M. A. Garrett
A5001110573- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Pulsars and Gravitational Waves Research
- Astronomical Observations and Instrumentation
- Space Science and Extraterrestrial Life
- GNSS positioning and interference
- Superconducting and THz Device Technology
- Astrophysics and Star Formation Studies
- Antenna Design and Optimization
- Radio Wave Propagation Studies
- Solar and Space Plasma Dynamics
- Planetary Science and Exploration
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- Adaptive optics and wavefront sensing
- History and Developments in Astronomy
- Astro and Planetary Science
- Ionosphere and magnetosphere dynamics
- Particle Accelerators and Free-Electron Lasers
- Fern and Epiphyte Biology
- Space exploration and regulation
Leiden University
2016-2025
University of Manchester
2016-2025
University of Malta
2024-2025
University College Cork
2023
California Institute of Technology
2022-2023
Cavendish Hospital
2023
Tasmanian Land Conservancy
2021
Istituto di Radioastronomia di Bologna
2019
Leiden Observatory
2009-2018
SKA Observatory
1998-2018
LOFAR, the LOw-Frequency ARray, is a new-generation radio interferometer constructed in north of Netherlands and across europe. Utilizing novel phased-array design, LOFAR covers largely unexplored low-frequency range from 10-240 MHz provides number unique observing capabilities. Spreading out core located near village Exloo northeast Netherlands, total 40 stations are nearing completion. A further five have been deployed throughout Germany, one station has built each France, Sweden, UK....
The LOFAR Two-metre Sky Survey (LoTSS) is a deep 120-168 MHz imaging survey that will eventually cover the entire Northern sky. Each of 3170 pointings be observed for 8 hrs, which, at most declinations, sufficient to produce ~5arcsec resolution images with sensitivity ~0.1mJy/beam and accomplish main scientific aims which are explore formation evolution massive black holes, galaxies, clusters galaxies large-scale structure. Due compact core long baselines LOFAR, provide excellent both highly...
The LOFAR Two-metre Sky Survey (LoTSS) is an ongoing sensitive, high-resolution 120-168MHz survey of the entire northern sky for which observations are now 20% complete. We present our first full-quality public data release. For this release 424 square degrees, or 2% eventual coverage, in region HETDEX Spring Field (right ascension 10h45m00s to 15h30m00s and declination 45$^\circ$00$'$00$''$ 57$^\circ$00$'$00$''$) were mapped using a fully automated direction-dependent calibration imaging...
Abstract The millisecond-duration radio flashes known as fast bursts (FRBs) represent an enigmatic astrophysical phenomenon. Recently, the sub-arcsecond localization (∼100 mas precision) of FRB 121102 using Very Large Array has led to its unambiguous association with persistent and optical counterparts, identification host galaxy. However, even more precise is needed in order probe direct physical relationship between millisecond themselves associated emission. Here, we report...
The Low Frequency Array (LOFAR) is an ideal instrument to conduct deep extragalactic surveys. It has a large field of view and sensitive large-scale compact emission. is, however, very challenging synthesize thermal noise limited maps at full resolution, mainly because the complexity low-frequency sky direction dependent effects (phased array beams ionosphere). In this first paper series, we present new calibration imaging pipeline that aims producing high fidelity, dynamic range images with...
We present the detection of a radio-emitting jet from black hole candidate and X-ray binary source Cygnus X-1. Evidence bright core with slightly extended structure was found on milliarcsecond resolution observations Very Long Baseline Array (VLBA) at 15.4 GHz. Later VLBA [and including phased-up, Large (VLA)] 8.4 GHz show an jet-like feature extending to ∼ 15 mas region, opening angle < 2°. In addition, lower MERLIN 5 that has 10 per cent linear polarization. The in low/hard state during...
Low frequency radio waves, while challenging to observe, are a rich source of information about pulsars. The LOw Frequency ARray (LOFAR) is new interferometer operating in the lowest 4 octaves ionospheric "radio window": 10-240MHz, that will greatly facilitate observing pulsars at low frequencies. Through huge collecting area, long baselines, and flexible digital hardware, it expected LOFAR revolutionize astronomy frequencies visible from Earth. next-generation telescope pathfinder Square...
Faraday rotation measurements using the current and next generation of low-frequency radio telescopes will provide a powerful probe astronomical magnetic fields. However, achieving full potential these requires accurate removal time-variable ionospheric contribution. We present ionFR, code that calculates amount for specific epoch, geographic location, line-of-sight. ionFR uses number publicly available, GPS-derived total electron content maps most recent release International Geomagnetic...
Pulsars emit low-frequency radio waves through to high-energy gamma-rays that are generated anywhere from the surface out edges of magnetosphere. Detecting correlated mode changes in multi-wavelength emission is therefore key understanding physical relationship between these sites. Through simultaneous observations, we have detected synchronous switching and X-ray properties PSR B0943+10. When pulsar a sustained 'bright' mode, X-rays show only an un-pulsed, non-thermal component. Conversely,...
The aim of the LOFAR Epoch Reionization (EoR) project is to detect spectral fluctuations redshifted HI 21cm signal. This signal weaker by several orders magnitude than astrophysical foreground signals and hence, in order achieve this, very long integrations, accurate calibration for stations ionosphere reliable removal are essential. One prospective observing windows EoR will be centered at North Celestial Pole (NCP). We present results from observations NCP window using highband antenna...
Context. The LOw Frequency ARray (LOFAR) radio telescope is a giant digital phased array interferometer with multiple antennas distributed in Europe. It provides discrete sets of Fourier components the sky brightness. Recovering original brightness distribution aperture synthesis forms an inverse problem that can be solved by various deconvolution and minimization methods Aims. Recent papers have established clear link between nature interferometry measurement "compressed sensing" (CS)...
We present the source associations, cross-identifications, and multi-wavelength properties of faint radio population detected in deep tier LOFAR Two Metre Sky Survey (LoTSS): LoTSS Deep Fields. The first Fields data release consists imaging at 150~MHz ELAIS-N1, Lockman Hole, Bo\"{o}tes fields, down to RMS sensitives around 20, 22, 32$~\mu$Jy\,beam$^{-1}$, respectively. These fields are some best studied extra-galactic northern sky, with existing deep, wide-area panchromatic photometry from...
The low frequency array (LOFAR), is the first radio telescope designed with capability to measure emission from cosmic-ray induced air showers in parallel interferometric observations. In $\sim 2\,\mathrm{years}$ of observing, 405 events energy range $10^{16} - 10^{18}\,\mathrm{eV}$ have been detected band $30 80\,\mathrm{MHz}$. Each these registered up $\sim1000$ independent antennas resulting measurements unprecedented detail. This article describes dataset, as well analysis pipeline, and...
We present here a new spectral energy distribution (SED) fitting approach that we adopt to select radio-excess sources amongst distant star-forming galaxies in the GOODS-Herschel (North) field and reveal presence of hidden, highly obscured AGN. Through extensive SED analysis 458 with radio 1.4 GHz mid-IR 24 um detections using some deepest Chandra X-ray, Spitzer Herschel infrared, VLA data available date, have robustly identified sample 51 AGN (~1300 deg^-2) out redshift z~3. These...
The characteristic outer scale of turbulence and the ratio random to ordered components magnetic field are key parameters characterise in interstellar gas, which affects propagation cosmic rays within Galaxy. We provide new constraints those two parameters. use LOw Frequency ARray (LOFAR) image diffuse continuum emission Fan region at (l,b) (137.0,+7.0) 80"x70" resolution range [146,174] MHz. detect multi-scale fluctuations Galactic synchrotron compute their power spectrum. Applying...
We have conducted two pilot surveys for radio pulsars and fast transients with the Low-Frequency Array (LOFAR) around 140 MHz here report on first low-frequency fast-radio burst limit discovery of new pulsars. The survey, LOFAR Pilot Pulsar Survey (LPPS), observed a large fraction northern sky, ~1.4 x 10^4 sq. deg, 1-hr dwell times. Each observation covered ~75 deg using 7 independent fields formed by incoherently summing high-band antenna fields. second Tied-Array (LOTAS), spanned ~600...
This study aims to characterise the polarized foreground emission in ELAIS-N1 field and address its possible implications for extraction of cosmological 21-cm signal from Low-Frequency Array - Epoch Reionization (LOFAR-EoR) data. We use high band antennas LOFAR image this region RM-synthesis unravel structures at Galactic latitudes. The brightness temperature detected is on average 4 K intensity covers range -10 +13rad m^-2 Faraday depth. total polarization angle show a wide morphological...
(abridged). We outline LBCS (the LOFAR Long-Baseline Calibrator Survey), whose aim is to identify sources suitable for calibrating the highest-resolution observations made with International Telescope, which include baselines >1000 km. Suitable must contain significant correlated flux density (50-100mJy) at frequencies around 110--190~MHz on scales of a few hundred mas. At least 200--300-km international baselines, we find 1 calibrator source per square degree over large part northern...
The International LOFAR Telescope is an interferometer with stations spread across Europe. With baselines of up to ~2000 km, has the unique capability achieving sub-arcsecond resolution at frequencies below 200 MHz. However, it technically and logistically challenging process data this resolution. To date only a handful publications have exploited capability. Here we present calibration strategy that builds on previous high-resolution work LOFAR. It implemented in pipeline using mostly...
Isoetes jarmaniae sp. nov. is described as a new lycophyte endemic to Tasmania, Australia, where it confined peat-bound karstic wetlands in several river valleys the south-west wilderness. While seemingly morphologically closest I. drummondii, this quillwort has features that are globally uncommon and unknown other Australasian taxa. Most notable its markedly flattened, strongly recurved leaves disproportionately large sporangium ligules more suggestive of South American than Australian As...