  We present a study of the metal-enriched halo gas, traced using MgII and
[OII] emission lines, in two large, blind galaxy surveys - the MUSE (Multi Unit
Spectroscopic Explorer) Analysis of Gas around Galaxies (MAGG) and the MUSE
Ultra Deep Field (MUDF). By stacking a sample of ~600 galaxies (stellar masses
M* ~10^{6-12} Msun), we characterize for the first time the average metal line
emission from a general population of galaxy haloes at 0.7 <= z <= 1.5. The
MgII and [OII] line emission extends farther out than the stellar continuum
emission, on average out to ~25 kpc and ~45 kpc, respectively, at a surface
brightness (SB) level of 10^{-20} erg/s/cm2/arcsec2. The radial profile of the
MgII SB is shallower than that of the [OII], suggesting that the resonant MgII
emission is affected by dust and radiative transfer effects. The [OII] to MgII
SB ratio is ~3 over ~20-40 kpc, also indicating a significant in situ origin of
the extended metal emission. The average SB profiles are intrinsically brighter
by a factor ~2-3 and more radially extended by a factor of ~1.3 at 1.0 < z <=
1.5 than at 0.7 <= z <= 1.0. The average extent of the metal emission also
increases independently with increasing stellar mass and in overdense group
environments. When considering individual detections, we find extended [OII]
emission up to ~50 kpc around ~30-40 percent of the group galaxies, and
extended (~30-40 kpc) MgII emission around two z~1 quasars in groups, which
could arise from outflows or environmental processes.
