The connection between internal structure of galaxy clusters and distribution of galaxy clusters
Credit: Sloan Digital Sky Survey, Kavli IPMU
An international team of researchers has found for the first time that the connection between a galaxy cluster and surrounding dark matter is not characterized solely by the mass of clusters, but also by their formation history.
Galaxy clusters are the biggest celestial objects in the sky
consisting of thousands of galaxies. They form from nonuniformity in the
matter distribution established by cosmic inflation in the beginning of
the Universe. Their growth is a constant fight between the gathering of
dark matter by gravity and the accelerated expansion of the universe
due to dark energy. By studying galaxy clusters, researchers can learn
more about these biggest and most mysterious building blocks of the
Universe.
Led by Hironao Miyatake, (formerly JSPS fellow, currently at NASA’s
Jet Propulsion Laboratory), Surhud More and Masahiro Takada of the Kavli
Institute for the Physics and Mathematics (Kavli IPMU), the research
team challenged the conventional idea that the connection between galaxy
clusters and the surrounding dark matter environment is solely
characterized by their mass. Based on the nature of the non-uniform
matter distribution established by cosmic inflation, it was
theoretically predicted that other factors should affect the connection.
However, no one had succeeded in seeing it in the real Universe until
now.
The team divided almost 9000 galaxy clusters from the Sloan Digital
Sky Survey DR8 galaxy catalog into two samples based on the spatial
distribution of galaxies inside each cluster. By using gravitational
lensing they confirmed the two samples have similar masses, but they
found that the distribution of clusters was different. Galaxy clusters
in which member galaxies bunched up towards the center were less clumpy
than clusters in which member galaxies were more spread out. The
difference in distribution is a result of the different dark matter
environment in which they form.
Researchers say their findings show that the connection between a galaxy cluster and surrounding dark matter is not characterized solely by the mass of clusters, but also by their formation history.
The results from this study would need to be taken into account in
future large scale studies of the universe, and research looking into
the nature of dark matter or dark energy, neutrinos, and the early
universe.
The study will be published on January 25 in Physical Review Letters, and has been selected as an Editor’s Suggestion.
Comment from Surhud More
“The signal we measure is puzzlingly large compared to naive
theoretical estimates. The sheer number of tests for systematics that we
had to perform to convince ourselves that the signal is real, was the
most difficult part of this research.”
Comment from Masahiro Takada
“This is truly exciting finding! We can use the upcoming Subaru Hyper
Suprime-Cam (HSC) data to further check and advance our understanding
of the assembly history of galaxy clusters.”
Comment from Hironao Miyatake
“I am thrilled that we have finally found clear evidence of the
connection between the internal structure of clusters and surrounding
dark matter environment. We checked lots of things to make sure this
result, and finally concluded this is real! I am also excited that our
findings will give insights on many aspects of the universe, such as
large scale structure, dark matter and dark energy, and inflation
physics. It is just starting. We hope we can get more exciting results
from the upcoming HSC data.”
Comment from David Spergel
“Cosmologist have long held a very simple theory: " the properties of
a cluster is determined solely by its mass”. These results show that
the situation is much more complex: the clusters environment also plays
an important role. Astronomers have been trying to detect evidence for
this more complex picture for many years: this is the first definitive
detection.”
Paper Details
Journal: Physical Review Letters, vol 116 (2016)
Title: Evidence of halo assembly bias in massive clusters
Authors: Hironao Miyatake (1, 2, 3), Surhud More (2), Masahiro Takada (2), David N. Spergel (1, 2), Rachel Mandelbaum (4), Eli S. Rykoff (5, 6), Eduardo Rozo (7)
Author affiliations:
1 Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ 08544, USA
2 Kavli Institute for the Physics and Mathematics of the Universe (WPI), UTIAS, The University of Tokyo, Chiba, 277-8583, Japan
3 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
4 McWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
5 Kavli Institute for Particle Astrophysics & Cosmology, P. O. Box 2450, Stanford University, Stanford, CA 94305, USA
6 SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
7 Department of Physics, University of Arizona, 1118 E 4th St, Tucson, AZ 85721, USA
Title: Evidence of halo assembly bias in massive clusters
Authors: Hironao Miyatake (1, 2, 3), Surhud More (2), Masahiro Takada (2), David N. Spergel (1, 2), Rachel Mandelbaum (4), Eli S. Rykoff (5, 6), Eduardo Rozo (7)
Author affiliations:
1 Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ 08544, USA
2 Kavli Institute for the Physics and Mathematics of the Universe (WPI), UTIAS, The University of Tokyo, Chiba, 277-8583, Japan
3 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
4 McWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
5 Kavli Institute for Particle Astrophysics & Cosmology, P. O. Box 2450, Stanford University, Stanford, CA 94305, USA
6 SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
7 Department of Physics, University of Arizona, 1118 E 4th St, Tucson, AZ 85721, USA
DOI: 10.1103/PhysRevLett.116.041301
Paper Abstract (Physical Review Letters) - link to be added once available
Preprint (arXiv.org archive website)
Media contacts:
Motoko Kakubayashi
Press Officer
Kavli Institute for the Physics and Mathematics of the Universe,
The University of Tokyo Institutes for Advanced Study,
The University of Tokyo
TEL: +81-04-7136-5980
E-mail: press@ipmu.jp
Research contacts:
Surhud More
Project Assistant Professor
The Kavli Institute for the Physics and Mathematics of the Universe
TEL (office): +81-04-7136-6566
E-mail: surhud.moreAipmu.jp