University of Texas | McDonald Observatory | 2015 Nov 19
[c][youtube]https://www.youtube.com/watch?v=aDZNe_RvVl0[/youtube]Credit: Avishai Dekel, Nir Mandelker, Daniel Ceverino,A study published in today’s Astrophysical Journal by University of Texas at Austin assistant professor Steven Finkelstein and colleagues reveals that galaxies were more efficient at making stars when the universe was younger. The announcement explains the team’s discovery, announced in the journal’s September 1 issue, that there are a lot more bright, highly star-forming galaxies in the early universe than scientists previously thought.
Joel Primack, and the VELA simulation team[/c][hr][/hr]
“This was an unexpected result,” Finkelstein said. “It has implications for galaxy formation at the earliest times” in the universe.
For both studies, his team used galaxy observations from Hubble Space Telescope’s CANDELS survey, of which he is a team member. Hubble’s largest survey to date, CANDELS stands for Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey.
Today’s finding stems from studies of about 8,000 CANDELS galaxies seen at times ranging from 0.75 to 1.5 billion years after the Big Bang (that is, between redshift four and redshift seven). As the universe is a little less than 14 billion years old, this corresponds to only the first five to 10 percent of the history of the universe.
The team deduced the rate of star formation in these galaxies from the Hubble images, by noting their brightness in ultraviolet light, and then correcting this measurement depending on how much light-absorbing dust the galaxy contains. The dust estimation comes from the Hubble images, too. The redder a galaxy is, the dustier it is.
Investigating the highly star-forming galaxies further, they compared the mass in stars in these galaxies to the theoretically predicted rate at which galaxies grow their mass in the early universe. They found higher masses than predicted, implying that galaxies are more efficient at turning gas into stars in the early universe than they are today. ...
An Increasing Stellar Baryon Fraction in Bright Galaxies at High Redshift - Steven L. Finkelstein et al
- Astrophysical Journal 814(2):95 (2015 Dec 01) DOI: 10.1088/0004-637X/814/2/95
arXiv.org > astro-ph > arXiv:1504.00005 > 31 Mar 2015 (v1), 18 Nov 2015 (v2)
- Astrophysical Journal 810(1):71 (2015 Sep 01) DOI: 10.1088/0004-637X/810/1/71
arXiv.org > astro-ph > arXiv:1410.5439 > 20 Oct 2014 (v1), 06 Jun 2015 (v2)