Connecting the Physical Properties of Galaxies with the Overdensity and Tidal Shear of the Large-Scale Environment

TL;DR

This study investigates how the physical properties of galaxies correlate with their large-scale environment, including density, shear, and structure type, revealing significant links especially in quasi-linear regions.

Contribution

It provides a comprehensive analysis of the correlations between galaxy properties and large-scale environmental factors using SDSS and 2Mass data, highlighting the role of tidal shear.

Findings

Luminosity and stellar mass are statistically linked to large-scale environment.

Galaxies in higher density, halo-like regions tend to be more luminous and massive.

The correlation between galaxy properties and environment is strongest in quasi-linear regions.

Abstract

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 $\sim 6 h^{-1}$Mpc. The large-scale 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 $r$-band absolute magnitude $M_{^{0.1}r}$, stellar mass $M_\ast$, $g-r$ colour, concentration parameter $R_{90}/R_{50}$ and surface stellar mass density $\mu_\ast$. Both luminosity and stellar mass are found to be statistically linked to the large-scale 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 $R_{90}/R_{50}$ and $\mu_\ast$. 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 $\delta_{\rm LS}\gg 1$.