A5076632986- Astrophysics and Cosmic Phenomena
- Gaussian Processes and Bayesian Inference
- Radio Astronomy Observations and Technology
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Statistical Methods and Bayesian Inference
- Bayesian Methods and Mixture Models
- Galaxies: Formation, Evolution, Phenomena
- Synthetic Aperture Radar (SAR) Applications and Techniques
- Time Series Analysis and Forecasting
- Data Analysis with R
- Astrophysical Phenomena and Observations
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Spectroscopy and Laser Applications
- Pulsars and Gravitational Waves Research
- Astronomical Observations and Instrumentation
- Particle Accelerators and Free-Electron Lasers
- Dark Matter and Cosmic Phenomena
- Atomic and Molecular Physics
- High-Energy Particle Collisions Research
- Particle physics theoretical and experimental studies
Leiden University
2014-2023
University of Toronto
2013
In this data release from the LOFAR Two-metre Sky Survey (LoTSS) we present 120-168MHz images covering 27% of northern sky. Our coverage is split into two regions centred at approximately 12h45m +44$^\circ$30' and 1h00m +28$^\circ$00' spanning 4178 1457 square degrees respectively. The were derived 3,451hrs (7.6PB) High Band Antenna which corrected for direction-independent instrumental properties as well direction-dependent ionospheric distortions during extensive, but fully automated,...
The GMRT Epoch of Reionization (EoR) experiment is an ongoing effort to measure the power spectrum from neutral hydrogen at high redshift. We have previously reported upper limit (70 mK)^2 wavenumbers k=0.65 h/Mpc using a basic piecewise-linear foreground subtraction. In this paper we explore use singular value decomposition remove foregrounds with fewer assumptions about structure. Using method also quantify, for first time, signal loss due filter and present new spectra adjusted loss,...
Hypervelocity stars (HVSs) are amongst the fastest objects in our Milky Way. These predicted to come from Galactic center (GC) and travel along unbound orbits across Galaxy. In coming years, ESA satellite Gaia will provide most complete accurate catalogue of Way, with full astrometric parameters for more than $1$ billion stars. this paper, we present expected sample size properties (mass, magnitude, spatial, velocity distributions) HVSs stellar catalogue. We build three mock catalogues...
Direction-dependent calibration and imaging is a vital part of producing radio images that are deep have high fidelity highly dynamic range with wide-field low-frequency array such as LOFAR. Currently, dedicated facet-based direction-dependent algorithms rely on the assumption size isoplanatic patch much larger than separation between bright in-field calibrators. This often violated owing to nature ionosphere, result, errors affect image quality In this paper we propose probabilistic...
Calibrating for direction-dependent ionospheric distortions in visibility data is one of the main technical challenges that must be overcome to advance low-frequency radio astronomy. In this paper, we propose a novel probabilistic, tomographic approach utilises Gaussian processes calibrate phase interferometric data. We suggest free electron density can modelled good approximation by process restricted thick single layer, and show under assumption differential total content also process....
Since its debut by John Skilling in 2004, nested sampling has proven a valuable tool to the scientist, providing hypothesis evidence calculations and parameter inference for complicated posterior distributions, particularly field of astronomy. Due computational complexity long-running nature, past, been reserved offline-type Bayesian inference, leaving tools such as variational MCMC online-type, time-constrained, computations. These do not easily handle multi-modal posteriors, discrete...
We present radio observations of the galaxy cluster PLCK G004.5-19.5 ($z=0.52$) using Giant Metrewave Radio Telescope at 150~MHz, 325~MHz, and 610~MHz. find an unusual arrangement diffuse emission in center periphery cluster, as well several galaxies with head-tail emission. A patch peripheral resembles a relic, central halo. Reanalysis archival XMM-Newton X-ray data shows that is disturbed, which has known correlation existence relics halos. Given number halos $z>0.5$ very limited,...
For several decades now, Bayesian inference techniques have been applied to theories of particle physics, cosmology and astrophysics obtain the probability density functions their free parameters. In this study, we review compare a wide range Markov Chain Monte Carlo (MCMC) nested sampling determine relative efficacy on that resemble those encountered most frequently in literature. Our first series tests explores high-dimensional analytic test exemplify particular challenges, for example...
The current sample of HVSs have small constraining power for Galactic Astrophysics. In this contribution, we show that Gaia will radically change situation. Our preliminary results suggests an increase at least order magnitude in the detected (a few hundreds total), with a much wider mass range, goes up to ∼5 M⊙. Detections be mostly within tens kpc from Sun, while outer halo, where were detected, likely remain out reach.
We introduce a novel technique within the Nested Sampling framework to enhance efficiency of computation Bayesian evidence, critical component in scientific data analysis. In higher dimensions, relies on Markov Chain-based likelihood-constrained prior samplers, which generate numerous 'phantom points' during parameter space exploration. These points are too auto-correlated be used standard scheme and so conventionally discarded, leading waste. Our approach discovers way integrate these...
Abstract We introduce a novel technique within the Nested Sampling framework to enhance efficiency of computation Bayesian evidence, critical component in scientific data analysis. In higher dimensions, relies on Markov Chain-based likelihood-constrained prior samplers, which generate numerous 'phantom points' during parameter space exploration. These points are too auto-correlated be used standard scheme and so conventionally discarded, leading waste. Our approach discovers way integrate...