Archive for September 16th, 2011

September 16, 2011

Small distant galaxies host supermassive black holes

There’s been an ongoing debate (of sorts) over the supermassive black holes that seem to exist in most medium to large-size galaxies – did their growth precede, parallel, or follow the growth of the galaxy itself? This arises out of the rough correlation that exists between the size of a galaxy and the size of its black hole. Relatively large black holes have been observed even in nearby dwarf galaxies. This suggests that black hole growth may precede galaxy growth.

The best way to investigate the issue is to observe many galaxies in the early universe, which is difficult because galaxies were smaller and dimmer then. Observations have been reported of very small samples and support the idea that the black holes grow first. There’s a new study out that surveys 28 small galaxies as they were about 3.3 billion years after the big bang. The galaxies are only about one seventh the size of previously studied galaxies of that age. However, by combining the data from all the galaxies, there is evidence for active galactic nuclei in the sample, and hence the presence of supermassive black holes.

Small distant galaxies host supermassive black holes

Using the Hubble Space Telescope to probe the distant universe, astronomers have found supermassive black holes growing in surprisingly small galaxies. The findings suggest that central black holes formed at an early stage in galaxy evolution.

“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 Jonathan Trump, a postdoctoral researcher at the University of California, Santa Cruz.

Further reading:

Small galaxies with large black holes

A CANDELS WFC3 Grism Study of Emission-Line Galaxies at z~2: A Mix of Nuclear Activity and Low-Metallicity Star Formation