Breakthrough in deciphering birth of supermassive black holes

A research team led by scientists from Cardiff University says it is closer to understanding how a supermassive black hole (SMBH) was born thanks to a new technique that allowed them to zoom in on one of these. enigmatic cosmic objects with unprecedented detail.

Scientists are unsure as to whether SMBHs were formed in the extreme conditions shortly after the big bang, in a process dubbed a ‘direct collapse’, or were grown much later from ‘seed’ black holes resulting from the death of massive stars. If the first method were true, SMBH would be born with extremely large masses – hundreds of thousands to millions of times more massive than our Sun – and would have a fixed minimum size. If the latter were true, the SMBH would start relatively small, about 100 times the mass of our Sun, and would begin to grow over time by feeding on the stars and the gas clouds that live around them.

Astronomers have long strived to find the lowest mass SMBHs, which are the missing links needed to decipher this problem. In a study released today, the Cardiff-led team pushed the boundaries, revealing one of the lowest mass SMBHs ever observed in the center of a nearby galaxy, weighing less than a million times the mass from our sun.

“On the left, a color composite image of the Hubble space telescope in the center of” Mirachs Ghost “. On the right, the new ALMA image of this same region, revealing the distribution of the cold and dense gas which swirls around this center of this object in exquisite detail. » Credit: Cardiff University

The SMBH lives in a galaxy known as “Mirach’s Ghost”, due to its proximity to a very bright star called Mirach, which gives it a ghostly shadow. The results were obtained using a new technique with the Atacama Large Millimeter / submillimeter Array (ALMA) network, an advanced telescope located at the top of the Chajnantor plateau in the Chilean Andes which is used to study the light of some of the coldest objects in the Universe.

“The SMBH in Mirach’s Ghost appears to have mass in the range predicted by” direct collapse “models,” said Dr. Tim Davis of the School of Physics and Astronomy at Cardiff University. “We know it is currently active and swallowing gas, so some of the more extreme” direct collapse “models that only do very massive SMBHs cannot be true. That alone is not enough to tell the difference between the ‘seed’ image and ‘direct collapse’ – we have to understand the statistics for that – but it is a giant step in the right direction. ”

Black holes are objects that have collapsed under the weight of gravity, leaving behind small but incredibly dense regions of space from which nothing can escape, not even light. A SMBH is the largest type of black hole which can represent hundreds of thousands, even billions of times the mass of the Sun. It is believed that almost all large galaxies, like our own Milky Way galaxy, contain an SMBH located at its center.

“SMBHs have also been found in very distant galaxies as they appeared a few hundred million years after the big bang,” said Dr. Marc Sarzi, a member of Dr. Davis’ team at the Armagh Observatory & Planetarium. “This suggests that at least some SMBHs could have become very massive in a very short time, which is difficult to explain according to the models of formation and evolution of galaxies. All black holes develop when they swallow clouds of gas and disturb stars that venture too close to them, but some have a more active life than others. Searching for the smallest SMBHs in nearby galaxies could therefore help us reveal how SMBHs start.”

In their study, the international team used new techniques to zoom further than ever before into the heart of a small neighboring galaxy, called NGC404, allowing them to observe the swirling clouds of gas that surrounded the SMBH in its center.

The ALMA telescope allowed the team to resolve gas clouds in the heart of the galaxy, revealing details just 1.5 light years in diameter, making it one of the gas maps to the Highest resolution ever in another galaxy. Being able to observe this galaxy with such high resolution allowed the team to overcome a decade of conflicting results and reveal the true nature of SMBH in the center of the galaxy.

“Our study shows that with this new technique, we can really begin to explore both the properties and the origins of these mysterious objects,” continued Dr. Davis. “If there is a minimum mass for a supermassive black hole, we have not yet found it. ”

The results of the study were published today in the Royal Astronomical Society Monthly Notices.