| The diffuse Circumgalactic Medium (CGM) can be observed in absorption using gravitational arcs as background sources. In this talk, I will show the second integral field spectroscopic observation using MUSE/VLT of a galactic-scale arc (Einstein radius ~ 3’’) that probes the cool gas (T ~ 10^4 K) at a projected distance of < 30 kpc from the lensing early-type galaxy (log M_h ~ 13). This setup enables spatial mapping of Mg II λλ2796, 2803 equivalent widths, and kinematics at 20 spatially independent positions. However, since this galaxy is part of a galaxy group at z ~ 0.9, knowing the origin of this gas becomes tricky. Along with semi-analytical models, I will demonstrate how the tomographic data suggest that the origin of this gas is likely not the CGM surrounding this early-type galaxy. |
