Speaker
Description
Magnification bias offers a powerful and independent route to cosmological information, probing galaxy-matter correlations without relying on galaxy shapes, PSF modelling, or intrinsic-alignment corrections. Its sensitivity spans both geometry and growth: it simultaneously constrains the matter density, the amplitude of structure, and crucially the redshift evolution of dark energy below z≤1. Importantly, its parameter degeneracy directions differ from those of shear, BAO, and CMB data, making it a uniquely complementary and high-diagnostic-value probe for the next decade of precision cosmology. Beyond large-scale structure, magnification bias also provides a shape-independent window into halo mass density profiles down to sub-10 kpc scales, with recent pilot studies revealing characteristic features such as the "Einstein Gap" and signatures of massive satellite galaxies; applications that further illustrate the versatility of the technique.
However, the current potential of magnification bias remains limited by restricted sky coverage, catalogue inhomogeneities, confusion noise, and insufficiently precise redshift or number-count characterisation. A next-generation wide-field submillimetre facility like AtLAST — capable of uniform, deep surveys and spectroscopic mapping — would overcome these limitations and transform magnification bias into a competitive, high-precision cosmological tool. Combined with optical surveys from Euclid and LSST, AtLAST will deliver decisive constraints on dark energy, structure growth, and small-scale halo structure alike.