Bounds on the mass and abundance of dark compact objects and black holes in dwarf spheroidal galaxy halos

We establish new dynamical constraints on the mass and abundance of compact objects in the halo of dwarf spheroidal galaxies. In order to preserve kinematically cold the second peak of the Ursa Minor dwarf spheroidal (UMi dSph) against gravitational scattering, we place upper limits on the density of compact objects as a function of their assumed mass. The mass of the dark matter constituents cannot be larger than 1000 solar masses at a halo density in UMi's core of 0.35 solar masses/pc^3. This constraint rules out a scenario in which dark halo cores are formed by two-body relaxation processes. Our bounds on the fraction of dark matter in compact objects with masses >3000 solar masses improve those based on dynamical arguments in the Galactic halo. In particular, objects with masses $\sim 10^{5}$ solar masses can comprise no more than a halo mass fraction $\sim 0.01$. Better determinations of the velocity dispersion of old overdense regions in dSphs may result in more stringent constraints on the mass of halo objects. For illustration, if the preliminary value of 0.5 km/s for the secondary peak of UMi is confirmed, compact objects with masses above $\sim 100$ solar masses could be excluded from comprising all its dark matter halo.Comment: 6 pages, 2 figures, accepted for publication in ApJ Letter

The thickness of HI in galactic discs under MOND: theory and application to the Galaxy

The outskirts of galaxies are a very good laboratory for testing the nature of the gravitational field at low accelerations. By assuming that the neutral hydrogen gas is in hydrostatic equilibrium in the gravitational potential of the host galaxy, the observed flaring of the gas layer can be used to test modified gravities. For the first time we construct a simple framework to derive the scaleheight of the neutral hydrogen gas disc in the MOND scenario and apply this to the Milky Way. It is shown that using a constant gas velocity dispersion of ~9 km/s, MOND is able to give a very good fit to the observed HI flaring beyond a galactocentric distance of 17 kpc up to the last measured point (~40 kpc). Between 10 and 16 kpc, however, the observed scaleheight is about 40% more than what MOND predicts for the standard interpolating function and 70% for the form suggested by Famaey & Binney. Given the uncertainties in the non-thermal pressure support by cosmic rays and magnetic fields, MOND seems to be a plausible alternative to dark matter in explaining the Milky Way flaring. Studying the flaring of extended HI discs in external edge-on galaxies may be a promising approach to assess the viability of MOND.Comment: 13 pages, 4 figure

Distant star clusters of the Milky Way in MOND

We determine the mean velocity dispersion of six Galactic outer halo globular clusters, AM 1, Eridanus, Pal 3, Pal 4, Pal 15, and Arp 2 in the weak acceleration regime to test classical vs. modified Newtonian dynamics (MOND). Owing to the non-linearity of MOND's Poisson equation, beyond tidal effects, the internal dynamics of clusters is affected by the external field in which they are immersed. For the studied clusters, particle accelerations are much lower than the critical acceleration a_0 of MOND, but the motion of stars is neither dominated by internal accelerations (a_i >> a_e) nor external accelerations (a_e >> a_i). We use the N-body code N-MODY in our analysis, which is a particle-mesh-based code with a numerical MOND potential solver developed by Ciotti, Londrillo, and Nipoti (2006) to derive the line-of-sight velocity dispersion by adding the external field effect. We show that Newtonian dynamics predicts a low-velocity dispersion for each cluster, while in modified Newtonian dynamics the velocity dispersion is much higher. We calculate the minimum number of measured stars necessary to distinguish between Newtonian gravity and MOND with the Kolmogorov-Smirnov test. We also show that for most clusters it is necessary to measure the velocities of between 30 to 80 stars to distinguish between both cases. Therefore the observational measurement of the line-of-sight velocity dispersion of these clusters will provide a test for MOND.Comment: A&A, accepted, LaTeX, 8 pages, 4 figure

Milky Way potentials in CDM and MOND. Is the Large Magellanic Cloud on a bound orbit?

We compute the Milky Way potential in different cold dark matter (CDM) based models, and compare these with the modified Newtonian dynamics (MOND) framework. We calculate the axis ratio of the potential in various models, and find that isopotentials are less spherical in MOND than in CDM potentials. As an application of these models, we predict the escape velocity as a function of the position in the Galaxy. This could be useful in comparing with future data from planned or already-underway kinematic surveys (RAVE, SDSS, SEGUE, SIM, GAIA or the hypervelocity stars survey). In addition, the predicted escape velocity is compared with the recently measured high proper motion velocity of the Large Magellanic Cloud (LMC). To bind the LMC to the Galaxy in a MOND model, while still being compatible with the RAVE-measured local escape speed at the Sun's position, we show that an external field modulus of less than $0.03 a_0$ is needed.Comment: Accepted for publication in MNRAS, 13 pages, 7 figures, 3 table

Semi-Analytical Models for the Formation of Disk Galaxies II. Dark Matter versus Modified Newtonian Dynamics

We present detailed semi-analytical models for the formation of disk galaxies both in a Universe dominated by dark matter (DM), and in one for which the force law is given by modified Newtonian dynamics (MOND). We tune the models to fit the observed near-infrared Tully-Fisher (TF) relation, and compare numerous predictions of the resulting models with observations. The DM and MOND models are almost indistinguishable. They both yield gas mass fractions and dynamical mass-to-light ratios which are in good agreement with observations. Both models reproduce the narrow relation between global mass-to-light ratio and central surface brightness, and reveal a characteristic acceleration, contrary to claims that these relations are not predicted by DM models. Both models require SN feedback in order to reproduce the lack of high surface brightness dwarf galaxies. However, the introduction of feedback to the MOND models steepens the TF relation and increases the scatter, making MOND only marginally consistent with observations. The most serious problem for the DM models is their prediction of steep central rotation curves. However, the DM rotation curves are only slightly steeper than those of MOND, and are only marginally inconsistent with the poor resolution data on LSB galaxies.Comment: 26 pages, 11 figures. Accepted for publication in Ap

The Met Office Global Coupled model 2.0 (GC2) configuration

The latest coupled configuration of the Met Office Unified Model (Global Coupled configuration 2, GC2) is presented. This paper documents the model components which make up the configuration (although the scientific description of these components is detailed elsewhere) and provides a description of the coupling between the components. The performance of GC2 in terms of its systematic errors is assessed using a variety of diagnostic techniques. The configuration is intended to be used by the Met Office and collaborating institutes across a range of timescales, with the seasonal forecast system (GloSea5) and climate projection system (HadGEM) being the initial users. In this paper GC2 is compared against the model currently used operationally in those two systems. Overall GC2 is shown to be an improvement on the configurations used currently, particularly in terms of modes of variability (e.g. mid-latitude and tropical cyclone intensities, the Madden–Julian Oscillation and El Niño Southern Oscillation). A number of outstanding errors are identified with the most significant being a considerable warm bias over the Southern Ocean and a dry precipitation bias in the Indian and West African summer monsoons. Research to address these is ongoing

Genes encoding α-amylase inhibitors are located in the short arms of chromosomes 3B, 3D and 6D of wheat (Triticum aestivum L.)

Three -amylase inhibitors, designated Inh. I, II and III have been purified from the 70% ethanol extract of hexaploid wheat (Triticum aestivum L.) and characterized by amino acid analysis, N-terminal amino acid sequencing and enzyme inhibition tests. Inhibitors I and III have identical N-terminal sequences and inhibitory properties to those of the previously described 0.19/0.53 group of dimeric inhibitors. Inhibitor II has an N-terminal sequence which is identical to that of the previously described 0.28 monomeric inhibitor, but differs from it in that in addition to being active against -amylase from Tenebrio molitor, it is also active against mammalian salivary and pancreatic -amylases. Compensating nulli-tetrasomic and ditelosomic lines of wheat cv. Chinese Spring have been analysed by two-dimensional electrophoresis, under conditions in which there is no overlap of the inhibitors with other proteins, and the chromosomal locations of the genes encoding these inhibitors have been established: genes for Inh. I and Inh. III are in the short arms of chromosomes 3B and 3D, respectively, and that for Inh. II in the short arm of chromosome 6D

Annihilation vs. Decay: Constraining dark matter properties from a gamma-ray detection

Most proposed dark matter candidates are stable and are produced thermally in the early Universe. However, there is also the possibility of unstable (but long-lived) dark matter, produced thermally or otherwise. We propose a strategy to distinguish between dark matter annihilation and/or decay in the case that a clear signal is detected in gamma-ray observations of Milky Way dwarf spheroidal galaxies with gamma-ray experiments. The sole measurement of the energy spectrum of an indirect signal would render the discrimination between these cases impossible. We show that by examining the dependence of the intensity and energy spectrum on the angular distribution of the emission, the origin could be identified as decay, annihilation, or both. In addition, once the type of signal is established, we show how these measurements could help to extract information about the dark matter properties, including mass, annihilation cross section, lifetime, dominant annihilation and decay channels, and the presence of substructure. Although an application of the approach presented here would likely be feasible with current experiments only for very optimistic dark matter scenarios, the improved sensitivity of upcoming experiments could enable this technique to be used to study a wider range of dark matter models.Comment: 29 pp, 8 figs; replaced to match published version (minor changes and some new references

Is COPD a Progressive Disease? A Long Term Bode Cohort Observation

Background: The Global Initiative for Obstructive Lung Diseases (GOLD) defines COPD as a disease that is usually progressive. GOLD also provides a spirometric classification of airflow limitation. However, little is known about the long-term changes of patients in different GOLD grades. Objective: Explore the proportion and characteristics of COPD patients that change their spirometric GOLD grade over long-term follow-up. Methods: Patients alive for at least 8 years since recruitment and those who died with at least 4 years of repeated spirometric measurements were selected from the BODE cohort database. We purposely included the group of non survivors to avoid a “survival selection” bias. The proportion of patients that had a change (improvement or worsening) in their spirometric GOLD grading was calculated and their characteristics compared with those that remained in the same grade. Results: A total of 318 patients were included in the survivor and 217 in the non-survivor groups. Nine percent of survivors and 11% of non survivors had an improvement of at least one GOLD grade. Seventy one percent of survivors and non-survivors remained in the same GOLD grade. Those that improved had a greater degree of airway obstruction at baseline. Conclusions: In this selected population of COPD patients, a high proportion of patients remained in the same spirometric GOLD grade or improved in a long-term follow-up. These findings suggest that once diagnosed, COPD is usually a non-progressive disease