AAS 207th Meeting, 8-12 January 2006
Session 148 Local Benchmarks of Galaxy Evolution
Oral, Wednesday, 10:00-11:30am, January 11, 2006, Delaware B

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[148.02] Hdelta in the Integrated Light of Galaxies: What are we Actually Measuring?

L. C. Prochaska, J. A. Rose (U.N.C.), R. P. Schiavon (U.VA.)

We have explored the effect of non-solar abundance ratios on age determinations of galaxies from integrated light observations of the Hdelta line. We have measured Hdelta using index definitions designed to assess contamination from the CN molecule in and around Hdelta by choosing combinations of bandpasses that both avoid and include a region of CN molecular lines redward of Hdelta. We find systematic differences in the ages derived from Hdelta measurements among the various definitions when extracting ages from Hdelta in old stellar populations. We propose that neighboring CN lines have a strong effect on continuum and central bandpass levels. We suggest using caution when extracting galaxy ages from the Hdelta line in the case of old stellar populations with significant non-solar abundance ratios. This study was funded by NSF grant AST-04-06443 to the University of North Carolina and by Hubble Space Telescope Treasury Program grant GO-09455.05-A to the University of Virginia.

The author(s) of this abstract have provided an email address for comments about the abstract: chaska@physics.unc.edu

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