Spatially Resolved Metal Gas Clouds

TL;DR

This study uses 3D spectroscopy to analyze metal gas clouds in the circumgalactic medium of a z~1 galaxy, revealing efficient metal mixing on kiloparsec scales and demonstrating a new method for mapping these clouds.

Contribution

It presents the first spatially resolved absorption study of metal clouds in the CGM using IFU observations, revealing small variations in absorption over 8 kpc scales.

Findings

Small (<30%) variation in FeII and MgII absorption over 8 kpc

Stronger variation in absorption over 25 kpc

Estimated cloud gas mass less than 2x10^9 solar masses

Abstract

We now have mounting evidences that the circumgalactic medium (CGM) of galaxies is polluted with metals processed through stars. The fate of these metals is however still an open question and several findings indicate that they remain poorly mixed. A powerful tool to study the low-density gas of the CGM is offered by absorption lines in quasar spectra, although the information retrieved is limited to 1D along the sightline. We report the serendipitous discovery of two close-by bright z_gal=1.148 extended galaxies with a fortuitous intervening z_abs=1.067 foreground absorber. MUSE IFU observations spatially probes kpc-scales in absorption in the plane of the sky over a total area spanning ~30 kpc^-2. We identify two OII emitters at z_abs down to 21 kpc with SFR~2 M_sun/yr. We measure small fractional variations (<30%) in the equivalent widths of FeII and MgII cold gas absorbers on coherence scales of 8kpc but stronger variation on larger scales (25kpc). We compute the corresponding cloud gas mass <2x10^9M_sun. Our results indicate a good efficiency of the metal mixing on kpc-scales in the CGM of a typical z~1 galaxy. This study show-cases new prospects for mapping the distribution and sizes of metal clouds observed in absorption against extended background sources with 3D spectroscopy.