Pandya, A.A.PandyaMigkas, K.K.MigkasReiprich, T. H.T. H.ReiprichStanford, A.A.StanfordPacaud, F.F.PacaudSchellenberger, G.G.SchellenbergerLOVISARI, LorenzoLorenzoLOVISARIRamos-Ceja, M. E.M. E.Ramos-CejaNguyen-Dang, N. T.N. T.Nguyen-DangPark, S.S.Park2025-03-212025-03-2120240004-6361http://hdl.handle.net/20.500.12386/36921In standard cosmology, the late Universe is assumed to be statistically homogeneous and isotropic. However, a recent study based on galaxy clusters by Migkas et al. (2021, arXiv:2103.13904) found an apparent spatial variation of approximately $9\%$ in the Hubble constant, $H_0$, across the sky. The authors utilised galaxy cluster scaling relations between various cosmology-dependent cluster properties and a cosmology-independent property, i.e., the temperature of the intracluster gas $(T)$. A position-dependent systematic bias of $T$ measurements can, in principle, result in an overestimation of apparent $H_0$ variations. In this study, we search for directional $T$ measurement biases by examining the scaling relation between the member galaxy velocity dispersion and the gas temperature $(\sigma_\mathrm{v}-T)$. Additionally, we search for apparent $H_0$ angular variations independently of $T$ by analysing the relations between the X-ray luminosity and Sunyaev-Zeldovich signal with the velocity dispersion, $L_\mathrm{X}-\sigma_\mathrm{v}$ and $Y_\mathrm{SZ}-\sigma_\mathrm{v}$. We utilise Monte Carlo simulations of isotropic cluster samples to quantify the statistical significance of any observed anisotropies. We find no significant directional $T$ measurement biases, and the probability that a directional $T$ bias causes the previously observed $H_0$ anisotropy is only $0.002\%$. On the other hand, from the joint analysis of the $L_\mathrm{X}-\sigma_\mathrm{v}$ and $Y_\mathrm{SZ}-\sigma_\mathrm{v}$ relations, the maximum variation of $H_0$ is found in the direction of $(295^\circ\pm71^\circ, -30^\circ\pm71^\circ)$ with a statistical significance of $3.64\sigma$, fully consistent with arXiv:2103.13904. Our findings strongly corroborate the previously detected spatial anisotropy of galaxy cluster scaling relations using a new independent cluster property, $\sigma_\mathrm{v}$.STAMPAenArticle10.1051/0004-6361/2024517552-s2.0-85210765895https://www.aanda.org/articles/aa/full_html/2024/11/aa51755-24/aa51755-24.htmlFIS/05 - ASTRONOMIA E ASTROFISICA