New step forward in 'multi-messenger astronomy', a new orientation in the discipline that improves the understanding of the universe. Two of the world's main 'telescopes' are searching neutrinos of astrophysical origin, which contain valuable information about the proximity of black holes and supernovae, among other extreme phenomenon. Led by Giulia Illuminati, researcher at the IFIC, the study has been published in The Astrophysical Journal.
It is a joint study of the experiments IceCube and ANTARES to look for neutrinos of astrophysical origin. Two of the world's main 'telescopes' are looking for this kind of elementary particles that contain valuable information about the location in the universe in which they take place, as the proximity of black holes or supernovae. The study is led by Giulia Illuminati, pre-doctoral researcher at the Institute of Corpuscular Physics (IFIC, Universitat de València-CSIC), a research centre leading the Spanish participation in ANTARES and its successor, KM3NeT.
The Astronomy no longer observes the universe using only the electromagnetic spectrum (light, infrared or radio waves). The advances in physics and technology allow to use other sources, such as neutrinos. This kind of elementary particles is a faithful messenger that contains valuable information about the location in which extreme phenomenon in the universe take place, such as black holes or supernovae. Due to their special characteristics (they have no electrical charge and hardly any mass), neutrinos travel directly to us from their origin, so they are a very useful tool to identify where these events take place.
However, it is difficult to detect them due to their properties. To detect them, the experiments that look for them use large volumes of matter, waiting for one of these neutrinos of astrophysical origin to interact, making a signal in their detectors. One of them is IceCube, which deploys more than 5,000 optical detectors in a cubic kilometre of Antarctic ice. The other one is ANTARES, which have almost 1,000 detectors at the bottom of the Mediterranean Sea, near the French coast.
Both collect data since more than a decade. IceCube was the first experiment able to detect neutrinos with very high energy, the origin of which was out of our solar system (see NOTE 1).However, the origin of the most part of the astrophysical neutrinos observed by IceCube is still unknown, which encourages further investigations.
This is where the work carried out by Giulia Illuminati in the group ANTARES-KM3NeT of the Institute of Corpuscular Physics becomes importance. The researcher has led up to five analysis combining data from IceCube and ANTARES to look for the origin of astrophysical neutrinos. "The reason to do it is that both telescopes complement each other tanks to their different characteristics, particularly in the large volume of IceCube and the excellent view to the sky from the South Hemisphere provided by ANTARES," explains Illuminati. (see NOTE 2).
Although the analyses did not find any significant neutrino emission from explored locations, they have served to demonstrate the potential of conducting joint searches with both experiments to achieve prospective discoveries. "To discover a source of neutrinos in the galactic centre area we would only need to observe half of the neutrino flow in comparison with what each study must separately observe," affirms the IFIC researcher. This means to double the sensitivity of both experiments in a joint way. With the launch of KM3NeT, which will deploy more than 10,000 sensors in different locations around the Mediterranean and whose first lines have been installed and data is being collected, and the forthcoming improvement of IceCube, the potential of joint analysis seems clear.
NOTE 1: In addition, it was the first telescope to observe a convincing association of astrophysical neutrinos with an individual cosmic source, the blazar TXS 0506+056 (a blazar is a very compact and variable source of energy, related to a black hole in the centre of a galaxy).
NOTE 2: The first two analysis consisted on the complete exploration of the sky in the South Hemisphere and of a restricted area around the centre of our galaxy, where it is believed that there is a supermassive black hole. The third analysis investigated the positions of a list of 57 astrophysical objects known by their gamma-ray emission (which are also associated to the production of neutrinos).Finally, two searches of the location of two candidates promising to be sources of neutrinos have been carried out: the radio source Sagittarius A* (associated to the supermassive black hole of the centre of the Milky Way) and the remaining of supernova RXJ 1713.7-3946."Since the surroundings of the supermassive black holes are a place where it is very likely that the acceleration of cosmic rays with very high energy takes place, and, therefore, possible sources of cosmic neutrinos, Sagittarius A*, located in the centre of our galaxy, is a candidate of particular interest," explains Illuminati. For their part, "the remaining of supernova are the most promising candidates for the acceleration of galactic cosmic rays. Therefore, the remaining of supernova RX-J1713.7-3946, which is the most brilliant object of this kind in the sky observed in gamma-ray with energies of TeV, represents an objective that is particularly interesting for the search of cosmic neutrinos," affirms.
Article:
“ANTARES and IceCube Combined Search for Neutrino Point-like and Extended Sources in the Southern Sky”, ANTARES and IceCube Collaboration
https://iopscience.iop.org/article/10.3847/1538-4357/ab7afb
Additional information: https://icecube.wisc.edu/news/view/710
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