A5078803125- Dark Matter and Cosmic Phenomena
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Cosmology and Gravitation Theories
- Scientific Research and Discoveries
- Gamma-ray bursts and supernovae
- Particle physics theoretical and experimental studies
- Gaussian Processes and Bayesian Inference
- Bayesian Methods and Mixture Models
- Planetary Science and Exploration
- Radio Astronomy Observations and Technology
- Astrophysics and Star Formation Studies
- Radiation Detection and Scintillator Technologies
- Vibrio bacteria research studies
- Legionella and Acanthamoeba research
- Pulsars and Gravitational Waves Research
- Astro and Planetary Science
- CCD and CMOS Imaging Sensors
- Statistical Methods and Inference
- Bacterial biofilms and quorum sensing
- Particle Detector Development and Performance
- Radioactive Decay and Measurement Techniques
Imperial College London
2018-2021
Carnegie Mellon University
2015-2017
Brown University
2011-2017
Center for Orthopaedics
2015
Columbia University
2004
Tel Aviv University
2004
Institut Pasteur
2004
Roswell Park Comprehensive Cancer Center
2004
We present the genomic sequence of Legionella pneumophila, bacterial agent Legionnaires' disease, a potentially fatal pneumonia acquired from aerosolized contaminated fresh water. The genome includes 45-kilobase pair element that can exist in chromosomal and episomal forms, selective expansions important gene families, genes for unexpected metabolic pathways, previously unknown candidate virulence determinants. highlight may account Legionella's ability to survive protozoa, mammalian...
Dwarf spheroidal galaxies are known to be excellent targets for the detection of annihilating dark matter. We present new limits on annihilation cross section weakly interacting massive particles based joint analysis seven Milky Way dwarfs using a frequentist Neyman construction and Pass 7 data from Fermi Gamma-Ray Space Telescope. exclude generic particle candidates into $b\overline{b}$ with mass less than 40 GeV that reproduce observed relic abundance. To within $95%$ systematic errors...
Gamma-ray searches for dark matter annihilation and decay in dwarf galaxies rely on an understanding of the density profiles these systems. Conversely, uncertainties propagate into derived particle physics limits as systematic errors. In this paper we quantify expected signal from 20 Milky Way dwarfs using a uniform analysis most recent stellar-kinematic data available. Assuming that observed stellar populations are equilibrium tracers spherically symmetric gravitational potentials dominated...
We report the discovery of a Milky Way satellite in constellation Antlia. The Antlia 2 dwarf galaxy is located behind Galactic disc at latitude $b\sim 11^{\circ}$ and spans $1.26$ degrees, which corresponds to $\sim2.9$ kpc its distance 130 kpc. While similar spatial extent Large Magellanic Cloud, orders magnitude fainter $M_V=-9$ mag, making it by far lowest surface brightness system known (at $\sim31.9$ mag/arcsec$^2$), $\sim100$ times more diffuse than so-called ultra galaxies. was...
Dwarf spheroidal (dSph) galaxies are prime targets for present and future γ-ray telescopes hunting indirect signals of particle dark matter. The interpretation the data requires careful assessment their matter content in order to derive robust constraints on candidate relic particles. Here, we use an optimized spherical Jeans analysis reconstruct 'astrophysical factor' both annihilating decaying 21 known dSphs. Improvements with respect previous works are: (i) more flexible luminosity...
We present a new formalism designed to discover dark matter annihilation occurring in the Milky Way's dwarf galaxies. The statistical framework extracts all available information data by simultaneously combining observations of galaxies and incorporating impact particle physics properties, distribution dwarfs, detector response. method performs maximally powerful frequentist searches produces confidence limits on parameters. Probability distributions test statistics under various hypotheses...
We present a search for γ-ray emission from the direction of newly discovered dwarf galaxy Reticulum II. Using Fermi-LAT Collaboration data, we detect signal that exceeds expected backgrounds between ∼2-10 GeV and is consistent with annihilation dark matter particle masses less than few ×10^{2} GeV. Modeling background as Poisson process based on diffuse models, taking into account trial factors, p value 9.8×10^{-5} (>3.7σ). An alternative, model-independent treatment reduces significance,...
Abstract We present results from MMT/Hectochelle spectroscopy of 390 red giant candidate stars along the line sight to recently discovered Galactic satellite Crater 2. Modeling joint distribution stellar positions, velocities, and metallicities as a mixture 2 foreground populations, we identify ∼62 members 2, for which resolve line-of-sight velocity dispersion <?CDATA ${\sigma }_{{v}_{\mathrm{los}}}$?> = ${2.7}_{-0.3}^{+0.3}$?> km s −1 mean $\langle {v}_{\mathrm{los}}\rangle $?>...
We search for a dark matter signal in 11 years of Fermi-LAT gamma-ray data from 27 Milky Way dwarf spheroidal galaxies with spectroscopically measured J-factors. Our analysis includes uncertainties J-factors and background normalisations compares results Bayesian frequentist perspective. revisit the galaxy Reticulum II, confirming that purported excess seen Pass 7 is much weaker 8, independently statistical approach adopted. introduce first time posterior predictive distributions to quantify...
We present constraints on the annihilation cross section of weakly interacting massive particles dark matter based joint statistical analysis four dwarf galaxies with VERITAS. These results are derived from an optimized photon weighting technique that improves standard imaging atmospheric Cherenkov telescope (IACT) analyses by utilizing spectral and spatial properties individual events. report $\ensuremath{\sim}230$ hours observations five galaxies. find no evidence gamma-ray emission any...
We report the discovery of a nearby dwarf galaxy in constellation Hydrus, between Large and Small Magellanic Clouds. Hydrus 1 is mildy elliptical ultra-faint system with luminosity $M_V\sim$ -4.7 size $\sim$ 50 pc, located 28 kpc from Sun 24 LMC. From spectroscopy 30 member stars, we measure velocity dispersion 2.7 km/s find tentative evidence for radial gradient consistent 3 rotation. 1's indicates that dark matter dominated, but its dynamical mass-to-light ratio M/L 66 significantly...
J-factors (or D-factors) describe the distribution of dark matter in an astrophysical system and determine strength signal provided by annihilating decaying) respectively. We provide simple analytic formulae to calculate for spherical cusps obeying empirical relationship between enclosed mass, velocity dispersion half-light radius. extend calculation Navarro-Frenk-White (NFW) model, demonstrate that our new give accurate results comparison more elaborate Jeans models driven Markov Chain...
The dwarf spheroidal galaxies (dSph) of the Milky Way are among most attractive targets for indirect searches dark matter. In this work, we reconstruct matter annihilation (J-factor) and decay profiles newly discovered dSph Reticulum II. Using an optimized spherical Jeans analysis kinematic data obtained from Michigan/Magellan Fiber System (M2FS), find II's J-factor to be largest any dSph. We have checked robustness result against several ingredients analysis. Unless it suffers tidal...
We present a new estimate of the mass Milky Way, inferred via Bayesian approach by making use tracers circular velocity in disk plane and stars stellar halo, as from publicly available galkin compilation. rotation curve method to determine dark matter distribution total under different assumptions for profile, while is constrained surface density microlensing measurements. also include uncertainties on baryonic morphology model averaging, thus converting potential source systematic error...
We perform a joint analysis of dwarf galaxy data from the Fermi Gamma-ray Space Telescope in search dark matter annihilation into gamma-ray line. employ novel statistical method that takes account spatial and spectral information individual photon events sample seven galaxies. Dwarf galaxies show no evidence line between 10 GeV 1 TeV. The subsequent upper limit on cross section to two-photon final state is...
Dwarf spheroidal galaxies that form in halo substructures provide stringent constraints on dark matter annihilation. Many ultrafaint dwarfs discovered with modern surveys contribute significantly to these constraints. At present, because of the lack abundant stellar kinematic data for ultrafaints, noninformative prior assumptions are usually made parameters density profiles. Based semianalytic models subhalos and their connection satellite galaxies, we present more informative realistic...
Gamma-ray experiments seeking to detect evidence of dark matter annihilation in dwarf spheroidal galaxies require knowledge the distribution within these systems. We analyze effects flattening on (J) and decay (D) factors with both analytic numerical methods. Flattening has two consequences: first, there is a geometric effect as squeezing (or stretching) enhances diminishes) J-factor; second, line sight velocity dispersion stars must hold up flattened baryonic component halo. provide...
We develop a novel Bayesian methodology aimed at reliably and precisely inferring the distribution of dark matter within Milky Way using rotation curve data. identify subset available tracers that are mutually consistent with each other, thus eliminating data sets might suffer from systematic bias. investigate three different models for mass luminous (baryonic) component bracket range likely morphologies. demonstrate statistical performance our method on simulated in terms coverage,...
We explore two possible scenarios to explain the observed γ-ray emission associated with atypical globular cluster ω-Centauri: from millisecond pulsars (MSP) and dark matter (DM) annihilation. In first case we predict total number of MSPs in (n=45+22−16) using a new Bayesian method that combines observational uncertainty counts intrinsic variation individual pulsar luminosities. A DM interpretation is motivated by possibility ω-Centauri being remnant core an ancient dwarf galaxy hosting...
The VERITAS array of Cherenkov telescopes, designed for the detection gamma-rays in 100 GeV-10 TeV energy range, performs dark matter searches over a wide variety targets. continues to carry out focused observations dwarf spheroidal galaxies Local Group, Milky Way galactic center, and Fermi-LAT unidentified sources. This report presents our extensive these targets, new statistical techniques, current constraints on particle physics derived from observations.
We present a statistical framework which can be used to determine the contribution of an unresolved population pulsars gamma-ray background. This formalism is based on joint analysis photon time series over extended regions sky. demonstrate robustness this technique in controlled simulations pulsar populations, and show that Fermi Gamma-ray Space Telescope detect as small 0.1 per cent sensitive populations with fluxes greater than ∼10−10 cm−2 s−1. The extensible arbitrarily complex searches...
In this white paper, submitted as a part of Snowmass 2013 (subgroup CF2), we examine the current status and future prospects VERITAS indirect dark matter detection program. The array imaging atmospheric Cherenkov telescopes (IACTs), sensitive in 0.1-50 TeV regime, is process completing multi-year program aimed at detecting signatures neutralino matter. This spread out over range astrophysical targets which can potentially yield definitive self-annihilation such dwarf spheroidal galaxies...
We present a statistical technique which can be used to detect the presence and properties of moving sources contributing diffuse background. The method is generalization two-point correlation function include temporal as well spatial information. develop formalism allows for derivation space–time in terms sources. test this simulated sky maps, demonstrate its robustness identifying stationary Applications gamma-ray background searches Solar system bodies, fast primordial black holes dense...
We present methods to assess whether gamma-ray excesses towards Milky Way dwarf galaxies can be attributed astrophysical sources rather than dark matter annihilation. As a case study we focus on Reticulum II, the which shows strongest evidence for signal in Fermi data. Dark models and those with curved energy spectra provide good fits data, while simple power law is ruled out at 97.5% confidence. compare RetII's spectrum known classes of find useful representation terms spectral curvature...