Our own Milky Way galaxy is part of a much larger formation, the local Supercluster structure, which contains several massive galaxy clusters and thousands of individual galaxies. Due to its pancake-like shape, which measures almost a billion light years across, it is also referred to as the Supergalactic Plane.

Most galaxies in the universe fall into one of two categories: Firstly, elliptical galaxies, made mostly of old stars and containing typically extremely massive central black holes, and secondly actively star-forming disk galaxies, with a spiral-like structure similar to the Milky Way’s. Both types of galaxies are also found in the Local Supercluster, but while the Supergalactic Plane is teeming with bright ellipticals, bright disk galaxies are conspicuously absent.

A cosmic anomaly challenges the standard model of cosmology

This peculiar segregation of galaxies in the Local Universe, which has been known since the 1960s, features prominently in a recent list of "cosmic anomalies" compiled by renowned cosmologist and 2019 Nobel laureate Jim Peebles.

An international research team, including researchers from Stockholm led by Jens Jasche, has recently uncovered an explanation. In an article published in Nature Astronomy, they show how the different distributions of elliptical and disk galaxies arise naturally due to the different environments found inside and outside of the Supergalactic Plane. “In the dense galaxy clusters that are found on the supergalactic plane, galaxies experience frequent interactions and mergers, which leads to the formation of ellipticals and the growth of supermassive black holes. By contrast, away from the plane, galaxies can evolve in relative isolation, which helps them preserve their spiral structure”.

In their work, the team utilized the SIBELIUS (Simulations Beyond The Local Universe) simulation, which traces the universe's evolution over 13.8 billion years from the early universe to the present. The largest and most accurate digital representation of our cosmic neighborhood, simulating its evolution from the Big Bang to the present, was made possible by the Stockholm team's novel statistical data analysis methods and innovative machine learning techniques. This essential tool aids in understanding fundamental physical processes, shaping the origin and evolution of cosmic structures, including observed galaxies. While most similar simulations consider random patches of the universe which cannot be directly compared to observations, the Stockholm team aimed to create initial conditions to precisely re-simulate the observed structures, including the Local Supercluster. The final simulation result is remarkably consistent with the observations.

Original publication

List of writers:  Till Sawala, Carlos Frenk, Jens Jasche, Peter H. Johansson, Guilhem Lavaux,
Name of Publication: “Distinct distributions of elliptical and disk galaxies across the Local Supercluster as a ΛCDM prediction”,
Published in Nature Astronomy, November 20, 2023

Contact Associate Professor Jens Jasche

Associate Professor Jens Jasche (in English and in German)
Stockholm University
+46 (0)8-553 780 37
jens.jasche@fysik.su.se