MUSE Analysis of Gas around Galaxies (MAGG) -- II: Metal-enriched halo gas around z~1 galaxies

TL;DR

This study investigates metal-enriched halo gas around z~1 galaxies using MgII absorption, finding that galaxy environment and properties significantly influence halo gas characteristics with no strong evolution over time.

Contribution

It provides new insights into how galaxy environment and interactions affect metal-enriched halo gas at z~1, highlighting the role of multiple galaxy associations.

Findings

Majority of MgII systems linked to multiple galaxies.

Enhanced MgII absorption in group environments compared to isolated galaxies.

No significant evolution in MgII absorption properties from lower to z~1.

Abstract

We present a study of the metal-enriched cool halo gas traced by MgII absorption around 228 galaxies at z~0.8-1.5 within 28 quasar fields from the MUSE Analysis of Gas around Galaxies (MAGG) survey. We observe no significant evolution in the MgII equivalent width versus impact parameter relation and in the MgII covering fraction compared to surveys at z<~0.5. The stellar mass, along with distance from galaxy centre, appears to be the dominant factor influencing the MgII absorption around galaxies. With a sample that is 90% complete down to a star formation rate of ~0.1 Msun/yr and up to impact parameters ~250-350 kpc from quasars, we find that the majority (67^{+12}_{-15}% or 14/21) of the MgII absorption systems are associated with more than one galaxy. The complex distribution of metals in these richer environments adds substantial scatter to previously-reported correlations. Multiple galaxy associations show on average five times stronger absorption and three times higher covering fraction within twice the virial radius than isolated galaxies. The dependence of MgII absorption on galaxy properties disfavours the scenario in which a widespread intra-group medium dominates the observed absorption. This leaves instead gravitational interactions among group members or hydrodynamic interactions of the galaxy haloes with the intra-group medium as favoured mechanisms to explain the observed enhancement in the MgII absorption strength and cross section in rich environments.