A5105755361- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Particle physics theoretical and experimental studies
- GNSS positioning and interference
- High-Energy Particle Collisions Research
- Ionosphere and magnetosphere dynamics
- Quantum Chromodynamics and Particle Interactions
- Radio Wave Propagation Studies
- Earthquake Detection and Analysis
- Galaxies: Formation, Evolution, Phenomena
- Geophysics and Gravity Measurements
- Antenna Design and Optimization
- Neutrino Physics Research
- Gamma-ray bursts and supernovae
- Superconducting and THz Device Technology
- Astronomy and Astrophysical Research
- Pulsars and Gravitational Waves Research
- Geomagnetism and Paleomagnetism Studies
- Astronomical Observations and Instrumentation
- Dark Matter and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Scientific Research and Discoveries
- Particle Detector Development and Performance
- Spacecraft Design and Technology
- Soil Moisture and Remote Sensing
Netherlands Institute for Radio Astronomy
2015-2024
AstroTec Holding (Netherlands)
2021-2023
Universität Hamburg
2023
University of Groningen
2010-2018
Vrije Universiteit Brussel
2017
Astronomy and Space
2010-2016
Zorginstituut Nederland
2011
Hamburg Institut (Germany)
2006-2009
University of Bologna
2004-2007
Istituto Nazionale di Fisica Nucleare, Sezione di Bologna
2004-2007
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$00$'$00$''$) were mapped using a fully automated direction-dependent calibration imaging...
In this data release from the LOFAR Two-metre Sky Survey (LoTSS) we present 120-168MHz images covering 27% of northern sky. Our coverage is split into two regions centred at approximately 12h45m +44$^\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,...
We present the first limits on Epoch of Reionization 21 cm H i power spectra, in redshift range z = 7.9–10.6, using Low-Frequency Array (LOFAR) High-Band Antenna (HBA). In total, 13.0 hr data were used from observations centered North Celestial Pole. After subtraction sky model and noise bias, we detect a non-zero (1-σ) excess variance best 2-σ upper limit at k 0.053 h cMpc−1 9.6–10.6. The decreases when optimizing smoothness direction- frequency-dependent gain calibration, with increasing...
ABSTRACT A new upper limit on the 21 cm signal power spectrum at a redshift of z ≈ 9.1 is presented, based 141 h data obtained with Low-Frequency Array (LOFAR). The analysis includes significant improvements in spectrally smooth gain-calibration, Gaussian Process Regression (GPR) foreground mitigation and optimally weighted inference. Previously seen ‘excess power’ due to spectral structure gain solutions has markedly reduced but some excess still remains correlation distinct from thermal...
We present deep LOFAR observations between 120-181 MHz of the "Toothbrush" (RX J0603.3+4214), a cluster that contains one brightest radio relic sources known. Our exploit new and novel calibration scheme to probe 10 times deeper than any previous study in this relatively unexplored part spectrum. The observations, when combined with VLA, GMRT, Chandra X-ray data, provide information about nature merger shocks their role re-accelerating relativistic particles. derive spectral index $\alpha =...
ABSTRACT LOFAR, the Low-Frequency Array, is a powerful new radio telescope operating between 10 and 240 MHz. LOFAR allows detailed sensitive high-resolution studies of low-frequency sky. At same time also provides excellent short baseline coverage to map diffuse extended emission. However, producing high-quality deep images challenging due presence direction-dependent calibration errors, caused by imperfect knowledge station beam shapes ionosphere. Furthermore, large data volume clock errors...
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...
ABSTRACT Observations of the redshifted 21-cm hyperfine line neutral hydrogen from early phases Universe such as Cosmic Dawn and Epoch Reionization promise to open a new window onto formation stars galaxies. We present first upper limits on power spectrum brightness temperature fluctuations in redshift range z = 19.8–25.2 (54–68 MHz frequency range) using 14 h data obtained with LOFAR-Low Band Antenna (LBA) array. also demonstrate application multiple pointing calibration technique calibrate...
The redshifted 21 cm line of neutral hydrogen is a promising probe the Epoch Reionization (EoR). However, its detection requires thorough understanding and control systematic errors. We study two biases observed in LOFAR EoR residual data after calibration subtraction bright discrete foreground sources. first effect suppression diffuse foregrounds, which could potentially mean signal. second an excess noise beyond thermal noise. shows fluctuations on small frequency scales, hence it can not...
ABSTRACT We derive constraints on the thermal and ionization states of intergalactic medium (IGM) at redshift ≈ 9.1 using new upper limits 21-cm power spectrum measured by LOFAR radio telescope a prior ionized fraction that estimated from recent cosmic microwave background (CMB) observations. have used results reionization simulation code grizzly Bayesian inference framework to constrain parameters which describe physical state IGM. find that, if gas heating remains negligible, an IGM with...
M87 is a giant elliptical galaxy located in the centre of Virgo cluster, which harbours supermassive black hole mass 6.4x10^9 M_sun, whose activity responsible for extended (80 kpc) radio lobes that surround galaxy. The energy generated by matter falling onto central ejected and transferred to intra-cluster medium via relativistic jet morphologically complex systems buoyant bubbles, rise towards edges halo. Here we present first observations made with new Low-Frequency Array (LOFAR) at...
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...
Dispersion in the interstellar medium is a well known phenomenon that follows simple relationship, which has been used to predict time delay of dispersed radio pulses since late 1960s. We performed wide-band simultaneous observations four pulsars with LOFAR (at 40-190 MHz), 76-m Lovell Telescope 1400 MHz) and Effelsberg 100-m 8000 test accuracy dispersion law over broad frequency range. In this paper we present results these show accurate better than 1 part 100000 across our observing band....
This study aims to characterize linear polarization structures in LOFAR observations of the interstellar medium (ISM) 3C196 field, one primary fields LOFAR-Epoch Reionization key science project. We have used high band antennas (HBA) image this region and Rotation Measure (RM) synthesis unravel distribution polarized Faraday depth. The brightness temperature detected Galactic emission is $5-15~{\rm K}$ intensity covers range from -3 +8 ${\rm rad~m^{-2}}$ most interesting morphological...
Aims. This paper discusses the spectral occupancy for performing radio astronomy with Low-Frequency Array (LOFAR), a focus on imaging observations.
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...
Context: New generation low-frequency telescopes are exploring a new parameter space in terms of depth and resolution. The data taken with these interferometers, for example the LOw Frequency ARray (LOFAR), often calibrated low signal-to-noise ratio regime removal critical systematic effects is challenging. process requires an understanding their origin properties. Aim: In this paper we describe major inherent to next telescopes, such as LOFAR. With knowledge, introduce processing pipeline...
Detection of the 21-cm signal coming from epoch reionization (EoR) is challenging especially because, even after removing foregrounds, residual Stokes I maps contain leakage polarized emission that can mimic signal. Here, we discuss instrumental polarization Low Frequency Array (LOFAR) and present realistic simulations leakages between parameters. From LOFAR observations in 3C196 field, have quantified level caused by nominal model beam LOFAR, compared it with EoR using power spectrum...
LOFAR is the LOw Frequency Radio interferometer ARray located at mid-latitude ($52^{\circ} 53'N$). Here, we present results on ionospheric structures derived from 29 nighttime observations during winters of 2012/2013 and 2013/2014. We show that able to determine differential TEC values with an accuracy better than 1 mTECU over distances ranging between 100 km. For all power law behavior phase structure function confirmed a long range baseline lengths, $1$ $80$ km, slope in general larger...
The redshifted 21 cm signal from neutral hydrogen is a direct probe of the physics early universe and has been an important science driver many present upcoming radio interferometers. In this study we use single night observations with New Extension in Nançay Upgrading LOFAR (NenuFAR) to place upper limits on power spectrum cosmic dawn at redshift z = 20.3. NenuFAR new low-frequency interferometer, operating 10–85 MHz frequency range, currently under construction Radio Observatory France. It...