March 22, 2013
Distant Quasars Teamed Up Billions Of Years Ago To Stifle Small Galaxy Formation
redOrbit Staff & Wire Reports - Your Universe Online
Astronomers from the University of Colorado Boulder (CU-Boulder) believe that so-called sideline quasars located on the outer fringes of a larger, brighter active galactic nucleus might have joined forces with it to prevent the formation of small galaxies billions of years ago.
Michael Shull, a professor of astrophysical and planetary sciences at the university´s Center for Astrophysics and Space Astronomy, and research associate David Syphers reached that conclusion after using the Hubble Space Telescope to observe one of the most luminous quasars in the universe as it appeared some 11 billion years ago.
Shull and Syphers used Hubble´s Cosmic Origins Spectrograph (COS) instrument — which breaks down light into its individual components and also provides information about the temperature, density, velocity, distance and chemical composition of galaxies, stars and gas clouds — in their research.
Their goal has been to investigate the so-called fossil record of the universe´s gases in an attempt to learn more about the conditions that existed in the earliest days of the universe.
As part of their research, the two CU-Boulder scientists reviewed 4.5 hours of information collected by Hubble about the quasar. Their findings about that quasar, which is officially known as HS1700+6416, are detailed in this week´s online edition of the Astrophysical Journal.
“While there are likely hundreds of millions of quasars in the universe, there are only a handful you can use for a study like this,” Shull said in a statement.
He and Syphers believe that HS1700+6416 and the smaller, sideline quasars teamed up to heat surrounding abundant intergalactic helium gases in the early universe. According to Shull, the quasars located outside of the telescope´s view reionized those gases from different directions, thus preventing them from gravitationally collapsing and giving rise to a new generation of stars.
That process likely occurred 11 billion years ago, during an era known as the “helium reionization era” in which ionizing radiation originating from black holes within quasar cores stripped electrons from primeval helium atoms, according to the CU-Boulder professor. He compared that early universe to a piece of Swiss cheese, in which “quasars cleared out zones of neutral helium gas in the intergalactic medium that were then ℠pierced´ by UV observations from the space telescope,” according to the university.
In addition, their work revealed evidence suggesting that the helium reionization era appeared to have occurred later than scientists had originally thought — 10 to 11 billion years ago instead of 12 billion years ago, as had been believed. The first galaxies began forming approximately 13.5 billion years ago, they said, and the rise of quasars some two billion years later ultimately gave rise to the helium reionization era, Shull said.
The radiation from those massive quasars heated gases to between 20,000 and 40,000 degrees Fahrenheit.
“It is important to understand that if the helium gas is heated during the epoch of galaxy formation, it makes it harder for proto-galaxies to hang on to the bulk of their gas. In a sense, it´s like intergalactic global warming,” the professor explained. He added that some experts have referred to quasars as feeding black holes, but that astronomers currently do not know whether they feed once or multiple times.