Washington: The find of supermassive black holes growing in surprisingly small galaxies suggest that central black holes form at an early stage in galaxy evolution, U.S. astronomers say.
All massive galaxies host a central supermassive black hole, but active black holes are rarely seen in small “dwarf” galaxies.
“It’s kind of a chicken or egg problem: Which came first, the supermassive black hole or the massive galaxy? This study shows that even low-mass galaxies have supermassive black holes,” said first author Jonathan Trump, a postdoctoral researcher at the University of California, Santa Cruz.
The galaxies observed with the help of the Hubble Space Telescope are about 10 billion light-years away, giving astronomers a view of galaxies as they appeared when the universe was less than a quarter of its current age.
“When we look 10 billion years ago, we’re looking at the teenage years of the universe. So these are very small, young galaxies,” Trump said.
The findings also challenge current beliefs about black hole formation.
“Up to now, observations of distant galaxies have consistently reinforced the local findings -- distant black holes actively accreting in big galaxies only,” said coauthor Sandra Faber, University Professor of astronomy and astrophysics at UC Santa Cruz and CANDELS principal investigator.
“We now have a big puzzle: What happened to these dwarf galaxies?”
One possibility is that at least some of them are the progenitors of present-day massive galaxies like the Milky Way.
“Their star formation rate is about ten times that of the Milky Way,” Trump said.
“There may be a connection between that and the active galactic nuclei. When gas is available to form new stars, it’s also available to feed the black hole,” he added.
The study will be published in the Astrophysical Journal.