A series of 14 articles published in Astronomy & Astrophysics, many of which were also attended by researchers from INAF, reports the discovery of very weak radio signals produced by young stars of great mass that exploded at the edge of the universe. Results obtained thanks to data from the Low Frequency Array (Lofar) radio telescope, among the most accurate ever collected at low radio frequencies
An international group of astronomers and astronomers, many of them from the National Institute of Astrophysics (Inaf), has published a series of articles concerning an important survey carried out with the powerful European Low Frequency Array ( Lofar ) telescope , the largest network in the world, currently operational, for low frequency radio astronomy observations. These are the most accurate images of the universe ever taken at low radio frequencies : by repeatedly observing the same regions of the sky and combining the data to create a single very long exposure image, the team detected the faint radio glow of exploding stars. in supernovae, in tens of thousands of galaxies at the edge of the universe. The first 14 articlesdescribing these results were published in a special issue of the scientific journal Astronomy & Astrophysics .
By combining the high sensitivity of Lofar and the large area of sky covered by the survey – about 300 times the apparent size of the full Moon – the researchers were able to reveal tens of thousands of galaxies similar to the Milky Way, but located in the most remote regions. of the universe. The light from these galaxies travels for billions of years before reaching Earth: this causes the galaxies to appear as they were ‘when young’, when their stars were in the process of forming.
Isabella Prandoni , researcher of INAF in Bologna, explains: «Stars are formed in regions rich in dust, which block much of the light produced by the stars themselves at optical wavelengths. Using radio band observations it is possible to penetrate these layers of dust and obtain a much more precise and complete measure of the star formation activity in progress in galaxies even very distant from us ».
The images of Lofar have made it possible to establish a new relationship between the radio emission of galaxies and the rate at which these galaxies are forming stars; this in turn has allowed a much more accurate estimate of the number of new stars that are forming in the early stages of galaxy life. With the ” Lofar Two-meter Sky Survey: Deep Fields ” survey, the researchers collected an enormous amount of data that allowed them to carry out further scientific studies, ranging from the nature of the spectacular radio emission jets produced by huge black holes, to that resulting from the collisions of huge clusters of galaxies.
Lofar does not directly produce maps of the sky: the signals coming from more than 70 thousand antennas must be suitably combined and processed in order to produce the final images. For this purpose, more than 4 petabytes of raw data have been acquired and processed, equivalent to about one million DVDs.
Equally important for the scientific exploitation of the survey was the comparison of the radio images with the data obtained at other wavelengths. “The regions of the sky observed with Lofar were chosen among the most studied in the northern hemisphere”, underlines Matteo Bonato , a young researcher of INAF from Bologna, “this allowed astronomers to combine optical data, in the near infrared, in the far infrared and sub-millimeter for the galaxies revealed by Lofar, a fundamental step for interpreting the results of the survey ».
“And this is just the beginning,” adds Marco Bondi , also a member of the INAF of Bologna. «The Italian community is analyzing the observations of another very interesting sky region, the so-called Euclid Deep Field North . These data will be part of the next release date » .
Lofar is a powerful tool of the latest generation managed by Astron and made up of thousands of antennas grouped in 51 radio stations scattered throughout Europe, the result of a great collaboration between 9 nations: France, Germany, Ireland, Italy, Latvia, Sweden, the Netherlands. , Poland and the United Kingdom. We recall that INAF leads the Italian consortium and from 2018 to 2022 has planned to invest approximately 2.5 million euros in Lofar, also participating with its staff in the development of the new generation of electronic devices that will equip the radio telescope and the software it regulates. the operation of the telescope. Lofar is designed to capture radio waves at the lowest frequencies that can be captured by the Earth, between 10 and 240 MHz (mega-Hertz).
Gianfranco Brunetti , INAF of Bologna and coordinator of the Italian consortium Lofar, concludes: «At low radio frequencies Lofar offers some observational potential that will remain unique even in the era of the Square Kilometer Array Observatory (Skao). For example, these observations and the ultra-sensitive observations already programmed by Lofar will provide us with very important information on the origin of relativistic particles and on the nature of dark matter in galaxy clusters ».
Featured image: The deepest Lofar image ever made, showing the region of the sky known as “Elais-N1”. Elais-N1 is one of the three fields studied within this research. The image arises from a single Lofar aiming observed repeatedly for a total of 164 hours. This revealed more than 80,000 radio sources, including some spectacular objects showing large-scale radio emission produced by huge black holes. However, most of the sources are associated with distant galaxies similar to the Milky Way, in the phase of star formation. Credits: Sabater et al. 2021
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