122713743
Dark Matter Distributions of the Milky Way Satellites and Implications for Indirect Detection
We review recent progress in understanding the mass distributions of the Milky Way dwarf satellite population, with a specific focus on the implications for gamma-ray fluxes from dark matter. We outline a method that self-consitently predicts the gamma-ray fluxes from the satellites using line-of-sight velocities, the Constrained Minimal Supersymmetric Standard Model (CMSSM), and a model for the boost from substructure in the dark matter halos. Combining all of these ingredients, and accounting for the reduced astrophysical backgrounds relative to the Galactic center, the dwarf satellites make strong candidates for indirect detection with Fermi/GLAST and future Air Cerenkov Telescopes.
28577443
STELLAR POPULATIONS IN THE CENTRAL 0.5 pc OF THE GALAXY. I. A NEW METHOD FOR CONSTRUCTING LUMINOSITY FUNCTIONS AND SURFACE-DENSITY PROFILES
We present new high angular resolution near-infrared spectroscopic observations of the nuclear star cluster surrounding the Milky Way's central supermassive black hole. Using the integral-field spectrograph OSIRIS on Keck II behind the laser-guide-star adaptive optics system, this spectroscopic survey enables us to separate early-type (young, 4-6 Myr) and late-type (old, >1 Gyr) stars with a completeness of 50% down to K' = 15.5 mag, which corresponds to ~10 M_☉ for the early-type stars. This work increases the radial extent of reported OSIRIS/Keck measurements by more than a factor of three from 4" to 14" (0.16 to 0.56 pc), along the projected disk of young stars. For our analysis, we implement a new method of completeness correction using a combination of star-planting simulations and Bayesian inference. We assign probabilities for the spectral type of every source detected in deep imaging down to K' = 15.5 mag using information from spectra, simulations, number counts, and the distribution of stars. The inferred radial surface-density profiles, Σ(R)∝ R^(-Γ), for the young stars and late-type giants are consistent with earlier results (Γ_(early) = 0.93 ± 0.09, Γ_(late) = 0.16 ± 0.07). The late-type surface-density profile is approximately flat out to the edge of the survey. While the late-type stellar luminosity function is consistent with the Galactic bulge, the completeness-corrected luminosity function of the early-type stars has significantly more young stars at faint magnitudes compared with previous surveys with similar depth. This luminosity function indicates that the corresponding mass function of the young stars is likely less top-heavy than that inferred from previous surveys.
119183376
A robust determination of Milky Way satellite properties using hierarchical mass modelling
We introduce a new methodology to robustly determine the mass profile, as well as the overall distribution, of Local Group satellite galaxies. Specifically, we employ a statistical multilevel modelling technique, Bayesian hierarchical modelling, to simultaneously constrain the properties of individual Local Group Milky Way satellite galaxies and the characteristics of the Milky Way satellite population. We show that this methodology reduces the uncertainty in individual dwarf galaxy mass measurements up to a factor of a few for the faintest galaxies. We find that the distribution of Milky Way satellites inferred by this analysis, with the exception of the apparent lack of high-mass haloes, is consistent with the Lambda cold dark matter (Lambda CDM) paradigm. In particular, we find that both the measured relationship between the maximum circular velocity and the radius at this velocity, as well as the inferred relationship between the mass within 300 pc and luminosity, match the values predicted by Lambda CDM simulations for haloes with maximum circular velocities below 20 km s(-1). Perhaps more striking is that this analysis seems to suggest a more cusped 'average' halo shape that is shared by these galaxies. While this study reconciles many of the observed properties of the Milky Way satellite distribution with that of Lambda CDM simulations, we find that there is still a deficit of satellites with maximum circular velocities of 20-40 km s(-1).
11410109
Evidence for substructure in Ursa minor dwarf spheroidal galaxy using a Bayesian object detection method
We present a method for identifying localized secondary populations in stellar velocity data using Bayesian statistical techniques. We apply this method to the dwarf spheroidal galaxy Ursa Minor and find two secondary objects in this satellite of the Milky Way. One object is kinematically cold with a velocity dispersion of 4.25 ± 0.75 km s-1 and centred at (9.1 arcmin ± 1.5, 7.2 arcmin ± 1.2) in relative RA and Dec. with respect to the centre of Ursa Minor. The second object has a large velocity offset of -12.8+1.75-1.5 km s-1 compared to Ursa Minor and centred at (-14.0 arcmin+2.4-5.8,-2.5 arcmin+0.4-1.0). The kinematically cold object has been found before using a smaller data set, but the prediction that this cold object has a velocity dispersion larger than 2.0 kms-1 at 95 per cent confidence level differs from previous work. We use two- and three-component models along with the information criteria and Bayesian evidence model selection methods to argue that Ursa Minor has additional localized secondary populations. The significant probability for a large velocity dispersion in each secondary object raises the intriguing possibility that each has its own dark matter halo, that is, it is a satellite of a satellite of the Milky Way. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.
122900110
Two-photon Correlations: from Young Experiments to Heavy-ion Collision Dynamics
Abstract Two-photon correlations are discussed within the formalism of Hanbury-Brown and Twiss interferometry and Bose-Einstein correlations. The technique is presented as a universal tool to study the properties of any boson source — light sources such as stars, or photon and meson sources in the early phase of heavy-ion collisions. The formalism is developed starting from optics and quantum statistics and is finally adapted to the dynamics of heavy-ion collisions. Emphasis is put on the experimental methods derived to display the interference between photons from nuclear reactions. The influence of one-dimensional projections and the detector response on the interpretation of the source properties are discussed. The method is illustrated using experimental data, available only in the intermediate (several tens of A MeV) energy domain. The observed interference signal is interpreted, guided by dynamical phase-space calculations, in terms of source size and reaction dynamics. It is found that photons are emitted as brief light flashes, the relative intensity of which can be linked via model calculations to the incompressibility modulus of nuclear matter. At ultrarelativistic energies, two-photon correlations are presented as a tool to observe the phase transition towards the quark-gluon plasma.
18444522
Thermal bremsstrahlung probing the nuclear liquid-gas phase transition
We present the results of the analysis of the hard photon production in the $^{129}${Xe}+$^{\rm nat}${Sn} at 50{\it A} MeV system studied in the GANIL E300 experiment. The energy and angular hard photon distributions confirm the existence of a thermal component which follows the recently measured thermal bremsstrahlung systematics. Exploiting the performances of our complete detection system, consisting of TAPS and 3 charged particle multidetectors, we have also measured the hard photon multiplicity as a function of the charged particle multiplicity.
17085075
Thermal bremsstrahlung photons probing the nuclear caloric curve
Abstract Hard-photon ( E γ > 30 MeV) emission from second-chance nucleon–nucleon bremsstrahlung collisions in intermediate energy heavy-ion reactions is studied employing a realistic thermal model. Photon spectra and yields measured in several nucleus–nucleus reactions are consistent with an emission from hot nuclear systems with temperatures T ≈4–7 MeV. The corresponding caloric curve in the region of excitation energies ϵ ★ ≈3 A –8 A  MeV shows lower values of T than those expected for a Fermi fluid.
117942297
Local slope analysis:a new tool to study hard photon spectra