2019/07/31 by N. Vale Asari, Guilherme S. Couto, G. S. Couto +9
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Dig #Emission spectrum #Galaxies: Formation, Evolution, Phenomena #Galaxy #H-alpha #Line (geometry) #Luminous infrared galaxy #Metallicity #Physics #Sky #Spectral line #Star formation #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stz2470
Accepted for publication in MNRAS
openalex created_date 2019/07/30 · arxiv created 2019/09/02 · openalex publication_date 2019/09/04 · arxiv updated 2019/10/02 · openalex updated_date 2026/08/06
ABSTRACT We investigate the impact of the diffuse ionized gas (DIG) on abundance determinations in star-forming (SF) galaxies. The DIG is characterized using the H α equivalent width (WH α). From a set of 1 409 SF galaxies from the Mapping Nearby Galaxies at APO (MaNGA) survey, we calculate the fractional contribution of the DIG to several emission lines using high-S/N data from SF spaxels (instead of using noisy emission-lines in DIG-dominated spaxels). Our method is applicable to spectra with observed WH α ≳ 10 Å (which are not dominated by DIG emission). Since the DIG contribution depends on galactocentric distance, we provide DIG-correction formulae for both entire galaxies and single aperture spectra. Applying those to a sample of \gt 90 000 SF galaxies from the Sloan Digital Sky Survey, we find the following. (1) The effect of the DIG on strong-line abundances depends on the index used. It is negligible for the ([O iii]/H β)/([N ii]/H α) index, but reaches ∼0.1 dex at the high-metallicity end for [N ii]/H α. (2) This result is based on the ∼kpc MaNGA resolution, so the real effect of the DIG is likely greater. (3) We revisit the mass–metallicity–star formation rate (SFR) relation by correcting for the DIG contribution in both abundances and SFR. The effect of DIG removal is more prominent at higher stellar masses. Using the [N ii]/Hα index, O/H increases with SFR at high stellar mass, contrary to previous claims.