The 1/2 BPS ’t Hooft loops in N=4 SYM as instantons in 2D Yang–Mills

We extend the recent conjecture on the relation between a certain 1/8 BPS subsector of 4D SYM on S2 and 2D Yang–Mills theory by turning on circular 1/2 BPS 't Hooft operators linked with S2. We show that localization predicts that these 't Hooft operators and their correlation functions with Wilson operators on S2 are captured by instanton contributions to the partition function of the 2D Yang–Mills theory. Based on this prediction, we compute explicitly correlation functions involving the 't Hooft operator, and observe precise agreement with S-duality predictions.