NRAO: ALMA Finds Best Evidence for Distant Galactic Merger

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NRAO: ALMA Finds Best Evidence for Distant Galactic Merger

Post by bystander » Tue Nov 11, 2014 1:22 am

ALMA Finds Best Evidence Yet for Distant Galactic Merger
National Radio Astronomy Observatory | 2014 Nov 10
Click to view full size image 1 or image 2
Artist's impression of the protocluster observed by ALMA. It shows the central starburst
galaxy AzTEC-3 along with its labeled cohorts of smaller, less active galaxies. New ALMA
observations suggest that AzTEC-3 recently merged with another young galaxy and that
the whole system represents the first steps toward forming a galaxy cluster.
Credit: B. Saxton (NRAO/AUI/NSF)
Nestled among a triplet of young galaxies more than 12.5 billion light-years away is a cosmic powerhouse: a galaxy that is producing stars nearly 1,000 times faster than our own Milky Way. This energetic starburst galaxy, known as AzTEC-3, together with its gang of calmer galaxies may represent the best evidence yet that large galaxies grow from the merger of smaller ones in the early Universe, a process known as hierarchical merging.

An international team of astronomers observed these remarkable objects with the Atacama Large Millimeter/submillimeter Array (ALMA).

"The ALMA data reveal that AzTEC-3 is a very compact, highly disturbed galaxy that is bursting with new stars at close to its theoretically predicted maximum limit and is surrounded by a population of more normal, but also actively star-forming galaxies," said Dominik Riechers, an astronomer and assistant professor at Cornell University in Ithaca, New York, and lead author on a paper published today (Nov. 10) in the Astrophysical Journal. "This particular grouping of galaxies represents an important milestone in the evolution of our Universe: the formation of a galaxy cluster and the early assemblage of large, mature galaxies."

In the early Universe, starburst galaxies like AzTEC-3 were forming new stars at a monstrous pace fueled by the enormous quantities of star-forming material they devoured and by merging with other adolescent galaxies. Over billions of years, these mergers continued, eventually producing the large galaxies and clusters of galaxies we see in the Universe today.

Evidence for this hierarchical model of galaxy evolution has been mounting, but these latest ALMA data show a strikingly clear picture of the all-important first steps along this process when the Universe was only 8 percent of its current age. ...

Primordial Galaxy Bursts with Starry Births
Cornell University | 2014 Nov 12

ALMA Imaging of Gas and Dust in a Galaxy Protocluster at Redshift 5.3: [CII] Emission in
"Typical" Galaxies and Dusty Starbursts ~1 Billion Years after the Big Bang
- Dominik A. Riechers et al
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