  Using ASCA data, we have measured the electron temperature in A2163 out to
1.5h^{-1} Mpc (10a_x) from the center, in three radial bins. The temperatures
are 12.2+1.9-1.2 keV, 11.5+2.7-2.9 keV and 3.8+1.1-0.9 keV (90%) in the 0-3 a_x
(0-3.5'), 3-6 a_x and 6-13 a_x spherical shells, respectively. Applying the
hydrostatic equilibrium and spherical symmetry assumptions and using these data
together with the Ginga spectral and the Rosat imaging data, we were able to
severely limit the possible binding mass distribution of the generic form
rho=rho_0 (1+r^2/a_b^2)^{-n/2}. All the allowed binding mass profiles are
steeper than the gas density profiles and mass profiles with the same slope as
gas are excluded at a greater than 99% confidence. The total mass inside
0.5h^{-1} Mpc is 4.3+-0.5 10^14 h^{-1} Msun, of which 0.074 h^{-3/2} is gas
while inside 1.5h^{-1} Mpc the mass is 1.07+-0.13 10^15 h^{-1} Msun.
  We note that in the cluster outer part, the timescale for electron-ion
temperature equlibration is comparable to the merger timescale, so the measured
electron temperature may give an underestimate of the gas pressure there.
Otherwise, if our low temperature is indeed representative of the gas
temperature in the outer shell, the cluster atmosphere should be convectionally
unstable and gas turbulence should exist. Bulk motions of the gas are also
expected during the merger. Their existense would increase the total gas
pressure above that indicated by the observed temperature. Thus, failure of the
"gas follows dark matter" model, favored by hydrodynamic simulations, may be
due to the neglect of these phenomena, leading to an underestimate of the total
density at large radii.
