Distant Galaxy EGS-zs8-1 in CANDELS Field
An international team of astronomers, led by Yale University and
University of California scientists, has pushed back the cosmic
frontier of galaxy exploration to a time when the universe was only 5
percent of its present age of 13.8 billion years. The team discovered an
exceptionally luminous galaxy more than 13 billion years in the past
and determined its exact distance from Earth using the combined data
from NASA's Hubble and Spitzer space telescopes, and the Keck I
10-meter telescope at the W. M. Keck Observatory in Hawaii. These
observations confirmed it to be the most distant galaxy currently
measured, setting a new record. The galaxy existed so long ago, it
appears to be only 100 million years old.
The galaxy, EGS-zs8-1, was originally identified based on its
particular colors in images from Hubble and Spitzer and is one of the
brightest and most massive objects in the early universe. "It has
already grown more than 15 percent of the mass of our own Milky Way
today," said Pascal Oesch, lead author of the study from Yale
University, New Haven, Connecticut. "But it had only 670 million years
to do so. The universe was still very young then." The new distance
measurement also enabled the astronomers to determine that EGS-zs8-1
was still forming stars very rapidly, about 80 times faster than our
Milky Way galaxy today (which has a star-formation rate of one star per
year.)
Only a handful of galaxies currently have accurate distances measured
in this very early universe. "Every confirmation adds another piece to
the puzzle of how the first generations of galaxies formed in the
early universe," said Pieter van Dokkum of Yale, second author of the
study. "Only the most sensitive telescopes are powerful enough to reach
to these large distances." The discovery was only possible thanks to
the relatively new Multi-Object Spectrometer For Infra-Red Exploration
(MOSFIRE) instrument on the Keck I telescope, which allows astronomers
to efficiently study several galaxies at the same time.
Measuring galaxies at these extreme distances and characterizing
their properties is a main goal of astronomers over the next decade.
The observations see EGS-zs8-1 at a time when the universe was
undergoing very important changes: the hydrogen between galaxies was
transitioning from an opaque to a transparent state. "It appears that
the young stars in the early galaxies like EGS-zs8-1 were the main
drivers for this transition, called reionization," said study
co-author, Rychard Bouwens of the Leiden Observatory, Leiden,
Netherlands.
These new Hubble, Spitzer, and Keck observations together give a new
glimpse into the nature of the infant universe. They confirm that
massive galaxies already existed early in the history of the universe,
but that their physical properties were very different from galaxies
seen around us today. Astronomers now have very strong evidence that the
peculiar colors of early galaxies seen in the Spitzer images originate
from a very rapid formation of massive, young stars, which interacted
with the primordial gas in these galaxies.
The new observations underline the very exciting discoveries that
NASA's James Webb Space Telescope will enable when it is launched in
2018. In addition to pushing the cosmic frontier to even earlier cosmic
times, the Webb telescope will be able to dissect the infrared galaxy
light of EGS-zs8-1 seen with the Spitzer Space Telescope and will
provide astronomers with much more detailed insights into its gas
properties. "Our current observations indicate that it will be very
easy to measure accurate distances to these distant galaxies in the
future with the James Webb Space Telescope," said Garth Illingworth of
the University of California, Santa Cruz. "The result of Webb's upcoming
measurements will provide a much more complete picture of the
formation of galaxies at the cosmic dawn." The team’s results will
appear May 5 in the online edition of The Astrophysical Journal Letters.
Contact
Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu
Felicia Chou
NASA Headquarters, Washington, DC
202-358-0257
felicia.chou@nasa.gov
Source: HubbleSite
