2026A&A...706A.288P

We consider the oxygen abundance distributions for a sample of massive (log(M_★/M_⊙) ≳ 10) spiral galaxies from the Mapping Nearby Galaxies at the Apache Point Observatory (MaNGA) survey in which the radial abundance gradient flattens to a constant value outside of the outer break radius, R_b, outer_. The outer break radius can be considered as a dividing radius between the galaxy and the circumgalactic medium (CGM). The values of the R_b, outer_ range from ∼0.8 R₂₅ to ∼1.45 R₂₅, where R₂₅ is the optical (isophotal) radius of the galaxy. The oxygen abundances in the CGM range from 12+log(O/H) ∼8.0 to ∼8.5. The oxygen abundance distribution in each of our galaxies also shows the inner break in the radial abundance profile at the radius R_b, inner_. The metallicity gradient in the outer part of the galaxy (R_b, inner_ < R < R_b, outer_) is steeper than in the inner part (R < R_b, inner_). The behaviour of the radial abundance distributions in these galaxies can be explained by assuming an interaction with (capture of the gas from) a small companion and adopting the model for the chemical evolution of galaxies with a radial gas flow. The interaction with a companion results in the mixing of gas and a flat metallicity gradient in the CGM. The capture of the gas from a companion increases the radial gas inflow rate and changes the slope of the radial abundance gradient in the outer part of the galaxy.