The Age-Redshift Relationship of Old Passive Galaxies
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}0={94.3}-35.8+32.7 km s-1 {{Mpc}}-1), fits the age-z data with a reduced {χ }{dof}2=0.428. Based solely on their {χ }{dof}2 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 }}}{{m}}=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 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}{{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}{{h}}={ct}. This difference in required sample size reflects the greater number of free parameters available to fit the data with ΛCDM.
- Publication:
-
The Astronomical Journal
- Pub Date:
- July 2015
- DOI:
- 10.1088/0004-6256/150/1/35
- arXiv:
- arXiv:1505.07671
- Bibcode:
- 2015AJ....150...35W
- Keywords:
-
- cosmology: observations;
- cosmology: theory;
- early universe;
- Galaxy: general;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 36 pages, 13 figures, 1 table