NOAO >   Observing Info >   Approved Programs >   2017B-0268

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Program Information for 2017B-0268


PI: Chun Ly, U. of Arizona, chunly@email.arizona.edu
Address: Department of Astronomy and Steward Observatory, 933 NORTH CHERRY AVENUE, TUCSON, AZ 85721-0065 USA

CoI: Matthew A Malkan, UCLA

Title: Recalibrating Strong-line Metallicity Diagnostics for z > 1 Chemical Enrichment Studies, with T_e-based Metallicities from MACT and DEEP2

Abstract: The gas-phase metallicity of galaxies---and how it depends on stellar mass and SFR---is a key test of galaxy evolution models with accretion and star-formation ``feedback.'' However, tracing the evolution of the mass--metallicity--SFR relation has been problematic since local "strong-line" metallicity diagnostics are _not_ valid for high-redshift galaxies. To directly solve this problem, electron temperature (T_e) based metallicities at high-z are needed to empirically recalibrate metallicity diagnostics for z>1. This is difficult as it requires [OIII]4363 detections. We have detected [OIII]4363 in ~100 star-forming galaxies at z=0.2-1. However, existing optical spectra lack coverage of H-alpha and [NII]6583 at z>0.5. These emission lines are used in almost _every_ chemical enrichment study. We propose to conduct GNIRS spectroscopy on five z~1 [OIII]4363-detected galaxies, for a total sample of 19 galaxies, to recalibrate metallicity diagnostics using T_e-based metallicities. Our program efficiently uses telescope time by targeting galaxies that already have [OII]-to-[OIII] nebular emission-line measurements. Also, we have found that these galaxies have similar ISM properties as z>2 galaxies. Our measurements will be incorporated within our existing framework for metallicity recalibration, which we find to be more robust than previous calibrations. Given the importance of metallicity diagnostics, our new calibration will be frequently used in chemical enrichment studies.

Program Type: Standard/Extragalactic

Scheduled Nights:
Run 1 (2017B):  GEM-NQ/GNIRS -- 3.8hrs band 3 (GN-2017B-Q-70)


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



NOAO >   Observing Info >   Approved Programs >   2017B-0268

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