No dependence of radio properties of brightest group galaxies on the luminosity gap

TL;DR

This study finds no significant correlation between the luminosity gap and the radio or optical properties of brightest group galaxies, indicating that galaxy interaction level does not influence these properties.

Contribution

It provides the first comprehensive analysis showing the independence of BGG radio and optical properties from the luminosity gap, supported by observational data and hydrodynamical simulations.

Findings

No variation in optical properties of BGGs with luminosity gap at fixed stellar mass.

No trend in the fraction of radio-loud BGGs with luminosity gap.

Simulation results agree with observational findings, showing no emerging trends beyond current luminosity gap range.

Abstract

We study the radio and optical properties of the brightest group galaxies (BGGs) in a sample of galaxy groups from the SDSS DR7. The luminosity difference between the BGG and the second ranked galaxy in the group (known as the luminosity, or magnitude, gap) has been used as a probe for the level of galaxy interaction for the BGG within the group. We study the properties of BGGs with magnitude gaps in the range 0-2.7 magnitudes, in order to investigate any relation between luminosity gap and the radio properties of the BGG. In order to eliminate selection biases, we ensure that all variations in stellar mass are accounted for. We then confirm that, at fixed stellar mass, there are no significant variations in the optical properties of the BGGs over the full range of luminosity gaps studied. We compare these optical results with the EAGLE hydrodynamical simulations and find broad consistency with the observational data. Using EAGLE we also confirm that no trends begin to arise in the simulated data at luminosity gaps beyond our observational limits. Finally, we find that, at fixed stellar mass, the fraction of BGGs that are radio-loud also shows no trends as a function of luminosity gap. We examine how the BGG offset from the center of group may affect the radio results and find no significant trend for the fraction of radio-loud BGGs with magnitude gap in either the BGG samples with greater or less than 100kpc offset from the center of group.