2004MNRAS.347..556Z

We present a statistical analysis of halo emission for a sample of 1047 edge-on disc galaxies imaged in five bands by the Sloan Digital Sky Survey (SDSS). Stacking the homogeneously rescaled images of the galaxies, we can measure surface brightnesses as deep as µ_r∼ 31 mag/arcsec2 . The results strongly support the almost ubiquitous presence of stellar haloes around disc galaxies, whose spatial distribution is well described by a power law ρ∝r ^–3, in a moderately flattened spheroid (c/a ∼ 0.6). The colour estimates in g -r and r -i, although uncertain, give a clear indication for extremely red stellar populations, hinting at old ages and/or non-negligible metal enrichment. These results support the idea of haloes being assembled via early merging of satellite galaxies.