Artist’s impression of the bright and highly active galactic core discovered by Bañados and colleagues, which has fundamental implications for the growth of black holes during the first billion years of cosmic history. Credit: NSF/AUI/NSF NRAO/B. Saxton
Astronomers have discovered an important piece of the puzzle explaining how supermassive black holes were able to grow so quickly in the early universe: a special type of active galactic core so distant that its light took more than 12.9 billion years to reach us. This so-called blazar serves as a statistical marker: its existence implies the presence of a large but hidden population of similar objects, all of which should emit powerful jets of particles.
This is where the discovery becomes important for cosmic evolution: black holes with jets are thought to be able to grow considerably faster than without jets. The research appears in an article published in Natural astronomy and another in Letters from the astrophysical journal.
Active galactic nuclei (AGN) are extremely bright centers of galaxies. The engines that drive their enormous energy output are supermassive black holes. Matter falling onto these black holes (accretion) is the most efficient mechanism known in physics when it comes to releasing enormous amounts of energy. This unparalleled efficiency explains why AGNs are capable of producing more light than all the stars in hundreds, thousands, or even more galaxies combined and in a volume of space smaller than our own solar system.
At least 10% of all AGNs are thought to emit focused beams of high-energy particles, called jets. These jets erupt from the direct vicinity of the black hole in two opposite directions, supported and guided by magnetic fields in the “accretion disk” of matter: the disk formed by gas swirling around the black hole and falling into it . For us to see an AGN as a blazar, something very improbable must happen: Earth, our observation base, must be in exactly the right place for the AGN jet to point directly at us.
The result is the astronomical analog of someone shining the beam of a very bright flashlight directly into your eyes: a particularly bright object in the sky. Characteristically for a blazar, we also observe rapid changes in brightness on time scales of days, hours or even less, a consequence of random changes in the swirling accretion disk at the base of the jet and instabilities in the interaction of the jet between magnetic fields and charged particles.
Finding active galactic nuclei at the very beginning of the universe
The new discovery is the result of a systematic search for active galactic nuclei in the early universe led by Eduardo Bañados, group leader at the Max Planck Institute for Astronomy specializing in the first billion years of cosmic history , and an international team of astronomers. .
Because light takes time to reach us, we see distant objects as they were millions or even billions of years ago. For the most distant objects, cosmological redshift, due to cosmic expansion, shifts their light to much longer wavelengths than the wavelengths at which the light was emitted. Bañados and his team exploited this fact, systematically searching for objects that were so red-shifted that they didn’t even appear in usual visible light (from the Dark Energy Legacy Survey, in this case) but were bright sources in a radio investigation. (the 3 GHz VLASS survey).
Of the 20 candidates meeting both criteria, only one, designated J0410-0139, met the additional criterion of exhibiting significant brightness fluctuations in the radio regime, suggesting that it was a blazar.
The researchers then dug deeper, using an unusually large array of telescopes, including near-infrared observations with ESO’s New Technology Telescope (NTT), a spectrum with ESO’s Very Large Telescope (VLT). ‘ESO, additional near-infrared spectra with the LBT, one of the Keck and Magellan telescopes, X-ray images from ESA’s XMM-Newton and NASA’s Chandra space telescopes, observations of millimeter waves with ALMA and NOEMA and more detailed radio observations with the VLA telescopes of the United States National Radio Astronomy Observatory to confirm the status of the object as an AGN, and more specifically in as blazar.
The observations also gave the distance to the AGN (via redshift) and even found traces of the host galaxy in which the AGN is embedded. Light from this active galactic core took 12.9 billion years to reach us (z=6.9964), carrying information about the universe as it was 12.9 billion years ago .
“Where there is one, there are a hundred more”
According to Bañados, “the fact that J0410-0139 is a blazar, a jet plane that happens to be pointing directly at Earth, has immediate statistical implications. To make a real-life analogy, imagine reading the story of someone who won $100 million. in a lottery. Given the rarity of such a win, you can immediately conclude that there must be many more people who participated in this lottery but did not win such an exorbitant amount.
“Similarly, finding an AGN with a jet pointing directly at us implies that at that time there must have been many AGNs during this period of cosmic history with jets that were not pointing at us.”
In short, in the words of Silvia Belladitta, post-doctoral fellow at MPIA and co-author of this publication, “Where there is one, there are a hundred more”.
The light from the previous record holder from the most distant blazar took about 100 million years less to reach us (z = 6.1). The extra 100 million years may seem short considering we’re looking back over 12 billion years ago, but they make a crucial difference. It is a time when the universe is evolving rapidly. Over these 100 million years, a supermassive black hole can increase its mass by an order of magnitude.
Based on current models, the number of AGN should have increased five to tenfold over these 100 million years. Finding that such a blazar existed 12.8 billion years ago would not be surprising. Finding out that such a blazar existed 12.9 billion years ago, as in this case, is another matter entirely.
Helping black holes grow for 12.9 billion years
The presence of an entire population of AGNs with jets at this early epoch has significant implications for cosmic history and the growth of supermassive black holes at the centers of galaxies in general. Black holes whose AGN has jets can potentially gain mass more quickly than black holes without jets.
Contrary to popular belief, it is difficult for gas to fall into a black hole. The natural thing the gas must do is rotate around the black hole, the same way a planet orbits the sun, with increasing speed as the gas gets closer to the black hole (“conservation of angular momentum” ). To fall, the gas must slow down and lose energy. The magnetic fields associated with the particle jet, which interact with the swirling disk of gas, can provide such a “braking mechanism” and help the gas fall.
This means that the consequences of this new discovery are likely to become a building block of any future model of black hole growth in the early universe: they imply the existence of an abundance of galactic nuclei active 12.9 years ago billions of years ago that had jets, and therefore had the associated magnetic fields that can help black holes grow at considerable speed.
More information:
Eduardo Bañados et al, A blazar in the era of reionization, Natural astronomy (2024). DOI: 10.1038/s41550-024-02431-4
Eduardo Bañados et al, (C ii) Properties and far infrared variability of az = 7 Blazar, Letters from the astrophysical journal (2024). DOI: 10.3847/2041-8213/ad823b
Provided by the Max Planck Society
Quote: Distant discovery of a blazar supports rapid formation of black holes in the early universe (December 18, 2024) retrieved December 19, 2024 from
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