A5026627615- Radio Astronomy Observations and Technology
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Remote Sensing and LiDAR Applications
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- History and Developments in Astronomy
Leiden University
2016-2022
Leiden Observatory
2016
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$00$'$00$''$) were mapped using a fully automated direction-dependent calibration imaging...
In this data release from the LOFAR Two-metre Sky Survey (LoTSS) we present 120-168MHz images covering 27% of northern sky. Our coverage is split into two regions centred at approximately 12h45m +44$^\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 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...
The Lockman Hole is a well-studied extragalactic field with extensive multi-band ancillary data covering wide range in frequency, essential for characterising the physical and evolutionary properties of various source populations detected deep radio fields (mainly star-forming galaxies AGNs). In this paper we present new 150-MHz observations carried out LOw Frequency ARray (LOFAR), allowing us to explore spectral window faint population. This image covers an area 34.7 square degrees...
Abstract We present LOFAR observations of one the most spectacular objects in radio sky: Abell 2255. This is a nearby ( z = 0.0806) merging galaxy cluster hosting first halos ever detected intracluster medium (ICM). The deep images at 144 MHz central ∼10 Mpc 2 region show plethora emission on different scales, from tens kiloparsecs to above megaparsec sizes. In this work, we focus innermost cluster. Among numerous interesting features observed, discover remarkable bright and filamentary...
Low-Frequency Array (LOFAR) observations at 144 MHz have revealed large-scale radio sources in the unrelaxed galaxy cluster Abell 1132. The hosts diffuse emission on scales of ∼650 kpc near centre and a head–tail (HT) galaxy, extending up to 1 Mpc, south centre. central is not seen NRAO VLA FIRST Survey, Westerbork Northern Sky nor C & D array 1.4 GHz, but detected our follow-up Giant Meterwave Radio Telescope (GMRT) 325 MHz. Using LOFAR GMRT data, we determine spectral index be α = −1.75 ±...
Radio halos and radio relics are diffuse synchrotron sources that extend over Mpc-scales found in a number of merger galaxy clusters. They believed to form as consequence the energy is dissipated by turbulence shocks intra-cluster medium (ICM). However, precise physical processes generate these steep spectrum still poorly constrained. We present new LOFAR observation double cluster Abell 1758. This system composed A1758N, massive hosting known giant halo, A1758S, which less whose emission...
It is well established that particle acceleration by shocks and turbulence in the intra-cluster medium can produce cluster-scale synchrotron emitting sources. However, detailed physics of these processes still not understood. One main open questions role fossil relativistic electrons have been deposited radio galaxies. These synchrotron-emitting are very difficult to study, as their radiative life time only tens Myrs at GHz frequencies, therefore a relatively unexplored population. Despite...
With the advent of new generation low-frequency telescopes, such as LOw Frequency ARray (LOFAR), and improved calibration techniques, we have now started to unveil sub GHz radio sky with unprecedented depth sensitivity. The LOFAR Two Meter Sky Survey (LoTSS) is an ongoing project in which whole northern will be observed at 150 MHz a sensitivity better than 100 $\mu$Jy beam$^{-1}$ resolution \asec{6}. Additionally, deeper observations are planned cover smaller areas higher Lockman Hole,...
In Generative AI (GenAI) models have proven effective in translating natural language queries into SQL. However, directly exposing database schema details, including table and column names, to GenAI poses significant security privacy concerns. This paper presents an approach preserve integrity by employing aliasing techniques. Aliased representations of elements are enriched with semantic metadata, ensuring can generate accurate SQL without direct access the original schema. The proposed...
Collisions between galaxy clusters dissipate enormous amounts of energy in the intra-cluster medium (ICM) through turbulence and shocks. In process, Mpc-scale diffuse synchrotron emission form radio halos relics can form. However, little is known about very early phase collision. We used deep observations from 53 MHz to 1.5 GHz study pre-merging A1758N A1758S that are $\sim2$ Mpc apart. confirm presence a giant bridge connecting two systems was reported only tentatively our earlier work....
Thermal gas in the center of galaxy clusters can show substantial motions that generate surface-brightness and temperature discontinuities known as cold fronts. The may be triggered by minor or off-axis mergers preserve cool core system. dynamics thermal also radio emission from intra-cluster medium (ICM) impact evolution clusters' sources. We aim to study central region Abell 1775, a system an ambiguous dynamical state at $z=0.072$ which is host extended head-tail galaxy, with goal...
Diffuse cluster radio sources, in the form of halos and relics, reveal presence cosmic rays magnetic fields intracluster medium (ICM). These are thought to be (re)accelerated through ICM turbulence shock waves generated by merger events. Here we characterize diffuse emission known galaxy clusters HETDEX Spring Field, covering 424 deg 2 . For this, developed a method extract individual targets from LOFAR observations processed with LoTSS DDF-pipeline software. This procedure enables improved...
Low-frequency radio observations are revealing an increasing number of diffuse synchrotron sources from galaxy clusters, primarily in the form halos or relics. The existence this emission indicates presence relativistic particles and magnetic fields. It is still open question as to exactly what mechanisms responsible for population electrons driving emission. LOFAR Two-metre Sky Survey Deep Fields offer a unique view problem. Reaching noise levels below 30 μ Jy beam −1 , these deepest images...
A number of radio observations have revealed the presence large synchrotron-emitting sources associated with intra-cluster medium. There is strong observational evidence that emitting particles been (re-)accelerated by shocks and turbulence generated during merger events. The are accelerated thought to higher initial energies than those in thermal pool but origin such mildly relativistic remains uncertain needs be further investigated. galaxy cluster Abell 1914 a massive which X-ray show...
The radio source at the center of galaxy cluster Abell 2626, also known as Kite, stands out for its unique morphology composed four, symmetric arcs. Previous studies have probed properties this different frequencies and interplay with surrounding thermal plasma, but puzzle origin is still unsolved. We use new LOw Frequency ARray (LOFAR) observation from LOFAR Two-meter Sky Survey 144 MHz to investigate Kite.} present a detailed analysis data which we combined archival X-ray observations....
A number of merging galaxy clusters show the presence large-scale radio emission associated with intra-cluster medium (ICM). These synchrotron sources are generally classified as haloes and relics. Whilst it is commonly accepted that mergers play a crucial role in formation relics, not all giant diffuse this provides important information concerning current models. The Abell 781 complex spectacular system composed an apparent chain on sky. Its main component undergoing merger hosts...