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Title:
Is the Na D Absorption Line Useful For Integrated Light Stellar Population Studies In Galaxies?
Authors:
Bergmann, Marcel; Milvang-Jensen, B.
Affiliation:
AA(Unaffiliated), AB(Royal Library & Dark Cosmology Center, University of Copenhagen, Denmark)
Publication:
American Astronomical Society, AAS Meeting #213, #444.11; Bulletin of the American Astronomical Society, Vol. 41, p.327
Publication Date:
01/2009
Origin:
AAS
Bibliographic Code:
2009AAS...21344411B

Abstract

The Sodium Na D absorption line at 5895 Angstroms is one of the strongest absorption features in stellar photospheres, but has been rarely used in integrated light stellar population studies of galaxies. A principal reason why it has not been used is the suspicion that interstellar absorption within the galaxies may enhance or alter the absorption profile of the combined stellar light, thus giving an errant description of the stellar population. As a project undertaken during the National Virtual Observatory Summer School, we have investigated to what extent ISM absorption seems to alter the measurements. We use VO tools to create multiple galaxy samples: a sample expected to have little ISM (cluster galaxies, which are mainly ellipticals), and two samples with higher expected levels of ISM (HI-detected galaxies and morphologically late-type galaxies). After culling the samples to match the same distribution of (older) ages and (higher) metallicities, we find that the Na D vs. velocity dispersion correlation is not significantly different for the samples with and without ISM, and all have similar levels of scatter. Consequently, the Na D line seems like a promising tool for evolutionary studies comparing high and low redshift galaxy samples. Our continuing work focuses on the effects of possible ISM absorption on the line-of-sight velocity profile as derived from the Na D line compared to Mgb and Ca H & K absorption features.

This research has made use of data obtained from and software provided by the US National Virtual Observatory, which is sponsored by the National Science Foundation. We thank the US-VO and the NSF for the partial funding they provided to attend this meeting.

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