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Lopsided Satellite Distributions around Isolated Host Galaxies

Presentation #156.02 in the session “Dwarf and Irregular Galaxies”.

Published onJan 11, 2021
Lopsided Satellite Distributions around Isolated Host Galaxies

We present an analysis of the locations of the satellites of isolated central (“host”) galaxies. Our sample was obtained from the NASA-Sloan Atlas and contains 3,575 host-satellite systems with a total of 13,090 satellites. More than 90% of the host galaxies are brighter than L* and, on average, the satellites are ~20 times fainter than their hosts. In agreement with previous studies of isolated host galaxies and their satellites, there is a strong color-color correlation in our sample, with the satellites of blue host galaxies being predominantly blue and the satellites of red host galaxies being predominately red. We compute the pairwise clustering of the satellite galaxies with each other and find a strong indication (> 99.9999% confidence level) that the satellite locations are inconsistent with a uniform elliptical distribution (i.e., the distribution that would be expected if the satellites faithfully traced the shapes of the dark matter halos of their host galaxies). When averaged over the entire sample, pairs of satellite galaxies show a strong tendency to be found on the same side of their host galaxy, creating “lopsided” distributions. This effect is greatest for the satellites of blue hosts, with the number of pairs of satellites on the same side of their host exceeding the number of pairs of satellites on opposite sides of their host by a factor of 1.8 ± 0.1. In the case of the satellites of red hosts, the number of pairs of satellites on the same side of their host exceeds the number of pairs of satellites on opposite sides of their host by a factor of 1.08 ± 0.03. Satellites located farther than 300 kpc from their hosts show a strong preference for being located on the same side of their host, while satellites that are found within 100 kpc of their hosts show a weak preference for being located on opposite sides of their host. While lopsided satellite distributions have been found previously for the satellites of pairs of bright galaxies, ours is the first large study to show significantly lopsided distributions for the satellites of isolated bright galaxies.


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