An Elliptical Galaxy Luminosity Function and Velocity Dispersion Sample of Relevance for Gravitational Lensing Statistics

We have selected 42 elliptical galaxies from the literature and estimated their velocity dispersions at the effective radius (\sigma_{\re}) and at 0.54 effective radii (\vff). We find by a dynamical analysis that the normalized velocity dispersion of the dark halo of an elliptical galaxy \vdm is roughly \sigma_{\re} multiplied by a constant, which is almost independent of the core radius or the anisotropy parameter of each galaxy. Our sample analysis suggests that \vdm^{*} lies in the range 178-198 km s$^{-1}$. The power law relation we find between the luminosity and the dark matter velocity dispersion measured in this way is (L/L^{*}) = (\vdm/\vdm^{*})^\gamma, where $\gamma$ is between 2-3. These results are of interest for strong gravitational lensing statistics studies. In order to determine the value of \vdm^{*}, we calculate \mstar in the same \bt band in which \vdm^{*} has been estimated. We select 131 elliptical galaxies as a complete sample set with apparent magnitudes \bt between 9.26 and 12.19. We find that the luminosity function is well fitted to the Schechter form, with parameters \mstar = -19.66 + 5$\cdot\log_{10}h \pm 0.30$, $\alpha = 0.15 \pm 0.55$, and the normalization constant $\phi^{*} = (1.34 \pm 0.30) \times 10^{-3} h^{3}$ Mpc$^{-3}$, with the Hubble constant \hnot = 100 $h$ km s$^{-1}$ Mpc$^{-1}$. This normalization implies that morphology type E galaxies make up (10.8 $\pm$ 1.2) per cent of all galaxies.Comment: 18 pages latex, with ps figs included. accepted by New Astronomy (revised to incorporate referees comments

Adverse Consequences to Assisting Victims of Campus Violence: Initial Investigations Among College Students

Despite growing interest in the use of bystander education programs to address the problems of sexual and relationship violence on college campuses, little knowledge exists on adverse consequences experienced by students intervening as a bystander. The current study examined the prevalence and correlates of adverse consequences of bystander intervention in two samples of first-year college students. In Study 1, 281 students completed a measure of negative consequences experienced when acting as a bystander to help someone at risk of sexual assault, relationship abuse, or stalking. Efficacy for bystander behavior was also assessed. Approximately one third of the students (97/281) reported having tried to help someone who had been at risk of violence during the previous academic year. Of these, approximately 17% (16/97) reported experiencing a negative consequence from having tried to help. Experiencing negative consequences was associated with lower levels of bystander efficacy. In Study 2, conducted at a different university, 299 students completed measures of negative consequences resulting from intervening as a bystander and efficacy for bystander behavior. Students also participated in virtual-reality simulations that provided opportunities to intervene as a bystander. Again, approximately one third of the students (99/299) reported having tried to help someone at risk of violence. Of these, 20% (20/99) reported experiencing a negative consequence. Two of the adverse consequences (physically hurt, got into trouble) were negatively associated with bystander efficacy and observed effectiveness of bystander behavior in the virtual simulations. Results of exploratory analyses suggest that training in bystander intervention might reduce the likelihood of experiencing adverse consequences

Gravitational Lensing and Dark Structures

We examine whether a cosmologically significant distribution of dark galaxy group or cluster-sized objects can have an optical depth for multiple imaging of distant background sources which is comparable to that from known galaxies while at the same time producing angular splittings of the same order of magnitude. Our purpose is to explore whether such objects could realistically account for some of the observed lenses. Modeling such systems as isothermal spheres with core radii, and assuming a Schechter-type distribution function, we find that independent of the cosmology (open, flat matter dominated, or flat cosmological constant dominated) an allowed parameter range exists which is comparable in velocity dispersion to that for known compact groups of galaxies, although the preferred core radii are somewhat smaller than that normally assumed for compact groups. Dark cluster-sized objects, on the other hand, cannot reproduce the observed lensing characteristics. If the one known Dark cluster were a good representative of such a distribution, most such objects would not produce multiple images. We also present a result for the angular splitting due to an isothermal sphere lens with non-zero core radius, extending earlier work of Hinshaw and Krauss (1987). Our results are expressed as contour plots for fixed lensing probabilities, and angular splittings.Comment: 20 pages (including 6 figures), AASTe

A Two Hour Quasi-Period in an Ultra-luminous X-Ray source in NGC628

Quasi-periodic oscillations and X-ray spectroscopy are powerful probes of black hole masses and accretion disks, and here we apply these diagnostics to an ultraluminous X-ray source (ULX) in the spiral galaxy NGC628 (M74). This object was observed four times over two years with the Chandra X-ray Observatory and XMM-Newton, with three long observations showing dramatic variability, distinguished by a series of outbursts with a quasi-period (QPO) of 4,000-7,000 seconds. This is unique behavior among both ULXs and Galactic X-ray binaries due to the combination of its burst-like peaks and deep troughs, its long quasi-periods, its high variation amplitudes of $>90$%, and its substantial variability between observations. The X-ray spectra is fitted by an absorbed accretion disk plus a power-law component, suggesting the ULX was in a spectral state analogous to the Low Hard state or the Very High state of Galactic black hole X-ray binaries. A black hole mass of $\sim2$--$20\times10^3 M_\odot$ is estimated from the $f_b$--$M_\bullet$ scaling relation found in the Galactic X-ray binaries and active galactic nuclei.Comment: 12 pages, 3 figures. accepted for publication in ApJ Lette

Nuclear Propelled Vessels and Neutrino Oscillation Experiments

We study the effect of naval nuclear reactors on the study of neutrino oscillations. We find that the presence of naval reactors at unknown locations and times may limit the accuracy of future very long baseline reactor-based neutrino oscillation experiments. At the same time we argue that a nuclear powered surface ship such as a large Russian ice-breaker may provide an ideal source for precision experiments. While the relatively low reactor power would in this case require a larger detector, the source could be conveniently located at essentially any distance from a detector built at an underground location near a shore in a region of the world far away from other nuclear installations. The variable baseline would allow for a precise measurement of backgrounds and greatly reduced systematics from reactor flux and detector efficiency. In addition, once the oscillation measurement is completed, the detector could perform geological neutrino and astrophysical measurements with minimal reactor background.Comment: 4 pages, 2 figure

H9N2 Influenza A Viruses from Poultry in Asia Have Human Virus-like Receptor Specificity

AbstractH9N2 influenza A viruses are currently widespread in chickens, quail, and other poultry in Asia and have caused a few cases of influenza in humans. In this study, we found that H9N2 viruses from Hong Kong live bird markets have receptor specificity similar to that of human H3N2 viruses. In addition, the neuraminidase of poultry H9N2 viruses has mutations in its hemadsorbing site, a characteristic resembling that of human H2N2 and H3N2 viruses but differing from that of other avian viruses. Peculiar features of surface glycoproteins of H9N2 viruses from Hong Kong suggest an enhanced propensity for introduction into humans and emphasize the importance of poultry in the zoonotic transmission of influenza viruses

Searching for Dark Matter at the LHC with a Mono-Z

We investigate a mono-Z process as a potential dark matter search strategy at the LHC. In this channel a single Z boson recoils against missing transverse momentum, attributed to dark matter particles, $\chi$, which escape the detector. This search strategy is related, and complementary to, monojet and monophoton searches. For illustrative purposes we consider the process $q\bar{q} -> \chi\chi Z$ in a toy dark matter model, where the Z boson is emitted from either the initial state quarks, or from the internal propagator. Among the signatures of this process will be a pair of muons with high pT that reconstruct to the invariant mass of the Z, and large amounts of missing transverse energy. Being a purely electroweak signal, QCD and other Standard Model backgrounds are relatively easily removed with modest selection cuts. We compare the signal to Standard Model backgrounds and demonstrate that, even for conservative cuts, there exist regions of parameter space where the signal may be clearly visible above background in future LHC data, allowing either new discovery potential or the possibility of supplementing information about the dark sector beyond that available from other observable channels.Comment: 11 pages, 13 figure