First results from Cosmological QUOKKAS (225th KDESci Meeting)
ABSTRACT
Abstract: Cosmological QUOKKAS (Quasar Observations on the KVN from Korea to Australia and South Africa) is a project that aims to measure cosmological parameters from quasars. The primary mechanism is known as the Standard Speed Gun and works by using the speed of light to calibrate a standard ruler and then measuring the apparent size using VLBI. Relativistic effects are corrected for by assuming a maximum energy density that blazars can achieve. Any cosmological evolution of the value of the maximum energy density is corrected for by fitting a jet model to multi-frequency VLBI (including Korean VLBI Network) data. This yields an early measure of Ωm of 0.27+0.32-0.19. The absolute scale of the Hubble Diagram can be set by using low redshift quasars with detected counter-jets. This has been demonstrated recently in 3C 84 (the bright radio source at the center of the Perseus Cluster), where under the assumption of a spherical geometry of the emitting region, the Hubble Constant is measured to be 75.8+8.1-10.6 km/s/Mpc. As we move into the SKA-VLBI era, many more sources will be detectable. I will finally briefly describe how space VLBI can be used to make direct distance measurements free of physical assumptions.
