and $r_c$. Even without considering the finite size of galaxies, nonzero values for $r_c$ are generally expected, for instance, for cold dark matter (CDM) models with a scale-invariant primordial spectrum. For these CDM models, a reasonable force softening r_s\le 100 \hikpc would have rather tiny effect. We present the CVT predictions for the small-scale pairwise velocity dispersion in the CDM models normalized by the COBE observation. The implication of our results for confrontation of observations of galaxy pair-wise velocity dispersions and theoretical predictions of the CVT is also discussed.Comment: 18 pages. LaTeX text and 8 postcript figures. submitted to Ap

Forage Suitability Group Report: A Tool for Grassland Management

Forage suitability groups (FSG\u27s) are USDA-Natural Resources Conservation Service (NRCS) interpretative reports used to develop conservation plans for forage-producing farms and ranches and provide grassland resource information to producers. These electronic reports use soil properties and climatic data to develop forage selection, management recommendations, seasonal distribution of growth, and yield potentials for groups of soil map unit components that have like agronomic characteristics. The information contained in a FSG report can help the user develop proper livestock-forage balances, grazing management plans, pasture and haycrop renovation options, and land treatment measures

The Omega Dependence of the Evolution of xi(r)

The evolution of the two-point correlation function, xi(r,z), and the pairwise velocity dispersion, sigma(r,z), for both the matter and halo population, in three different cosmological models: (Omega_M,Omega_Lambda)=(1,0), (0.2,0) and (0.2,0.8) are described. If the evolution of xi is parameterized by xi(r,z)=(1+z)^{-(3+eps)}xi(r,0), where xi(r,0)=(r/r_0)^{-gamma}, then eps(mass) ranges from 1.04 +/- 0.09 for (1,0) to 0.18 +/- 0.12 for (0.2,0), as measured by the evolution of at 1 Mpc (from z ~ 5 to the present epoch). For halos, eps depends on their mean overdensity. Halos with a mean overdensity of about 2000 were used to compute the halo two-point correlation function tested with two different group finding algorithms: the friends of friends and the spherical overdensity algorithm. It is certainly believed that the rate of growth of this xihh will give a good estimate of the evolution of the galaxy two-point correlation function, at least from z ~ 1 to the present epoch. The values we get for eps(halos) range from 1.54 for (1,0) to -0.36 for (0.2,0), as measured by the evolution of xi(halos) from z ~ 1.0 to the present epoch. These values could be used to constrain the cosmological scenario. The evolution of the pairwise velocity dispersion for the mass and halo distribution is measured and compared with the evolution predicted by the Cosmic Virial Theorem (CVT). According to the CVT, sigma(r,z)^2 ~ G Q rho(z) r^2 xi(r,z) or sigma proportional to (1+z)^{-eps/2}. The values of eps measured from our simulated velocities differ from those given by the evolution of xi and the CVT, keeping gamma and Q constant: eps(CVT) = 1.78 +/- 0.13 for (1,0) or 1.40 +/- 0.28 for (0.2,0).Comment: Accepted for publication in the ApJ. Also available at http://manaslu.astro.utoronto.ca/~carlberg/cnoc/xiev/xi_evo.ps.g

Redshift Evolution of the Nonlinear Two-Point Correlation Function

This paper presents a detailed theoretical study of the two-point correlation function $\xi$ for both dark matter halos and the matter density field in five cosmological models with varying matter density $\Omega_m$ and neutrino fraction $\Omega_\nu$. The objectives of this systematic study are to evaluate the nonlinear gravitational effects on $\xi$, to contrast the behavior of $\xi$ for halos vs. matter, and to quantify the redshift evolution of $\xi$ and its dependence on cosmological parameters. Overall, $\xi$ for halos exhibits markedly slower evolution than $\xi$ for matter, and its redshift dependence is much more intricate than the single power-law parameterization used in the literature. Of particular interest is that the redshift evolution of the halo-halo correlation length $r_0$ depends strongly on $\Omega_m$ and $\Omega_\nu$, being slower in models with lower $\Omega_m$ or higher $\Omega_\nu$. Measurements of $\xi$ to higher redshifts can therefore be a potential discriminator of cosmological parameters. The evolution rate of $r_0$ for halos within a given model increases with time, passing the phase of fixed comoving clustering at $z\sim 1$ to 3 toward the regime of stable clustering at $z\sim 0$. The shape of the halo-halo $\xi$, on the other hand, is well approximated by a power law with slope -1.8 in all models and is not a sensitive model discriminator.Comment: 22 pages, 8 postscript figures, AAS LaTeX v4.0. Accepted for publication in The Astrophysical Journal, Vol. 510 (January 1 1999

Using White Dish CMB Anisotropy Data to Probe Open and Flat-Lambda CDM Cosmogonies

We use data from the White Dish experiment to set limits on cosmic microwave background radiation anisotropies in open and spatially-flat-Lambda cold dark matter cosmogonies. We account for the White Dish calibration uncertainty, and marginalize over the offset and gradient removed from the data. Our 2-sigma upper limits are larger than those derived previously. These upper limits are consistent with those derived from the $COBE$-DMR data for all models tested.Comment: 17 pages of latex. Uses aasms4.sty. 4 figures included. Submitted to ApJ

Designing a mobile augmented memory system for people with traumatic brain injuries

Augmented memory systems help people remember events in their lives. Individuals with Traumatic Brain Injury (TBI) often have memory impairments. We conducted a user study to learn about strategies individuals with TBI use to remember events in their lives. We explored what characteristics individuals with TBI expect of an augmented memory system. We then investigated these aspects in an initial mobile app design, and propose here a concept for a rehearsal application that addresses the issues found in our studies

Hierarchical clustering and formation of power-law correlation in 1-dimensional self-gravitating system

The process of formation of fractal structure in one-dimensional self-gravitating system is examined numerically. It is clarified that structures created in small spatial scale grow up to larger scale through clustering of clusters, and form power-law correlation.Comment: 9pages,4figure

The EXOSAT medium-energy slew survey catalog

We present a catalog of X-ray sources observed during slew maneuvers by the Medium Energy Detector Array onboard the EXOSAT Observatory. The EXOSAT Medium Energy slew-survey catalog (EXMS) provides a unique record of the 1--8 keV X-ray sky between 1983 and 1986. 98% of the sky was observed, with 85% receiving an exposure of >60 s. 1210 sources were detected. By comparing these source positions with other catalogs, identifications are given for 992 detections (82% of the sample). These identifications consist of 250 distinct objects, including 95 different X-ray binary systems, and 14 different AGN. A further 58 detections have multiple candidates, while 160 detections remain unidentified. Collimator transmission corrected 1-8 keV count rates are given for the identified sources, together with raw count rates for the other detections. The construction of the EXMS and the checks performed to ensure the validity of the derived source properties are discussed. A publically available version of this catalog is maintained on the EXOSAT database and archive system (telnet://[email protected]).Comment: 52 pages. 22 Figures. To be published in A&AS. For more information, see http://astro.estec.esa.nl/SA-general/Projects/Exosat/exmsintro.htm