In recent years, astrophysicists have discovered supermassive black holes (SMBHs) in the early universe that are much larger than they should be. Black hole growth is limited by the Eddington mass limit, which is an upper limit on the growth rate of black holes. However, in certain situations objects can exceed this limit, which is called super-Eddington accretion. Does super-Eddington accretion explain these early SMBHs?
As the SMBH draws material into the accretion disk, it heats the material within the disk. This creates an outward radiation pressure that limits the amount of material that the SMBH can accrete. Gravity in SMBH pulls matter in, while radiation pushes matter away. That is the Eddington limit.
Super-Eddington accretion is when the material within the SMBH’s disk is so strong that radiation becomes trapped within it. The radiation is sucked into the SMBH before pushing out the gas. Excess radiation can also be emitted in jets, both of which enable super-Eddington accretion. Astrophysicists want to know whether supereddingtons can explain the surprisingly large SMBHs in the early universe.
A team of scientists has discovered an extremely bright quasar equivalent to an SMBH with mysterious multi-wavelength emission. It emits both X-rays and radio waves, and could be the key to understanding super-Eddington accretion in the early Universe.
Their research is published in “The Astrophysical Journal” as “.Discovery of X-ray emitting radio loud quasar at z = 3.4: Possibility of transitional super-Eddington phase” The first author is Saki Obuchi of the Department of Physics, Waseda University, Tokyo.
As the SMBH draws material into the accretion disk, it heats the material and produces X-rays. When a small company develops a polar jet, radio waves are emitted. As the researchers point out, the SMBH they discovered produces abundant amounts of both. “We report the multiwavelength properties of eROSITA Final Equatorial Depth Survey (eFEDS) J084222.9+001000 (hereafter ID830), a quasar with z = 3.4351 that is the most X-ray emitting and highest radio power quasar in the eFEDS field,” they explain. eROSITA is the X-ray instrument of the Spektr-RG space observatory.
This quasar formed only about 1.5 billion years after the Big Bang and has accumulated nearly 15 times more gas than the Eddington limit. The problem is that because of its super-Eddington accretion, it shouldn’t be that bright in X-rays, and it shouldn’t be that bright in radio waves either. Much of that energy should be drawn into the black hole. These findings suggest an unknown mechanism in SMBH attachment.
This diagram shows the black hole’s mass on the X-axis and its luminosity indicating its growth rate on the Y-axis. ID830 is off by itself when plotted with other black holes. The solid line shows the theoretical upper limit of the black hole accretion rate (Eddington limit), and the dashed line shows the accretion of gas at 10 times this limit (super-Eddington). Image provided by: National Astronomical Observatory of Japan.
“One cause of the excess X-rays is contamination from components associated with the jet,” the authors write. Previous studies have shown that electrons that reach relativistic speeds within these jets can transfer some of their energy to lower-energy photons during collisions. These photons emit X-rays.
“ID830 is a rare example of a super-Eddington radio-loud quasar that exhibits extreme X-ray excess,” the authors write.
The researchers believe that ID830 may be in a transitional stage between super-Eddington and sub-Eddington accretion after explosive accretion. This stage is probably very short-lived. They believe that a sudden accretion burst of incoming gas pushed the SMBH into Super Eddington, briefly activating both a bright X-ray corona and a loud radioactive jet. But that didn’t last long, and the system returned to equilibrium.
*In this artist’s illustration of a supermassive black hole, the hot corona appears as a pale, conical spiral above the accretion disk. Image credit: NASA/Aurore Simonnet (Sonoma State University)
If these results are correct, they could explain the large mass of the SMBH at high redshifts.
“This discovery may bring us closer to understanding how supermassive black holes formed so rapidly in the early universe,” lead author Ohbuchi said in the paper. press release. “We would like to investigate the cause of the unusually strong X-ray and radio wave emissions and whether similar objects are hidden in the survey data.”
These results also touch on black hole feedback. ID830’s powerful radio emissions suggest it carries a very powerful jet. These jets can influence the host galaxy by injecting energy into the star-forming gas. This has the potential to control star formation and implies that there may be a link between the super-Eddington accretion of SMBHs and the star formation rate of their galaxies.
The scientific significance of ID830 extends beyond its potential to explain the surprisingly large SMBH of the early Universe. This and others like it could be important test cases for understanding super-Eddington accretion and feedback from SMBH jets.