***cfa/melissa weiss
Astronomers have discovered that the supermassive black hole at the center of early galaxies is much larger than expected. These surprisingly massive black holes provide new insights into the origin of all supermassive black holes, as well as the earliest stages of life in their host galaxies.
In nearby mature galaxies like the Milky Way, the total mass of the stars far exceeds the mass of the great black hole found at the center of the Milky Way by about 1,000 to 1. However, in newly discovered distant galaxies, the mass difference drops to 100 or 10 to 1, or even to 1 to 1, meaning that the black hole can be equal to the total mass of the star in its host galaxy.
This unexpectedly large black hole of a fledgling galaxy comes from NASA's newest flagship observatory, the James Webb Space Telescope (JWST). Prior to the JWST launched in late 2021, astronomers' research on distant black holes was generally limited to very bright quasars, which consisted of matter-devouring monster black holes that completely surpassed the brightness of the stars in the host galaxy.
With JWST, we can now finally observe low-mass but still supermassive black holes in small, distant galaxies, and we can also see stars in these host galaxies," said Fabio Pacucci, a Clay researcher at the Center for Astrophysics. Harvard University and Smithsonian (CFA). "This allows us to study early black holes and their host galaxies for the first time, as they evolved together.
Pakuchi is the lead author of a new study published in the Astrophysical Journal Letters, which studies the findings and presented the results at the 243rd meeting of the American Astronomical Society in New Orleans, Los Angeles.
We have learned that distant young galaxies violate the relationship between the mass of black holes and the mass of stars, which is very mature in nearby mature galaxies: these primordial black holes are undoubtedly supermassive in relation to the number of stars in their hosts," said Roberto Maiolino, professor at the University of Cambridge (UK), co-author of the study. With JWST, it is possible to determine how the first supermassive black holes formed by discovering black holes that are farther away and smaller than those discovered so far, and our research is very rich in them.
For the study, Pacucci and colleagues performed statistical analyses of a group of 21 galaxies, ranging from about 12 billion to 13 billion light-years, and observed them through three published JWST surveys.
These 21 galaxies have central black holes, whose typical masses are estimated to be tens or hundreds of millions of times that of the Sun – still supermassive, but relatively speaking, black holes are the driving force behind most of the distant quasars observed to date, which are billions of times more massive than the Sun.
Overall, we see that the mass of black holes observed by JWST in young galaxies is about ten to a hundred times greater than that of the scaling relationship in the local universe,**," said Xiaohui Fan, a professor at the University of Arizona and co-author of the study. "The ratio of star mass to black hole mass in early galaxies was much lower than it is today, more than 10 billion years ago. This result is of great significance for the study of the first black holes.
An accurate estimate of this ratio should help show how supermassive black hole precursors, known as black hole seeds, originated. Broadly speaking, astronomers have sketched out two main pathways: "light" or "heavy" seeds.
Light black hole seeds have a relatively low mass, about 100 to 1,000 times the mass of the Sun. These seeds of light were originally formed as the remnants of the first giant stars in the universe. At the other end, the heavy black hole seed has an initial mass of about 10,000 to 100,000 solar masses. Theoretically, such heavy seeds were created by the direct gravitational collapse of the Titanic gas cloud.
The heavy seed route, by laying the groundwork for growth from a higher starting point, should help form very early supermassive black holes in time, which the research team has discovered over the past two decades, and are getting farther and farther away. The new discovery of supermassive black holes lends credibility to the idea of heavy seeds, because simulations and theoretical calculations of this pathway suggest that the mass of black holes should be roughly as large as the stellar composition of the young galaxies they inhabit, if not larger.
How galaxies then formed and co-evolved around the primordial black hole seed remains an open astrophysics question. Do black holes grow primarily by inhaling gas, or by merging with other black holes?Is the mass of the star mostly formed within the Milky Way, or does it need to merge with other larger galaxies?However, Pacucci and the team expect the answer to begin to materialize as further research by JWST takes place.
In cosmic time, we know that the ratio of stars to black hole masses is gradually catching up with the local 1000 to 1 of the modern universe. This happens when a black hole and its host system of galaxies evolve together, merging with other galaxies to form legions of stars," Pakuchi said. "What we're still trying to do is go deep into the universe to piece together how it all started.
In addition to Xiaohui Fan and Roberto Maiolino, the co-authors of this ** are Bao Nguyen from the University of Arizona and Stefano Carniani from Scuola Normale Superiore in Pisa, Italy. The JWST surveys used are the JWST Advanced Deep Extragalactic Survey (JADES), the Early Release Scientific Survey of Cosmological Evolution (CEERS), and the Survey of Galaxy Assembly with NIRSPEC IFS (GA-NIFS).
More information: Fabio Pacucci et al., JWST Ceers and Jads Z = 4 7 Active galaxies violate local MM relation at >3: Implications for low-mass black holes and seeding models, Astrophysical Journal Letters (2023). doi： 10.3847/2041-8213/ad0158