Irvine, Calif., Sept. 7, 2015 – Astronomers from the University of California, Irvine and Baltimore’s Space Telescope Science Institute have generated the most accurate statistical description yet of faint, early galaxies as they existed in the universe 500 million years after the Big Bang.
In a research paper published today in Nature Communications, the team describes its use of a new statistical method to analyze Hubble Space Telescope data captured during lengthy sky surveys. The method enabled the scientists to parse out signals from the noise in Hubble’s deep-sky images, providing the first estimate of the number of small, primordial galaxies in the early universe. The researchers concluded that there are close to 10 times more of these galaxies than were previously detected in deep Hubble surveys.
UCI Ph.D. student Ketron Mitchell-Wynne, lead author on the paper, said the time period under investigation is known as the “epoch of reionization.” Coming after the Big Bang and a few hundred million years in which a dark universe was dominated by photon-absorbing neutral hydrogen, the epoch of reionization was characterized by a phase transition of hydrogen gas due to the accelerated process of star and galaxy formation. Learn More
September 9, 2015: Astronomers at the University of California at Irvine (UCI) and the Space Telescope Science Institute have made the most accurate statistical estimate of the number of faint, small galaxies that existed only 500 million years after the big bang. This was culled from an analysis of the deepest Hubble Space Telescope sky survey, CANDELS (Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey). Previously, studies using Caltech's CIBER (the Cosmic Infrared Background Experiment) rocket-borne instrument and NASA's Spitzer Space Telescope images confirmed the presence of "intra-halo light" from stars distributed outside of galaxies. The Hubble data found a new component in the infrared background in addition to intra-halo light — the collective glow of entire galaxies that formed first in the universe. UCI's Asantha Cooray believes that these early galaxies are very different from the well-defined spiral and disk-shaped galaxies seen in the present-day universe. They were more diffuse and populated by giant stars. This discovery paves the way for NASA's James Webb Space Telescope to see these very faint galaxies individually, after its launch in 2018. Learn More
Creating stars is a lot like cooking: You need the right ingredients in the proper proportions to make everything shine. One of those ingredients is dark matter, and a new study has pinpointed the lower limit of this elusive substance needed to ignite a frenzy of star formation: a mass equal to 300 billion of our suns.
Dark matter is an invisible substance that astronomers can measure only indirectly by its gravitational influence over regular, visible matter. But while it has yet to be directly observed, it's a vital ingredient for galaxies in the act of forming stars.
And if 300 billion solar masses' worth of dark matter sounds like a lot to start with, scientists say it is actually about 10 times less than the amount previously estimated. Learn More
NASA has selected UCI astrophysicist Asantha Cooray as community chair of a study group to design and set requirements for a possible successor to the James Webb Space Telescope. The group, which includes scientists and engineers from about 30 leading international research institutions and space agencies, will work over the next three years toward a next-generation spacecraft and far-infrared surveying instrument with enhanced capabilities to detect faint, distant galaxies; study exoplanet systems around the Milky Way; and provide clues about the evolution of our own solar system. Learn More