Approaches to tackle the redshift distribution calibration challenge for weak lensing cosmology

by Dr Tianqing Zhang (University of Pittsburgh)

Thursday 19 Feb 2026, 15:00 → 16:00 US/Eastern

small seminar room (510A)

Weak gravitational lensing and galaxy clustering are some of the most powerful probes of cosmology, with current surveys reaching percent-level precision on parameters such as S_8. As we enter the Rubin LSST and Roman era, statistical uncertainties will shrink dramatically, and systematic errors – particularly the calibration of the source redshift distribution n(z) – will become the dominant limitation. Achieving sub-percent precision of n(z) is therefore essential for realizing the full cosmological potential of next-generation imaging surveys.
This talk presents a coordinated program developed through my work with HSC, DESC, and DESI to tackle redshift distribution calibration from three complementary angles. First, I show how RAIL provides a unified framework for photometric redshift estimation, evaluation, and n(z) calibration, validated through simulations in the DESC Photo-z Data Challenge and already demonstrated on Rubin DP1 data. Second, I describe how DESI clustering redshifts are used to calibrate the redshift distribution of the HSC shear catalog, with methods that translate directly to the DESIxLSST overlap and extend calibration beyond z>1.5. Finally, I demonstrate how 3x2pt analysis enables internal redshift self-calibration and consistency checks of the redshift distribution.
These approaches form a coherent strategy to overcome the central systematic challenge for weak lensing cosmology in the LSST era.


Zoom link:  https://bnl.zoomgov.com/j/16001410126?pwd=LO1VgLQipgjIfQpOlKB6szuFxr7L7g.1