NOAO >   Observing Info >   Approved Programs >   2011A-0163

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Proposal Information for 2011A-0163


PI: Maria A. Pena, Instituto de Astronomia - UNAM, guerrero@astroscu.unam.mx
Address: Interstellar Medium, Apdo. Postal 70-264, Ciudad de Mexico, D.F. 04510, Mexico

CoI: Antonio Peimbert, Instituto de Astronomia - UNAM

Title: Metallicity indicators for metal-poor HII regions and Blue Compact Galaxies

Abstract: To test galactic chemical evolution models, it is important to have accurate abundance ratios as observational constraints. There are two effects that increase the O/H ratio over the usually adopted constraints based on HII regions: (a) The fraction of O trapped in dust grains that increase O/H by about 0.1 dex (Peimbert & Peimbert, 2010); (b) the presence of temperature inhomogeneities that increase the O/H by approximately 0.3 dex. The objective of this proposal is to study the second of these effects. Our main goal is to measure several \ionHe1 lines with high signal to noise in order to determine the helium temperature which is rarely measured. In order to do this we want to observe long slit spectra for a small sample of extragalactic low and very low metallicity \ionH2 regions (most of them dwarf \ionH2 galaxies). From the comparison of such temperature with the oxygen temperature we will obtain the temperature inhomogeneities (t^2) and use them to determine the abundance discrepancy factor for oxygen, and recalibrate the diagram O_23 vs. O/H.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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