A catalog of ringed galaxies in the TNG50 simulation: Analysis of their properties and structure

Aims. We explore galaxies with ringed structures in the TNG50 simulation to study their frequency and the influence of physical processes on their properties and morphologies. Methods. The catalog of ringed galaxies was compiled through visual classification of synthetic images from the TNG50 simulation. Galaxies were selected based on specific criteria: a redshift range of 0.01 < z < 0.1, stellar mass M ⋆ > 10 9 M ⊙ , stellar half-mass radius r 50 > 1 kpc, and a specific star formation rate (sSFR), log(sSFR/yr −1 ) > −13. Our classification allowed for differentiation between inner rings, outer rings, combinations of rings – inner + outer (i+o) –, and partial rings (pseudo-rings), including barred and non-barred ringed galaxies. We constructed a suitable control sample of non-ringed galaxies with similar redshift, stellar mass, and environmental density distributions to those of the ringed ones. The comparison between the galaxies in both samples enabled the analysis of their properties and differences. Finally, we analyzed the surface density of stellar mass (Σ * ( r )) to better understand the distribution and structure of the rings in relation to the properties of their host galaxies. Results. We identified 807 ringed galaxies within the TNG50 simulation. Approximately 59% of these galaxies possess an inner ring, 22% a partial ring, 12% an outer ring, and 7% have i+o rings. Furthermore, our statistical analysis reveals that a notable 64% (507 galaxies) exhibit bars. In terms of physical properties, we find that ringed galaxies exhibit a lower efficiency for star formation activity, reduced gas fractions, redder colors, and higher metallicities with respect to non-ringed disk objects. Moreover, ringed galaxies display greater variability in metallicity for a given stellar mass compared to their non-ringed counterparts, indicating distinct evolutionary processes. From the analysis of radial profiles, we find that galaxies with outer rings exhibit a r 50 similar to or slightly larger than their control group, while those with inner or partial rings tend to have smaller sizes. A deeper exploration of radial density profiles revealed a pronounced central mass deficit preceding the ring structures, with inner and outer rings located approximately at r 50 and 1.5 r 50 , respectively. Galaxies with both i+o rings have inner rings that are more compact and massive. Additionally, galaxies with partial rings exhibit deeper mass profiles than their controls, particularly in central areas where pseudo-rings extend beyond r 50 . These findings not only improve our understanding of galactic evolution in ringed galaxies but also underline the complex interplay between mass distribution and galactic morphology.