A Standard Siren Cosmological Measurement from the Potential GW190521 Electromagnetic Counterpart ZTF19abanrhr

TL;DR

This paper demonstrates the potential of using the electromagnetic counterpart ZTF19abanrhr to GW190521 as a standard siren for cosmological measurements, providing estimates of the Hubble constant and other parameters.

Contribution

It presents the first cosmological inference from a binary black hole merger with an identified electromagnetic counterpart, extending standard siren methods beyond neutron star mergers.

Findings

Consistent spatial localization of ZTF19abanrhr with GW190521.

Estimated Hubble constant of 48^{+24}_{-10} km/s/Mpc using the counterpart.

Hubble constant of 69.1^{+8.7}_{-6.0} km/s/Mpc when using GW170817 prior.

Abstract

The identification of the electromagnetic counterpart candidate ZTF19abanrhr to the binary black hole merger GW190521 opens the possibility to infer cosmological parameters from this standard siren with a uniquely identified host galaxy. The distant merger allows for cosmological inference beyond the Hubble constant. Here we show that the three-dimensional spatial location of ZTF19abanrhr calculated from the electromagnetic data remains consistent with the updated sky localization of GW190521 provided by the LIGO-Virgo Collaboration. If ZTF19abanrhr is associated with the GW190521 merger and assuming a flat wCDM model we find that $H_0 =48^{+24}_{-10}$ km/s/Mpc, $\Omega_m =0.39^{+0.38}_{-0.29}$, and $w_0 = -1.29^{+0.63}_{-0.50}$ (median and 68% credible interval). If we use the Hubble constant value inferred from another gravitational-wave event, GW170817, as a prior for our analysis, together with assumption of a flat ${\Lambda}$CDM and the model-independent constraint on the physical matter density ${\omega}_m$ from Planck, we find $H_0 = 69.1^{8.7}_{-6.0}$ km/s/Mpc.