Distribution of clusters in the P_{1.4 GHz}−M₅₀₀ diagram. Different symbols indicate giant radio halos (black filled dots), ultra steep spectrum radio halos (black empty dots) and upper limits (black arrows) belonging to the Cassano et al. (2013) sample. The red dots represent the two clusters presented in this paper. The best fit relation for giant radio halos (black line) and the 95% confidence level (shadowed region) from Cassano et al. (2013) are shown.