One of the farthest known quasars seems to have shut down the creation of new stars in all the galaxies within its vicinity.
A quasar is a powerful source of light, created by torrid gas orbiting a gargantuan black hole at the center of a galaxy. The intense radiation from one quasar, named VIK J2348-3054, has probably stopped star formation at least 16 million light-years away from itself, astronomer Trystan Lambert and colleagues report in a paper to appear in Astronomy and Astrophysics.
The quasar is so distant that its light took 13.0 billion years to reach us, so we see it when the universe was just 770 million years old. By that early epoch, however, the black hole powering the quasar was already 2 billion times as massive as the sun, which means the black hole had swallowed a lot of material in a relatively short time (SN: 1/18/21). That, in turn, means the quasar’s galaxy must reside in a dense part of the universe: the center of a big cluster of galaxies, many of which should be creating new stars.
And yet that doesn’t appear to be the case. “It was shocking,” says Lambert, of the Universidad Diego Portales in Santiago, Chile. “You would expect more [star-forming galaxies] near the quasar than far away, and we found the exact opposite. There’s a big hole around the quasar.” The nearest star-making galaxy is at least 16.8 million light-years from the quasar. That’s more than six times the distance between the Milky Way and its giant neighbor, the Andromeda galaxy.
The discovery occurred because Lambert’s team searched a much larger region around this quasar for star-forming galaxies than similar searches had in the past.
“Quasars aren’t quiet neighbors,” Lambert says. “They’re violent; they are bursting with energy, and that energy is influencing the nearby galaxies.” The quasar’s radiation, he suspects, heats up gas in other galaxies, which prevents it from collapsing and making new stars.
But further work is needed to make a persuasive case for this scenario, says Martin Rees, an astronomer at the University of Cambridge. The large number of star-making galaxies found far from the quasar — 38 in all — could merely reflect the larger volume of space surrounding the quasar at those greater distances. After all, the volume of space around the quasar is proportional to the third power of the distance from the quasar. Thus, Rees says, the absence of a star-forming galaxy in the small volume right around the quasar may arise simply by chance.
“It’s a fair point,” Lambert says, but he notes that no other similarly sized region near the one closest to the quasar lacks a star-making galaxy. Rees says that if more sensitive observations reveal additional star-forming galaxies far from the quasar but none near it, that will strengthen the statistical significance of the finding.
Our own galaxy may have once been the victim of a quasar. M87, an enormous galaxy about 54 million light-years from the Milky Way, hosts a huge black hole that probably powered a quasar when the universe was young. But at the time that quasar was active, it was much closer to our galaxy. When the universe was a quarter of its current size, for example, the distance between us and M87 was presumably a fourth of what it is now. A quasar that close could have caused a lull in star formation that astronomers might someday detect by measuring precise ages for our galaxy’s oldest stars (SN: 3/23/22).
