1,721,117 research outputs found
Mapping dark matter in the Milky Way, a synopsis
No full textMapping the dark matter distribution across our Galaxy represents a central challenge for the near future as a new generation of space-borne and ground-based astronomical surveys swiftly comes online. Here we present a synopsis of the present status of the field, reviewing briefly the baryonic content and the kinematics of the MilkyWay and outlining the methods used to infer the dark matter component. The discussion then proceeds with some of the latest developments based on our own work. In particular, we present a new compilation of kinematic measurements tracing the rotation curve of the Galaxy and an exhaustive array of observation-based baryonic models setting the contribution of stellar bulge, stellar disc and gas to the total gravitational potential. The discrepancy between these two components is then quantified to derive the latest constraints on the dark matter distribution and on modified Newtonian dynamics. We shall end with an overview of future directions to improve our mapping of the dark matter distribution in the Milky Way
Lithium synthesis around stellar mass black holes
No full textWe present a study of nucleosynthesis of light elements in the accretion disk of stellar mass black holes. The amount of both stable isotopes of lithium produced is sizeable for a host of values of black hole mass, disk viscosity and accretion rate. We discuss our results in the context of the lithium problem and propose observational tests for this mechanism
Dynamical constraints on the dark matter distribution in the Milky Way
No full textAn accurate knowledge of the dark matter distribution in the Milky Way is of crucial importance for galaxy formation studies and current searches for particle dark matter. In this paper we set new dynamical constraints on the Galactic dark matter profile by comparing the observed rotation curve, updated with a comprehensive compilation of kinematic tracers, with that inferred from a wide range of observation-based morphologies of the bulge, disc and gas. The generalised Navarro-Frenk-White (NFW) and Einasto dark matter profiles are fitted to the data in order to determine the favoured ranges of local density, slope and scale radius. For a representative baryonic model, a typical local circular velocity v0=230 km/s and a distance of the Sun to the Galactic centre R0=8 kpc, we find a local dark matter density ρ0 = 0.420+0.021-0.018 (2σ) ± 0.025 GeV/cm3 (ρ0 = 0.420+0.019-0.021 (2σ) ± 0.026 GeV/cm3) for NFW (Einasto), where the second error is an estimate of the systematic due to baryonic modelling. Apart from the Galactic parameters, the main sources of uncertainty inside and outside the solar circle are baryonic modelling and rotation curve measurements, respectively. Upcoming astronomical observations are expected to reduce all these uncertainties substantially over the coming years
Lithium synthesis in microquasar accretion
No full textWe study the synthesis of lithium isotopes in the hot tori formed around stellar mass black holes by accretion of the companion star. We find that sizable amounts of both stable isotopes Li6 and Li7 can be produced, the exact figures varying with the characteristics of the torus and reaching as much as 10 -2MTM for each isotope. This mass output is enough to contaminate the entire Galaxy at a level comparable with the original, pregalactic amount of lithium and to overcome other sources such as cosmic-ray spallation or stellar nucleosynthesis. © 2012 American Physical Society
Dark Matter distribution in the Milky Way: Microlensing and dynamical constraints
No full textWe show that current microlensing and dynamical observations of the Galaxy permit to set interesting constraints on the Dark Matter local density and profile slope towards the galactic centre. Assuming state-of-the-art models for the distribution of baryons in the Galaxy, we find that the most commonly discussed Dark Matter profiles (viz. Navarro-Frenk-White and Einasto) are consistent with microlensing and dynamical observations, while extreme adiabatically compressed profiles are robustly ruled out. When a baryonic model that also includes a description of the gas is adopted, our analysis provides a determination of the local Dark Matter density, ρ0 = 0.20-0.56GeV/cm3 at 1σ, that is found to be compatible with estimates in the literature based on different techniques. © 2011 IOP Publishing Ltd and SISSA
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
On the dark matter distribution in the Milky Way
No full textThe distribution of dark matter in the Milky Way is a crucial input for ongoing studies in cosmology, astrophysics and particle physics. This motivates the effort over the next years to improve our mapping of dark matter, which has indeed become a top priority in the field. We report briefly on the state of the art regarding the dark matter distribution in our Galaxy, with a special emphasis in the inner part of the Galaxy where baryons start to give an important dynamical contribute to the total gravitational potential. After introducing the kinematic data used to trace the rotation curve and the photometric data used to model the different baryonic components, we combine kinematics and photometry to single out the dark matter content. The procedure is then used to assess the evidence for dark matter and to constrain the underlying dark matter distribution with two conceptually distinct approaches, which we dub profile fitting and profile reconstruction. Finally, in view of the swarm of astronomical data soon to become available, we shortly address the expected progress in pinpointing dark matter across the Galaxy
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