Small-scale chemical abundance analysis in a blue compact dwarf galaxy SBS 1415+437

Abstract

We use integral field spectroscopic (IFS) observations from Gemini Multi-Object Spectrograph-North (GMOS-N) to analyse the ionized gas in the principal star-forming region in the blue compact dwarf galaxy SBS 1415+437. The IFS data enable us to map the weak auroral line [O iii] λ4363 at a spatial scale of ∼6.5 pc across a region of ∼143 × 143 pc2. This in turn allows us to use the robust direct Te-method to map the ionic and elemental abundances of nitrogen (N) along with the alpha-elements, oxygen (O), neon (Ne), sulphur (S), and argon (Ar). We utilize these abundances to map the relative abundances of N, Ne, S, and Ar with respect to O. We segment this pre-dominantly photoionized region of study into elliptical annuli on the basis of the H α flux distribution to study the variation of chemical abundances and their ratios, and find no significant chemical variation. We also perform chemical abundance analysis on the integrated spectra of the region under study and elliptical annuli within it. We find that the inferred abundances are in agreement with the median of the abundances obtained from the chemical abundance maps of the principal star-forming region and the mapped values within annuli. The finding has important implications for direct comparison with high-redshift observations, where spatial resolution is not available, and for a consistent approach to track chemical evolution across cosmic time.