Hydrodynamical Simulations of the IGM at High Mach Numbers

We present a new approach to doing Eulerian computational fluid dynamics that is designed to work at high Mach numbers encountered in hydrodynamical simulations of the IGM. In conventional Eulerian CFD, the thermal energy is poorly tracked in supersonic bulk flows where local fluid variables cannot be accurately separated from the much larger bulk flow components. We described a method in which local fluid quantities can be directly tracked and the Eulerian fluid equations solved in a local frame moving with the flow. The new algorithm has been used to run large hydrodynamical simulations on a 1024^3 grid to study the kinetic SZ effect. The KSZ power spectrum is broadly peaked at l~10^4 with temperature fluctuations on micro Kelvin levels.Comment: 6 pages, to appear in the Proc. from the IGM/Galaxy Connection conferenc

Linguistics

Contains reports on four research projects.National Institute of Mental Health (Grant 1 PO1 MH-13390-04

Indications of a positive feedback between coastal development and beach nourishment

Beach nourishment, a method for mitigating coastal storm damage or chronic erosion by deliberately replacing sand on an eroded beach, has been the leading form of coastal protection in the United States for four decades. However, investment in hazard protection can have the unintended consequence of encouraging development in places especially vulnerable to damage. In a comprehensive, parcel-scale analysis of all shorefront single-family homes in the state of Florida, we find that houses in nourishing zones are significantly larger and more numerous than in non-nourishing zones. The predominance of larger homes in nourishing zones suggests a positive feedback between nourishment and development that is compounding coastal risk in zones already characterized by high vulnerability

Linguistics

Contains research objectives and reports on five research projects.National Institutes of Health (Grant 1 P01 MH-13390-02

On the pulsation of a star in which there is a prevalent magnetic field

In this paper a simple approximate formula is obtained for the frequency (σ) of radial pulsation of a gaseous star in which there is a prevalent magnetic field. The formula is σ2I = - (3γ - 4) (Ω + B) , where γ is the ratio of the specific heats, I = ∫0Mr2dm (r) , and Ω and B denote the gravitational potential energy and the magnetic energy of the star, respectively. The formula is derived from the virial theorem in the form recently established by Chandrasekhar and Fermi; and it supports their conclusion that the period of pulsation can be made as long as one may desire by letting the magnetic energy approach the upper limit (namely, |Ω|) set by the virial theorem

Galaxy Flow in the Canes Venatici I Cloud

We present an analysis of Hubble Space Telescope/WFPC2 images of eighteen galaxies in the Canes Venatici I cloud. We derive their distances from the luminosity of the tip of the red giant branch stars with a typical accuracy of ~12 %. The resulting distances are 3.9 Mpc (UGC 6541), 4.9 Mpc (NGC 3738), 3.0 Mpc (NGC 3741), 4.5 Mpc (KK 109), >6.3 Mpc (NGC 4150), 4.2 Mpc (UGC 7298), 4.5 Mpc (NGC 4244), 4.6 Mpc (NGC 4395), 4.9 Mpc (UGC 7559), 4.2 Mpc (NGC 4449), 4.4 Mpc (UGC 7605), 4.6 Mpc (IC 3687), 4.7 Mpc (KK 166), 4.7 Mpc (NGC 4736), 4.2 Mpc (UGC 8308), 4.3 Mpc (UGC 8320), 4.6 Mpc (NGC 5204), and 3.2 Mpc (UGC 8833). The CVn I cloud has a mean radial velocity of 286 +- 9 km/s, a mean distance of 4.1 +- 0.2 Mpc, a radial velocity dispersion of 50 km/s, a mean projected radius of 760 kpc, and a total blue luminosity of 2.2 * 10^{10} L_{\sun}. Assuming virial or closed orbital motions for the galaxies, we estimated their virial and their orbital mass-to-luminosity ratio to be 176 and 88 M_{\sun}/L_{\sun}, respectively. However, the CVn I cloud is characterized by a crossing time of 15 Gyr, and is thus far from a state of dynamical equilibrium. The large crossing time for the cloud, its low content of dSph galaxies ($< 6$ %), and the almost ``primordial'' shape of its luminosity function show that the CVn I complex is in a transient dynamical state, driven rather by the free Hubble expansion than by galaxy interactions.Comment: 23 pages, 6 figures, A&A in preparation. The version does not include Figure 2. High resolution figures 1 and 2 (11311k) are available at http://luna.sao.ru/~sme/figsCVn.tar.g

Large Scale Pressure Fluctuations and Sunyaev-Zel'dovich Effect

The Sunyaev-Zel'dovich (SZ) effect associated with pressure fluctuations of the large scale structure gas distribution will be probed with current and upcoming wide-field small angular scale cosmic microwave background experiments. We study the generation of pressure fluctuations by baryons which are present in virialized dark matter halos and by baryons present in small overdensities. For collapsed halos, assuming the gas distribution is in hydrostatic equilibrium with matter density distribution, we predict the pressure power spectrum and bispectrum associated with the large scale structure gas distribution by extending the dark matter halo approach which describes the density field in terms of correlations between and within halos. The projected pressure power spectrum allows a determination of the resulting SZ power spectrum due to virialized structures. The unshocked photoionized baryons present in smaller overdensities trace the Jeans-scale smoothed dark matter distribution. They provide a lower limit to the SZ effect due to large scale structure in the absence of massive collapsed halos. We extend our calculations to discuss higher order statistics, such as bispectrum and skewness in SZ data. The SZ-weak lensing cross-correlation is suggested as a probe of correlations between dark matter and baryon density fields, while the probability distribution functions of peak statistics of SZ halos in wide field CMB data can be used as a probe of cosmology and non-Gaussian evolution of large scale structure pressure fluctuations.Comment: 16 pages, 9 figures; Revised with expanded discussions. Phys. Rev. D. (in press

The Canada-France deep fields survey-I: 100,000 galaxies, 1 deg^2: a precise measurement of \omega(\theta) to IAB~25

(abridged) Using the UH8K mosaic camera, we have measured the angular correlation function \omega(\theta) for 100,000 galaxies over four widely separated fields totalling ~1\deg^2 and reaching IAB~25.5. With this sample we investigate the dependence of \omega(\theta) at 1', A_\omega(1'), on sample median IAB magnitude in the range 19.5<I(AB-med)<24. Our results show that A_\omega(1') decreases monotonically to IAB~25. At bright magnitudes, \omega(\theta) is consistent with a power-law of slope \delta = -0.8 for 0.2'<\theta<3.0' but at fainter magnitudes we find \delta ~ -0.6. At the 3\sigma level, our observations are still consistent with \delta=-0.8. Furthermore, in the magnitude ranges 18.5<IAB<24.0 and 18.5<IAB<23.0 we find galaxies with 2.6<(V-I)AB<2.9 have A_\omega(1')'s which are ~10x higher than field values. We demonstrate that our model redshift distributions for the faint galaxy population are in good agreement with current spectroscopic observations. Using these predictions, we find that for low-omega cosmologies and assuming r_0=4.3/h Mpc, in the range 19.5<I(AB-med)<22, the growth of galaxy clustering is \epsilon~0. However, at 22<I(AB-med)<24.0, our observations are consistent with \epsilon>1. Models with \epsilon~0 cannot simultaneously match both bright and faint measurements of A_\omega(1`). We show how this result is a natural consequence of the ``bias-free'' nature of the \epsilon formalism and is consistent with the field galaxy population in the range 22.0<IAB<24.0 being dominated by galaxies of low intrinsic luminosity.Comment: 20 pages, 21 figures, requires natbib.sty, accepted for publication in Astronomy and Astrophysic

Internal dynamics of the galaxy cluster Abell 545

Diffuse radio emission in galaxy clusters, and their connection with cluster mergers, are still debated. We seek to explore the internal dynamics of the radio halo cluster Abell 545. This cluster is also peculiar for hosting in its center a very bright, red, diffuse intracluster light due to an old, stellar population, so bright to be named as "star pile". Our analysis is based on redshift data for 110 galaxies. We identify 95 cluster members and analyze the cluster internal dynamics by combining galaxy velocities and positions. We also use both photometric and X-ray data. We estimate the cluster redshift, z=0.1580, a velocity dispersion of 1200 km/s, and ICM temperature kT_X~8 keV. Our optical and X-ray analyses detect substructures. Optical data reveal three main galaxy clumps (center, NNW, and NE), and possibly a fourth clump at South. There is not a dominant galaxy and the four brightest galaxies avoid the cluster core (>~0.4h distant from the cluster center) and are >~1500 km/s far from the mean cluster velocity. The analysis of the X-ray surface brightness distribution provides us evidence of a disturbed dynamical phase. Located in the star pile region there is the brightest galaxies of the cluster core (CBCG) and a very compact elliptical galaxy. We show that the star pile has a similar redshift to that of the CBCG. Both the star pile and the CBCG are at rest in the cluster rest frame. The emerging picture of Abell 545 is that of a massive, M(R<1.6 h_70^-1 Mpc)=1.1-1.8x10^15 h_70^-1 Msun, very complex cluster with merging occurring along two directions. A545 gives another proof in the favor of the connection between cluster merger and extended, diffuse radio emission. The star pile, likely due to the process of a brightest galaxy forming in the cluster core. A545 represents a textbook cluster where to study the simultaneous formation of a galaxy system and its brightest galaxy.Comment: 16 pages, 11 figures and 2 tables. Accepted in A&