We present a survey , using the Chandra X-ray observatory , of the central gravitating mass profiles in a sample of 10 galaxies , groups and clusters , spanning \sim 2 orders of magnitude in virial mass .
We find the total mass distributions from \sim 0.2–10 { R _ { e } } , where { R _ { e } } is the optical effective radius of the central galaxy , are remarkably similar to powerlaw density profiles .
The negative logarithmic slope of the mass density profiles , \alpha , systematically varies with { R _ { e } } , from \alpha \simeq 2 , for systems with { R _ { e } } \sim 4 kpc to \alpha \simeq 1.2 for systems with { R _ { e } } \mathrel { \hbox to 0.0 pt { \lower 3.0 pt \hbox { $ \sim$ } \hss } \raise 2.0 pt \hbox { $ > $ } } 30 kpc .
Departures from hydrostatic equilibrium are likely to be small and can not easily explain this trend .
We show that the conspiracy between the baryonic ( Sersic ) and dark matter ( NFW/ Einasto ) components required to maintain a powerlaw total mass distribution naturally predicts an anti-correlation between \alpha and { R _ { e } } that is very close to what is observed .
The systematic variation of \alpha with { R _ { e } } implies a dark matter fraction within { R _ { e } } that varies systematically with the properties of the galaxy in such a manner as to reproduce , without fine tuning , the observed tilt of the fundamental plane .
We speculate that establishing a nearly powerlaw total mass distribution is therefore a fundamental feature of galaxy formation and the primary factor which determines the tilt of the fundamental plane .