Non parametric constraints of gravitational-electromagnetic luminosity distance ratio

Abstract

The ratio between the gravitational waves (GW) and electromagnetic waves (EMW) luminosity distance ratio is a key observable that allows to test the nature of gravity, using gravitational waves emitted from compact binary coalescences. We develop a new non parametric method for constraining the GW-EMW distance ratio, in order to perform model independent analysis of observational data, not based on any specific theoretical of phenomenological assumption. We apply the method to the analysis of binary black hole mergers data from the GWTC-3 catalogue, performing a joint analysis of cosmological and population parameters. The results are consistent with general relativity and with previous analyses based on parametric methods.

Figures (5)

• Figure 1: The PCHIP distance ratio is plotted as a function of redshift for $n=2$, for fixed $\rho_2$ and different values of $\rho_1$. The plot for $r(z)$ on the left (right) corresponds to a monotonic decreasing (increasing) function because $\rho_1$ takes negative (positive) values.
• Figure 2: The PCHIP distance ratio is plotted as a function of redshift for $n=2$, for fixed $\rho_1$ and different values of $\rho_2$. The plot for $r(z)$ on the left (right) corresponds to a monotonic decreasing (increasing) function because $\rho_1$ takes negative (positive) values.
• Figure 3: Selected corner plot showing the joint constrains obtained for the analysis with gwcosmo of 42 BBHs from the GWTC-3 catalogue. The full corner plot is shown in Figure \ref{['fig:full_corner_plot']}.
• Figure 4: Corner plot showing the joint constrains on the cosmological ($H_0$), population, and GW-EMW luminosity distance ratio nodes ($\rho_1$ and $\rho_2$) parameters. The GW-EMW luminosity distance ratio predicted by GR is obtained when $\rho_1 = 0$. We can see from this result that the analysis with gwcosmo of 42 BBHs from the GWTC-3 catalogue is consistent with GR for our non-parametric PCHIP reconstruction of $r(z)$.
• Figure 5: PCHIP GW-EMW luminosity distance ratio median and confidence $68\%$ and $95\%$ bands estimated from for the analysis with gwcosmo of 42 BBHs from the GWTC-3 catalogue. The GW-EMW luminosity distance ratio predicted by General Relativity is plotted in black, showing that the reconstructed PCHIP $r(z)$ is consistent with GR within the $68\%$ C.L.