ENW-M-2 grant to locate merging black holes through gravitational lensing

Recently the NWO Domain Board Science approved twenty-six grant applications in the Open Competition Domain Science-M programme. An ENW-M-2 proposal for over 0.5 million euros has been awarded to Prof. Chris Van Den Broeck (GRASP, Utrecht University) and Prof. Léon Koopmans (Kapteyn Astronomical Institute, University of Groningen), who will join forces to exploit gravitational lensing using complementary channels: gravitational waves and electromagnetic observations. 

Finding the invisible: Localizing merging black holes through gravitational lensing

Gravitational wave detectors such as LIGO and Virgo have been recording signals from binary black hole mergers on a regular basis. However, the poor localization accuracy of the current detector network, and the fact that black holes emit no electromagnetic radiation, generally make it impossible to establish the location of such events in the Universe. Gravitational wave lensing allows an exception to this rule. Like ordinary light, a gravitational wave can be lensed by a massive object (a galaxy or galaxy cluster) on its path. When this happens, the light from the host galaxy of the binary black hole merger must also be lensed, in a way that will be closely correlated with the characteristics of the lensed gravitational wave. 

By utilizing this correlation it will be possible to identify the host galaxy. Once this is done, further constraints coming from the properties of the object that does the lensing will enable scientists to locate, with sub-arcsecond precision, where inside the host galaxy the binary black hole merger happened. The aim of the project is to develop a concrete methodology combining gravitational and electromagnetic observations to make this a reality. Other than this being the only way to find out precisely where a binary black hole merger occurred, it will enable a number of other pursuits, such as studying the connection between binary black holes and their host galaxies, independently probing the evolution of the Universe at high redshift, superior tests of general relativity, and much improved modeling of the lens systems themselves.