Size distribution of galaxies in SDSS DR7: weak dependence on halo environment

TL;DR

This study analyzes how galaxy sizes in SDSS DR7 depend mainly on intrinsic properties like morphology and bulge fraction, with only weak influence from large-scale environment factors such as halo mass or cosmic web structures.

Contribution

It provides a detailed analysis of the size distribution of galaxies, highlighting the dominant role of intrinsic properties over environmental factors, and offers fitting formulas for different galaxy types.

Findings

Galaxy size strongly depends on intrinsic properties like morphology and bulge fraction.

Early-type galaxies are generally smaller and have steeper size-mass relations than late-type galaxies.

Large-scale environment has minimal impact on galaxy sizes within the studied mass range.

Abstract

Using a sample of galaxies selected from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) and a catalog of bulge-disk decompositions, we study how the size distribution of galaxies depends on the intrinsic properties of galaxies, such as concentration, morphology, specific star formation rate (sSFR), and bulge fraction, and on the large-scale environments in the context of central/satellite decomposition, halo environment, the cosmic web: \cluster, \filament, \sheet ~and \void, as well as galaxy number density. We find that there is a strong dependence of the luminosity- or mass-size relation on the galaxy concentration, morphology, sSFR, and bulge fraction. Compared with late-type (spiral) galaxies, there is a clear trend of smaller sizes and steeper slope for early-type (elliptical) galaxies. Similarly, galaxies with high bulge fraction have smaller sizes and steeper slope than those with low bulge fraction. Fitting formula of the average luminosity- and mass-size relations are provided for galaxies of these different intrinsic properties. Examining galaxies in terms of their large scale environments, we find that the mass-size relation has some weak dependence on the halo mass and central/satellite segregation for galaxies within mass range $9.0\le \log M_{\ast} \le 10.5$, where satellites or galaxies in more massive halos have slightly smaller sizes than their counterparts. While the cosmic web and local number density dependence of the mass-size relation is almost negligible.