Optical Spectroscopy and Nebular Oxygen Abundances of the Spitzer/SINGS Galaxies
Abstract
We present intermediate-resolution optical spectrophotometry of 65 galaxies obtained in support of the Spitzer Infrared Nearby Galaxies Survey (SINGS). For each galaxy we obtain a nuclear, circumnuclear, and semi-integrated optical spectrum designed to coincide spatially with mid- and far-infrared spectroscopy from the Spitzer Space Telescope. We make the reduced, spectrophotometrically calibrated one-dimensional spectra, as well as measurements of the fluxes and equivalent widths of the strong nebular emission lines, publically available. We use optical emission-line ratios measured on all three spatial scales to classify the sample into star-forming, active galactic nuclei (AGNs), and galaxies with a mixture of star formation and nuclear activity. We find that the relative fraction of the sample classified as star forming versus AGN is a strong function of the integrated light enclosed by the spectroscopic aperture. We supplement our observations with a large database of nebular emission-line measurements of individual H II regions in the SINGS galaxies culled from the literature. We use these ancillary data to conduct a detailed analysis of the radial abundance gradients and average H II-region abundances of a large fraction of the sample. We combine these results with our new integrated spectra to estimate the central and characteristic (globally averaged) gas-phase oxygen abundances of all 75 SINGS galaxies. We conclude with an in-depth discussion of the absolute uncertainty in the nebular oxygen abundance scale.
- Publication:
-
The Astrophysical Journal Supplement Series
- Pub Date:
- October 2010
- DOI:
- 10.1088/0067-0049/190/2/233
- arXiv:
- arXiv:1007.4547
- Bibcode:
- 2010ApJS..190..233M
- Keywords:
-
- atlases;
- galaxies: abundances;
- galaxies: fundamental parameters;
- galaxies: ISM;
- galaxies: stellar content;
- techniques: spectroscopic;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- ApJS, in press