Astronomers have discovered the largest galaxy ever discovered

This Galaxy The giant, baptized Alcionius – like one of the giants of Greek mythology – is 5 megaporsecs or 16.3 million light years long. This was detected using data collected by the LOW Frequency ARray (LOFAR) for an interferometric network of approximately 20,000 radio antennas spread across Europe. It is an elliptical galaxy, hosting a Black hole At its core is the largest, the source of Plasma’s giant jets. His discovery will help improve our understanding of giant radio galaxies, especially how they form.

About 3 billion light-years from Earth, Alcionius is called a radio galaxy because the energy emitted from it is mainly emitted by radio waves, synchrotron radiation. It consists of a host galaxy – a cluster of stars orbiting a nucleus with a supermassive black hole – and gigantic jets and radio lobes; These accelerate Electrons, Which generates radio emissions. The central black hole, whose mass is estimated to be about 400 million solar masses, is the origin of the observed plasma jets.

These large, high-speed jets are relatively common in space. The Black holes Assets in the center Constellations Do not absorb all the surrounding material: part of it is directed towards the poles of the accumulator disk, where it is in the form of a jet at extreme speeds. These can travel long distances, eventually becoming known as radio lobes, which continue to feed over time. But in some cases, this phenomenon leads to the formation of giant radio galaxies several megaporsecs in length. However, the physical mechanisms that support this radical development are not yet well understood.

The largest system created by a galaxy

Some radio galaxies actually reach 100 times the diameter of their host galaxy! Scientists are therefore trying to determine whether host galaxies have specific properties or specific large-scale environments conducive to the growth of giant radio galaxies; The discovery of Alcyonius, the largest radio galaxy ever discovered, offers an excellent lesson for research. ” Being a serious example in its class, Alcionius radio can shed light on the key mechanisms that govern the growth of galaxies. ”, The researchers explain in their pre-print article to appear Astronomy & Astronomy.

By studying the characteristics of the host galaxy Alcionius, researchers hope to find the key elements and conditions necessary for the growth of such galaxies. By examining the LOFAR data – making sure to remove any radio sources that might interfere with the waves emitted by the radio lobes – they discovered Alcionius, whom they describe as “the largest system formed by a single galaxy”. Estimated size is at least 5 megaparsecs or more than 16 million light-years. Compare, The diameter of the galaxy is Messier 87Another giant radio galaxy, Virgo, is estimated to be nearly a million light-years away.

Data show that the host galaxy is an elliptical type, with a mass of about 2.4 x 10 stars.¹¹ Solar masses and it provides a large black hole measuring about 4 x 10 at its center⁸ Solar masses. The volumes of the two flaps were rated at 1.5 Mpc³ And 1 MPC³ Respectively and between them, they have a total of 10 arrays of internal energy⁵³ Jules.

An expansion may be associated with a less dense environment

However, according to astronomer Martijn Oei and his colleagues at the Leiden Laboratory in the Netherlands, Alcyoneus and its host galaxy appear to be “suspiciously normal”: total low-frequency luminosity density (approximately 8 x 10).²⁵ W / Hz), the mass of the galaxy and the mass of the largest black hole are all similar to the values ​​commonly found for this type of galaxy, but are smaller. In comparison, the weight of the M87 is in the 10 line¹² The mass of the Sun, while the mass of M87 * – the largest black hole at its center – is estimated to be about 6.5 billion solar masses.

Thus, it appears that the formation of giant galaxies does not require very large galaxies or central black holes; There is also no high radio power, the researchers add. On the other hand, a less dense environment is a viable explanation. Furthermore, the host galaxy resides in a cosmic web fiber, with which it may have significant thermodynamic interactions.

Alcyonus is located in a low-density space and / or its interactions with intercellular media may be important for its disproportionate expansion. According to the researchers, the estimated pressures at the level of the flaps (in the range of 5 x 10)^-16 B) the fewest ever discovered; Alcionus therefore refers to “the most promising radio star to date for exploring hot interleaved media.” Although the group has not yet been able to determine the exact cause of its expansion, they believe that the flaps of Alcyonus continue to expand.

Source: M. Oei et al., ArXiv