The HII galaxy Hubble diagram strongly favours Rh = ct over ΛCDM

Jun Jie Wei, Xue Feng Wu, Fulvio Melia

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


We continue to build support for the proposal to useHII galaxies (HIIGx) and giant extragalactic HII regions (GEHR) as standard candles to construct the Hubble diagram at redshifts beyond the current reach of Type Ia supernovae. Using a sample of 25 high-redshift HIIGx, 107 local HIIGx, and 24 GEHR, we confirm that the correlation between the emission-line luminosity and ionized-gas velocity dispersion is a viable luminosity indicator, and use it to test and compare the standard model ΛCDM and the Rh = ct universe by optimizing the parameters in each cosmology using a maximization of the likelihood function. For the flat ΛCDM model, the best fit is obtained with Ωm = 0.40 -0.09+0.09. However, statistical tools, such as the Akaike (AIC), Kullback (KIC) and Bayes (BIC) Information Criteria favour Rh = ct over the standard model with a likelihood of ≈94.8-98.8 per cent versus only ≈1.2-5.2 per cent. For wCDM (the version of ΛCDM with a dark-energy equation of state wde = pde/ρde rather than wde = wΛ =-1), a statistically acceptable fit is realized with Ωm = 0.22 -0.14 +0.16 and wde = -0.51+0.15 -0.25 which, however, are not fully consistent with their concordance values. In this case, wCDM has two more free parameters than Rh = ct, and is penalized more heavily by these criteria. We find that Rh = ct is strongly favoured over wCDM with a likelihood of ≈92.9-99.6 per cent versus only 0.4-7.1 per cent. The current HIIGx sample is already large enough for the BIC to rule out ΛCDM/wCDM in favour of Rh = ct at a confidence level approaching 3σ.

Original languageEnglish (US)
Pages (from-to)1144-1152
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
StatePublished - Dec 1 2016


  • Cosmological parameters
  • Cosmology: observations
  • Cosmology: theory
  • Distance scale
  • Galaxies: general
  • HII regions

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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