Over the past five years, LOFAR’s Low Band Antenna (LBA) system has opened a new observational window in the electromagnetic spectrum, enabling imaging at unprecedented resolution and sensitivity. Until now the Dutch array has mainly been used for science. We present results from observations using both the Dutch and full International LOFAR Telescope where we imaged bright 3C sources at...
Diffuse radio emission in galaxy clusters has been established to be linked with the presence of (re-)accelerated particles (i.e. cosmic rays, CRs) and magnetic fields (B). In the last years, thanks to the advent of highly-sensitive radio telescopes such as LOFAR and MeerKAT, the detection of diffuse radio emission has become possible also in clusters at high redshift (z>0.6). This allowed a...
Understanding how often, and for how long, radio-loud AGN switch their jets on and off remains a central problem in extragalactic astrophysics. Double-double radio galaxies (DDRGs), whose two distinct pairs of lobes preserve the imprint of successive jet episodes, are rare laboratories for tackling this issue, particularly when the systems reach giant ( >1 Mpc) dimensions, giving exceptionally...
Aims. The origin of the morphological dichotomy between Fanaroff–Riley Class I (FRI) and Class II (FRII) radio galaxies has long
been debated, and some theories propose that it may be influenced by their environments. In this study, we use galaxy clusters as
tracers of environment to investigate whether environmental conditions play a significant role in shaping the FRI/FRII...
The ViCTORIA (Virgo Cluster multi-Telescope Observations in Radio of Interacting galaxies and AGN) project is a unique multi-frequency radio survey of the Virgo cluster, combining LOFAR-LBA, LOFAR-HBA, and MeerKAT data to achieve unprecedented depth, resolution, and spectral coverage. The Virgo cluster, the closest rich cluster in the Universe, is a key target for understanding galaxy...
The Square Kilometre Array is expected to measure the 21-cm signal from the Epoch of Reionization (EoR) in the coming decade, and currently operating radio-interferometers might provide a detection even earlier. Recently reported upper limits, including the latest LOFAR results, have already started constraining the astrophysical parameters of the models of the EoR. The challenges that lie...
Recent LOFAR observations of massive galaxy clusters revealed the presence of very extended and low brightness radio emission, named megahalo. Due to their size, megahalos could allow us to probe cluster volumes roughly 30 times larger than those covered by radio halos, opening a new window to study non-thermal components (cosmic rays and magnetic fields) and acceleration mechanisms in the...
The morphologies of extended, double-lobed radio quasars beyond z>2.5 remain largely uncharted, and no systematic census of their structural properties across cosmic time has yet been undertaken. Filling this gap is essential for understanding how powerful jets couple to their evolving environments from the early Universe to the present day. Understanding how powerful FR II radio quasars...
A key component of AGN feedback is the injection of kinetic energy from radio jets. However, there’s a fundamental lack of understanding of why quasars, otherwise very similar, have such a wide range of radio jet powers and, therefore, the impact of AGN jets. Using large samples from LoTSS DR2 coupled with a Bayesian parametric model, we can separate and quantify the jet and host galaxy...
Recently, the discovery of so-called ``Little Red Dots'' by JWST has brought the topic of obscured Active Galactic Nuclei (AGN) to the forefront of observational astronomy. Although these systems are potentially quite surprising to see at high redshift, previous studies of obscured AGN have revealed a plethora of populations and properties (red quasars, ERQs, HoTDoGS, etc.). These dusty...
The properties and structure of magnetic fields in the intracluster medium (ICM) and how cosmic rays are distributed/(re)energised are still open questions in the study of galaxy clusters.
Of late, thanks to sensitive low frequency observations, a new type of extended radio emission is being detected in the ICM, known as radio phoenixes.
Unlike other types of diffuse emission associated...
Active galactic nuclei (AGN) can have a significant effect on their host galaxies by regulating their growth or suppressing star formation (known as AGN feedback). Of particular importance for massive galaxies and clusters are jet-mode AGN which display powerful radio jets and keep galaxies ‘red and dead’ once quenched. However, until recently, the cosmic evolution of jet-mode AGN has remained...
Abell 168 is among the lowest mass galaxy clusters known to host multiple-component diffuse radio emission in its outskirts. Previous observations with GLEAM and GMRT revealed two extended radio sources with elongated and circular morphologies, which were classified as radio relics (Dwarakanath et al. 2018). In this study, we present a comprehensive multi-wavelength analysis of Abell 168 using...
The evolution of active galactic nuclei (AGN) is closely connected to their host galaxies and surroundings. Via feedback processes, AGN can counteract the cooling of the intracluster medium and suppress star formation in their host galaxies. Especially radio observations at low frequencies are able to provide a glimpse into the history of AGN activity, due to the ability to trace old AGN...
With the availability of new large area and deep 0.3" resolution LOFAR surveys in combination with Euclid imaging, it is now finally possible to carry out large statistical studies of the radio loud Active Galactic Nuclei (AGN) population across cosmic time in combination with host galaxy properties. Whereas previous studies were limited to z~2, constrained by either the depth of observations...
Peaked-spectrum (PS) sources, known for their distinct peaked radio spectra, represent a type of radio-loud active galactic nuclei (AGN). Among these, megahertz-peaked spectrum (MPS) sources, which exhibit a spectral peak at a frequency of a hundred megahertz, have emerged as a potential tool for identifying high-redshift candidates. However, the potential evolutionary link between the...
The Sun is an extended, bright and variable source. Solar radio emission of our interest is often brief and intense, with a typical duration of a few seconds and a flux exceeding $10^7$ Jy. Due to these features, one can only use the brightest calibrators during calibration and cannot benefit from a long integration time for solar observations. This talk presents a new calibration method...
Remote diagnostic of solar wind is of utmost importance for our understanding of the space weather and its impact on space and ground technologies. With help of interplanetary scintillation (IPS) observations we are able to asses some of the parameters of the solar wind plasma. Using LOFAR radio telescope we compare and analyse couple of SW velocity estimators, which we believe can improve...
Astronomical facilities generate ever-increasing data volumes, rapidly approaching the exascale. This is especially true for modern radio-interferometers for which the foreseen data rate raises strong concerns regarding the scaling capability of classical analysis methods.
In this talk, I will introduce YOLO-CIANNA (Cornu et al. 2024), a deep-learning object detector designed for...
The May 2024 Mother’s Day superstorm, classified as a G5-level geomagnetic event, was the strongest since November 2003. While the ionospheric response to such extreme space weather is typically monitored by conventional tools like Global Navigation Satellite System (GNSS), ionosondes, and ground-based magnetometers, this study underscores the unique and pivotal contributions that LOFAR can...
Type II radio bursts are solar radio emissions associated with coronal shock waves and are believed to be produced by electrons accelerated by these shocks. As radio signatures of coronal shocks, they are typically found near the expanding edges of coronal mass ejections (CMEs), making them valuable for studying the dynamics of CME-related shocks in the solar corona. Here, we aim to determine...
We present first simultaneous observations of the different types of the solar radio bursts made with LOFAR Baldy station and CALLISTO spectrometers located in Baldy (Poland) and Neustrelitz (Germany). The CALLISTO spectrometer (Compound Astronomical Low frequency Low cost Instrument for Spectroscopy and Transportable Observatory) is a programmable heterodyne receiver operating in the 10-80...
Sub-second fine structures of solar radio bursts reveal complex dynamics in the corona, yet their observed features are additionally complicated by radio-wave scattering in the turbulent corona. LOFAR imaging of individual fine structures during a single event revealed puzzling, non-radial motions of apparent sources at superluminal speeds and rapid expansion on millisecond timescales. We...
The CARMENES high-resolution spectrograph located at the 3.5m Calar Alto telescope, which provides simultaneous coverage at 0.52-1.71 micrometers, is a powerful instrument for the study of nearby M-dwarf stars. It has been central to a monitoring campaign of more than 2200 such objects, complementing its excellent infrared coverage with information from other bands ranging from the optical to...
Double-bump showers are a rare class of extensive air showers (EAS) predicted by Monte Carlo simulations. They occur when a high-energy secondary particle, the leading particle, travels significantly farther than the rest, creating a distinct double-peaked longitudinal profile. So far, no experiment has been able to directly detect these showers. The unique radio footprint of double-bump...
Observations of diffuse interstellar polarization at meter wavelengths reveal intricate Faraday depth structures, likely tracing interactions between magnetized plasma and neutral gas. A strong correlation with CNM filaments has been proposed, but not reproduced in simulations with low CNM fractions, suggesting the CNM content may shape Faraday structures.
We investigate whether the CNM...
I will present the initial results and planning on implementing constraints for LOFAR observation scheduling. These constraints are based on the metrics for the state of the ionosphere as well as solar activity (and radio emission) derived from dedicated monitoring. LOFAR station data reduction and the corresponding metrics will be discussed, as well the plans for their integration into the...
The LOw Frequency Array (LOFAR) is a hierarchical array of dipole and bowtie antennas, distributed across Europe. The Irish LOFAR station (IE613) is located at Birr Castle, Co. Offaly. As one of the 14 international stations, it comprises a set of Low Band Antennas (LBA) and 96 High Band Antennas (HBA) tiles. The response of a single station is trivial and different works have been carried out...
Microwave and radio observations exhibit some interesting features in the Galactic plane. One of those is the Fan region which is an extended region located in the Perseus arm at a distance of 500 pc. Fan region has highly polarized emission from several MHz up to 353 GHz, which is ascribed to synchrotron but nowadays is largely unexplained. Here we present new measurements in intensity and in...
The Earth's ionosphere significantly influences low-frequency radio wave propagation, introducing distortions that challenge the precision of radio astronomical observations. The LOFAR Ionospheric Research Group (LIRG) leverages the unique capabilities of the LOw Frequency ARray (LOFAR) to study these ionospheric effects. LIRG fosters collaboration between ionospheric scientists and radio...
In recent years, a new class of radio transients has emerged: Long Period Transients (LPTs). These radio transients have unexpectedly long periods of minutes to hours, with burst durations of seconds to minutes. In this project, we have developed a new method of analysing data from LOFAR to detect radio transients on intermediate timecales (seconds to minutes) in real time. It has been tested...
Radio diagnostics of the ionosphere based on measurements using LOFAR and GNSS and their combination, and using data from ionosondes, satellites, incoherent scatter radar, etc. is being used to solve a number of practical (such as ultra-high-precision positioning) and fundamental problems in the physics of ionospheric plasma and coupling in the system Sun-Solar Wind (SSW)-Lithosphere...
The advent of next-generation radio surveys, such as those conducted with LOFAR, ASKAP, and the upcoming SKA, is expected to revolutionise our understanding of the radio universe. However, the vast volume and complexity of data generated by these instruments present significant challenges for traditional manual cataloguing and data analysis techniques. To fully exploit these datasets, the...
