Dark matter

The map of dark matter based on observations from the Atacama Cosmology Telescope

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During the Future Science with CMB x LSS conference underway at Kyoto University, Japan, the results of a detailed mapping of dark matter in a part of the universe were presented. Three articles available in preview and submitted to “The Astrophysical Journal” illustrate these results, obtained using observations conducted at the Atacama Cosmology Telescope (ACT) in Chile, which operated between 2007 and 2022. This map (Image courtesy ACT Collaboration) was obtained by analyzing the cosmic microwave background radiation and its deviations caused to the gravity of massive structures such as concentrations of dark matter.

The galaxy clusters MOO J1014+0038 (left panel) and SPT-CL J2106-5844 (right panel) as seen by the Hubble Space Telescope's Wide Field Camera 3 instrument at infrareds

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An article published in the journal “Nature” reports the results of a study on the so-called intracluster light that permeates galaxy clusters. Hyungjin Joo and M. James Jee of Yonsei University in Seoul, South Korea, used the Hubble Space Telescope to examine ten galaxy clusters and the glow within them. The surprising and therefore interesting discovery was that intracluster light is abundant even in the oldest clusters, a sign that the stars that emit it were ejected from their galaxies a long time ago. This suggests that this happened at the same time as the formation and growth of the clusters.

The SMACS-J0723.3-7327 galaxy cluster seen by the James Webb Space Telescope

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An article published in “The Astrophysical Journal Letters” reports the results of the most complete analysis of the so-called intracluster light conducted so far. Mireia Montes and Ignacio Trujillo of the Instituto de Astrofísica de Canarias (IAC) used the James Webb Space Telescope to observe the SMACS-J0723.3-7327 galaxy cluster. In particular, they exploited the NIRCam instrument to detect intracluster light, which is extremely dim but useful to study galaxy clusters in ways other than visible light observations. These studies are also useful for understanding the distribution of dark matter.

NGC 1427A, one of the dwarf galaxies in the Fornax cluster that appear to be devoid of dark matter halos (Image ESO)

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An article published in the journal “Monthly Notices of the Royal Astronomical Society” reports the results of a study of the distribution and morphology of the dwarf galaxies of the Fornax cluster which concludes that they are free of dark matter halos. A team of researchers coordinated by the German University of Bonn and the Scottish University of Saint Andrews examined those dwarf galaxies to see how perturbed they are by gravitational tides generated by nearby galaxies.

An artistic representation of the combination of the observations obtained in the HSC-SSP survey and the cosmic microwave background data collected by the Planck Surveyor space probe

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An article published in the journal “Physical Review Letters” reports the results of an analysis of dark matter distribution around 1.5 million primordial galaxies. A team of researchers led by Hironao Miyatake of the Japanese University of Nagoya used observations conducted with the Subaru telescope and analyzed data collected by the Planck Surveyor space probe to detect distortion of the cosmic microwave background (CMB).

The results of this study show fluctuations in dark matter distribution in the early universe that led to inhomogeneity in the aggregation of ordinary matter that formed galaxies. That aggregation is lower than predicted by the Lambda-CDM model, the one that currently best describes the observations. The uncertainty lies in the difficulty of obtaining precise results in examining very distant galaxies.