Revealing ringed galaxies in group environments

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Aims. We explore galaxies with ringed structures inhabiting poor and rich groups with the aim of assessing the effects of local density environments on ringed galaxy properties. Methods. We identified galaxies with inner, outer, nuclear, inner+outer (inner and outer rings combined), and partial rings that reside in groups by cross-correlating a sample of ringed galaxies with a group catalog obtained from Sloan Digital Sky Survey (SDSS). The resulting sample was divided based on group richness, with groups having 3 ≤ Nrich ≤ 10 members classified as poor, while groups having 11 ≤ Nrich ≤ 50 were classified as rich. To quantify the effects of rings and the role of local density environment on galaxy properties, we constructed a suitable control sample for each catalog of ringed galaxies in poor and rich groups, consisting of non-ringed galaxies with similar values for the redshift, magnitude, morphology, group masses, and environmental density distributions as those of ringed ones. We explored the occurrence of ringed galaxies in poor and rich groups and analyzed several galaxy properties, such as star formation activity, stellar populations, and colors, with respect to the corresponding comparison samples. Results. We obtained a sample of 637 ringed galaxies residing in groups. We found that about 76% of these galaxies inhabit poor groups, whereas only about 24% are present in rich groups. Inner rings are prevalent in both rich and poor groups, while nuclear rings are the least common in both groups. Regarding the control sample, about 81% galaxies are found in poor groups and about 19% in rich ones. We find that the percentages of ringed galaxies with bar structures are similar, regardless of whether the group is rich or poor. In addition, ringed galaxies inhabiting groups display a reduction in their star formation activity and aged stellar populations, compared to non-ringed ones in the corresponding control samples. However, the star formation rate is higher for nuclear rings in poor groups than for other types. This disparity may stem from the environmental influence on the internal processes of galaxies, either enhancing or diminishing star formation. Ringed galaxies also show an excess of red colors and tend to populate the green valley and the red sequence of color-magnitude and color-color diagrams, with a surplus of galaxies in the red sequence, while non-ringed galaxies are found in the green valley and the blue region. These trends are more significant in galaxies with ringed structures residing in rich groups. Our findings provide valuable insights into the relationship between ringed structures and their surrounding environments, paving the way for further explorations in this area of study.

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