Comparisons of the environmental dependence of galaxy properties between galaxies above and below M

TL;DR

This study compares how galaxy properties depend on environment for galaxies above and below a certain luminosity threshold, revealing that luminosity dependence varies with this threshold while other properties do not.

Contribution

It introduces a method to analyze environmental effects on galaxy properties relative to a luminosity threshold M, highlighting the different dependencies for galaxies above and below M.

Findings

Luminosity depends on environment mainly for galaxies above M.

Color, concentration index, and morphology depend on environment for all galaxies.

M is a key parameter for luminosity-environment relation, not for other properties.

Abstract

From the Main galaxy sample of the Sloan Digital Sky Survey Data Release 6 (SDSS DR6), we construct two volume-limited samples above and below the value of M, to explore the difference of the environmental dependence of galaxy properties between galaxies above and below the value of M . We measure the local three-dimensional galaxy density in a comoving sphere with a radius of the distance to the 5th nearest galaxy for each galaxy, and compare basic properties of galaxies in the lowest density regime with those of galaxies in the densest regime. It is found that the galaxy luminosity strongly depend on local environments only for galaxies above M, but this dependence is very weak for galaxies below M . It is worth noting that g-r color, concentration index ci and galaxy morphologies strongly depend on local environments for all galaxies with different luminosities. This shows that M is an characteristic parameter only for the environmental dependence of galaxy luminosity.