Can a galaxy’s mass be measured?

A team of researchers from the Institute of Physics of the Astrophysics Laboratory of the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland has found a way to use the phenomenon of gravitational lens strong To pinpoint accurately (about 3 times more accurate than any other technology) galaxy cluster It contains a quasar, that is, a luminous manifestation of a supermassive black hole located in the center of the galaxy, as well as its evolution in cosmic time.

As they explain, knowing this data provides information about the evolution of galaxies in the early universe. It’s even a starting point for building scenarios of how new black holes form and black holes evolve. The results are published in natural astronomy.

“the Accuracy and the Accuracy The unprecedented results achieved using gravitational lensing provide a new way to obtain robust estimates of mass in the distant universe, where traditional techniques lack precision and are susceptible to bias. The masses of host galaxies have been measured in the past, but thanks to gravitational lensing, this is the first time a measurement has been so precise in the distant universe,” said EPFL astrophysicist Frederic Corbin, lead author of the study.

a quasar It is the luminous manifestation of a supermassive black hole accreting matter around it, settling at the center of a host galaxy. In general, it is difficult to measure how massive they are because quasars are very distant objects and also because they are so bright that they dwarf anything around them. However, gravitational lensing allows Calculate the mass of the lens body.

Thanks to Albert Einstein’s theory of gravity, it is known how massive objects in the foreground of the night sky can deflect light from background objects. The result is strange Rings of light, which is actually a distortion of the background object’s illumination by gravitational lensing. And more than a decade ago, Corbin realized, riding his bicycle to the Sauverny Observatory, that he could combine quasars with gravitational lensing, to measure the mass of host galaxy from a quasar. To do this, he had to find a quasar in a galaxy that would also act as a gravitational lens.

Database Sloan Digital Sky Survey (SDSS) It was a great place to look for candidates for a gravitationally lensed quasar, but to be sure Corbin had to see the lensing rings. In 2010, he and his colleagues spent time in the Hubble Space Telescope To observe 4 candidates, 3 of them showed lenses.

Among them, one featured distinct gravitational lensing rings: SDSS J0919+2720. Its HST image showed two bright objects in the foreground, each acting as a gravitational lens. “It is likely that two galaxies are in the process of merging,” Corbin said.

One is a bright quasar, inside a host galaxy too dim to see. The other is another galaxy, the main gravitational lens. while a weak light object It is a companion galaxy and the featured rings are light twisted from a galaxy background.

By carefully analyzing these rings, it was possible to determine the masses of the two bright objects. It would have been impossible to separate the masses of different organisms without the recent development of Lens forming technology Based on Waves by co-author Aymeric Galan, currently at the Technical University of Munich (TUM).

“One of the biggest challenges in astrophysics is understanding How does a supermassive black hole form?. Galan explained that knowing its mass, how it compares to its host galaxy, and how it has evolved through cosmic times, is what allows us to rule out or validate some of the formation theories.

In the local universe, we notice that the most massive galaxies also host supermassive black holes at their centers. This may indicate that its growth is regulated by it The amount of radiated energy through its central black hole and injected into the galaxy. However, to test this theory we still need to study these interactions not only locally but also at distant universeexplains Martin Mellon, lead author of the study and currently at Stanford University on an SNF grant.

Gravitational reversal events are very rare, with only one galaxy in a thousand experiencing this phenomenon. Since quasars have been seen in about one of Every thousand galaxiesthe quasar that acts as a lens is one in a million.

(With information from Europa Press)

Read on