Data base for the Colorado profiling network

The Colorado profiling system developed by the Wave Propagation Laboratory (WPL) includes five (soon to be six) Doppler radar wind Profilers; four operate at 49 MHz (6 m) and are located at Platteville, Fleming, Lay Creek, and Cahone, and one operates at 915 MHz (33 cm) and is located at Denver. The sixth radar, now under construction, will operate at 405 MHz (UHF) and will be located at Boulder. Microwave radiometers and surface meteorological stations are at some of the radar sites. The data base for the wind Profilers is discussed

Time-Dependent Models for Dark Matter at the Galactic Center

The prospects of indirect detection of dark matter at the galactic center depend sensitively on the mass profile within the inner parsec. We calculate the distribution of dark matter on sub-parsec scales by integrating the time-dependent Fokker-Planck equation, including the effects of self-annihilations, scattering of dark matter particles by stars, and capture in the supermassive black hole. We consider a variety of initial dark matter distributions, including models with very high densities ("spikes") near the black hole, and models with "adiabatic compression" of the baryons. The annihilation signal after 10 Gyr is found to be substantially reduced from its initial value, but in dark matter models with an initial spike, order-of-magnitude enhancements can persist compared with the rate in spike-free models, with important implications for indirect dark matter searches with GLAST and Air Cherenkov Telescopes like HESS and CANGAROO.Comment: Four page

Gravitational waves from galaxy encounters

We discuss the emission of gravitational radiation produced in encounters of dark matter galactic halos. To this aim we perform a number of numerical simulations of typical galaxy mergers, computing the associated gravitational radiation waveforms as well as the energy released in the processes. Our simulations yield dimensionless gravitational wave amplitudes of the order of $10^{-13}$ and gravitational wave frequencies of the order of $10^{-16}$ Hz, when the galaxies are located at a distance of 10 Mpc. These values are of the same order as those arising in the gravitational radiation originated by strong variations of the gravitational field in the early Universe, and therefore, such gravitational waves cannot be directly observed by ground-based detectors. We discuss the feasibility of an indirect detection by means of the B-mode polarization of the Cosmic Microwave Background (CMB) induced by such waves. Our results show that the gravitational waves from encounters of dark matter galactic halos leave much too small an imprint on the CMB polarization to be actually observed with ongoing and future missions.Comment: 9 pages with revtex style, 3 ps figures; to be published in Physical Review

Self-consistent models of cuspy triaxial galaxies with dark matter haloes

We have constructed realistic, self-consistent models of triaxial elliptical galaxies embedded in triaxial dark matter haloes. We examined three different models for the shape of the dark matter halo: (i) the same axis ratios as the luminous matter (0.7:0.86:1); (ii) a more prolate shape (0.5:0.66:1); (iii) a more oblate shape (0.7:0.93:1). The models were obtained by means of the standard orbital superposition technique introduced by Schwarzschild. Self-consistent solutions were found in each of the three cases. Chaotic orbits were found to be important in all of the models,and their presence was shown to imply a possible slow evolution of the shapes of the haloes. Our results demonstrate for the first time that triaxial dark matter haloes can co-exist with triaxial galaxies.Comment: Latex paper based on the AASTEX format, 20 pages, 11 figures, 2 tables. Paper submitted to Ap

Performance of the Colorado wind-profiling network, part 1.5A

The Wave Propagation Laboratory (WPL) has operated a network of radar wind Profilers in Colorado for about 1 year. The network consists of four VHF (50-MHz) radars and a UHF (915-MHz) radar. The Platteville VHF radar was developed by the Aeronomy Laboratory (AL) and has been operated jointly by WPL and AL for several years. The other radars were installed between February and May 1983. Experiences with these radars and some general aspects of tropospheric wind measurements with Doppler radar are discussed

Spin Flips and Precession in Black-Hole-Binary Mergers

We use the `moving puncture' approach to perform fully non-linear evolutions of spinning quasi-circular black-hole binaries with individual spins not aligned with the orbital angular momentum. We evolve configurations with the individual spins (parallel and equal in magnitude) pointing in the orbital plane and 45-degrees above the orbital plane. We introduce a technique to measure the spin direction and track the precession of the spin during the merger, as well as measure the spin flip in the remnant horizon. The former configuration completes 1.75 orbits before merging, with the spin precessing by 98-degrees and the final remnant horizon spin flipped by ~72-degrees with respect to the component spins. The latter configuration completes 2.25 orbits, with the spins precessing by 151-degrees and the final remnant horizon spin flipped ~34-degrees with respect to the component spins. These simulations show for the first time how the spins are reoriented during the final stage of binary black hole mergers verifying the hypothesis of the spin-flip phenomenon. We also compute the track of the holes before merger and observe a precession of the orbital plane with frequency similar to the orbital frequency and amplitude increasing with time.Comment: Revtex4, 17 figures, 14 pages. Accepted for publication in PR