Mg2 gradients as a signature of brightest cluster galaxy evolution

TL;DR

This study measures Mg2 absorption index gradients in 21 brightest cluster galaxies, revealing their stellar population profiles are influenced by the cluster environment and potential well, unlike normal ellipticals.

Contribution

It provides the first detailed analysis of Mg2 gradients in BCGs and links these gradients to cluster properties, highlighting environmental effects on galaxy evolution.

Findings

Mg2 gradients are steeper in more massive BCGs.

Weak correlation between Mg2 gradients and central velocity dispersion.

Mg2 gradients correlate with the BCG's distance to the cluster's X-ray peak.

Abstract

We have fitted the Mg2 absorption index gradients for 21 brightest cluster galaxies (BCGs), in the nearby Universe, for which we have obtained high signal-to-noise ratio, long-slit spectra on the Gemini telescopes. This is a sub-sample of a large optical, spatially-resolved, spectroscopic sample of BCGs which allows possible connections between the kinematical, dynamical and stellar population properties to be studied. We find a weak correlation between the Mg2 gradients and central velocity dispersion, with gradients becoming steeper with increasing mass. An equivalent correlation for normal ellipticals in the same mass range is not found, suggesting that the BCG stellar population profiles are shaped by mechanisms related to the potential well of the cluster where they live. This suggestion is reinforced by the existence of a correlation between the Mg2 gradients and the BCG distance to the X-ray peak luminosity of the cluster.