Metal line emission around z<1 galaxies

TL;DR

This study investigates the extended metal line emission around galaxies at z<1, revealing how emission properties vary with distance, redshift, and stellar mass, and providing insights into the gas conditions and metallicity distribution.

Contribution

First characterization of extended [OII], [OIII], and Hbeta emission around a large galaxy sample at z<1 using MUSE data, revealing spatial and physical gas properties.

Findings

[OII] emission extends up to ~40 kpc, [OIII] and Hbeta up to ~30 kpc.

Line emission at 20-30 kpc likely originates from the disk-halo interface.

[OII] surface brightness increases with redshift and stellar mass, driven by star formation and gas conditions.

Abstract

We characterize, for the first time, the average extended emission in multiple lines ([OII], [OIII], and Hbeta) around a statistical sample of 560 galaxies at z~0.25-0.85. By stacking the Multi Unit Spectroscopic Explorer (MUSE) 3D data from two large surveys, the MUSE Analysis of Gas around Galaxies (MAGG) and the MUSE Ultra Deep Field (MUDF), we detect significant [OII] emission out to ~40 kpc, while [OIII] and Hbeta emission is detected out to ~30 kpc. Via comparisons with the nearby average stellar continuum emission, we find that the line emission at 20-30 kpc likely arises from the disk-halo interface. Combining our results with that of our previous study at z~1, we find that the average [OII] surface brightness increases independently with redshift over z~0.4-1.3 and with stellar mass over M* ~10^{6-12} Msun, which is likely driven by the star formation rate as well as the physical conditions of the gas. By comparing the observed line fluxes with photoionization models, we find that the ionization parameter declines with distance, going from log q (cm/s) ~7.7 at <=5 kpc to ~7.3 at 20-30 kpc, which reflects a weaker radiation field in the outer regions of galaxies. The gas-phase metallicity shows no significant variation over 30 kpc, with a metallicity gradient of ~0.003 dex/kpc, which indicates an efficient mixing of metals on these scales. Alternatively, there could be a significant contribution from shocks and diffuse ionized gas to the line emission in the outer regions.