We present line-of-sight gas sloshing first found in a cool core in a galaxy cluster .
The galaxy cluster Abell 907 is identified as a relaxed cluster owing to its global X-ray surface brightness taken by the Chandra X-ray Observatory .
The X-ray residual image after removing the global emission of the intracluster medium ( ICM ) , however , shows an arc-like positive excess and a negative excess surrounding the central positive excess in the cluster core , which in turn indicates a disturbance of the ICM .
We analyze the X-ray spectra extracted from both regions and find that ( 1 ) the ICM temperature and the metal abundance in the positive excess are lower and higher than those in the negative excess , respectively , and ( 2 ) the ICM is nearly in pressure equilibrium .
We also find a slight redshift difference between the positive and the negative excesses , which corresponds to the velocity shear of 1680 ^ { +1300 } _ { -920 } km s ^ { -1 } ( 1 \sigma ) .
The X-ray residual image and the ICM properties are consistent with those expected by line-of-sight gas sloshing .
Assuming that the gas is moving toward inverse-parallel to each other along the line-of-sight , the shear velocity is expected to be \sim 800 km s ^ { -1 } .
The velocity field of this level is able to provide non-thermal pressure support by \sim 34 \% relative to the thermal one .
The total kinetic energy inferred from the shear velocity corresponds to \sim 30 % of the bolometric luminosity of the sloshing ICM .
Abell 907 is therefore complementary to galaxy clusters in which gas sloshing takes place in the plane of the sky , and is important for understanding gas dynamics driven by sloshing and its influence on the heating to prevent runaway cooling .