Cosmography with strong lensing of LISA gravitational wave sources

Abstract

LISA might detect gravitational waves from mergers of massive black hole binaries strongly lensed by intervening galaxies (Sereno et al. 2010). The detection of multiple gravitational lensing events would provide a new tool for cosmography. Constraints on cosmological parameters could be placed by exploiting either lensing statistics of strongly lensed sources or time delay measurements of lensed gravitational wave signals. These lensing methods do not need the measurement of the redshifts of the sources and the identification of their electromagnetic counterparts. They would extend cosmological probes to redshift z <= 10 and are then complementary to other lower or higher redshift tests, such as type Ia supernovae or cosmic microwave background. The accuracy of lensing tests strongly depends on the formation history of the merging binaries, and the related number of total detectable multiple images. Lensing amplification might also help to find the host galaxies. Any measurement of the source redshifts would allow to exploit the distance-redshift test in combination with lensing methods. Time-delay analyses might measure the Hubble parameter H_0 with accuracy of >= 10 km s^{-1}Mpc^{-1}. With prior knowledge of H_0, lensing statistics and time delays might constrain the dark matter density (delta Omega_M >= 0.08, due to parameter degeneracy). Inclusion of our methods with other available orthogonal techniques might significantly reduce the uncertainty contours for Omega_M and the dark energy equation of state

What drives the growth of black holes?

“…Even for such BHs, the hard radiation field may produce characteristic nebular line emission (in particular, He II λ1640) that could be detected with NIRSpec on the James Webb Space Telescope (Johnson et al, 2011), while quasistars could produce a significant population of sources observable at mid-IR wavelengths with JWST (Volonteri & Begelman, 2010). In the more distant future, these BHs may also be detectable through gravitational wave signatures when they merge (e.g., Sesana et al, 2007;Arun et al, 2009;Sereno et al, 2011).…”

“…For an initial BH formed at a high redshift (say z = 20) to reach 10 9 M ≈0.7 Gyr later at z = 6, assuming standard = 0.1 and continuous accretion at the Eddington limit, it must have started with M in ∼ 100 M (with the caveat that some additional growth can occur through BH-BH mergers; e.g., Sesana et al 2007;Arun et al 2009;Sereno et al 2011). For a lower formation redshift or more stochastic accretion (and thus lower average λ) intial BH masses would necessarily have been higher.…”

The Wave Nature of Continuous Gravitational Waves from Microlensing

“…The event rates of GW lensing by galaxies were studied by (Wang et al 1996;Sereno et al 2010;Biesiada et al 2014;Ding et al 2015;Li et al 2018) leading to a robust predicition that third generation of GW interferometric detectors would yield 50 − 100 lensed GW events per year. Strongly lensed GW signals, observed together with their EM counterparts have been demonstrated to enhance our understanding regarding fundamental physics Collett & Bacon 2017), astrophysics (Liao et al 2018) and cosmology (Sereno et al 2011;Liao et al 2017;Wei & Wu 2017;Li et al 2019). It is noteworthy that a very recent work showed the events GW170809 and GW170814 could come from the same source (Broadhurst et al 2019), but see Hannuksela et al (2019) On the contrary, if the wavelength is much longer than the lens mass scale (i.e.…”

What if LIGO’s gravitational wave detections are strongly lensed by massive galaxy clusters?

“…Strong lensing of gravitational waves (GWs) had been considered by numerous authors in advance of the advent of direct GW detections (Wang, Stebbins & Turner 1996;Takahashi & Nakamura 2003;Seto 2004;Takahashi 2004;Varvella, Angonin & Tourrenc 2004;Sereno et al 2010Sereno et al , 2011Piórkowska, Biesiada & Zhu 2013;Biesiada et al 2014). In particular, the degeneracy between the luminosity distance to and thus source-frame mass of a GW source, and any gravitational magnification suffered by the source noted by Wang et al (1996) is interesting in light of the reported BH masses thus far (see also Dai, Venumadhav & Sigurdson 2017).…”