2018MNRAS.480.5046R

Projected quasar galaxy pairs provide powerful means to study the circumgalactic medium (CGM) that maintains the relics of galactic feedback and the accreted gas from the intergalactic medium. Here, we study the nature of a Lyman Limit system (LLS) with N(H I) = 10^19.1 ± 0.3^ cm^–2 and a dust-uncorrected metallicity of [Fe/H] = -1.1 ± 0.3 at z = 0.78 towards Q0152 - 020. The Mg II absorption profiles are composed of a main saturated and a few weaker optically thin components. Using MUSE observations, we detect one galaxy close to the absorption redshift at an impact parameter of 54 kpc. This galaxy exhibits nebular emission lines from which we measure a dust-corrected star formation rate of 10⁺⁸_–5 M_☉ yr^–1 and an emission metallicity of [O/H] = -0.1 ± 0.2. By combining the absorption line kinematics with the host galaxy morphokinematics we find that while the main absorption component can originate from a galactic wind at V_w = 110 ± 4 km s^–1 the weaker components cannot. We estimate a mass ejection rate of {dot}M≳0.8 M_☉ yr^–1 that translates to a loading factor of η >= 0.1. Since the local escape velocity of the halo, V_esc ≃ 430 km s^–1, is a few times larger than V_w, we expect this gas will remain bound to the host galaxy. These observations provide additional constraints on the physical properties of winds predicted by galaxy formation models. We also present the VLT/X-Shooter data analysis of four other absorbing systems at 1.1 < z < 1.5 in this sightline with their host galaxies identified in the MUSE data.