Lorena Hernández, researcher at the MAS Millennium Institute of Astrophysics in Chile. This research, in which the astronomer Lorena Hernández from the Millennium Institute of Astrophysics participates, was highlighted by a prestigious magazine from the University of Oxford.
PBC J2333.9-2343 is the name of the galaxy, which has special characteristics that allow us to better understand how the dynamics work within these important stellar objects.
Particularities that have made it the object of study for years by the Chilean astronomer Lorena Hernández, a researcher at the Millennium Institute of Astrophysics MAS in Chile, and her colleague Francesca Panessa, from the Istituto di Astrofisica e Planetologia Spaziali (IAPS-INAF) in Italy.
“We started to study this galaxy because it showed peculiar properties at different frequencies or energies. Our hypothesis was that the relativistic jet from its black hole had changed direction, but to corroborate this idea, we had to make different observations”, explains Lorena, who is part of the astronomical broker ALeRCE (Automatic learning for the rapid classification of event). For this, the scientists proposed a monitoring program in different energy ranges of the galaxy, since the changes they were able to observe in it gave them information about the nature of the regions that emit it, and allows them to understand the processes in better detail. physics that take place.
With this work, which has just been published in the prestigious Monthly Notices of the Royal Astronomical Society, University of Oxford, they discovered that in this galaxy the jet of particles originated in the vicinity of its supermassive hole, known as jet and which is observed as a conical structure thrown at a great distance by black holes, when accelerated to relativistic speeds, this “jet” changed its direction drastically, going from being in the plane of the sky, to being aligned with the line of sight of the Earth, pointing towards it, which is the first time it has been observed.
What is a jet? A jet or a “relativistic jet” is composed of elementary particles such as electrons and protons that move at speeds close to that of light, and move in a circular way around a strong magnetic field, causing the emission of radiation through the entire electromagnetic spectrum.
There are 10% of galaxies that show nuclear activity, which are the active nuclei of galaxies and within those, there are 10% that have these relativistic jets. This nuclear activity at certain moments in the lives of galaxies, which are billions of years, can go through phases that are active, then cease, and then it may be that at another moment the activity restarts.
So in the case of galaxies that have jets, that activity that restarts may restart in a different direction, and that is something that is observed in radio galaxies – that is, at radio frequencies – and jets are observed in two directions ( up and down from the core) in the direction of the plane of the sky.
In the case of PBC J2333.9-2343, it is that “if we look at it in radio frequency, we do not see the nuclear activity, that is, we do not see the new jet, due to the fact that a jet is pointing towards us, then we do not directly see it.” we see” explains Hernández. The discovery allowed this galaxy to change its classification, from being a radio galaxy to being a blazar, which is when one of those two jets is pointed towards us. Called astronomical phenomena that are a great source of energy and one of the most intense studied in the universe.
“It is not something obvious to observe it, but rather we had to look for alternative ways to prove that the hypothesis that we had that there was a blazar within this galaxy was true,” says the astronomer.
Although changes in the direction of the jets have been described previously, as in the case of X-shaped radio galaxies, this is the first time that this morphology has been observed, which does not give us clues regarding jets or jets in different directions. “This does not mean that there are no other cases, but they are difficult to identify” explains the astronomer.
Now that what happened at PBC J2333.9-2343 is known, it’s easier to think of ways to search for similar ones. What we can say about this particular case is that it is a galaxy that is outside the norm of what we know, since its active nucleus does not fit into the general concepts that the authors have discovered. “Studying this type of galaxies that do not follow common rules can give us a lot of information about how they evolve, it can open our minds to new discoveries about what happens in the depths of galaxies,” says Hernández.
Observing at different frequencies The observation program with which the astronomers managed to reach these conclusions was based on data obtained with radio frequency studies obtained with the Effelsberg Radio Telescope (Max Planck Institute for Radio Astronomy in Germany), the SMARTS-1.3m instrument, of the Yale University, with which it was observed at the same time in the optical and in the infrared, and for simultaneous X-ray and ultraviolet observations, data obtained by the Neil Gehrels Swift Observatory (Penn State University) were used.
In addition to these analyses, the scientists compared variation properties of PBC J2333.9-2343 with large samples of galaxies with and without jets that were achieved with the ALeRCE project in Chile with data from the Zwicky Transient Facility (ZTF) and the ATLAS project ( Asteroid Terrestrial-impact Last Alert System). “With the monitoring data we were able to study the changes that occur in the galaxy over time, and we saw that it varied in all the energies in which we observed it, from radio frequencies to gamma rays,” explains Lorena Hernández, who She is also a researcher at the University of Valparaíso. In addition to all this, they included public data obtained from other instruments. “Although these are not useful for studying variability, they are useful for other aspects of the analysis,” explains Hernández.
With this information, the experts concluded that this galaxy has a bright active nucleus in the center, with two lobes that are the outermost parts of the jet. The interesting thing about this type of galaxies is that, for matter to be able to move from the nucleus to those lobes, a long time must have passed, which can be of the order of one hundred million years. “During that time, many things could have happened in the galaxy, among them nuclear activity could have ceased and reactivated after a period of inactivity, or there could have been a collision with another galaxy or some relatively large object that caused those jets to change their address. We don’t know what happened in this case, because it happened a long time ago, but we can be sure that some violent event occurred,” says Hernández.