摘要：We present the results of Suzaku and XMM-Newton X-ray
observations of the cluster pair 1E2216.0-0401
and 1E2215.7-0404. We discover an X-ray bridge
between the clusters. Suzaku and XMM-Newton observations
revealed that each cluster hosts gas with moderate temperature of kT0401 = 4.8 ±
0.1 keV and kT0404 = 5.8 ± 0.2 keV,
respectively. On the other hand, the bridge region shows a remarkably high temperature
(kT = 6.6 ±
0.5 keV). Furthermore, at the position of the bridge, we detected an
enhancement in the wavelet-decomposed soft-band (0.5−4.0 keV) XMM-Newton image
at 3 sigma significance, this is most likely due to a compression of the intracluster
medium (ICM) as a consequence of the merging activity. This X-ray intensity and
temperature enhancement are not consistent with those expected from a late phase, but are
in agreement with the predictions by numerical simulations of an early phase merger. From
the temperature jump at the location of the bridge, the Mach number is estimated to be
ℳ = 1.4 ± 0.1, which
corresponds to a shock propagation velocity of about 1570 km s-1. From the shock properties, we
estimate that core-passage will occur in 0.3−0.6 Gyr and that the age of the shock structure is 50−100 Myr. Based on the measured properties
of the ICM at the bridge and estimation of timescales, we find indications for
non-equilibrium ionization. We also discover possible diffuse radio emission located
between the merging clusters. Combining the radio, X-ray, and optical image data, we
speculate that the detected radio sources are most likely related to the merger event.
Thus, 1E2216.0-0401 and 1E2215.7-0404 is a new example of an early phase cluster
merger with remarkable characteristics.
