EIGER IV. The Cool 104 K Circumgalactic Environment of High-redshift Galaxies Reveals Remarkably Efficient Intergalactic Medium Enrichment

Abstract We report new observations of the cool diffuse gas around 29, 2.3 7.1 ≤ log M ∗ / M ⊙ ≤ 10.7 , and star formation rates (SFRs) of − 0.1 log SFR/ M ⊙ yr −1 log M ∗ / M ⊙ > 9. The Mg ii absorption kinematics are shifted from the systemic redshifts of host galaxies with a median absolute velocity ≈ 135 km s −1 and standard deviation ≈ 85 km s −1 . The high kinematic offset and large radial separation ( R > 1.3 R 200 ), suggest that five out of the seven Mg ii absorption systems are not gravitationally bound to their host galaxy. In contrast, most of the cool circumgalactic medium at z 4.