Merger of massive galaxy cluster CL0238.3+2005 at z~0.4: just after pericenter passage?

• Main Authors: Lyskova, N, Churazov, E, Khabibullin, I, Bikmaev, I. F, Burenin, R. A, Forman, W. R, Khamitov, I. M, Rajpurohit, K, Sunyaev, R, Jones, C, Kraft, R, Zaznobin, I, Gorbachev, M. A, Suslikov, M. V, Gumerov, R. I, Sakhibullin, N. A
• Format: Journal Article
• Language: English
• Published: 12-09-2024
• Subjects: Physics - Cosmology and Nongalactic Astrophysics; Physics - High Energy Astrophysical Phenomena
• DOI: 10.48550/arxiv.2409.07856

Massive clusters of galaxies are very rare in the observable Universe. Even
rarer are mergers of such clusters observed close to pericenter passage. Here,
we report on one such case: a massive (~ $10^{15}\,M_\odot$) and hot (kT ~ 10
keV) cluster CL0238.3+2005 at $z\approx 0.42$. For this cluster, we combine
X-ray data from SRG/eROSITA and Chandra, optical images from DESI, and
spectroscopy from BTA and RTT-150 telescopes. The X-ray and optical
morphologies suggest an ongoing merger with the projected separation of
subhalos of $\sim 200$ kpc. The line-of-sight velocity of galaxies tentatively
associated with the two merging halos differs by 2000-3000 km/s. We conclude
that, most plausibly, the merger axis is neither close to the line of sight nor
to the sky plane. We compare CL0238 with two well-known clusters MACS0416 and
Bullet, and conclude that CL0238 corresponds to an intermediate phase between
the pre-merging MACS0416 cluster and the post-merger Bullet cluster. Namely,
this cluster has recently (only $\lesssim 0.1$ Gyr ago) experienced an almost
head-on merger. We argue that this "just after" system is a very rare case and
an excellent target for lensing, Sunyaev-Zeldovich effect, and X-ray studies
that can constrain properties ranging from dynamics of mergers to
self-interacting dark matter, and plasma effects in intracluster medium that
are associated with shock waves, e.g., electron-ion equilibration efficiency
and relativistic particle acceleration.