Oxygen and nitrogen abundances in cold H II regions from Sloan Digital Sky Survey

Abstract

Oxygen and nitrogen abundances for a selection of 113607 cold objects from the Sloan Digital Sky Survey (SDSS) spectra are derived. Values of oxygen abundances 12 + log(O/H) are obtained using three parametric N calibrations, one of which is constructed in this work. Values of nitrogen abundances 12 + log(N/H) are found with two N calibrations. The values of oxygen abundances that are derived using three parametric N calibrations are consistent within 0.05 dex for the vast majority of the objects. It is not improbable that there are systematic differences between the values of oxygen abundances which do not exceed 0.05 dex. The differences between the values of nitrogen abundances which are obtained using ON and NS calibrations reach 0.1 dex. We show that the vast majority of cold SDSS objects are in the same area of the diagram O/H—N/O as cold H2 regions of nearby galaxies, for which the oxygen and nitrogen abundances are derived through the Te-method. This is indirect evidence that the values of oxygen and nitrogen abundances that are found with parametric N calibrations are reliable.