Subaru: Tracing the Cosmic Web with Remote Star-Forming Galaxies

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Subaru: Tracing the Cosmic Web with Remote Star-Forming Galaxies

Post by bystander » Tue Jan 31, 2017 6:17 pm

Tracing the Cosmic Web with Remote Star-Forming Galaxies
Subaru Telescope | NAOJ | Hiroshima University | 2017 Jan 30
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A research group led by Hiroshima University has revealed a picture of the increasing fraction of massive star-forming galaxies in the distant universe. Massive star-forming galaxies in the distant universe, about 5 billion years ago, trace large-scale structure in the universe. In the nearby universe, about 3 billion years ago, massive star-forming galaxies are not apparent. This change in the way star-forming galaxies trace the matter distribution is consistent with the picture of galaxy evolution established by other independent studies.

Galaxies in the universe trace patterns on very large scales; there are large empty regions (called “voids”) and dense regions where the galaxies exist. This distribution is called the cosmic web. The most massive concentrations of galaxies are clusters. The formation of the cosmic web is governed by the action of gravity on the invisible mysterious “dark matter” that exists throughout the universe. The normal baryonic material one can see falls into the dark matter halos and forms galaxies. The action of gravity over about the 14-billion-year history of the universe makes the halos cluster together. The location of galaxies or clusters in this enormous cosmic web tests our understanding of the way structure forms in the universe.

Increasingly, deeper and more extensive observations with telescopes like the 8-meter Subaru Telescope on Maunakea, Hawaii, provide a clearer picture of the way galaxies evolve within the cosmic web. Of course, one cannot see the dark matter directly. However, one can use the galaxies that are seen to trace the dark matter. It is also possible to use the way the gravity of clusters of galaxies distort more distant background galaxies, weak gravitational lensing, as another tracer.

The Hiroshima group combined these two tracers: galaxies and their weak lensing signal to map the changing role of massive star-forming galaxies as the universe evolves. ...

A Weak Lensing View of the Downsizing of Star-Forming Galaxies - Yousuke Utsumi et al
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A close-up view of the cluster of galaxies observed. The image is a composite <br />of the i-band data (in red) from the Hyper Suprime-Cam at the Subaru Telescope <br />and R-band (in green) and V-band (in blue) images from the Mayall 4-m telescope <br />at the Kitt Peak National Observatory of National Optical Astronomy Observatory. <br />Contour lines show the mass distribution. Red and blue circles show galaxies <br />that stopped star formation and galaxies with star formation, respectively. The <br />research team was able to study the evolution of the large scale structure in the <br />Universe by comparing the mass distribution in the Universe and the distribution <br />of the galaxies. (Credit: Hiroshima University/NAOJ)
A close-up view of the cluster of galaxies observed. The image is a composite
of the i-band data (in red) from the Hyper Suprime-Cam at the Subaru Telescope
and R-band (in green) and V-band (in blue) images from the Mayall 4-m telescope
at the Kitt Peak National Observatory of National Optical Astronomy Observatory.
Contour lines show the mass distribution. Red and blue circles show galaxies
that stopped star formation and galaxies with star formation, respectively. The
research team was able to study the evolution of the large scale structure in the
Universe by comparing the mass distribution in the Universe and the distribution
of the galaxies. (Credit: Hiroshima University/NAOJ)
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