Abell 1758 was classified as a single rich cluster of galaxies by Abell , but a ROSAT observation showed that this system consists of two distinct clusters ( A1758N and A1758S ) separated by approximately 8 \arcmin ( a projected separation of 2 Mpc in the rest frame of the clusters ) .
Only a few galaxy redshifts have been published for these two clusters , but the redshift of the Fe lines in the Chandra and XMM-Newton spectra shows that the recessional velocities of A1758N and A1758S are within 2,100 km s ^ { -1 } .
Thus , these two clusters most likely form a gravitationally bound system , but our imaging and spectroscopic analyses of the X-ray data do not reveal any sign of interaction between the two clusters .
The Chandra and XMM-Newton observations show that A1758N and A1758S are both undergoing major mergers .

A1758N is in the late stages of a large impact parameter merger between two 7 keV clusters .
The two remnant cores have a projected separation of 800 kpc .
Based on the measured pressure jumps preceding the two cores , they are receding from one another at less than 1,600 km s ^ { -1 } .
The two cores are surrounded by hotter gas ( \mathrm { kT } = 9 –12 keV ) that was probably shock heated during the early stages of the merger .
The gas entropy in the two remnant cores is comparable with the central entropy observed in dynamically relaxed clusters , indicating that the merger-induced shocks stalled as they tried to penetrate the high pressure cores of the two merging systems .
Each core also has a wake of low entropy gas indicating that this gas was ram pressure stripped without being strongly shocked .

A1758S is undergoing a more symmetric ( lower impact parameter ) merger between two 5 keV clusters .
The two remnant cores are nearly coincident as seen in projection on the sky .
The two cores are surrounded by hotter gas ( 9–11 keV ) which was probably shock heated during the merger .
Based on the pressure jumps preceding the two cores , they must have a relative velocity of less than 1,400 km s ^ { -1 } .
Unlike A1758N , there is no evidence for wakes of low entropy gas .