Can the splashback radius be an observable boundary of galaxy clusters?
Journal
Date Issued
2024
Author(s)
Abstract
The splashback radius was proposed as a physically motivated boundary of
clusters as it sets the limit between the infalling and the orbitally dominated
regions. However, galaxy clusters are complex objects connected to filaments of
the cosmic web from which they accrete matter that disturbs them and modifies
their morphology. In this context, estimating the splashback radius and the
cluster boundary becomes challenging. In this work, we use a constrained
hydrodynamical simulation of the Virgo cluster's replica embedded in its
large-scale structure to investigate the impact of its local environment on the
splashback radius estimate. We identify the splashback radius from 3D radial
profiles of dark matter density, baryons density, and pressure in three regions
representative of different dynamical states: accretion from spherical
collapse, filaments, and matter outflow. We also identify the splashback radius
from 2D-projected radial profiles of observation-like quantities: mass surface
density, emission measure, and Compton-y. We show that the splashback radius
mainly depends on the dynamics in each region and the physical processes traced
by the different probes. We find multiple values for the splashback radius
ranging from 3.3$\pm$0.2 to 5.5$\pm$0.3 Mpc. Particularly, in the regions of
collapsing and outflowing material, the splashback radii estimated from baryon
density and pressure radial profiles overestimate that of the dark matter
density profiles, which is considered the reference value originally defined
from dark matter simulations. Consequently, caution is required when using the
splashback radius as a boundary of clusters, particularly in the case of highly
disturbed clusters like Virgo. We also discuss the detection of the splashback
radius from pressure radial profiles, which could be more related to an
accretion shock, and its detection from stacked radial profiles.
Volume
689
Start page
A19
Issn Identifier
0004-6361
Rights
open.access
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