Contaminating Weak Lensing Cosmology with Active Galactic Nuclei
Nialh McCallum
University of Manchester
Ian Harrison (University of Manchester), Michael Brown (University of Manchester)
With the arrival of the SKA the dawn of a new era of weak gravitational lensing observations is imminent, with scope to probe cosmic shear fields at radio wavelengths to a precision competitive with optical results. However though weak gravitational lensing analysis in the radio regime has a number of benefits it also brings with it new difficulties not encountered in the optical range that must be considered. Since the effect of cosmic shear on a galaxy's intrinsic shape is only on the order of a few percent the measurements are highly susceptible to bias, with one possible contributor to this bias in the radio regime being galaxies containing Active Galactic Nuclei (AGN) whose complex shapes are not well constrained by conventional models. Though the number of AGN galaxies is not dominant in the redshift regions usually probed by weak gravitational lensing surveys, they still make up a factor between 20% and 40% of the total population which could lead to a significant bias on the cosmic shear measured and the cosmological parameters inferred from this shear. As such the contamination of weak lensing cosmology by AGN is an important effect to consider when proceeding with weak lensing observations in the radio regime. This poster presents the latest results on this bias due to AGN.