2015/05/28 by Jun-Jie Wei, Xue-Feng Wu, Fulvio Melia +2
Physics and Astronomy · #astro-ph.CO
paper · pdf · doi:10.1088/0004-6256/150/1/35
36 pages, 13 figures, 1 table; accepted for publication in The Astronomical Journal. arXiv admin note: text overlap with arXiv:1405.2388
arxiv created 2015/05/28 · arxiv updated 2015/07/15
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\rm h=ct Universe. We show that the latter fits the data with a reduced χ2\rm dof=0.435 for a Hubble constant H0= 67.2-4.0+4.5 km \rm s-1 \rm Mpc-1. By comparison, the optimal flat ΛCDM model, with two free parameters (including Ω\rm m=0.12-0.11+0.54 and H0=94.3-35.8+32.7 km \rm s-1 \rm Mpc-1), fits the age-z data with a reduced χ2\rm dof=0.428. Based solely on their χ2\rm dof values, both models appear to account for the data very well, though the optimized ΛCDM parameters are only marginally consistent with those of the concordance model (Ω\rm m=0.27 and H0= 70 km \rm s-1 \rm Mpc-1). Fitting the age-z data with the latter results in a reduced χ2\rm dof=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, favour R\rm h=ct over ΛCDM 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 R\rm h=ct at this level of accuracy, while ∼ 350 galaxy ages would be required to rule out ΛCDM if the real Universe were instead R\rm h=ct.