Dependence of galactic bars on the tidal density field in the SDSS

As a key driver of the secular evolution of disc galaxies, bar formation is potentially linked to the surrounding tidal field. We systematically investigate the dependence of bars on both the small ( < 2 Mpc h-1) and large ( > 5 Mpc h-1) scale tidal fields using galaxies observed in the range 0.01 < z < 0.11 by the Sloan Digital Sky Survey (SDSS). We characterize bar strength using the ellipticity of the isophote that corresponds to each bar, e(bar), derived from its galaxy image after subtracting the 2D disc component. We demonstrate the efficacy of our bar detection method by performing an e xtensiv e comparison with the visual identifications from SDSS and the DESI Le gac y Surv e ys. Using the Yang et al. SDSS group catalogue, we confirm the results from a recent study that the average e(bar) of galaxies within interacting clusters is higher than that within isolated ones at 0.01 < z < 0.06, but this small-scale tidal enhancement of bars disappears after we increase the cluster sample by a factor of 5 to z = 0.11. On large scales, we explore the dependence of e(bar) on a5, the tidal anisotropy of the density field defined o v er 5 Mpc h -1. We do not detect any such dependence for 98 per cent of the galaxies with a5 < 10. Intriguingly, among the 2 per cent with a5 = 10, we detect some hint of a boost in bar strength in the underdense regions and a suppression in the o v erdense re gions. Combining our results on both scales, we conclude that there is little evidence for the tidal dependence of bar formation in the local Universe, except for the extremely anisotropic environments.