“The entire dataset could be processed on Spider, the high-performance data processing platform hosted at SURF in the Netherlands, in just a few months,” said Jurjen de Jong, a postdoctoral researcher at Leiden Observatory and ASTRON.
An international team led by researchers from Leiden University has produced the deepest and most detailed view of low-frequency radio galaxies in the Universe. The team used the LOw Frequency ARray (LOFAR) to observe ELAIS-N1, a region of the northern sky containing very little galactic dust, gas, or stars.
This field is highly favorable for deep multi-wavelength studies that probe the distant Universe. Astronomers at the LOFAR observatory have spent years observing ELAIS-N1 to map low-frequency radio sources.
Resolving Sky with Combined Telescopes
The latest image has twenty times the resolution of the previous LOFAR image. This leap was made possible through advances in modern interferometry, a technique where light from multiple telescopes is combined to produce a single clearer image.
The full image features 63,000 radio sources, including quasars and star-forming galaxies. This new view of the low-frequency radio sky comes from 200 hours of observation and amounts to 400 terabytes of data in an 8-billion-pixel image.
Processing this amount of data from radio telescopes at such high resolution was impossible a few years ago. Researchers from the Netherlands Institute for Radio Astronomy (ASTRON) and their collaborators developed the Spider data-processing platform to handle the load.
Filaments and Star Formation
Improvements in calibration and data-reduction methods alongside Spider reduced processing times by a factor of ten. High sensitivity also revealed numerous filaments surrounding radio galaxies, especially near galaxy clusters.
Active Galactic Nuclei (AGN), also known as quasars, dominate the image. These bright centers of galaxies are powered by supermassive black holes and their accretion disks.
AGNs produce relativistic jets of superheated gas and dust that emanate from polar regions and emit considerable radiation. LOFAR is especially well suited to observe these structures due to its sensitivity to extended low-frequency radio emissions.
Individual Sources Revealed
In previous, lower-resolution surveys, distant galaxies and their relativistic jets appeared as featureless blobs. High-resolution LOFAR data allow scientists to discern individual radio sources and massive jets in detail.
The other major population in the image consists of small, young galaxies experiencing high rates of star formation. Radio waves pass through gas and dust that obscure visible and infrared light, providing a clear view of processes taking place within these galaxies.
The LOFAR2.0 Upgrade
The research team said that this work demonstrates the potential of the upgraded LOFAR2.0 telescope. ASTRON is currently working on this upgrade with its European partners.
These upgrades will enable wider, higher-resolution images. This will allow LOFAR to remain competitive with next-generation radio telescopes like the Square Kilometer Array (SKA).
The SKA will combine the MeerKAT array in South Africa and the Inyarrimanha Ilgari Bundara Murchison Radio-astronomy Observatory in Australia. The data will be especially useful when combined with images of the same patch of sky taken by other telescopes at other wavelengths.
Astronomers can determine properties like the distance and mass of each radio source by combining optical, infrared, and X-ray observations with the LOFAR data.
