Matter Distribution around Galaxies

TL;DR

This paper investigates the extended matter distribution around galaxies using gravitational lensing and simulations, revealing that galaxy halos lack sharp edges and extend beyond the virial radius, affecting cosmological mass estimates.

Contribution

It introduces a method combining weak lensing observations with N-body simulations to better characterize galaxy matter profiles beyond the virial radius.

Findings

Galaxies have no clear boundary in their matter distribution.

Matter extends beyond the virial radius with a density profile ~ r^{-2.4}.

The extended matter accounts for the observed mass density gap and cosmological parameters.

Abstract

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.