Many new galaxies light up with bright stars forming every now and then in a rapid fashion. However, the formation of stars halts as the galaxy evolves. In the latest study published in the journal Nature depicts that the black hole in the center of any galaxy determines the rate at which this star formation occurs.
Any gigantic galaxy in the vast space has a massive black hole that is more than a million times the size of the sun. This reveals the gravitational effects on the stars inside the galaxy which at times powers the energetic radiation from an active galactic nucleus or AGN. The energy that pours into the galaxy from the AGN is speculated to cause the star formation to turn-off. This happens by heating and dispelling the gas that would have otherwise turned into stars as it gets condensed and cools down.
This particular idea has been around for a long time. The astrophysicists have also found that simulations the evolution of any galaxy must devise feedback from the respective black hole in order to mimic the observable properties present in the galaxy. However, any visible evidence for the determination of a connection between supermassive black holes and the formation of the star was missing.
Jean Brodie, co-author of the paper and professor of astronomy and astrophysics at UC Santa Cruz said, “We’ve been dialling in the feedback to make the simulations work out, without really knowing how it happens. This is the first direct observational evidence where we can see the effect of the black hole on the star formation history of the galaxy.”
This new study reveals the continuous relation between black hole activity and the formation of a star as long as the galaxy exists. This interplay between the two affects the generation of each star as the galaxy evolves.
The study was led by Ignacio Martin-Navarro, a postdoctoral researcher at UC Santa Cruz. The study’s prime focus was the massive galaxies in which the mass carried by the central black hole was measured by the researchers in a previous study. The mass of black hole was determined by surveying the motion of stars that tread in the center of these massive galaxies. Martin-Navarro determined the star formation history in the galaxies by detailing their spectra of light which was obtained via the Hobby-Eberly Telescope Massive Galaxy Survey.
On comparison of the star formation history with the black holes of varying masses, the team found striking differences. The differences observed was only correlated with the mass of the black hole without bringing into account the galactic morphology, size or any other properties.
Martin-Navarro described these findings as he said,” For galaxies with the same mass of stars but different black hole mass in the centre, those galaxies with bigger black holes were quenched earlier and faster than those with smaller black holes. So star formation lasted longer in those galaxies with smaller central black holes.”
Numerous other researchers have been trying to establish a correlation between the luminosity of the AGN and star formation with no success. This might be due to the fact that timescales vary here. The formation of a star takes hundreds of millions of years while the outbursts from the AGN occur over a much shorter timescale.
Any supermassive black hole is luminous only when it is eating up matter from the inner regions of the galaxy in an active manner. AGNs are highly variable with their properties varying according to the size of the respective black hole, the rate of acceleration of any new material diving into the hole and many other factors.
According to coauthor Aaron Romanowsky, an astronomer at San Jose State University and UC Observatories, the exact nature of the black holes that helps star formation are still uncertain. Theorists have been coming up with various ideas related to the quenching activity and there might be numerous ways a black hole radiates out its energy into a certain galaxy. More work is required in this field with observable models to determine the exact properties of star formation by black holes.