The Non Parametric Reconstruction of Binary Black Hole Mass Evolution from GWTC-4.0 Gravitational Wave Catalog

Abstract: The distribution of binary black hole (BBH) masses and its evolution with redshift provide key insights into the different formation channels of the compact objects and their evolution with cosmic time and stellar properties such stellar metallicity and star formation rate history. We present a non parametric, model-independent joint reconstruction of the redshift evolution of BBH mass distribution from gravitational wave (GW) catalog GWTC-4.0 from the fourth observation of LIGO-Virgo-KAGRA (LVK). This method simultaneously searches for the signature of any linear and quadratic redshift evolution with respect to the low redshift in a Bayesian framework taking into accounting the detector selection effects. We find tentative evidence for a linear redshift-dependent evolution of the mass distribution, consistent over a mass range ($m \gtrsim 50\,M_\odot$). While lower mass systems shows no signature of evolution. The quadratic term remains consistent with zero, indicating that a simple linear dependence adequately describes the population up to redshift $z \sim 1$. In future with more GW sources, this technique can shed light into the true nature of the redshift dependence and possibility to uncover subtle evolutionary features in BBH populations and to probe the cosmic history of black hole formation.