Have Supermassive Black Holes Collapsed Directly From Giant Gas Clouds? It could depend on the magnetic fields

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Have Supermassive Black Holes Collapsed Directly From Giant Gas Clouds?  It could depend on the magnetic fields

This artist’s impression shows a possible germ for the formation of a supermassive black hole. Credit: NASA/CXC/M. Weiss

About half a century ago, astronomers realized that the powerful radio source coming from the center of our galaxy (Sagitarrius A*) was a “monstrous” black hole. Since then, they have discovered that supermassive black holes (SMBHs) reside at the center of most massive galaxies. This leads to what are called active galactic nuclei (AGNs) or quasars, where the central region of a galaxy is so energetic that it eclipses all the stars in its galactic disk. All the while, astronomers have wondered about the origin of these behemoths (which play a crucial role in galactic evolution).

Astronomers suspect that the seeds that formed SMBHs were created from giant dust clouds that collapsed without first becoming stars, i.e. direct collapsing black holes (DCBHs). ). However, the role of magnetic fields in the formation of DCBHs has remained unclear because none of the previous studies have been able to simulate full accretion periods. To investigate this, an international team of astronomers ran a series of 3D magneto-hydrodynamic (MHD) cosmological simulations that depicted DCBH formation and showed that magnetic fields grow with accretion disks and stabilize them over time. time.

The research was led by Muhammad A. Latif, Assistant Professor of Physics at the College of Science, United Arab Emirates University (UAEU). He was joined by Associate Professor Dominik RG Schleicher from the Universidad de Concepcion in Chile and Sadegh Khochfar, personal chair of theoretical astrophysics from the University of Edinburgh and the Royal Observatory. The article that describes their findings recently appeared online on the preprint server arXiv and is currently being reviewed for publication in The Astrophysical Journal.

As they state in their paper, DCBHs are seeds of high-mass black holes (usually about 1 million solar masses) that existed in the early universe – ca. 100 to 250 million years old. As their name suggests, DCBHs form directly from massive clouds of dust and gas (due to instabilities predicted by Einstein’s theory of general relativity). This distinguishes them from black holes that arose from early supermassive stars (SMS), also known as population III stars. As Dr. Latif told Universe Today via email, astrophysicists have long suspected that this may be how SMBHs formed in the early universe:

Have Supermassive Black Holes Collapsed Directly From Giant Gas Clouds?  It could depend on the magnetic fields

According to recent studies, the first stars (Population III) were not the only source of primordial black holes. Credit: NASA/WMAP science team

“DCBHs are about two orders of magnitude more massive (105 solar mass) than black holes from other scenarios, such as stellar-mass black holes (~100 solar mass) or black holes forming via stellar collisions (~1000 solar mass). This makes them prime candidates, especially for the first SMBHs observed in the first Gyr after the Big Bang.”

The existence of SMBHs was originally proposed to explain the existence of high redshift primordial SMBHs that existed within 1 billion years of the Big Bang. But as Latif and his colleagues explain, there were inconsistencies between what astrophysicists theoretically predicted and what astronomers observed. In particular, there is the role that magnetic fields played in the accretion of material with primordial dust clouds, which ultimately resulted in gravitational collapse and the formation of DCBH.

“The standard physical model provides no constraint on the initial magnetic field strength, and some models predict small B fields on the order of 10-20 G,” Latif said. “They are about several orders of magnitude smaller than the observed fields (about 1G). Therefore, the scientific community thought that their role might only be secondary.”

This mystery has persisted because previous attempts to digitally simulate DCBH formation have been limited in scope. Previous simulations lacked the computing power to simulate the full duration of the accretion process, which is considered to be comparable to the predicted SMS lifetime of 1.6 million years. Thanks to advances in supercomputing over the past decade, different research groups have conducted numerical simulations over the past decade that show that magnetic fields can be amplified in a short period of time.

Have Supermassive Black Holes Collapsed Directly From Giant Gas Clouds?  It could depend on the magnetic fields

This view of the supermassive black hole M87 in polarized light highlights the signature of magnetic fields. Credit: EHT Collaboration

Likewise, there is growing evidence that magnetic fields were present around 13 billion years ago, when DCBHs should have formed. To solve this mystery, Latif and his colleagues conducted a series of 3D magneto-hydrodynamic (MHD) cosmological models that represented a lifetime of 1.6 million years:

“We model accretion on the central block forming in our simulation, which is a proxy for a protostar. mass that accumulates on the block, which tells us the rate of accretion.Previous work has only scaled the simulation for a short period up to one kyr (1000 years), which is much shorter than the lifespan of SMS (~2 million years). Therefore, it is important to know if accretion can be sustained for a long enough time, which shows us that it is possible.”

Their findings are consistent with previous research by Latif and his colleagues (and other groups) showing how magnetic fields play a vital role in the formation of massive stars and black holes. These studies have shown how the magnetic fields are amplified (increase in Jean’s mass) by the accretion of gas and dust disks. These fields are responsible for reducing fragmentation and stabilizing the disks, eventually allowing these disks to reach the necessary mass (i.e., Jean’s mass) to undergo gravitational collapse and form stars. supermassives and black holes.

“Such strong magnetic fields can even launch jets and outflows and also help carry angular momentum, which is believed to be a hindrance to star formation,” Latif explained. “Therefore, they will have important implications for the magnetization of interstellar and intergalactic media (similar to what we observe in the local universe) and shape the formation of high redshift galaxies as well as the evolution of black holes. massive.”

These findings also provide insight into what future studies might reveal about magnetic fields and their role in the formation and evolution of early galaxies. Over the next decade and beyond, astronomers are expected to study the jets and outflows of early black holes using powerful radio observatories like the Square Kilometer Array (SKA) and the Next Generation Very Large Array (ng-VLA ) – which are expected to become operational by 2027 and 2029 (respectively).

More information:
Muhammad A. Latif et al, Role of Magnetic Fields in the Formation of Directly Collapsing Black Holes, arXiv (2022). DOI: 10.48550/arxiv.2210.05611

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