The N/O-O/H relation across large-scale environments

Abstract

The large-scale structure (LSS) of the Universe shapes galaxy evolution through its intricate web-like morphology, yet its specific influence on gas-phase chemical abundances remains uncertain. Particularly, a homogeneous comparison of the N/O$-$O/H relation, a tracer of the mass assembly and baryonic cycle, across distinct LSS environments has been lacking. In this study, we analyse a local SDSS galaxy sample curated within the framework of the CAVITY project -- dedicated to studying void galaxies -- in which galaxies are classified by their LSS environment into three groups: clusters, voids, and non-cluster/non-void (NCNV). We extract spectroscopic emission line fluxes from the central SDSS spectra and analyse how different galaxy properties affect the scatter in the N/O$-$O/H relation. For that, we subtract the main N/O$-$O/H relation from the data and study the dependence of the resulting residuals (${\xi }_{\text{N/O}}$) on a set of parameters, including stellar mass ($M_{\star }$), $g-r$ colour, and star formation rate (SFR). We find that $M_{\star }-$related variables are the best predictors of the scatter in the N/O$-$O/H relation, with little influence of the recent star formation history. Regarding the LSS comparison, no significant differences are found for void and NCNV galaxies. Cluster galaxies, however, present a N/O$-$O/H relation systematically lower (with ${\xi }_{\text{N/O}}\sim -0.02$). Consistent with this shift and with $M_{\star }$ as a good predictor of N/O$-$O/H deviations, we find that environmental dependences are also reflected in fundamental scaling relations: both the MZR and N/O$-M_{\star }$ relations are different for cluster galaxies. These combined results point to mechanisms in the dense intracluster medium (such as strangulation or re-accretion of metal-enriched gas) as the primary drivers of these chemical offsets for galaxies in cluster environments.

arXiv commentAccepted for publication in A&A. 17 pages, 11 figures