Properties of barred galaxies with the environment. I. The case of the Virgo cluster

Aguerri, J. Alfonso L.; Cuomo, Virginia; Rojas-Roncero, Azahara; Morelli, Lorenzo
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Astronomy and Astrophysics

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Context. Barred structures are widespread in a considerable fraction of galactic disks, spanning diverse environments and galaxy luminosities. The environment likely exerts a significant influence on bar formation, with tidal interactions leading to the emergence of elongated features resembling bars within galaxy disks. It is plausible that the structural parameters of bars resulting from tidal interactions in high-density galactic environments differ from those that formed through internal disk instabilities in isolated galaxies. To empirically test this scenario, a viable approach is to compare the structural parameters of bars in galaxies situated within distinct environments.
Aims: The objective of this study is to study environmental effects on the properties of bars by conducting a comparison between the two key structural parameters of bars, namely strength and radius, in galaxies situated within the Virgo cluster and galaxies of comparable luminosities found in environments characterized by lower galaxy densities.
Methods: We have collected data on the bar radius and bar strength for a sample of 36 SB0 and SBa galaxies located within the Virgo cluster. These galaxies exhibit a large range of magnitudes, with values ranging from Mr = −22 to Mr = −17. Additionally, we analyzed a sample of 46 field galaxies with similar morphologies and luminosity ranges. The measurements of bar parameters were conducted by employing Fourier decomposition on the r-band photometric images of the galaxies.
Results: The analysis reveals that the bar radius exhibits a correlation with the galaxy luminosity, indicating that larger bars are typically found in more luminous galaxies. When comparing galaxies with fixed luminosities, the field galaxies display larger bar radii compared to those in the Virgo cluster. However, when the bar radius is scaled by the size of the galaxy, the disparity diminishes and the scaled bars in the Virgo cluster and the field exhibit similar sizes. This is because galaxies of similar luminosities tend to be larger in the field environment compared to the cluster and because the bars adapt to the disks in which they live. Regarding the bar strength, no significant differences were observed for bright galaxies (Mr < −19.5) between those located in the Virgo cluster and those in the field. In contrast, faint galaxies (Mr > −19.5) show stronger bars in the field than in the cluster.
Conclusions: The findings of this study indicate that the size of galaxies is the parameter that is influenced by the environment, while the bar radius remains independent of the environment when scaled by the galaxy size. The findings of this study indicate that the environment influences the size of galaxies rather than the bar radius, which remains independent of the environment when scaled by the galaxy size. Regarding the bar strength, there is no influence of the environment for bright galaxies. However, bars in faint galaxies are weaker in the cluster environment. This could be explained by an enhancement of disk thickness in dense environments which is more efficient in faint galaxies. These results support the notion that the internal dynamics and intrinsic characteristics of galaxies play a dominant role in the formation and evolution of bars, regardless of the surrounding environment.
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