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A New Definition for the Ca4227 Feature: Is Calcium Really Underabundant in Early-type Galaxies?

L. C. Prochaska·James A. Rose·Ricardo P. Schiavon
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Abstract

We have investigated the abundance of calcium in early-type galaxies by measuring the strength of the Ca I 4227 absorption line in their integrated spectra. The database used is the large sample of early-type galaxy integrated spectra in Caldwell, Rose, & Concannon (2003). We have measured Ca abundances from the Ca I 4227 feature both by using the Lick Ca4227 index and also by defining a new index, Ca4227_r, that avoids the CN4216 molecular band in the continuum on the blueward side of the line. With the new index definition we measure Ca abundances that are systematically ~0.3 dex higher than with the Lick Ca4227 index. The result is that with the new index definition we obtain higher [Ca/Fe] abundances in early-type galaxies which are more consistent with their well known [Mg/Fe] over-abundances. Hence, we suggest that Ca might be slightly enhanced, relative to Fe, in early-type galaxies.

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L. C. Prochaska, James A. Rose, Ricardo P. Schiavon. 2005-09-26. A New Definition for the Ca4227 Feature: Is Calcium Really Underabundant in Early-type Galaxies?. https://doi.org/10.1086/497642

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