Probing coherence in metal absorption towards multiple images of strong gravitationally lensed quasars

We present a tomographic analysis of metal absorption lines arising from the circumgalactic medium (CGM) of galaxies at z approximate to 0.5-2, using Multi Unit Spectroscopic Explorer (MUSE) observations of two background quasars at z approximate to 2.2 and 2.8, which are two of the few currently known quasars with multiple images due to strong gravitational lensing by galaxy clusters at z approximate to 0.6 and 0.5, respectively. The angular separations between different pairs of quasar multiple images enable us to probe the absorption over transverse physical separations of approximate to 0.4-150 kpc, which are based on strong lensing models exploiting MUSE observations. The fractional difference in rest-frame equivalent width (Delta W-r) of Mg II, Fe II, and C IV absorption increases on average with physical separation, indicating that the metal-enriched gaseous structures become less coherent with distance, with a likely coherence length-scale of approximate to 10 kpc. However, Delta W-r for all the ions vary considerably over approximate to 0.08-0.9, indicating a clumpy CGM over the full range of length-scales probed. At the same time, paired Mg II absorption is detected across approximate to 100-150 kpc at similar line-of-sight velocities, which could be probing cool gas clouds within the same halo. No significant dependence of Delta W-r is found on the equivalent width and redshift of the absorbing gas and on the galaxy environment associated with the absorption. The high-ionization gas phase traced by C IV shows a higher degree of coherence than the low-ionization gas phase traced by Mg II, with approximate to 90 per cent of C IV systems exhibiting Delta W-r <= 0.5 at separations <= 10 kpc compared to approximate to 50 per cent of Mg II systems.