Cold Gas Caused First Black Holes To Grow Faster Than Anything Else In The Universe
December 15, 2011 Leave a Comment
Researchers at Carnegie Mellon University’s Bruce and Astrid McWilliams Center for Cosmology have discovered what caused the rapid growth of early supermassive black holes.
Studies done at the National Institute for Computational Sciences and the Pittsburgh Supercomputing Center, using GigaPan Time Machine technology, show that thin streams of cold gas flow uncontrolled into the center of the first black holes, causing them to grow faster than anything else in the universe.
In the early days of the universe, a mere 700 to 800 million years after the Big Bang, most things were small. The first stars and galaxies were just beginning to form and grow in isolated parts of the universe. According to astrophysical theory, black holes found during this era also should be small in proportion with the galaxies in which they reside. Recent observations from the Sloan Digital Sky Survey (SDSS) have shown that this isn’t the case: enormous supermassive black holes existed as early as 700 million years after the Big Bang.
Supermassive black holes are the largest black holes, with masses billions of times larger than that of the sun. Typical black holes have masses only up to 30 times larger than the sun’s. These kind of black holes can form when two galaxies collide and their two black holes merge into one. These galaxy collisions happened in the later years of the universe, but not in the early days. In the first few millions of years after the Big Bang, galaxies were too few and too far apart to merge.
“If you write the equations for how galaxies and black holes form, it doesn’t seem possible that these huge masses could form that early,” said Rupert Croft, an associate professor of physics at Carnegie Mellon.“But we look to the sky and there they are.”
To find out exactly how these supermassive black holes came to be, Di Matteo, Croft and Carnegie Mellon post-doctoral researcher Nishikanta Khandai created the largest cosmological simulation to-date. Called MassiveBlack, the simulation focused on recreating the first billion years after the Big Bang.
“This simulation is truly gigantic. It’s the largest in terms of the level of physics and the actual volume. We did that because we were interested in looking at rare things in the universe, like the first black holes. Because they are so rare, you need to search over a large volume of space,” said Di Matteo.
Normally, when cold gas flows toward a black hole it collides with other gas in the surrounding galaxy. This causes the cold gas to heat up and then cool back down before it enters the black hole. This process, called shock heating, would stop black holes in the early universe from growing fast enough to reach the masses we see. Instead, Di Matteo and Croft saw in their simulation thin streams of cold dense gas flowing along the filaments that give structure to the universe and straight into the center of the black holes at breakneck speed, making for cold, fast food for the black holes. This uncontrolled consumption caused the black holes to grow exponentially faster than the galaxies in which they reside.
Information from: http://www.cmu.edu/cosmology/