The splashback radius of groups and clusters of galaxies at low redshifts
October 03, 2022
We present a study of the distribution of galaxies along the radius of 157 groups and
clusters of galaxies (200 km s−1 < σ < 1100 km s−1 ) of the local Universe (0.01 < z < 0.1). We
introduced a new boundary of galaxy systems and identified it with the splashback radius Rsp. We
also identified the central region of galaxy systems with a radius of Rc. These radii are defined
by the observed intergral distribution of the number of galaxies depending on the squared
distance from the center of the groups/clusters coinciding, as a rule, with the brightest galaxy.
We show that the radius Rsp is proportional to the radius R200c (radius of the virialized region of
galaxy cluster) and to the radius of the central region Rc with a slope close to 1. Among the
obtained dependences of the radii on X-ray luminosity the log Rsp - log LX relation
has the lowest scatter. We measured < Rsp > = 1.67 ± 0.05 for total sample, < R sp > = 1.14 ±
0.14 for galaxy groups with σ ≤ 400 km s−1 , < Rsp > = 2.00 ± 0.20 for galaxy clusters with σ >
400 km s-1 . We found the average ratio of the radii Rsp/R200c = 1.40 ± 0.02 or Rsp /R200m =
0.88 ± 0.02.
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