Matter Distribution around Galaxies
  We explore the mass distribution of material associated with galaxies from
the observation of gravitational weak lensing for the galaxy mass correlation
function with the aid of $N$-body simulations of dark matter. The latter is
employed to unfold various contributions that contribute to the integrated line
of sight mass density. We conclude that galaxies have no definite edges of the
matter distribution, extending to the middle to neighbouring galaxies with the
density profile roughly $r^{-2.4}$ beyond the virial radius. The mass
distributed beyond the virial radius (gravitationally bound radius) explains
the gap seen in the mass density estimates, the global value $\Omega_m\sim
0.27$ and typically $\Omega_{\rm gal} \sim 0.15$ from the luminosity density
multiplied by the mass to light ratio. We suggest to use a physical method of
gravitational lensing to characterise galaxy samples rather than characterise
them with photometric means.
