Signatures of dynamical activity in the hot gas profiles of groups and clusters in the FLAMINGO simulations

Abstract

In anticipation of upcoming cosmological surveys, we use the large volume Flamingo hydrodynamical simulations to look for signatures of dynamical activity, focusing on the hot gas profiles of groups and clusters out to redshift $z=1$. To determine the dynamical state of each object, we consider the halo mass accretion rate, $\Gamma$, as well as three observational proxies: stellar mass gap, $\Mstar$; X-ray concentration, $c_\mathrm{x}$, and X-ray centroid shift, $\left<w\right>$. In general, the median values of these indicators vary in accordance with an increase in dynamical activity with both mass and redshift. We find $\left<w\right>$ to be the most reliable proxy, while $c_\mathrm{x}$ and $\Mstar$ are more sensitive to resolution and feedback model details. Looking at the profiles, the correlation between dark matter density and $\Gamma$ has a characteristic radial dependence, being negatively (positively) correlated at small (large) radii. This trend is insensitive to both halo mass and redshift. Similar behaviour is also seen for the hot gas densities in low redshift clusters, particularly when using $\left<w\right>$, but the correlations become weaker in groups, at higher redshift and when stronger feedback is employed. We also find the intrinsic scatter in the gas density profiles to decrease with redshift, particularly in groups, contrary to what is seen for the dark matter. Interestingly, the radius of minimum gas density scatter increases with feedback strength, suggesting that this property could be a useful feedback diagnostic in future observational studies.