H-delta in the Integrated Light of Galaxies: What Are We Actually Measuring?

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dc.creatorProchaska, L. C.
dc.creatorRose, J. A.
dc.creatorCaldwell, N.
dc.creatorCastilho, B. V.
dc.creatorConcannon, K.
dc.creatorHarding, P.
dc.creatorMorrison, H.
dc.creatorSchiavon, R. P.
dc.date2007-02-21
dc.date.accessioned2026-07-07T11:21:12Z
dc.date.available2026-07-07T11:21:12Z
dc.descriptionWe present a cautionary study exploring the reliability of the H-delta line in the integrated spectra of galaxies for determining galaxy ages. Our database consists of the observed integrated spectra of ~120 early-type galaxies, of 7 metal-rich globular clusters in M31 and the Galactic globular cluster 47 Tuc, and of the open cluster M67. We have measured H-delta using index definitions designed to assess contamination from the CN molecule in and around H-delta by choosing combinations of bandpasses that both avoid and include a region of CN molecular lines redward of H-delta. We find systematic differences in the ages derived from H-delta measurements among the various definitions when extracting ages from H-delta in old stellar populations with enhanced CN bands due to non-solar abundance ratios. We propose that neighboring CN lines have a strong effect on pseudocontinuum and central bandpass levels. For stellar populations which have non-solar abundance ratios in C and/or N, population synthesis models that do not account for abundance ratio variations cannot reproduce accurately the CN 4216 Åband, which leads to a corresponding inaccuracy in reproducing the various H-delta indices. Hence, caution must be used when extracting galaxy ages from the H-delta line in old stellar populations with significant non-solar abundance ratios.
dc.description8 figures, 2 tables
dc.identifierhttps://arxiv.org/abs/astro-ph/0702589
dc.identifierhttp://arxiv.org/abs/astro-ph/0702589
dc.identifierAstron.J.134:321-333,2007
dc.identifierdoi:10.1086/516754
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/194197
dc.subjectAstrophysics
dc.titleH-delta in the Integrated Light of Galaxies: What Are We Actually Measuring?
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