The galactic centre

I would like to start by bringing the good wishes of Australian radio astronomers to this new group which is joining us in the radio study of the southern sky. The nuclear regions of galaxies are generally considered as regions of high density, with population II stars in a "nuclear bulge". In some galaxies, the presence of gas in the nucleus is shown by the appearance of the OII 3727 doublet, sometimes with a high velocity dispersion. Some nearby galaxies (e.g. M31, M33, M51) show a small very bright spot, right at the nucleus, of the order of 10 pc in diameter. Non-circular velocities have been found near the centre in some galaxies.Asociación Argentina de Astronomí

The galactic centre

I would like to start by bringing the good wishes of Australian radio astronomers to this new group which is joining us in the radio study of the southern sky. The nuclear regions of galaxies are generally considered as regions of high density, with population II stars in a "nuclear bulge". In some galaxies, the presence of gas in the nucleus is shown by the appearance of the OII 3727 doublet, sometimes with a high velocity dispersion. Some nearby galaxies (e.g. M31, M33, M51) show a small very bright spot, right at the nucleus, of the order of 10 pc in diameter. Non-circular velocities have been found near the centre in some galaxies.Asociación Argentina de Astronomí

The galactic centre

I would like to start by bringing the good wishes of Australian radio astronomers to this new group which is joining us in the radio study of the southern sky. The nuclear regions of galaxies are generally considered as regions of high density, with population II stars in a "nuclear bulge". In some galaxies, the presence of gas in the nucleus is shown by the appearance of the OII 3727 doublet, sometimes with a high velocity dispersion. Some nearby galaxies (e.g. M31, M33, M51) show a small very bright spot, right at the nucleus, of the order of 10 pc in diameter. Non-circular velocities have been found near the centre in some galaxies.Asociación Argentina de Astronomí

Evolution of virulence: triggering host inflammation allows invading pathogens to exclude competitors.

Virulence is generally considered to benefit parasites by enhancing resource-transfer from host to pathogen. Here, we offer an alternative framework where virulent immune-provoking behaviours and enhanced immune resistance are joint tactics of invading pathogens to eliminate resident competitors (transferring resources from resident to invading pathogen). The pathogen wins by creating a novel immunological challenge to which it is already adapted. We analyse a general ecological model of 'proactive invasion' where invaders not adapted to a local environment can succeed by changing it to one where they are better adapted than residents. However, the two-trait nature of the 'proactive' strategy (provocation of, and adaptation to environmental change) presents an evolutionary conundrum, as neither trait alone is favoured in a homogenous host population. We show that this conundrum can be resolved by allowing for host heterogeneity. We relate our model to emerging empirical findings on immunological mediation of parasite competition

Exterior and interior metrics with quadrupole moment

We present the Ernst potential and the line element of an exact solution of Einstein's vacuum field equations that contains as arbitrary parameters the total mass, the angular momentum, and the quadrupole moment of a rotating mass distribution. We show that in the limiting case of slowly rotating and slightly deformed configuration, there exists a coordinate transformation that relates the exact solution with the approximate Hartle solution. It is shown that this approximate solution can be smoothly matched with an interior perfect fluid solution with physically reasonable properties. This opens the possibility of considering the quadrupole moment as an additional physical degree of freedom that could be used to search for a realistic exact solution, representing both the interior and exterior gravitational field generated by a self-gravitating axisymmetric distribution of mass of perfect fluid in stationary rotation.Comment: Latex, 15 pages, 3 figures, final versio

Interacting dark matter contribution to the Galactic 511 keV gamma ray emission: constraining the morphology with INTEGRAL/SPI observations

We compare the full-sky morphology of the 511 keV gamma ray excess measured by the INTEGRAL/SPI experiment to predictions of models based on dark matter (DM) scatterings that produce low-energy positrons: either MeV-scale DM that annihilates directly into e+e- pairs, or heavy DM that inelastically scatters into an excited state (XDM) followed by decay into e+e- and the ground state.By direct comparison to the data, we find that such explanations are consistent with dark matter halo profiles predicted by numerical many-body simulations for a Milky Way-like galaxy. Our results favor an Einasto profile over the cuspier NFW distribution and exclude decaying dark matter scenarios whose predicted spatial distribution is too broad. We obtain a good fit to the shape of the signal using six fewer degrees of freedom than previous empirical fits to the 511 keV data. We find that the ratio of flux at Earth from the galactic bulge to that of the disk is between 1.9 and 2.4, taking into account that 73% of the disk contribution may be attributed to the beta decay of radioactive 26Al.Comment: 7 pages, 4 figures. Includes minor corrections, and a discussion of threshold energies in XDM models. Published in JCA

Changes in Alcohol Consumption and Subsequent Risk of Type 2 Diabetes in Men

Objective -The objective of this study was to investigate the association of four-year changes in alcohol consumption with subsequent risk of type 2 diabetes. Research Design and Methods - We prospectively examined 38,031 men from the Health Professionals Follow-up Study free of diagnosed diabetes or cancer in 1990. Alcohol consumption was reported on food frequency questionnaires and updated every four years. Results - A total of 1905 cases of type 2 diabetes occurred during 428,497 person-years of follow-up. A 7.5 g/day (~half a glass) increase in alcohol consumption over four years was associated with lower diabetes risk among initial nondrinkers (multivariable hazard ratio [HR] 0.78; 95% confidence interval [CI] 0.60-1.00) and drinkers initially consumin

Approximate gravitational field of a rotating deformed mass

A new approximate solution of vacuum and stationary Einstein field equations is obtained. This solution is constructed by means of a power series expansion of the Ernst potential in terms of two independent and dimensionless parameters representing the quadrupole and the angular momentum respectively. The main feature of the solution is a suitable description of small deviations from spherical symmetry through perturbations of the static configuration and the massive multipole structure by using those parameters. This quality of the solution might eventually provide relevant differences with respect to the description provided by the Kerr solution.Comment: 16 pages. Latex. To appear in General Relativity and Gravitatio

Dark Matter Direct Detection with Non-Maxwellian Velocity Structure

The velocity distribution function of dark matter particles is expected to show significant departures from a Maxwell-Boltzmann distribution. This can have profound effects on the predicted dark matter - nucleon scattering rates in direct detection experiments, especially for dark matter models in which the scattering is sensitive to the high velocity tail of the distribution, such as inelastic dark matter (iDM) or light (few GeV) dark matter (LDM), and for experiments that require high energy recoil events, such as many directionally sensitive experiments. Here we determine the velocity distribution functions from two of the highest resolution numerical simulations of Galactic dark matter structure (Via Lactea II and GHALO), and study the effects for these scenarios. For directional detection, we find that the observed departures from Maxwell-Boltzmann increase the contrast of the signal and change the typical direction of incoming DM particles. For iDM, the expected signals at direct detection experiments are changed dramatically: the annual modulation can be enhanced by more than a factor two, and the relative rates of DAMA compared to CDMS can change by an order of magnitude, while those compared to CRESST can change by a factor of two. The spectrum of the signal can also change dramatically, with many features arising due to substructure. For LDM the spectral effects are smaller, but changes do arise that improve the compatibility with existing experiments. We find that the phase of the modulation can depend upon energy, which would help discriminate against background should it be found.Comment: 34 pages, 16 figures, submitted to JCAP. Tables of g(v_min), the integral of f(v)/v from v_min to infinity, derived from our simulations, are available for download at http://astro.berkeley.edu/~mqk/dmdd

Dependence of direct detection signals on the WIMP velocity distribution

The signals expected in WIMP direct detection experiments depend on the ultra-local dark matter distribution. Observations probe the local density, circular speed and escape speed, while simulations find velocity distributions that deviate significantly from the standard Maxwellian distribution. We calculate the energy, time and direction dependence of the event rate for a range of velocity distributions motivated by recent observations and simulations, and also investigate the uncertainty in the determination of WIMP parameters. The dominant uncertainties are the systematic error in the local circular speed and whether or not the MW has a high density dark disc. In both cases there are substantial changes in the mean differential event rate and the annual modulation signal, and hence exclusion limits and determinations of the WIMP mass. The uncertainty in the shape of the halo velocity distribution is less important, however it leads to a 5% systematic error in the WIMP mass. The detailed direction dependence of the event rate is sensitive to the velocity distribution. However the numbers of events required to detect anisotropy and confirm the median recoil direction do not change substantially.Comment: 21 pages, 7 figures, v2 version to appear in JCAP, minor change