We present a statistical analysis of the photometric properties and spatial distribution of more than 2,800 MgII absorbers with 0.37 < z < 1 and rest equivalent width W _ { 0 } ( \lambda 2796 ) > 0.8 Å detected in SDSS quasar spectra .
Using an improved image stacking technique , we measure the cross-correlation between MgII gas and light ( in the g , r , i and z -bands ) from 10 to 200 kpc and infer the light-weighted impact parameter distribution of MgII absorbers .
Such a quantity is well described by a power-law with an index that strongly depends on absorption rest equivalent width W _ { 0 } , ranging from \sim - 1 for W _ { 0 } \lesssim 1 Å to \sim - 2 for W _ { 0 } \gtrsim 1.5 Å .

At redshift 0.37 < z _ { abs } \leq 0.55 , we find the average luminosity enclosed within 100 kpc around MgII absorbers to be M _ { g } = -20.65 \pm 0.11 mag , which is \sim 0.5 ~ { } L _ { g } ^ { \star } .
The global luminosity-weighted colors are typical of present-day intermediate type galaxies .
We then investigate these colors as a function of MgII rest equivalent width and find that they follow the track between spiral and elliptical galaxies in color space : while the light of weaker absorbers originates mostly from red passive galaxies , stronger systems display the colors of blue star-forming galaxies .
Based on these observations , we argue that the origin of strong MgII absorber systems might be better explained by models of metal-enriched gas outflows from star-forming/bursting galaxies .

Our analysis does not show any redshift dependence for both impact parameter and rest-frame colors up to z = 1 .
However , we do observe a brightening of the absorbers related light at high redshift ( \sim 50 \% from z _ { abs } \sim 0.4 to 1 ) .
We argue that MgII absorbers are a phenomenon typical of a given evolutionary phase that more massive galaxies experience earlier than less massive ones , in a downsizing fashion .

This analysis provides us with robust and quantitative constraints of interest for further modeling of the gas distribution around galaxies .
As a side product we also show that the stacking technique allows us to detect the light of quasar hosts and their environment .