Connecting the physical properties of galaxies with the overdensity and tidal shear of the large-scale environment

We have examined the correlations between the large-scale environment of galaxies and their physical properties, using a sample of 28,354 nearby galaxies drawn from the Sloan Digital Sky Survey, and the large-scale tidal field reconstructed in real space from the 2Mass Redshift Survey and smoothed over a radius of ∼ 6hMpc. The largescale environment is expressed in terms of the overdensity, the ellipticity of the shear and the type of the large-scale structure. The physical properties analyzed include rband absolute magnitudeM0.1 r , stellar massM∗, g−r colour, concentration parameter R90/R50 and surface stellar mass density μ∗. Both luminosity and stellar mass are found to be statistically linked to the largescale environment, regardless of how the environment is quantified. More luminous (massive) galaxies reside preferentially in the regions with higher densities, lower ellipticities and halo-like structures. At fixed luminosity, the large-scale overdensity depends strongly on parameters related to the recent star formation history, that is colour and D(4000), but is almost independent of the structural parameters R90/R50 and μ∗. All the physical properties are statistically linked to the shear of the large-scale environment even when the large-scale density is constrained to a narrow range. This statistical link has been found to be most significant in the quasi-linear regions where the large-scale density approximates to an order of unity, but no longer significant in highly nonlinear regimes with δLS ≫ 1. Our results suggest that the initial conditions have made nonnegligible contributions to establishing the environmental dependence of galaxy properties. It is expected that our results may give a new clue to the unknown physical mechanism of the galaxyenvironment relationships.