Velocity dispersion versus X-ray temperature. Left panel: velocity dispersion versus temperature for the XMM-Newton subsample used in this work in comparison with the literature. The G and NG groups in our AXES-2MRS-XMM sample are represented by purple and red squares, respectively. The grey transparent band is 1σ confidence interval for the slope and intercept. Right panel: comparison of the slope of the σ_v–kT relation with the literature. The grey solid line is the theoretical self-similar expectation. The asterisk mark (*) refers to works using Bayesian linear regression, while the dagger mark (†) refers to works using ODR. The slope of Wilson et al. (2016) is subject to a potential bias, as claimed in Farahi et al. (2018).