Mar 15 – 20, 2020
Europe/Berlin timezone

Optically defined merging clusters and multi-wavelength follow-up observations

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Nobuhiro Okabe (Hiroshima Univ.)


We present multi-wavelength studies (optical, weak-lensing, X-ray, SZE and radio synchrotron) of optically defined major-mergers from the CAMIRA cluster catalog of the HSC-SSP Survey and results of follow-up observations of high angular resolution GBT/MUSTANG-2 SZE measurements and XMM-XXL X-ray images of three CAMIRA clusters. Luminous red galaxies make a homogeneous sample of cluster mergers at various merging stages and unbiased with respect to the merger boost of the ICM. However, it is difficult to discriminate between pre- and post- mergers and thus multi-wavelength follow-up observations are crucial for understanding merger physics. The average halo concentration for the merging clusters is $\sim$70% smaller than that of the other clusters. We find a signature of the merger boost of the ICM from the stacked Planck Sunyaev-Zel'dovich effect and ROSAT X-ray luminosity, but not in optical richness. The stacked X-ray surface brightness distribution, aligned with the main subhalo pairs of low-redshift and massive clusters, shows that the central gas core is elongated along the merger axis, and overall gas distribution is misaligned by $\sim$ 60 deg. The combination of high angular resolution SZE and X-ray imaging enables a spatially resolved multi-component analysis. The $S_X$ and $y$ distributions are perturbed at some level, regardless of the optical properties. In particular, the joint SZE and X-ray analysis reveal that temperatures of double $y$ peaks in an optically-defined major merger reach $\sim 20−30$ keV in contrast to the cool core component of $\sim 2$ keV. We find that an integrated Compton $y$ parameter and a temperature for a major merger are significantly boosted from those expected by the weak-lensing mass and those for the other two clusters show no significant deviations.

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Nobuhiro Okabe (Hiroshima Univ.)

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