The presence of a large number of elliptical galaxies near a supergalactic plane is not unusual, but is well explained within the framework of cold dark matter theory. Astronomers reached this conclusion after analyzing computer simulation data on the distribution of different types of galaxies within the local supercluster. This paper was published in the journal Nature Astronomy. The standard theory of galaxy formation assumes that disk galaxies evolve in a relatively isolated manner, primarily through star formation driven by the continuous accumulation of gas from the intergalactic medium. As the ambient temperature outside the galaxy increases, it limits the supply of gas to the galaxy’s halo, stopping star formation. This is typical of dense regions where dark matter halos are widespread, and galaxy mergers leading to the formation of elliptical galaxies are also more common.
The local supercluster of galaxies is the largest structure in the local universe, including the Milky Way. Associated with the supergalactic plane, it has an excess of bright elliptical and radial galaxies, but not an excess of disk galaxies. A team of astronomers led by Thiru Sawala from the University of Helsinki has published the results of his SIBELIUS DARK cosmology simulations using the supercomputer COSMA 8 and his CSC Mahti. This simulation reproduces the distribution of galaxies at distances of up to 200 megaparsecs from the Local Group. Galaxies within the framework of the ΛCDM model (cold dark matter model) and the standard theory of galaxy formation. Initial simulation conditions were chosen to match the large-scale structure of galaxies from the 2M++ sky survey data and compared with observational data from the 2MASS survey. In the simulations, star formation due to galaxy mergers and disk instability were the main processes that could lead to the growth of the galactic bulge and the transformation of disk galaxies into elliptical galaxies.
This simulation was able to reproduce the observed spatial distribution of disk and elliptical galaxies, especially the excessively massive elliptical galaxies observed near the supergalactic equator. First, the most massive elliptical galaxies in the redshift range z=0.01 to 0.02 are much more massive than the most massive disk galaxies, and the strength of group formation strongly depends on the mass of the galaxy. Second, the environment of the supergalactic plane appears to preclude the conditions necessary for the formation of massive disk galaxies, such as relatively quiet merger events and a constant influx of cold gas. Therefore, the observed galaxy distribution does not appear to be anomalous, but rather fits the predictions of the ΛCDM model and the standard model of galaxy formation.