“On the left is a composite color image of the Hubble Space Telescope at the center of ‘Mirachs Ghost.’ On the right is the new ALMA image of this same region, revealing the distribution of the cold, dense gas that revolves around this center of this object in exquisite detail. “Credit: Cardiff University
Astronomers approach dungeon with one of the lowest masses ever observed in the nearby “ghost” galaxy.
A research team led by scientists from Cardiff University says they are closer to understanding how a supermassive black hole (SMBH) is born thanks to a new technique that has allowed them to get closer to one of these enigmatic cosmic objects in unprecedented detail.
Scientists are unsure whether SMBHs formed under extreme conditions shortly after the big bang, in a process called “ direct collapse, ” or whether they grew much later from “ seed ” black holes resulting from the death of massive stars.
If the above method were true, SMBHs 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, SMBHs would start relatively small, around 100 times the mass of our Sun, and would begin to grow over time by feeding on the stars and gas clouds that live around them.
Astronomers have long struggled to find the lowest-mass SMBHs, which are the missing links to decipher this problem.
In a study released today, the Cardiff-led team has pushed the limits, revealing one of the lowest-mass SMBHs ever observed at the center of a nearby galaxy, weighing in at less than a million times the mass of our sun.
SMBH lives in a galaxy that is familiarly known as the “Mirach Ghost” due to its proximity to a very bright star called Mirach, giving it a ghostly shadow.
The findings were made using a new technique with the Atacama Large Millimeter / submillimeter Array matrix (SOUL), a state-of-the-art telescope located high on 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 at Mirach’s Ghost appears to have a mass within the range predicted by the” direct collapse “models,” said Dr. Tim Davis of Cardiff University’s School of Physics and Astronomy.
“We know that it is currently active and is swallowing gas, so some of the more extreme ‘direct collapse’ models that only produce very massive SMBHs may not be true.
“This alone is not enough to definitely distinguish the difference between the ‘seed’ image and the ‘direct collapse’, we need to understand the statistics for that, but this is a massive 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.
An SMBH is the largest type of black hole that can have hundreds of thousands, if not billions, of times the mass of the Sun.
Almost all large galaxies, like ours, are believed to be Milky Way, 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’s team at the Armagh Observatory and Planetarium.
“This suggests that at least some SMBHs could have grown a lot in a very short time, which is difficult to explain by model for the formation and evolution of galaxies.”
“All black holes grow as they swallow gas clouds and disrupt stars that venture too close to them, but some have more active lives than others.”
“Searching for the smallest SMBHs in nearby galaxies could help us reveal how SMBHs begin,” continued Dr. Sarzi.
In their study, the international team used entirely new techniques to get closer to the heart of a small nearby galaxy, called NGC404, than ever before, allowing them to observe the gas clouds surrounding the SMBH at its center.
The ALMA telescope allowed the team to resolve gas clouds at the heart of the galaxy, revealing details only 1.5 light-years across, making it one of the highest-resolution gas maps ever created in another galaxy.
Being able to observe this galaxy in such high resolution allowed the team to overcome a decade of conflicting results and reveal the true nature of SMBH at the center of the galaxy.
“Our study shows that with this new technique we can really begin to explore the properties and origins of these mysterious objects,” continued Dr. Davis.
“If there is a minimum mass for a supermassive black hole, we haven’t found it yet.”
Reference: “Revealing the intermediate-mass black hole at the heart of the dwarf galaxy NGC 404 with ALMA observations of subparsec resolution” by Timothy A Davis, Dieu D Nguyen, Anil C Seth, Jenny E Greene, Kristina Nyland, Aaron J Barth, Martin Bureau, Michele Cappellari, Mark den Brok, Satoru Iguchi, Federico Lelli, Lijie Liu, Nadine Neumayer, Eve V North, Kyoko Onishi, Marc Sarzi, Mark D Smith and Thomas G Williams, July 14, 2020, Monthly notices from the Royal Astronomical Society.
DOI: 10.1093 / mnras / staa1567
