H I asymmetries of galaxies in the Ursa Major and Perseus-Pisces environments

Context. The morphology and kinematics of atomic hydrogen (H I ) gas in galaxies are affected by local and large-scale cosmic environments. Differences in global environment and galaxy interactions can leave distinct signatures in H I asymmetry, which offers insight into environmental effects on the galaxy evolution. Aims. We investigate the role of the environment on H I asymmetries in galaxies located in two contrasting cosmic structures: the Ursa Major (UMa) group, and the Perseus-Pisces (PP) filament. We quantify asymmetries in H I global profiles and column density maps to assess their relation to local and large-scale environments. Methods. We analysed H I 21 cm spectral line imaging from the Westerbork Synthesis Radio Telescope (WSRT) and the Very Large Array (VLA), targeting the UMa and PP volumes. The data cubes were homogenised in resolution for a fair comparison. The asymmetries were measured using observational constraints defined in previous work, and the results were compared with those obtained for mock galaxies from the EAGLE simulations presented in that study. Results. The PP volume contains a significantly higher fraction of galaxies with asymmetric global H I profiles (33%) compared to the UMa volume (9%). Similarly, the proportion of galaxies with H I morphological asymmetries greater than 0.5, measured above a column density threshold of 15 × 10 19 cm −2 , is also higher in the PP sample (46%) than in the UMa sample (13%). The higher column density sensitivity of the UMa data allowed us to detect lopsided features in interacting galaxies and close pairs down to 5 × 10 19 cm −2 and a reliable measurement of H I morphological asymmetries at this threshold. We identified a category of mock galaxies that are not representative of real galaxies because the feedback models in the EAGLE simulations are unrealistic. In both volumes, the stellar asymmetries and H I morphological asymmetries are uncorrelated. Global profile asymmetries and morphological asymmetries are found to be uncorrelated, consistent with our previous results and external studies.