2024ApJ...969...54W

The luminosities (L) and velocity dispersions (σ) of the extinction-corrected Balmer emission lines of giant H II regions in nearby galaxies exhibit a tight correlation (∼0.35 dex scatter). There are few constraints, however, on whether giant H II regions at significant look-back times follow an L-σ relation, given the angular resolution and sensitivity required to study them individually. We measure the luminosities and velocity dispersions of Hα and Hβ emission from 11 H II regions in Sp1149, a spiral galaxy at redshift (z) z = 1.49 multiply imaged by the MACS J1149 galaxy cluster. Sp1149 is also the host galaxy of the first-known strongly lensed supernova with resolved images, SN Refsdal. We employ archival Keck I OSIRIS observations, and newly acquired Keck I MOSFIRE and Large Binocular Telescope LUCI long-slit spectra of Sp1149. When we use the GLAFIC simply parameterized lens model, we find that the Hα luminosities of the H II regions at z = 1.49 are a factor of ${6.4}_{-2.0}^{+2.9}$ brighter than predicted by the low-redshift L-σ relation we measure from Very Large Telescope MUSE spectroscopy. If the lens model is accurate, then the H II regions in Sp1149 differ from their low-redshift counterparts. We identify an H II region in Sp1149 that is dramatically brighter (by 2.03 ± 0.44 dex) than our low-redshift L-σ relation predicts given its low velocity dispersion. Finally, the H II regions in Sp1149 are consistent, perhaps surprisingly, with the z ≈ 0 star-forming locus on the Baldwin-Phillips-Terlevich diagram.