K. Bechtol
A5054292749- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- Dark Matter and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Radio Astronomy Observations and Technology
- Cosmology and Gravitation Theories
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Neutrino Physics Research
- Particle Detector Development and Performance
- Astrophysics and Star Formation Studies
- Adaptive optics and wavefront sensing
- CCD and CMOS Imaging Sensors
- Particle physics theoretical and experimental studies
- Geophysics and Gravity Measurements
- Scientific Research and Discoveries
- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Radiation Detection and Scintillator Technologies
- Gaussian Processes and Bayesian Inference
- Nuclear Physics and Applications
- Calibration and Measurement Techniques
University of Wisconsin System
2019-2025
University of Wisconsin–Madison
2015-2024
Office of Legacy Management
2022-2023
Large Synoptic Survey Telescope Corporation
2017-2022
University of Chicago
2013-2022
Campbell Collaboration
2021
University of Arizona
2018-2020
Fermi National Accelerator Laboratory
2012-2019
Energy Center of Wisconsin
2015-2019
Kavli Institute for Particle Astrophysics and Cosmology
2008-2016
(Abridged) The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on Fermi Gamma-ray Space (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering energy range from below 20 MeV to more than 300 GeV. This paper describes LAT, its pre-flight expected performance, and summarizes key science objectives that will be addressed. On-orbit performance presented in detail a subsequent paper. LAT pair-conversion telescope with precision...
(Abridged) We describe here the most ambitious survey currently planned in optical, Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST have unique capability faint time domain. The design is driven four main themes: probing dark energy matter, taking an inventory Solar System, exploring transient optical sky, mapping Milky Way. wide-field ground-based system sited at Cerro Pach\'{o}n northern Chile. telescope 8.4 m...
ABSTRACT We present a catalog of high-energy gamma-ray sources detected by the Large Area Telescope (LAT), primary science instrument on Fermi Gamma-ray Space (Fermi) , during first 11 months phase mission, which began 2008 August 4. The First -LAT (1FGL) contains 1451 and characterized in 100 MeV to GeV range. Source detection was based average flux over month period, threshold likelihood Test Statistic is 25, corresponding significance just 4σ. 1FGL includes source location regions,...
We present the second catalog of high-energy gamma-ray sources detected by Large Area Telescope (LAT), primary science instrument on Fermi Gamma-ray Space (Fermi), derived from data taken during first 24 months phase mission, which began 2008 August 4. Source detection is based average flux over 24-month period. The Second Fermi-LAT (2FGL) includes source location regions, defined in terms elliptical fits to 95% confidence regions and spectral power-law, exponentially cutoff or log-normal...
We present cosmological results from a combined analysis of galaxy clustering and weak gravitational lensing, using 1321 deg$^2$ $griz$ imaging data the first year Dark Energy Survey (DES Y1). combine three two-point functions: (i) cosmic shear correlation function 26 million source galaxies in four redshift bins, (ii) angular autocorrelation 650,000 luminous red five (iii) galaxy-shear cross-correlation positions shears. To demonstrate robustness these results, we use independent pairs...
The dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are some most dark matter (DM) dominated objects known. We report on gamma-ray observations dSphs based 6 years Fermi Large Area Telescope data processed with new Pass 8 event-level analysis. None significantly detected in gamma rays, and we present upper limits DM annihilation cross section from a combined analysis 15 dSphs. These constraints among strongest robust to date lie below canonical thermal relic for mass $\lesssim$...
Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build next generation instrument, factor 5-10 improvement sensitivity 100 GeV 10 TeV range extension energies well below above TeV. will consist two arrays (one north, one south) for full sky coverage be operated as open observatory....
(Abridged) We have conducted a detailed investigation of the broad-band spectral properties \gamma-ray selected blazars Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated gamma-ray spectra with Swift, radio, infra-red, optical and other hard X-ray/gamma-ray data, collected within three months LBAS data taking period, we were able to assemble high-quality quasi-simultaneous Spectral Energy Distributions (SED) for 48 blazars.The SED these sources is similar that...
Designed as a high-sensitivity gamma-ray observatory, the Fermi Large Area Telescope is also an electron detector with large acceptance exceeding 2 m;{2} sr at 300 GeV. Building on analysis, we have developed efficient detection strategy which provides sufficient background rejection for measurement of steeply falling spectrum up to 1 TeV. Our high precision data show that falls energy E-3.0 and does not exhibit prominent spectral features. Interpretations in terms conventional diffusive...
We present the first cosmology results from large-scale structure in Dark Energy Survey (DES) spanning 5000 deg$^2$. perform an analysis combining three two-point correlation functions (3$\times$2pt): (i) cosmic shear using 100 million source galaxies, (ii) galaxy clustering, and (iii) cross-correlation of with lens positions. The was designed to mitigate confirmation or observer bias; we describe specific changes made sample following unblinding results. model data within flat $\Lambda$CDM...
Cosmic rays are particles (mostly protons) accelerated to relativistic speeds. Despite wide agreement that supernova remnants (SNRs) the sources of galactic cosmic rays, unequivocal evidence for acceleration protons in these objects is still lacking. When encounter interstellar material, they produce neutral pions, which turn decay into gamma rays. This offers a compelling way detect sites protons. The identification pion-decay has been difficult because high-energy electrons also via...
The γ-ray sky can be decomposed into individually detected sources, diffuse emission attributed to the interactions of Galactic cosmic rays with gas and radiation fields, a residual all-sky component commonly called isotropic background (IGRB). IGRB comprises all extragalactic emissions too faint or resolved in given survey, as well any foregrounds that are approximately isotropic. first measurement Large Area Telescope (LAT) on board Fermi Gamma-ray Space (Fermi) used 10 months sky-survey...
The gamma-ray sky >100 MeV is dominated by the diffuse emissions from interactions of cosmic rays with interstellar gas and radiation fields Milky Way. Observations these provide a tool to study cosmic-ray origin propagation, medium. We present measurements first 21 months Fermi-LAT mission compare models emission generated using GALPROP code. are fitted data incorporate astrophysical input for distribution sources, fields. To assess uncertainties associated input, grid created varying...
The second catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area Telescope (LAT) in two years scientific operation is presented. LAT AGN (2LAC) includes 1017 γ-ray sources located at high Galactic latitudes (|b| > 10°) that are with a test statistic (TS) greater than 25 and associated statistically AGNs. However, some these affected analysis issues multiple Consequently, we define Clean Sample which 886 AGNs, comprising 395 BL Lacertae objects (BL Lac objects), 310...
We measured separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope. Because instrument does not have an onboard magnet, we distinguish two species by exploiting Earth's shadow, which is offset in opposite directions for charges due to magnetic field. estimate subtract proton background using different methods that produce consistent results. report electron-only spectrum, positron-only fraction between 20 GeV 200 GeV. confirm rises energy 20-100 range. The...
Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Burst Monitor and Large Area Telescope onboard Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades gammaray energy. In September 2008, observed exceptionally luminous GRB 080916C, with largest apparent release yet measured. high-energy gamma rays to start later persist longer than lower photons. A simple spectral form fits entire...
Abstract We describe the first public data release of Dark Energy Survey, DES DR1, consisting reduced single-epoch images, co-added source catalogs, and associated products services assembled over 3 yr science operations. DR1 is based on optical/near-infrared imaging from 345 distinct nights (2013 August to 2016 February) by Camera mounted 4 m Blanco telescope at Cerro Tololo Inter-American Observatory in Chile. wide-area survey covering ∼5000 deg 2 southern Galactic cap five broad...
We use 26×106 galaxies from the Dark Energy Survey (DES) Year 1 shape catalogs over 1321 deg2 of sky to produce most significant measurement cosmic shear in a galaxy survey date. constrain cosmological parameters both flat ΛCDM and wCDM models, while also varying neutrino mass density. These results are shown be robust using two independent catalogs, photo-z calibration methods, analysis pipelines blind analysis. find 3.5% fractional uncertainty on σ8(Ωm/0.3)0.5=0.782+0.027−0.027 at 68%...
Satellite galaxies of the Milky Way are among most promising targets for dark matter searches in gamma rays. We present a search consisting weakly interacting massive particles, applying joint likelihood analysis to 10 satellite with 24 months data Fermi Large Area Telescope. No signal is detected. Including uncertainty distribution, robust upper limits placed on annihilation cross sections. The 95% confidence level range from about 10(-26) cm3 s(-1) at 5 GeV 5×10(-23) 1 TeV, depending final...
We report on the first Fermi Large Area Telescope (LAT) measurements of so-called "extragalactic" diffuse gamma-ray emission (EGB). This component is generally considered to have an isotropic or nearly distribution sky with diverse contributions discussed in literature. The derivation EGB based detailed modeling bright foreground Galactic emission, detected LAT sources, and solar emission. find spectrum consistent a power law differential spectral index gamma = 2.41 +/- 0.05 intensity I(>100...
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...
The Fermi Large Area Telescope (Fermi-LAT, hereafter LAT), the primary instrument on Gamma-ray Space (Fermi) mission, is an imaging, wide field-of-view, high-energy γ-ray telescope, covering energy range from 20 MeV to more than 300 GeV. During first years of LAT team has gained considerable insight into in-flight performance instrument. Accordingly, we have updated analysis used reduce data for public release as well response functions (IRFs), description provided analysis. In this paper,...
We report the discovery of eight new ultra-faint dwarf galaxy candidates in second year optical imaging data from Dark Energy Survey (DES). Six these are detected at high confidence, while two lower-confidence identified regions non-uniform survey coverage. The stellar systems found by three independent automated search techniques and as overdensities stars, consistent with isochrone luminosity function an old metal-poor simple population. faint (Mv > -4.7 mag) span a range physical sizes...
We present the first catalog of active galactic nuclei (AGNs) detected by Large Area Telescope (LAT), corresponding to 11 months data collected in scientific operation mode. The First LAT AGN Catalog (1LAC) includes 671 γ-ray sources located at high Galactic latitudes (|b|>10°) that are with a test statistic greater than 25 and associated statistically AGNs. Some multiple AGNs, consequently, 709 comprising 300 BL Lacertae objects, 296 flat-spectrum radio quasars, 41 AGNs other types, 72...