Iron hydride in stellar atmospheres

Calculations are presented of the FeH column density in late-type stellar atmospheres. The predicted column densities are consistent with the FeH identification of the Wing–Ford band (9900 Å) observed in spectra of M dwarfs and sunspots. The calculations indicate a strong gravity dependence in the FeH band strength, which is also in accord with observations. Of importance for galaxy population synthesis is the predicted weak dependence of FeH band strength on metal abundance. The blue and green systems of FeH are discussed.