The effect of supernova heating on cluster properties and constraints on galaxy formation models

Models of galaxy formation should be able to predict the properties of clusters of galaxies, in particular their gas fractions, metallicities, X-ray luminosity-temperature relation, temperature function and mass-deposition-rate function. Fitting these properties places important constaints on galaxy formation on all scales. By following gas processes in detail, our semi-analytic model (based on that of Nulsen & Fabian 1997) is the only such model able to predict all of the above cluster properties. We use realistic gas fractions and gas density profiles, and as required by observations we break the self-similarity of cluster structure by including supernova heating of intracluster gas, the amount of which is indicated by the observed metallicities. We also highlight the importance of the mass-deposition-rate function as an independent and very sensitive probe of cluster structure.Comment: 5 pages, 4 figures, accepted for publication in MNRAS as a lette

The soft X-ray background: evidence for widespread disruption of the gas halos of galaxy groups

Almost all of the extragalactic X-ray background (XRB) at 0.25 keV can be accounted for by radio-quiet quasars, allowing us to derive an upper limit of 4 \bgunit\ for the remaining background at 0.25 keV. However, the XRB from the gas halos of groups of galaxies, with gas removal due to cooling accounted for, exceeds this upper limit by an order of magnitude if non-gravitational heating is not included. We calculate this using simulations of halo merger trees and realistic gas density profiles, which we require to reproduce the observed gas fractions and abundances of X-ray clusters. In addition, we find that the entire mass range of groups, from $\sim 5\times 10^{12}$ to $\sim 10^{14}$\Ms, contributes to the 0.25 keV background in this case. In a further study, we reduce the luminosities of groups by maximally heating their gas halos while maintaining the same gas fractions. This only reduces the XRB by a factor of 2 or less. We thus argue that most of the gas associated with groups must be outside their virial radii. This conclusion is supported by X-ray studies of individual groups. The properties of both groups and X-ray clusters can be naturally explained by a model in which the gas is given excess specific energies of $\sim 1$ keV/particle by non-gravitational heating. With this excess energy, the gas is gravitationally unbound from groups, but recollapses with the formation of a cluster of temperature \ga 1 keV. This is similar to a model proposed by Pen, but is contrary to the evolution of baryons described by Cen \& Ostriker. (abridged)Comment: 14 pages, 14 figures, submitted to MNRA

Neutrino oscillations in a stochastic model for space-time foam

We study decoherence models for flavour oscillations in four-dimensional stochastically fluctuating space times and discuss briefly the sensitivity of current neutrino experiments to such models. We pay emphasis on demonstrating the model dependence of the associated decoherence-induced damping coefficients in front of the oscillatory terms in the respective transition probabilities between flavours. Within the context of specific models of foam, involving point-like D-branes and leading to decoherence-induced damping which is inversely proportional to the neutrino energies, we also argue that future limits on the relevant decoherence parameters coming from TeV astrophysical neutrinos, to be observed in ICE-CUBE, are not far from theoretically expected values with Planck mass suppression. Ultra high energy neutrinos from Gamma Ray Bursts at cosmological distances can also exhibit in principle sensitivity to such effects.Comment: 12 pages RevTex4, no figure

Collisional stability of fermionic Feshbach molecules

Using a Feshbach resonance, we create ultracold fermionic molecules starting from a Bose-Fermi atom gas mixture. The resulting mixture of atoms and weakly bound molecules provides a rich system for studying few-body collisions because of the variety of atomic collision partners for molecules; either bosonic, fermionic, or distinguishable atoms. Inelastic loss of the molecules near the Feshbach resonance is dramatically affected by the quantum statistics of the colliding particles and the scattering length. In particular, we observe a molecule lifetime as long as 100 ms near the Feshbach resonance.Comment: 4 pages, 4 figures, 1 tabl

Radiative Models of Sagittarius A* and M87 from Relativistic MHD Simulations

Ongoing millimeter VLBI observations with the Event Horizon Telescope allow unprecedented study of the innermost portion of black hole accretion flows. Interpreting the observations requires relativistic, time-dependent physical modeling. We discuss the comparison of radiative transfer calculations from general relativistic MHD simulations of Sagittarius A* and M87 with current and future mm-VLBI observations. This comparison allows estimates of the viewing geometry and physical conditions of the Sgr A* accretion flow. The viewing geometry for M87 is already constrained from observations of its large-scale jet, but, unlike Sgr A*, there is no consensus for its millimeter emission geometry or electron population. Despite this uncertainty, as long as the emission region is compact, robust predictions for the size of its jet launching region can be made. For both sources, the black hole shadow may be detected with future observations including ALMA and/or the LMT, which would constitute the first direct evidence for a black hole event horizon.Comment: 8 pages, 2 figures, submitted to the proceedings of AHAR 2011: The Central Kiloparse

Molecular beam epitaxial growth of high-quality InSb on InP and GaAs substrates

Epitaxial layers of InSb were grown on InP and GaAs substrates by molecular beam epitaxy. The dependence of the epilayer quality on flux ratio, J sub Sb4/J sub In, was studied. Deviation from an optimum value of J sub Sb4/J sub In (approx. 2) during growth led to deterioration in the surface morphology and the electrical and crystalline qualities of the films. Room temperature electron mobilities as high as 70,000 and 53,000 sq cm /V-s were measured in InSb layers grown on InP and GaAs substrates, respectively. Unlike the previous results, the conductivity in these films is n-type even at T = 13 K, and no degradation of the electron mobility due to the high density of dislocations was observed. The measured electron mobilities (and carrier concentrations) at 77 K in InSb layers grown on InP and GaAs substrates are 110,000 sq cm/V-s (3 x 10(15) cm(-3)) and 55,000 sq cm/V-s (4.95 x 10(15) cm(-3)), respectively, suggesting their application to electronic devices at cryogenic temperatures

Bayesian Error Estimation in Density Functional Theory

We present a practical scheme for performing error estimates for Density Functional Theory calculations. The approach which is based on ideas from Bayesian statistics involves creating an ensemble of exchange-correlation functionals by comparing with an experimental database of binding energies for molecules and solids. Fluctuations within the ensemble can then be used to estimate errors relative to experiment on calculated quantities like binding energies, bond lengths, and vibrational frequencies. It is demonstrated that the error bars on energy differences may vary by orders of magnitude for different systems in good agreement with existing experience.Comment: 5 pages, 3 figure

Mechanically Detecting and Avoiding the Quantum Fluctuations of a Microwave Field

During the theoretical investigation of the ultimate sensitivity of gravitational wave detectors through the 1970's and '80's, it was debated whether quantum fluctuations of the light field used for detection, also known as photon shot noise, would ultimately produce a force noise which would disturb the detector and limit the sensitivity. Carlton Caves famously answered this question with "They do." With this understanding came ideas how to avoid this limitation by giving up complete knowledge of the detector's motion. In these back-action evading (BAE) or quantum non-demolition (QND) schemes, one manipulates the required quantum measurement back-action by placing it into a component of the motion which is unobserved and dynamically isolated. Using a superconducting, electro-mechanical device, we realize a sensitive measurement of a single motional quadrature with imprecision below the zero-point fluctuations of motion, detect both the classical and quantum measurement back-action, and demonstrate BAE avoiding the quantum back-action from the microwave photons by 9 dB. Further improvements of these techniques are expected to provide a practical route to manipulate and prepare a squeezed state of motion with mechanical fluctuations below the quantum zero-point level, which is of interest both fundamentally and for the detection of very weak forces

Studies of Tiros and Nimbus radiometric observations Final report

Data analyses of Tiros and Nimbus radiometric observation

A Bose-condensed, simultaneous dual species Mach-Zehnder atom interferometer

This paper presents the first realisation of a simultaneous $^{87}$Rb -$^{85}$Rb Mach-Zehnder atom interferometer with Bose-condensed atoms. A number of ambitious proposals for precise terrestrial and space based tests of the Weak Equivalence Principle rely on such a system. This implementation utilises hybrid magnetic-optical trapping to produce spatially overlapped condensates with a duty cycle of 20s. A horizontal optical waveguide with co-linear Bragg beamsplitters and mirrors is used to simultaneously address both isotopes in the interferometer. We observe a non-linear phase shift on a non-interacting $^{85}$Rb interferometer as a function of interferometer time, $T$, which we show arises from inter-isotope scattering with the co-incident $^{87}$Rb interferometer. A discussion of implications for future experiments is given.Comment: 7 pages, 5 figures. The authors welcome comments and feedback on this manuscrip