Dark Energy Survey Year 3: Blue shear

Modeling the intrinsic alignment (IA) of galaxies poses a challenge to weak lensing analyses. The Dark Energy Survey is expected to be less impacted by IA when limited to blue, star-forming galaxies. The cosmological parameter constraints from this blue cosmic shear sample are stable to IA model choice, unlike passive galaxies in the full DES Y3 sample, the goodness-of-fit is improved and the $Ω_{m}$ and $S_8$ better agree with the cosmic microwave background. Mitigating IA with sample selection, instead of flexible model choices, can reduce uncertainty in $S_8$ by a factor of 1.5.

• NS
  National Science Foundation

  Awards: AST-1536171, AST-1138766
• UD
  U.S. Department of Energy

  Award: DE-AC02-07CH11359
• TA
  Texas A and M University
• NC
  National Centre for Supercomputing Applications
• HE
  Higher Education Funding Council for England
• DF
  Deutsche Forschungsgemeinschaft
• GD
  Generalitat de Catalunya
• MD
  Ministerio de Economía y Competitividad
• CN
  Conselho Nacional de Desenvolvimento Científico e Tecnológico

  Award: 465376/2014-2
• FC
  Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro
• FD
  Financiadora de Estudos e Projetos
• MD
  Ministerio de Ciencia e Innovación

  Awards: PID2021-123012, CEX2020-001007-S, CEX2020-001058-M, PID2022-141079, SEV-2016-0588, PID2021-128989
• IN
  Instituto Nacional de Ciência e Tecnologia: Física Nuclear e Aplicações
• BH
  Bayerisch-Kalifornischen Hochschulzentrum
• OO
  Office of Science
• CF
  Center for Cosmology and Astroparticle Physics, Ohio State University
• KI
  Kavli Institute for Cosmological Physics, University of Chicago
• SA
  Science and Technology Facilities Council
• ER
  European Regional Development Fund
• HE
  High Energy Physics