Reducing the Impact of Weak-lensing Errors on Gravitational-wave Standard Sirens by Zhao-Feng Wu et al. on Monday 28 November

The mergers of supermassive black hole binaries (SMBHBs) can serve as

standard sirens: the gravitational wave (GW) analog of standard candles. The

upcoming space-borne GW detectors will be able to discover such systems and

estimate their luminosity distances precisely. Unfortunately, weak

gravitational lensing can induce significant errors in the measured distance of

these standard sirens at high redshift, severely limiting their usefulness as

precise distance probes. The uncertainty due to weak lensing can be reduced if

the lensing magnification of the siren can be estimated independently, a

procedure called 'delensing'. With the help of up-to-date numerical

simulations, here we investigate how much the weak-lensing errors can be

reduced using convergence maps reconstructed from shear measurements. We also

evaluate the impact of delensing on cosmological parameter estimation with

bright standard sirens. We find that the weak-lensing errors for sirens at $z_s

= 2.9$ can be reduced by about a factor of two on average, but to achieve this

would require expensive ultra-deep field observations for every siren. Such an

approach is likely to be practical in only limited cases, and the reduction in

the weak-lensing error is therefore likely to be insufficient to significantly

improve the cosmological parameter estimation. We conclude that performing

delensing corrections is unlikely to be worthwhile, in contrast to the more

positive expectations presented in previous studies. For delensing to become

more practicable and useful in the future will require significant improvements

in the resolution/depth of the weak-lensing surveys themselves and/or the

accuracy of the methods to reconstruct convergence maps from these surveys.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.15160v1