L. Fortson
A5033082144- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Particle Detector Development and Performance
- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Neutrino Physics Research
- Species Distribution and Climate Change
- Particle physics theoretical and experimental studies
- Stellar, planetary, and galactic studies
- Particle Accelerators and Free-Electron Lasers
- Pulsars and Gravitational Waves Research
- High-Energy Particle Collisions Research
- Astronomical Observations and Instrumentation
- Scientific Computing and Data Management
- Quantum Chromodynamics and Particle Interactions
- Remote Sensing in Agriculture
- Radiation Detection and Scintillator Technologies
- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Atomic and Subatomic Physics Research
- Advanced Vision and Imaging
- Geophysics and Gravity Measurements
University of Minnesota
2016-2025
University of Minnesota System
2013-2024
Universidad Veritas
2020-2023
Deutsches Elektronen-Synchrotron DESY
2021-2023
Instituto de Astrofísica de Canarias
2021-2023
Universidad de La Laguna
2021-2023
Université Côte d'Azur
2021
Institut de Physique de Nice
2021
University of Utah
2021
Centre National de la Recherche Scientifique
2021
We use SDSS+\textit{GALEX}+Galaxy Zoo data to study the quenching of star formation in low-redshift galaxies. show that green valley between blue cloud star-forming galaxies and red sequence quiescent colour-mass diagram is not a single transitional state through which most evolve into Rather, an analysis takes morphology account makes clear only small population early-type move rapidly across after morphologies are transformed from disk spheroid quenched rapidly. In contrast, majority have...
We present the data release for Galaxy Zoo 2 (GZ2), a citizen science project with more than 16 million morphological classifications of 304 122 galaxies drawn from Sloan Digital Sky Survey (SDSS). Morphology is powerful probe quantifying galaxy's dynamical history; however, automatic morphology (either by computer analysis images or using other physical parameters as proxies) still have drawbacks when compared to visual inspection. The large number available in current surveys makes...
Abstract Ecologists often study wildlife populations by deploying camera traps. Large datasets are generated using this approach which can be difficult for research teams to manually evaluate. Researchers increasingly enlist volunteers from the general public as citizen scientists help classify images. The growing number of trap studies, however, makes it ever more challenging find enough process all projects in a timely manner. Advances machine learning, especially deep allow accurate...
We present first results from Galaxy Zoo 2, the second phase of highly successful project (www.galaxyzoo.org). Using a volume-limited sample 13665 disk galaxies (0.01< z < 0.06 and M_r<-19.38), we study fraction with bars as function global galaxy properties like colour, luminosity bulge prominence. Overall, 29.4+/-0.5% in our have bar, excellent agreement previous visually classified samples (although this overall is lower than measured by automated bar-finding methods). see clear increase...
We present Galaxy Zoo DECaLS: detailed visual morphological classifications for Dark Energy Camera Legacy Survey images of galaxies within the SDSS DR8 footprint. Deeper DECaLS (r=23.6 vs. r=22.2 from SDSS) reveal spiral arms, weak bars, and tidal features not previously visible in imaging. To best exploit greater depth images, volunteers select a new set answers designed to improve our sensitivity mergers bars. provide 7.5 million individual over 314,000 galaxies. 140,000 receive at least...
The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles energies exceeding 10^12 electron Volts (eV) and are bright sources very-high-energy (VHE) gamma-ray emission, it not yet known where VHE emission originates. Here we report on radio observations galaxy M87, revealing period extremely strong flares accompanied by increase flux from its nucleus. These results...
We report results from an intensive multiwavelength monitoring campaign on the TeV blazar Mrk 421 over period of 2003-2004. The source was observed simultaneously at energies with Whipple 10 m telescope and X-ray Rossi X-Ray Timing Explorer (RXTE) during each clear night within observing windows. Supporting observations were also frequently carried out optical radio wavelengths to provide simultaneous or contemporaneous coverages. large amount data has allowed us examine variability in...
This detection constrains the mechanism and emission region of gamma-ray radiation in pulsar’s magnetosphere.
We report the discovery of TeV gamma-ray emission from Type Ia supernova remnant (SNR) G120.1+1.4, known as Tycho's remnant. Observations performed in period 2008-2010 with VERITAS ground-based observatory reveal weak coming direction remnant, compatible a point source located at $00^{\rm h} \ 25^{\rm m} 27.0^{\rm s},\ +64^{\circ} 10^{\prime} 50^{\prime\prime}$ (J2000). The photon spectrum measured by can be described power-law $dN/dE = C(E/3.42\;\textrm{TeV})^{-\Gamma}$ $\Gamma 1.95 \pm...
LS I +61 303 is one of only a few high-mass X-ray binaries currently detected at high significance in very energy gamma-rays. The system was observed over several orbital cycles (between September 2006 and February 2007) with the VERITAS array imaging air-Cherenkov telescopes. A signal gamma-rays energies above 300 GeV found statistical 8.4 standard deviations. flux measured to be strongly variable; maximum during most apastron. spectrum for period emission can characterized by power law...
We present evidence that the very high energy (VHE, E > 100 GeV) gamma-ray emission coincident with supernova remnant IC 443 is extended. contains one of best studied sites remnant/molecular cloud interaction and pulsar wind nebula CXOU J061705.3+222127, both which are important targets for VHE observations. VERITAS observed 37.9 hr during 2007 detected above 300 GeV an excess 247 events, resulting in a significance 8.3 standard deviations (σ) before trials 7.5σ after point-source search....
We report on TeV γ-ray observations of the blazar Mrk 421 (redshift 0.031) with VERITAS observatory and Whipple 10 m Cherenkov telescope. The excellent sensitivity allowed us to sample fluxes energy spectra unprecedented accuracy where was detected in each pointings. A total 47.3 hr 96 data were acquired between 2006 January 2008 June. present results a study as function time for different flux levels. On May 2 3, bright flares reaching level Crab. complemented radio, optical, X-ray...
We use Bayesian convolutional neural networks and a novel generative model of Galaxy Zoo volunteer responses to infer posteriors for the visual morphology galaxies. CNN can learn from galaxy images with uncertain labels then, previously unlabelled galaxies, predict probability each possible label. Our are well-calibrated (e.g. predicting bars, we achieve coverage errors 11.8% within vote fraction deviation 0.2) hence reliable practical use. Further, using our posteriors, apply active...
We measure the redshift evolution of bar fraction in a sample 2380 visually selected disc galaxies found Cosmic Evolution Survey (COSMOS) Hubble Space Telescope (HST) images. The visual classifications used to identify both and indicate presence stellar bars were provided by citizen scientists via Galaxy Zoo: (GZH) project. find that overall decreases factor two, from 22+/-5% at z=0.4 (tlb = 4.2 Gyr) 11+/-2% z=1.0 7.8 Gyr), consistent with previous analysis. show this decrease, strong volume...
We present results from the first twelve months of operation Radio Galaxy Zoo, which upon completion will enable visual inspection over 170,000 radio sources to determine host galaxy emission and morphology. Zoo uses $1.4\,$GHz images both Faint Images Sky at Twenty Centimeters (FIRST) Australia Telescope Large Area Survey (ATLAS) in combination with mid-infrared $3.4\,\mu$m {\it Wide-field Infrared Explorer} (WISE) $3.6\,\mu$m Spitzer Space Telescope}. early analysis WISE colours galaxies....
We present coordinated multiwavelength observations of the bright, nearby BL Lac object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations instruments, providing data from radio to very-high-energy (VHE) gamma-ray bands. NuSTAR yielded previously unattainable sensitivity 3-79 keV range, revealing that spectrum softens when source is dimmer until X-ray spectral shape saturates into a steep power law with photon index...
Does galaxy evolution proceed through the green valley via multiple pathways or as a single population? Motivated by recent results highlighting radically different evolutionary between early- and late-type galaxies, we present from simple Bayesian approach to this problem wherein model star formation history (SFH) of with two parameters, [t, τ] compare predicted observed optical near-ultraviolet colours. We use novel method investigate morphological differences most probable SFHs for both...
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...
The Zwicky Transient Facility is a large optical survey in multiple filters producing hundreds of thousands transient alerts per night. We describe here various machine learning (ML) implementations and plans to make the maximal use data set by taking advantage temporal nature data, further combining it with other sets. start initial steps separating bogus candidates from real ones, stars galaxies, go on classification objects into classes. Besides usual methods (e.g., based features...
We present quantified visual morphologies of approximately 48,000 galaxies observed in three Hubble Space Telescope legacy fields by the Cosmic And Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and classified participants Galaxy Zoo project. 90% have z < 3 are rest-frame optical wavelengths CANDELS. Each galaxy received an average 40 independent classifications, which we combine into detailed morphological information on features such as clumpiness, bar instabilities, spiral...
Citizen science has proved to be a unique and effective tool in helping society cope with the ever-growing data rates volumes that characterize modern research landscape. It also serves critical role engaging public direct, authentic fashion by doing so promotes better understanding of processes science. To take full advantage onslaught being experienced across disciplines, it is essential citizen platforms leverage complementary strengths humans machines. This Perspectives piece explores...