Astronomers using the Atacama Large Millimeter/submillimeter Array have discovered a cluster of monstrous young galaxies, called submillimeter galaxies, about 11.5 billion light-years away.
Visualization of the proto-Great Wall and submillimeter galaxies. Image credit: National Astronomical Observatory of Japan.
Submillimeter galaxies (SMGs) are massive gas-rich galaxies characterized as being enshrouded by dust and undergoing intense star-forming activity.
They are one of the most important populations in unveiling the environmental dependence of galaxy formation on a large-scale in the early Universe.
A research group led by Dr Hideki Umehata of European Southern Observatory and the University of Tokyo used the Atacama Large Millimeter/submillimeter Array to look for SMGs in a distant protocluster of galaxies called SSA22. This giant structure lies 11.5 billion light-years from Earth in the constellation Aquarius.
As a result, the group made the exciting discovery of a cluster of eight monstrous young galaxies.
The shape of this cluster, according to Dr Umehata and co-authors, suggests the presence of a huge web of invisible dark matter, which is thought to be a progenitor of large scale structures in the Universe.
One of the best known examples of large scale structure in the Universe is the cosmic Great Wall, a huge filamentary structure spanning over 500 million light-years.
This image from Subaru Telescope shows three submillimeter galaxies (circles) in the protocluster SSA22. Image credit: ALMA / ESO / NAOJ / NRAO / H. Umehata, University of Tokyo.
“The filamentary structure in SSA22 could be called a proto-Great Wall,” the astronomers said.
They found that their SMGs seemed to bewere located right at the intersection of the dark matter filaments. This finding supports the model that monstrous submillimeter galaxies form in areas where dark matter is concentrated.
“And since modern large elliptical galaxies are simply monstrous galaxies which have mellowed with age, they too must have originated at nexuses in the large scale structure,” Dr Umehata and his colleagues said.
“This result is a very important step for a comprehensive understanding of the relation between the dark matter distribution and monstrous galaxies.”
The research has been accepted for publication in the Astrophysical Journal Letters (arXiv.org preprint).
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H. Umehata et al. 2015. ALMA Deep Field in SSA22: A concentration of dusty starbursts in a z=3.09 protocluster core. ApJL, accepted for publication; arXiv: 1510.08861
