860-million-year-old quasars had already accumulated 1.4 billion times the mass of the Sun

It wasn’t long after the Big Bang that the first galaxies began to change the universe. Less than a billion years later, they had already put on a lot of weight. In particular, their central supermassive black holes were behemoths. New images from JWST show two massive galaxies as they appeared less than a billion years after the universe began.

One of the galaxies weighs a whopping 130 billion times the mass of the Sun. Its quasar driven by a black hole has 1.4 billion solar masses. (A quasar is the bright active nucleus of a galaxy thought to be powered by a supermassive black hole.) It turns out that these galaxies and their central black holes are completely different sizes from each other. Plus, those spectacular masses raise some challenging questions. How did they get so massive so fast in the newborn Universe? And which came first? The galaxy or black holes?

Those make up a puzzle in front of an international team of researchers led by Xuheng Ding and John Silverman (both of the Kavli Institute for the Physics and Mathematics of the Universe). They announced their initial findings in the June 28, 2023 edition of the journal Nature.

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JWST NIRCam 3.6 µm image of HSC J2236+0032.  The zoomed-in image, the quasar image, and the host galaxy image after subtracting the light from the quasar (from left to right).  The image scale in light years is indicated in each panel.  Credits: Ding, Onoue, Silverman et al.
JWST NIRCam 3.6 µm image of HSC J2236+0032. The zoomed-in image, the quasar image, and the host galaxy image after subtracting the light from the quasar (from left to right). The image scale in light years is indicated in each panel. Credits: Ding, Onoue, Silverman et al.

Exploring the Quasar Hearts

The quasars they observed are called J2236+0032 and J2255+0251. Their host galaxies were first observed by the Subaru telescope in Hawaii. Both galaxies are relatively faint and are good targets for studies of the early universe. They are located at redshifts of 6.4 and 6.34. Those place them at a time when the universe was only 860 million years old. Kavli’s research team then used JWST to take a deeper look at these objects.

JWST examined them at infrared wavelengths of 3.56 and 1.50 microns. Additionally, JWST’s NIRSPEC spectrometer refined the galaxy’s stellar populations. Data analysis has further refined the mass of the two galaxies. It also revealed the speed of the gases moving in their hearts. This allowed the team to determine the masses of the two central supermassive black holes that power these quasars.

Answer questions about these quasars

One thing immediately jumps out of the data: the relationship between the masses of galaxies and their black holes. It turns out that the size of a supermassive black hole apparently follows the size of its host galaxy. Astronomers are exploring this relationship in galaxies in the nearby universe and find that the bigger a galaxy, the bigger its central black hole should be. The two galaxies in the JWST discovery show the same relationship between their masses and the masses of their black holes.

The implication here is that the relationship was actually in effect very early in cosmic history. This raises other questions about the mechanisms that link galaxies and their black hole nuclei to create this relationship. Astronomers suggest several scenarios. First, because they are active galactic nuclei (quasars), they can trigger further star formation in the galaxy via their jets and winds. But those same activities can appease the birth of new stars. This is an interesting feedback mechanism that causes the rate of star formation to follow the accretion rate of the black hole. In essence, the AGN puts checks and balances on the growth of the galaxy.

Another idea is that the ratio of galaxies to black holes’ masses is driven by black hole growth and star formation using the same fuel sources. This scenario could happen quite easily after the merger of two fuel-rich galaxies. Mergers often stimulate star formation, so this could have happened with these early galaxies at a time when mergers were a dominant activity. A third scenario suggests that there may only be a statistical relationship and that more study is needed.

You need more data

Data from the galaxies HSC J2236+0032 and HSC J2255+0251 have raised questions. Now it’s time for astronomers to look at more of these objects in the early universe to see if they can respond. The team will continue their observations using JWST during the current Cycle 1. They already have telescope time to study J2236+0032 in more detail to answer some of the outstanding questions raised by this current work. In particular, these studies may be able to tell us whether galaxies or black holes came first. They will also reveal more details about the growth rates of both galaxies and their black hole-guided quasars in these early epochs in the history of the Universe.

For more information

Starlight and the first black holes: Researchers detect the host galaxies of quasars in the early universe
Feedback from AGN-driven winds
The link between black holes and their galaxies

Detection of starlight from host galaxies of quasars a
red shifts above 6

Preliminary release of ArXiv

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