## Abstract

We use 32 age measurements of passively evolving galaxies as a function of redshift to test and compare the standard model (λCDM) with the R_{h} = ct universe. We show that the latter fits the data with a reduced χ_{dof}^{2} = 0.435 for a Hubble constant = H_{0} 67.2_{-4.0} ^{+4.5} km s^{-1} Mpc^{-1}. By comparison, the optimal flat λCDM model, with two free parameters (including ω_{m} = 0.12_{-0.11}^{+0.54} and = - H 94.3+ 0 35.8 32.7 km s?1 Mpc-1), fits the age-z data with a reduced c = 0.428 dof 2 . Based solely on their cdof 2 values, both models appear to account for the data very well, though the optimized ?CDM parameters are only marginally consistent with those of the concordance model (Wm = 0.27 and H0 = 70 km s-1 Mpc-1). Fitting the age-z data with the latter results in a reduced χ_{dof}^{2} = 0.523. However, because of the different number of free parameters in these models, selection tools, such as the Akaike, Kullback and Bayes Information Criteria, favor R_{h} = ct over ?CDM with a likelihood of ?66.5%80.5% versus ∼19.5%33.5%. These results are suggestive, though not yet compelling, given the current limited galaxy age-z sample. We carry out Monte Carlo simulations based on these current age measurements to estimate how large the sample would have to be in order to rule out either model at a ∼99.7% confidence level. We find that if the real cosmology is λCDM, a sample of ?45 galaxy ages would be sufficient to rule out Rh = ct at this level of accuracy, while ?350 galaxy ages would be required to rule out λCDM if the real universe were instead Rh = ct. This difference in required sample size reflects the greater number of free parameters available to fit the data with λCDM.

Original language | English (US) |
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Article number | 35 |

Journal | Astronomical Journal |

Volume | 150 |

Issue number | 1 |

DOIs | |

State | Published - Jul 1 2015 |

## Keywords

- Galaxy: general
- cosmology: observations
- cosmology: theory
- early universe

## ASJC Scopus subject areas

- Astronomy and Astrophysics
- Space and Planetary Science