The gravitational lensing mass includes dark matter, hot intracluster gas, stars, and any other material in the projected aperture. Most is not stellar: in the literal convention above the stellar fraction is only .
Assume the cluster shares the cosmic cosmic baryon fraction, , and compare the same aperture for all components. Then
Neglecting stars entirely would give . Thus the assumed hot gas dominates the baryonic matter, and the remainder is dark matter. The budget is consistent: stars are about of the inferred baryonic matter, and all components sum to .
For a thermal scale, take gas extent and mean particle mass with for ionized gas. A simple spherical virial theorem estimate with gas binding energy and thermal kinetic energy gives
This is the scale of a very hot, massive X-ray emitting galaxy cluster. The numerical prefactor depends on the radial mass density profile, gas distribution and boundary pressure; for example an isothermal-sphere estimate gives about . Moreover is a projected aperture mass at , whereas the estimate needs a spherical enclosed mass at ; the given data do not determine that conversion. The quoted temperature is therefore an order-of-magnitude estimate, not a uniquely measured value. Nor do the data determine the total gas mass outside the Einstein ring without a profile. The gas budget above pertains to the matched aperture under the cosmic-fraction assumption.