Giannini: Why are photo-z so hard? / Noriega: Are current neutrino mass constraints reliable? Insights from full-shape analyses

Speaker: Guilia Giannini (The University of Chicago) / Hernán Noriega (UNAM) In Person and zoom 

Zoom info: https://stanford.zoom.us/j/98604058568

Giannini: Photometric redshifts are a cornerstone of modern cosmological surveys, allowing us to estimate galaxy distances from broad-band photometry alone. While this approach enables vast statistical power, it also presents unique challenges — from color–redshift degeneracies to calibration biases. I’ll outline why photo-z are intrinsically hard, review the main estimation and calibration techniques, and highlight how surveys like DES have developed robust strategies to meet the precision requirements for cosmology. I’ll close with a look at how upcoming surveys are pushing these methods even further.

Noriega: Cosmological findings from the combination of DESI and Planck (and more recently ACT) data have placed very tight constraints on the total neutrino mass within the $\Lambda$CDM model, leading to tension with particle physics experiments. In this talk, we show that the neutrino mass signal is highly sensitive to background effects, clouding the reliability of its measurement. However, by disregarding the background and focusing on the effect of structure suppression, we discover that most of the neutrino information is extracted from the relative amplitude of the wiggles, rather than the broadband suppression of the power spectrum, contrary to common belief. This insight offers a promising pathway for robustly extracting the neutrino signal.

This talk is based on Phys. Rev. D 111 (2025) 6, L061307.