A5056166415- Dark Matter and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Scientific Research and Discoveries
- Particle physics theoretical and experimental studies
- Astronomy and Astrophysical Research
- Pulsars and Gravitational Waves Research
- Stellar, planetary, and galactic studies
- Black Holes and Theoretical Physics
- Gamma-ray bursts and supernovae
- Particle Detector Development and Performance
- Relativity and Gravitational Theory
- Radio Astronomy Observations and Technology
- Computational Physics and Python Applications
- Solar and Space Plasma Dynamics
- Advanced Thermodynamics and Statistical Mechanics
- Health, Environment, Cognitive Aging
- Radioactive Decay and Measurement Techniques
- Cold Fusion and Nuclear Reactions
- Radiation Detection and Scintillator Technologies
- Climate Change and Health Impacts
- Noncommutative and Quantum Gravity Theories
- Statistical and numerical algorithms
- Space Science and Extraterrestrial Life
John Brown University
2009-2025
Massachusetts Institute of Technology
2025
Brown University
2014-2023
Harvard University
2017
Los Alamos National Laboratory
2006-2008
California Institute of Technology
2008
ETH Zurich
2006
The Ohio State University
2003-2004
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...
One of the most intriguing current puzzles in cosmology is discrepancy present values Hubble constant ${H}_{0}$, obtained either from direct model-independent distance measurements or CMB, i.e. its value about 13 billion years ago and interpreted through standard model ($\mathrm{\ensuremath{\Lambda}}\phantom{\rule{0}{0ex}}C\phantom{\rule{0}{0ex}}D\phantom{\rule{0}{0ex}}M$). The authors outline a scenario based on dark matter decays late time Universe, which potentially testable with near...
We present a cosmologically motivated model in which the seeds of supermassive black holes form out lowest angular momentum gas protogalaxies at high redshift. show that, under reasonable assumptions, this leads naturally to correlation between hole masses and spheroid properties, as observed today. assume that early‐forming, rare‐peak haloes has distribution specific similar derived for dark matter cosmological N‐body simulations. This significant low tail, implies every protogalaxy should...
We examine the prospects for detecting $\ensuremath{\gamma}$-rays from dark matter annihilation in six most promising dwarf spheroidal (dSph) satellite galaxies of Milky Way. use recently measured velocity dispersion profiles to provide a systematic investigation mass distribution each galaxy, and show that uncertainty $\ensuremath{\gamma}$-ray flux modeling is less than factor $\ensuremath{\sim}5$ dSph if we assume smooth Navarro-Frenk-White (NFW) profile. Ursa Minor Draco are dSphs...
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 use kinematic data from three new, nearby, extremely low-luminosity Milky Way dwarf galaxies (Ursa Major II, Willman 1, and Coma Berenices) to constrain the properties of their dark matter halos, these make predictions for gamma-ray flux annihilation particles in halos. show that 10^3 solar luminosity dwarfs are most dominated Universe, with total masses within 100 pc excess 10^6 masses. Coupled relative proximity, large imply they should have mean fluxes comparable or greater than any...
We study the effects of black hole dark matter on dynamical evolution stars in dwarf galaxies. find that mass segregation leads to a depletion center galaxies and appearance ring projected stellar surface density profile. Using Segue 1 as an example we show current observations rule out at 99.9% confidence level possibility more than 6% is composed holes with few tens solar masses.
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,...
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...
An only early or late time alteration to $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ has been inadequate at resolving both the ${H}_{0}$ and ${S}_{8}$ tensions simultaneously; however, a combination of alterations can provide solution tensions. As an illustration, we examine combined dark energy, decaying matter model. While energy ability resolve tension, it leads discrepancy in measurements. We show that addition helps would otherwise be enhanced model, while latter is able relieve...
We present a comprehensive analysis of constraints on the sterile neutrino as dark matter candidate. The minimal production scenario with standard thermal history and negligible cosmological lepton number is in conflict conservative radiative decay from cosmic X-ray background combination stringent small-scale structure limits Lyman-alpha forest. show that entropy release through massive particle after does not alleviate these constraints. further local group dwarf galaxies are subject to...
We study the effects of substructure on rate dark-matter annihilation in Galactic halo. use an analytic model for that can extend numerical simulation results to scales too small be resolved by simulations. first calibrate simulations, and then determine boost factor, standard WIMP models as well those with Sommerfeld (or other) enhancements, a function Galactocentric radius Milky Way. provide estimate dependence gamma-ray intensity angular distance from center. This methodology, coupled...
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...
Our current understanding of the Universe is established through pristine measurements structure in cosmic microwave background (CMB) and distribution shapes galaxies tracing large scale (LSS) Universe. One key ingredient that underlies cosmological observables field sources observed assumed to be initially Gaussian with high precision. Nevertheless, a minimal deviation from Gaussianityis perhaps most robust theoretical prediction models explain Universe; itis necessarily present even...
Inflation may provide unique insight into the physics at highest available energy scales that cannot be replicated in any realistic terrestrial experiment. Features primordial power spectrum are generically predicted a wide class of models inflation and its alternatives, observationally one most overlooked channels for finding evidence non-minimal inflationary models. Constraints from observations cosmic microwave background cover widest range feature frequencies, but sensitive constraints...
It has been suggested that late-Universe dark matter decays can alleviate the tension between measurements of ${H}_{0}$ in local Universe and its value inferred from cosmic microwave background fluctuations. decaying potentially account for this discrepancy as it reshuffles energy density radiation a result allows to become dominant at earlier times. In work, we show low multipole amplitude anisotropy power spectrum severely constrains feasibility late-time solution tension.
On June 20, 2020, the LIGO-Virgo collaboration announced discovery of GW190814, a gravitational wave event originating from binary system merger between black hole mass ${M}_{1}={23.2}_{\ensuremath{-}1.0}^{+1.1}\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ and an unidentified object with ${M}_{2}=2.5{9}_{\ensuremath{-}0.09}^{+0.08}\text{ }{M}_{\ensuremath{\bigodot}}$. This second would be either heaviest neutron star or lightest observed to date. Here we investigate possibility...
We study the effects of substructure in Galactic halo on direct detection dark matter, searches for energetic neutrinos from weakly interacting massive particles (WIMP) annihilation Sun and Earth, enhancement WIMP rate halo. Our central result is a probability distribution function (PDF) $P(\ensuremath{\rho})$ local dark-matter density. This must be taken into account when using null to constrain properties candidates. take two approaches calculating PDF. The first an analytic model that...
We present upper limits on line emission in the Cosmic X-ray background (CXB) that would be produced by decay of sterile neutrino dark matter. employ spectra unresolved component CXB Chandra Deep Fields North and South obtained with CCD detector $E=0.8--9\text{ }\text{ }\mathrm{keV}$ band. The expected flux comes from matter lines sight through Milky Way galactic halo. Our constraints rate are sensitive to modeling highest halo mass estimates provide a limit ${m}_{s}<2.9\text{...
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...
The hot dense environment of the early universe is known to have produced large numbers baryons, photons, and neutrinos. These extreme conditions may also other long-lived species, including new light particles (such as axions or sterile neutrinos) gravitational waves. effects any such relics can be observed through their unique imprint in cosmic microwave background (CMB), large-scale structure, primordial element abundances, are important determining initial universe. We argue that future...
Future generations of gravitational wave detectors will have the sensitivity to detect events at redshifts far beyond any detectable electromagnetic sources. We show that if observed event rate is greater than one per year z≥40, then probability distribution primordial density fluctuations must be significantly non-Gaussian or originate from black holes. The nature excess can determined redshift merger rate.Received 24 August 2017DOI:https://doi.org/10.1103/PhysRevLett.119.221104© 2017...