Observational Cosmology Seminar

SPHEREx is a near-infrared space telescope launched in March 2025 to conduct an all-sky spectral survey, with a primary cosmology goal of constraining primordial non-Gaussianity from 3D galaxy clustering as a probe of inflation. This requires accurate redshift measurements over a large area of the sky. SPHEREx measures redshifts primarily via continuum SED template fitting, with emission lines independently fitted to further tighten constraints. The all-sky coverage and moderate spectral resolution across 0.75 to 5 um enable unprecedented SED characterization and the ability to spectrally resolve bright emission lines.

My work focuses on improving the redshift measurements for SPHEREx cosmology. I build empirical SED templates directly from SPHEREx galaxies with known spectroscopic redshifts, significantly improving photometric redshift accuracy over existing external templates. Incorporating emission line fitting provides a spectroscopic redshift subsample that further tightens constraints when combined with continuum-based estimates. I also characterize spectral confusion from faint background galaxies and blending from beam overlaps, informing selection strategies that preserve redshift quality. Together, these efforts advance the redshift precision needed for SPHEREx to directly probe the microphysics of inflation.