The Ratio of α-Elements to Iron in Early-Type Galaxies from T[CLC]i[/CLC]O and M[CLC]g[/CLC][TINF]2[/TINF]

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Abstract
In order to derive the ratio of α-elements to iron in galaxies, we have observed the strongest TiO band heads of the γ and γ' systems at 7000–7500 Å in a sample of a dozen early-type galaxies. The equivalent widths of the TiO bands are compared with synthetic spectra for single-aged stellar populations and composite galaxy models, all computed with [α/Fe] = 0.0 and +0.3. The same method is also applied to the Fe and Mg2 Lick indices for the sample galaxies. The results obtained are [Ti/Fe] ≈ [Mg/Fe] ≈ +0.3, indicating a clear enhancement of the α-elements–to–iron ratio for our sample of early-type galaxies.