A5078363905- Stellar, planetary, and galactic studies
- Astrophysical Phenomena and Observations
- Dark Matter and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Particle physics theoretical and experimental studies
- Pulsars and Gravitational Waves Research
- Cosmology and Gravitation Theories
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Adaptive optics and wavefront sensing
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Particle Detector Development and Performance
- Radio Astronomy Observations and Technology
- Mechanics and Biomechanics Studies
- Astronomical Observations and Instrumentation
- Ionosphere and magnetosphere dynamics
- History and Developments in Astronomy
- Statistical and numerical algorithms
- Neutrino Physics Research
- Heat Transfer Mechanisms
- Computational Physics and Python Applications
- Scientific Research and Discoveries
University of California, Los Angeles
2016-2024
UCLA Health
2023
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
2019
Universidad Complutense de Madrid
2019
Stockholm University
2013-2015
University of California, Irvine
2009-2014
AlbaNova
2014
Centre National de la Recherche Scientifique
2011
Université Joseph Fourier
2011
Institute of Astronomy and Space Physics
2005-2009
We derive an accurate mass estimator for dispersion-supported stellar systems and demonstrate its validity by analyzing resolved line-of-sight velocity data globular clusters, dwarf galaxies, elliptical galaxies. Specifically, manipulating the spherical Jeans equation we show that dynamical enclosed within 3D deprojected half-light radius r_1/2 can be determined with only mild assumptions about spatial variation of dispersion anisotropy. find M_1/2 = 3 \sigma_los^2 / G ~ 4 R_eff G, where is...
The dwarf spheroidal satellite galaxies of the Milky Way are some most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack astrophysical backgrounds, widely considered be among promising targets for indirect detection via $\ensuremath{\gamma}$ rays. Here we report on $\ensuremath{\gamma}$-ray observations 25 based 4 years Fermi Large Area Telescope (LAT) data. None significantly detected in rays, present flux upper limits between 500 MeV GeV. We...
We present new, more precise measurements of the mass and distance our Galaxy's central supermassive black hole, Sgr A*. These results stem from a new analysis that than doubles time baseline for astrometry faint stars orbiting A*, combining two decades speckle imaging adaptive optics data. Specifically, we improve images by using information about star's orbit deep data (2005 - 2013) to inform search star in years (1995 2005). When this technique is combined with first complete re-reduction...
We present the results of a comprehensive Keck/DEIMOS spectroscopic survey ultra-faint Milky Way satellite galaxy Segue 1. have obtained velocity measurements for 98.2% stars within 67 pc (10 arcmin, or 2.3 half-light radii) center 1 that colors and magnitudes consistent with membership, down to magnitude limit r=21.7. Based on photometric, kinematic, metallicity information, we identify 71 as probable members, including some far out 87 pc. After correcting influence binary using repeated...
In this Letter, we demonstrate that short-period stars orbiting around the supermassive black hole in our Galactic Center can successfully be used to probe gravitational theory a strong regime. We use 19 years of observations two best measured constrain hypothetical fifth force arises various scenarios motivated by development unification or some models dark matter and energy. No deviation from General Relativity is reported strength restricted an upper 95% confidence limit...
One of the simplest viable models for dark matter is an additional neutral scalar, stabilised by a Z2 symmetry. Using GAMBIT package and combining results from four independent samplers, we present Bayesian frequentist global fits this model. We vary singlet mass coupling along with 13 nuisance parameters, including nuclear uncertainties relevant direct detection, local density, selected quark masses couplings. include relic density measured Planck, searches LUX, PandaX, SuperCDMS XENON100,...
We present global analyses of effective Higgs portal dark matter models in the frequentist and Bayesian statistical frameworks. Complementing earlier studies scalar portal, we use GAMBIT to determine preferred mass coupling ranges for with vector, Majorana Dirac fermion matter. also assess relative plausibility all four using model comparison. Our analysis includes up-to-date likelihood functions relic density, invisible decays, direct indirect searches weakly-interacting including latest...
We describe the open-source global fitting package GAMBIT: Global And Modular Beyond-the-Standard-Model Inference Tool. GAMBIT combines extensive calculations of observables and likelihoods in particle astroparticle physics with a hierarchical model database, advanced tools for automatically building analyses essentially any model, flexible powerful system interfacing to external codes, suite different statistical methods parameter scanning algorithms, host other utilities designed make...
We present new high angular resolution near-infrared spectroscopic observations of the nuclear star cluster surrounding Milky Way's central supermassive black hole. Using integral-field spectrograph OSIRIS on Keck II behind laser-guide-star adaptive optics system, this survey enables us to separate early-type (young, 4-6 Myr) and late-type (old, >1 Gyr) stars with a completeness 50% down K' = 15.5 mag, which corresponds ~10 \msun for stars. This work increases radial extent reported...
Gravitational redshift in the Galactic Center General relativity predicts that light emitted by an object a strong gravitational field—for example, close to black hole—should be shifted longer wavelengths. This does not exist Newtonian theory of gravity. Do et al. monitored position and spectrum star S0-2 as it passed Sagittarius A*, supermassive hole at center Milky Way. Around closest part S0-2's 16-year orbit, they detected effect on its spectrum. These results are more consistent with...
OJ287 is the best candidate active galactic nucleus (AGN) for hosting a supermassive binary black hole (SMBBH) at very close separation.We present 120 Very Long Baseline Array (VLBA) observations (at 15 GHz) covering time between April 1995 and 2017.We find that radio jet precessing on time-scale of ∼22 yr.In addition, our data are consistent with jet-axis rotation yearly time-scale.We model precession (24 ± 2 yr) combined motion rotation.The explains variability total flux-density via...
Sagittarius A* (Sgr A*) is the variable radio, near-infrared (NIR), and X-ray source associated with accretion onto Galactic center black hole. We present an analysis of most comprehensive NIR variability data set Sgr to date: eight 24 hr epochs continuous monitoring at 4.5 μm IRAC instrument on Spitzer Space Telescope, 93 2.18 from Naos Conica Very Large 30 2.12 NIRC2 camera Keck Observatory, in total 94,929 measurements. A new approximate Bayesian computation method for fitting first-order...
We introduce a new methodology to robustly determine the mass profile, as well overall distribution, of Local Group satellite galaxies. Specifically we employ statistical multilevel modelling technique, Bayesian hierarchical modelling, simultaneously constrain properties individual Milky Way galaxies and characteristics population. show that this reduces uncertainty in dwarf galaxy measurements up factor few for faintest find distribution satellites inferred by analysis, with exception...
We present the most comprehensive global fits to date of three supersymmetric models motivated by grand unification: Constrained Minimal Supersymmetric Standard Model (CMSSM), and its Non-Universal Higgs Mass generalisations NUHM1 NUHM2. include likelihoods from a number direct indirect dark matter searches, large collection electroweak precision flavour observables, searches for supersymmetry at LEP Runs I II LHC, constraints observables. Our analysis improves on existing results not only...
Searches for supersymmetric electroweakinos have entered a crucial phase, as the integrated luminosity of Large Hadron Collider is now high enough to compensate their weak production cross-sections. Working in framework where neutralinos and charginos are only light sparticles Minimal Supersymmetric Standard Model, we use gambit perform detailed likelihood analysis electroweakino sector. We focus on impacts recent ATLAS CMS searches with 36 fb$^{-1}$ 13 TeV proton-proton collision data. also...
The electromagnetic counterpart to the Galactic center supermassive black hole, Sgr A*, has been observed in near-infrared for over 20 years and is known be highly variable. We report new Keck Telescope observations showing that A* reached much brighter flux levels 2019 than ever measured at wavelengths. In K$^\prime$ band, of $\sim6$ mJy, twice level previously peak from $>13,000$ measurements 130 nights with VLT Telescopes. also observe a factor 75 change 2-hour time span no obvious color...
We present a general methodology for determining the gamma-ray flux from annihilation of dark matter particles in Milky Way satellite galaxies, focusing on two promising satellites as examples: Segue 1 and Draco. use SuperBayeS code to explore best-fitting regions Constrained Minimal Supersymmetric Standard Model (CMSSM) parameter space, an independent MCMC analysis halo properties using published radial velocities. formalism boost substructure these galaxies show that its value depends...
We introduce a comprehensive analysis of multi-epoch stellar line-of-sight velocities to determine the intrinsic velocity dispersion ultrafaint satellites Milky Way. Our method includes simultaneous Bayesian both membership probabilities and contribution binary orbital motion observed within 14-parameter likelihood. apply our Segue 1 dwarf galaxy conclude that is dark-matter-dominated at high probability with an 3.7+1.4− 1.1 km s−1. The dark matter halo required produce this must have...
We study the seven-dimensional Minimal Supersymmetric Standard Model (MSSM7) with new GAMBIT software framework, all parameters defined at weak scale. Our analysis significantly extends previous weak-scale, phenomenological MSSM fits, by adding more and newer experimental analyses, improving accuracy detail of theoretical predictions, including dominant uncertainties from Model, Galactic dark matter halo quark content nucleon, employing novel highly-efficient statistical sampling methods to...
We introduce ScannerBit, the statistics and sampling module of public, open-source global fitting framework GAMBIT. ScannerBit provides a standardised interface to different algorithms, enabling use comparison multiple computational methods for inferring profile likelihoods, Bayesian posteriors, other statistical quantities. The current version offers random, grid, raster, nested sampling, differential evolution, Markov Chain Monte Carlo (MCMC) ensemble samplers. also announce release new...
Abstract Using the global fitting framework, we constrain MSSM with an eV-scale gravitino as lightest supersymmetric particle, and six electroweakinos (neutralinos charginos) only other light new states. We combine 15 ATLAS 12 CMS searches at 13 TeV, along a large collection of measurements Standard Model signatures. This model, which refer to $${{\tilde{G}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mi>G</mml:mi> <mml:mo>~</mml:mo> </mml:mover> </mml:math>...
Abstract The eccentricity of a substellar companion is an important tracer its formation history. Directly imaged companions often present poorly constrained eccentricities. A recently developed prior framework for orbit fitting called “observable-based priors” has the advantage improving biases in derived parameters objects with minimal phase coverage, which case majority directly companions. We use observable-based priors to fit orbits 21 exoplanets and brown dwarfs effort obtain...
Warm dark matter (WDM) and self-interacting (SIDM) are often motivated by the inferred cores in halos of low surface brightness (LSB) galaxies. We test thermal WDM, non-thermal SIDM using high-resolution rotation curves nine LSB fit these models to data determine halo core radii central densities. While minimum size WDM is predicted decrease with mass, we find that increase mass also cannot be explained a single value primordial phase-space density. Moreover, if set particle properties, then...
The energy dependence of the electronic scattering time is probed by Landau level spectroscopy in quasineutral multilayer epitaxial graphene. From broadening overlapping levels we find that rate 1/τ increases linearly with ϵ. This implies a surprising property spectrum graphene-the number resolved remains constant applied magnetic field. Insights are given about possible mechanisms and carrier mobilities graphene system investigated.
We present 3D kinematic observations of stars within the central 0.5 pc Milky Way nuclear star cluster using adaptive optics imaging and spectroscopy from Keck telescopes. Recent have shown that has a shallower surface density profile than expected for dynamically relaxed cusp, leading to important implications its formation evolution. However, true three dimensional is unknown due difficulty in de-projecting stellar number counts. Here, we use spherical Jeans modeling individual proper...