Where are the neutrinos born?

“In the nuclei of active galaxies,” a group of Russian scientists from the Astrosmic Center Fian (ACC Fian), the Moscow Physical and Technical Institute (IFTI) and the IIAI RAS (IYAI RAS) that had long been disturbed by the Astrophysicists. Alexander Plavin , Yuri Kovalev-Ml. , Yuri Kovalev-st. And Sergey Troitsky told a three-hobby about the discovery they made.

Neutrino is difficult particles, so light that even their mass has not yet been measured. They easily pass through us, through the Earth and through any other obstacles. However, sensitive detectors can capture neutrinos that fly to us from distant space. For half a century, such particles born inside the Sun have been recorded. It turned out that through each of us, billions flies into them per second. Much more rare, but also more energetic, neutrinos reach us from supernova stars - most of the energy from the explosion of the stars is carried precisely by the neutrino.

The most energetic neutrinos are observed by such modern neutrian telescopes as ICECUBE at the South Pole and the Baikal-GVD detector, the main scientific organizations are JIND and Iya). Particles are regularly found that carry energy into several Petaelectronolt (1 PEV - a unit with fifteen zeros of electron -volt). Where they come from, until recently it was unknown, and the numerous searches of sources among bright objects in the sky or among powerful outbreaks did not give a convincing result.

How do neutrino telescopes work? They use the planet Earth to filter the incoming particles. Neutrino, experiencing only weak and gravitational interaction, easily pass through the Earth. It is possible to detect them in the ice at the South Pole or in the water of Lake Baikal. As a result of such interaction, muons are born, they fly through ice and water at a speed higher than the speed of light in this environment. As a result, the so -called radiation of Vavilov - Cherenkov in the visible light appears. And these flashes of light are recorded by photodetectors that allow you to obtain energy for analysis and the direction of the arrival of neutrinos, as well as the moment of registration of these particles. It is clear that these data are measured with some mistake. And as always in astronomy, the accuracy of determining the position in the sky (or the direction of the parish - in the case of neutrino) is critical. Next, we will return to this issue.

So, we focused on neutrinos, having the greatest energy, and were able to find where they are born. Why is it important and interesting? The fact is that neutrinos of ultra -high energies (up to the energy of a hockey puck flying at a speed of 100 km/h) are most likely born as a result of the interaction of relativistic protons with each other or with radiation. And it is very difficult to accelerate the proton almost to the speed of light, because it is a massive particle. That is, neutrinos of high energies - a key to space super -colladers!

It turned out that many neutrinos of high energies (we analyzed the energies more than 0.2 PEV) are born in the most centers of quasars, near supermainable black holes and relativistic emissions of a substance from them [1]. So, there are suitable conditions and energy for the formation of such neutrinos: there are protons accelerated almost to the speed of light.

The main difficulty in establishing the sources of neutrinos is a weak angular resolution of modern detectors in comparison with the usual astronomical telescopes is a typical error in measuring directions in the sky and in ICECUBE and the Baikal telescope more than a degree. It is difficult to reliably understand many distant space objects at once, and it is difficult to understand which of them is responsible for neutrinos.

Theoretical predictions that active galaxies have been sources of neutrino have been made for a long time. It was assumed that neutrinos are born in their nuclei or on the fronts of shock waves in plasma clouds at a distance of kiloparsec from the center. However, experimentally this could not be confirmed.

In the centers of active galaxies, massive black holes are “sitting” and accelerate light particles falling on them almost to the speed of light. The latter are thrown out in the form of jets observed by astronomers. Moreover, if Jet looks directly at the observer, astronomers call such a galaxy quasar or blazar. But can jets also accelerate massive protons? Recall the readers that the proton is almost 2 thousand times more massive than the electron.

The fact is that together with neutrinos should be born and photons of high energies. Accordingly, scientists were searching for “under the lantern”, comparing the directions of the parish of the neutrino and photons of gamma radiation from quasars using the remarkable space telescope Fermi Lat. Nevertheless, with mass attempts throughout the sky, to identify the coming of the neutrino with the advent of gamma-photons, it was not possible to get a positive result. Only one quasar with the sonorous name 0506+056 was found [ 2 ]. He found a gamma-ray gamma simultaneously with the advent of the neutrino. The National Scientific Fund of the United States has devoted a large press conference in this unique event in 2018. But many colleagues had doubts. The argument is simple: if you wait 10 years, at least once it can be “lucky”.

We approached this issue on the other hand: we combined data at once by all the neutrino high energies that ICECUBE saw and compared them with mass and regular observations in the radiodApason. It seems mad-what does the radio with the meager energies of his photons are compared to the gigantic energies of neutrinos or gamma quanta? And at first we did not particularly count on success. And yet: in the radiadal radiation is radiated by hot jets of plasma, accelerated to the speed of light. Suddenly they help? And helped!

It was this approach that made it possible to discover the following pattern: it turned out that the brightest quasars “prefer” to be in the sky near the regions, from where some neutrinos came. Their brightness is measured using international radio telescopes - the so -called radio interferometers. They filter out all the extended radiation and see only the most compact radiation of jets near the central black hole. It turns out that fast protons do not have time to go far from a black hole and partially lose their energy, while creating a neutrino in a cascade of births and decays of other unstable elementary particles (peonies and muons).

But not everything is so simple. Many “suspiciously bright” quasars lay close to the place of arrival of the neutrino, but not close enough to explain the differences in their positions with the published random errors ICECUBE. How so? But the fact is that the ice in which the neutrino interacts in IceCube is heterogeneous. And as a result, in addition to well -known random errors, there are systematic errors in determining the directions of neutrino. It is extremely difficult to evaluate them. There is very little this information in the scientific literature. We decided to evaluate such errors from the comparison of the directions of the arrival of neutrino and directions to the cores of the quasarov according to their most accurate radio coordinates today.

As a result, a systematic error was estimated at about half a degree. We expected that IceCube group from its understanding of the characteristics of the telescope would make this assessment severe criticism. What was our surprise when, according to the results of the scientific seminar in the ICecube group, we heard: “Colleagues, perhaps this is the best way to evaluate our systematic errors.”

Further - more. It seems logical to assume that protons is “easier” to speed up during flashes observed from Quasars. To verify this assumption, we used the results of long-term observations of a large sample of quasars on the Russian Radio Telescope RATAN-600 of the special Astrophysical Observatory of the Russian Academy of Sciences in the North Caucasus. Indeed, it turned out that neutrinos prefer to come at those moments when a splash of radio radiation is observed in Quasara. Such behavior can only be explained by the fact that neutrinos are formed in the centers of the Quasar.

Why was the radiodiapason the key to detect neutrino sources in distant space? Here, several factors played a role here: the extremely high accuracy of determining the coordinates of compact nuclei of active galaxies using radio interferometers-the best in all astronomy, and the excellent coating of the whole sky with the help of international radio telescopes, and regular mass perennial and multi-frequency observations on a unique ranga-600. But all this would not work without a beautiful and simple effect of relativistic aberration [ 3 ]. As a result of this effect, quasars look brighter when their jets are directed almost exactly at the observer. Thus, the radiostronomy “automatically selected” those active galaxies in the sky whose jets are looking in our direction. And since the substance of the radiating jets is dispersed in the direction of us, then the neutrino born of the relativistic proton flies in our direction.

An attentive reader will ask: what about the accompanying gamma radiation, the search for which other researchers focused? Radive observation indicates the neutrinos of the neutrino so close to the very center of the galaxy that the density of photons there may not allow this gamma radiation to leave it: photons are scattered on photons. Most likely, the origin of the gamma radiation observed from Blazars and their neutrino are not directly related to each other.

The work does not stop there - rather, the beginning of the use of neutrinum astronomy of high energies to the study of cosmic supercuters, quasars is laid. In the coming years, the rapid development of neutrino telescopes is expected: in particular, the installation of a new generation is being completed in Baikal, which will increase the sensitivity and accuracy of measuring the directions of the neutrino arrival. The new impulse receives quasar observations both on the Ratan-600 and on international radio interferometers.

What awaits us? The first result was obtained with the significance of 3 σ or the probability of a random coincidence of 0.2%. And both ours and independent assessments of colleagues have already confirmed this result with greater significance (which will allow us to win a bottle of cognac in a recent dispute). In the course of further work, we hope to figure out whether the observed neutrino is obtained during the interaction of a relativistic proton and a photon or two relativistic protons? Are relativistic jets in quasars electronic or proton? Where are the neutrinos are born: very close to a black hole or a little further - at the beginning of Jet? And how are the protons are still accelerated to such huge energies?

1. Plavin A., Kovalev Yy, Kovalev Ya, Troitsky S. Observational Evience for the Origin of High-Energy in Parsec-Scale of Radio-Bright Active Active Active Galaxies // The Astrophysical Journal. Vol. 894. N. 2. Doi.org/10.3847/1538-4357/AB86BD ; arxiv.org/abs/2001.00930
2. Stern B. The first cry of neutrinal astronomy // TRV-hobby. No. 258 dated 07.07.2018.
3. ru.wikipedia.org/wiki/versikhiki_Aberration