This Black Hole is a Total Underachiever

Anyone can be an underachiever, even if you’re an astronomical singularity weighing over four billion times the mass of the Sun. At least the quasar H1821+643 doesn’t have parents to be disappointed in it. But its underachievement could shed light on how quasars, a potent type of black hole, can come to influence entire clusters of galaxies, as described in a new paper from researchers at the University of Nottingham and Harvard.

Using X-ray data from the Chandra observatory, the researchers looked closely at H1821+643 and decided it influenced its local environment much less than expected. Granted, a lot was expected of it – quasars are super powerful black holes that rapidly pull in new material rapidly and eject radiation as well as sometimes emitting powerful streams of particles. In particular, H1821+643 is a quasar located about 3.4 billion light-years away from Earth at the center of a cluster of galaxies. 

Both the quasar and its surrounding galaxy are shrouded in a field of hot gas that showed up as a fuzzy haze in Chandra’s X-ray dataset. That fuzzy haze, which would let astronomers understand what was happening to the gas in the galaxy at large, was massively overwhelmed by the brightness of the X-rays emitted from the quasar itself.

To study the effects of the quasar on the location gas population, the researchers had to remove the effects of its own X-rays, leaving only the light emitted from the gas itself. They found that the gas is significantly less hot than might be expected given its proximity to such a forceful quasar, showing that the quasar itself isn’t outputting as much energy as might otherwise be expected.

Counterintuitively, the Chandra data shows that the density of gas around the quasar is higher. At the same time, the temperature is cooler than areas of the galaxy that are further away from the center. If the quasar were emitting the typical series of outbursts, they would have expected there to be not as much gas close to the quasar itself, as the outbursts would have blown it away and that what gas there was close in would be heated to extraordinarily high temperature by those same outbursts.

Without those outbursts, though, the local environment appears to be rife for star formation. The authors estimate that gas equivalent to about 3,000 times the mass of our Sun cools below the point where it emits X-rays every year. Some of that cooling gas is formed into about 120 solar masses worth of new stars yearly, while the black hole itself swallows up another 40 solar masses. What happens with the thousands of solar masses of gas left over after those two processes is anyone’s guess.

However, the quasar itself isn’t cooling the gas surrounding it. At least not much. This process can happen when photons emitted from the black hole run into the electrons of the surrounding gas, resulting in an energy transfer that increases the energy of the photon but decreases the energy of the electron – hence causing the gas to cool down. While that process might be ongoing near H1821-643, the authors calculate that it would only explain a small percentage of the cooling of the gas they observed.

In short, much is still unknown about this seemingly unique quasar system. Studying it further can help scientists understand the influence these massive singularities can have on their immediate surroundings and physical properties more generally. At least, no matter what H1821-643’s physical properties might be, it won’t be getting chewed out by its parents.

Learn More:
NASA / CXC – NASA’s Chandra Identifies an Underachieving Black Hole
Russell et al. – A cooling flow around the low-redshift quasar H1821+643
UT – What Is A Quasar?
UT – This New Map of 1.3 Million Quasars Is A Powerful Tool

Lead Image:
Image of the H1821-643 quasar.
Credit: X-ray: NASA/CXC/Univ. of Nottingham/H. Russell et al.
Radio: NSF/NRAO/VLA
Image Processing: NASA/CXC/SAO/N. Wolk

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