Kavli Affiliate: Sunil Golwala
| First 5 Authors: Emily M. Silich, Elena Bellomi, Jack Sayers, John ZuHone, Urmila Chadayammuri
| Summary:
Galaxy cluster mergers are rich sources of information to test cluster
astrophysics and cosmology. However, cluster mergers produce complex projected
signals that are difficult to interpret physically from individual
observational probes. Multi-probe constraints on both the baryonic and dark
matter cluster components are necessary to infer merger parameters that are
otherwise degenerate. We present ICM-SHOX (Improved Constraints on Mergers with
SZ, Hydrodynamical simulations, Optical, and X-ray), a systematic framework to
jointly infer multiple merger parameters quantitatively via a pipeline that
directly compares a novel combination of multi-probe observables to mock
observables derived from hydrodynamical simulations. We report on a first
application of the ICM-SHOX pipeline to the MACS J0018.5+1626 system, wherein
we systematically examine simulated snapshots characterized by a wide range of
initial parameters to constrain the MACS J0018.5+1626 merger parameters. We
strongly constrain the observed epoch of MACS J0018.5+1626 to within $approx
-10$–$50$ Myr of the pericenter passage, and the observed viewing angle is
inclined $approx 25$–$38$ degrees from the merger axis. We obtain less
precise constraints for the impact parameter ($approx 100$–250 kpc), the mass
ratio ($approx 1.5$–$3.0$), and the initial relative velocity when the
cluster components are separated by 3 Mpc ($approx 1700$–3000 km s$^{-1}$).
The primary and secondary cluster components initially (at 3 Mpc) have gas
distributions that are moderately and strongly disturbed, respectively. We
further discover a velocity space decoupling of the dark matter and baryonic
distributions in MACS J0018.5+1626, which we attribute to the different
collisional natures of the two distributions.
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