New method improves distance measurements between quasar pairs
University of Alberta researchers have developed a technique to more accurately measure the line-of-sight separation between double quasars, addressing the depth-perception problem in 3D space. This measurement is crucial for determining how long it takes for quasar-hosting galaxies to merge. The feasibility study appears in The Astrophysical Journal Letters.
The conventional approach relies on redshift measurements, which gauge how fast space expansion moves a galaxy away from an observer. However, active supermassive black holes can push surrounding gas outward so forcefully that measured velocities deviate substantially from true recessional velocities, introducing systematic errors that can shift inferred separations by roughly 10 million light-years.
The alternative method examines regions of gas illuminated and heated by quasar light, which become transparent and visible in spectra. By comparing these transparent zones between paired quasars, researchers can estimate how far one sits in front of the other. The feasibility study, based on simulated data, demonstrated that this approach can reduce separation uncertainty to roughly half a million light-years in many cases.
This research could refine our understanding of galaxy merger timelines and supermassive black hole evolution, potentially reshaping models of cosmic structure formation. Astronomers may gain a more reliable tool for interpreting quasar pair observations, which could lead to revised estimates of how frequently and how quickly such mergers occur. The broader scientific community might benefit from improved distance measurements that strengthen the foundation for future deep-space surveys, while the public gains a clearer picture of the dynamic processes shaping the universe.