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GOODS Field Containing Distant Dwarf Galaxies Forming Stars at an Incredible Rate
Photo Credit:NASA,ESA, the GOODS Team, and M. Giavalisco (University of Massachusetts, Amherst)
Science Credit:NASA,ESA, and H. Atek and J.-P. Kneib (EPFL, Switzerland)
They may be little, but they pack a big star-forming punch. New
observations from NASA's Hubble Space Telescope show that small
galaxies, also known as dwarf galaxies, are responsible for forming a
large proportion of the universe's stars.
Studying this early epoch of the universe's history is critical to
fully understanding how these stars formed and how galaxies have grown
and evolved 2 billion to 6 billion years after the beginning of the
universe. This result supports a decade-long investigation into whether
there is a link between a galaxy's mass and its star-forming activity,
and helps paint a consistent picture of events in the early universe.
"We already suspected these kinds of galaxies would contribute to the
early wave of star formation, but this is the first time we've been
able to measure the effect they actually had," said Hakim Atek of the
École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, lead
author of the study published in the June 19 online issue of The
Astrophysical Journal. "They appear to have had a surprisingly huge
role to play."
Previous studies of star-forming galaxies were restricted to the
analysis of mid- or high-mass galaxies, leaving out the numerous dwarf
galaxies that existed in this era of prolific star formation.
Astronomers conducted a recent study using data from Hubble's Wide
Field Camera 3 (WFC3) to take a further and significant step forward in
understanding this formative era by examining a sample of starburst
galaxies in the young universe. Starburst galaxies form stars at a
furiously fast rate, far above what is considered by experts to be a
normal rate of star formation.
The infrared capabilities of WFC3 have allowed astronomers to finally
calculate how much these low-mass dwarf galaxies contributed to the
star population in our universe.
"These galaxies are forming stars so quickly that they could actually
double their entire mass of stars in only 150 million years — an
incredibly short astronomical timescale," added co-author Jean-Paul
Kneib, also of EPFL.
Researchers say such a mass gain would take most normal galaxies 1 billion to 3 billion years to accomplish.
In addition to adding new insight to how and where the stars in our
universe formed, this finding may also help to unravel the secrets of
galactic evolution. Galaxies evolve through a jumble of complex
processes. As galaxies merge, they are consumed by newly formed stars
that feed on their combined gases, and exploding stars and supermassive
black holes emit galactic material — a process that depletes the mass
of a galaxy.
It is unusual to find a galaxy in a state of starburst, which
suggests to researchers that starburst galaxies are the result of an
unusual incident in the past, such as a violent merger.
Space Telescope Science Institute, Baltimore, Maryland