Radial Distribution of Star Formation and Gas-phase Metallicity in Spiral-Elliptical Galaxy Pairs

TL;DR

This study uses integral field spectroscopy to analyze how star formation and metallicity vary radially in spiral galaxies within spiral-elliptical pairs, revealing suppression and enhancement patterns linked to interactions and companion mass.

Contribution

It provides new insights into how galaxy interactions influence star formation and metallicity distributions, highlighting the role of companion mass and gas velocity field symmetry.

Findings

Spirals in S+E pairs show suppressed central star formation and higher metallicities.

The degree of suppression and enrichment depends on the mass of the elliptical companion.

Galaxies with asymmetric gas velocity fields exhibit enhanced SFR and metallicity.

Abstract

Using integral field spectroscopy from SDSS-IV MaNGA, we investigate the radial distributions of star formation rate (SFR) and gas-phase metallicity in spiral galaxies that reside in spiral-elliptical (S+E) pairs. Spirals in S+E pairs show suppressed central star formation and elevated metallicities, whereas spirals in spiral-spiral pairs exhibit centrally enhanced star formation and reduced metallicities. The degree of SFR suppression and metallicity enhancement in S+E pairs depends on the masses of the pair members. Spirals with more massive elliptical companions experience stronger star-formation suppression and larger increases in metallicity, while lower-mass spirals show more pronounced metallicity enhancement. In addition, within S+E systems, galaxies with asymmetric gas velocity fields display enhanced SFR and higher metallicities, whereas those with symmetric velocity fields exhibit clear central suppression. Based on these results, we infer that in S+E pairs, the spiral galaxy experiences suppressed gas accretion once it enters the hot circumgalactic medium of its early-type companion, which leads to the observed decline in star-formation activity. When a close encounter takes place, tidal perturbations can compress the remaining cold gas and trigger enhanced star formation, producing rapid chemical enrichment and the associated increase in metallicity.