James Webb Space Telescope Feed Post

Harvard ADS: Reconstructing Cosmic History: JWST-Extended Mapping of the Hubble Flow from z \sim 0 to z \sim7.5 with HII Galaxies

Paper abstract: Over twenty years ago, Type Ia Supernovae (SNIa) [arXiv:astro-ph/9805201, arXiv:astro-ph/9812133] observations revealed an accelerating Universe expansion, suggesting a significant dark energy presence, often modelled as a cosmological constant, \Lambda. Despite its pivotal role in cosmology, the standard \LambdaCDM model remains largely underexplored in the redshift range between distant SNIa and the Cosmic Microwave Background (CMB). This study harnesses the James Webb Space Telescope's advanced capabilities to extend the Hubble flow mapping across an unprecedented redshift range, from z ~ 0 to z ~ 7.5. Utilising a dataset of 231 HII galaxies and extragalactic HII regions, we employ the \text{L}-\sigma relation, correlating the luminosity of Balmer lines with their velocity dispersion, to define a competitive technique for measuring cosmic distances. This approach maps the Universe's expansion over more than 12 billion years, covering 95\% of its age. Our analysis, using Bayesian inference, constrains the parameter space \lbrace h, \Omega_m, w_0\rbrace = \lbrace 0.731\pm0.039, 0.302^{+0.12}_{-0.069}, -1.01^{+0.52}_{-0.29}\rbrace (statistical) for a flat Universe. These results provide new insights into cosmic evolution and suggest uniformity in the photo-kinematical properties of young massive ionizing clusters in giant HII regions and HII galaxies across most of the Universe's history.