Implications of the WMAP Age Measurement for Stellar Evolution and Dark Energy

Abstract

The WMAP satellite has provided a new measurement of the age of the Universe, of $13.7 \pm 0.2$ Gyr. A comparison of this limit with constraints from stellar evolution imply that the oldest globular clusters in the Milky Way galaxy have a reasonable probability of have formed significantly after reionization. At the same time, one can derive a direct {\it upper limit} on the time after the big bang before globular clusters in our galaxies formed of $\approx 3$ Gyr, which significantly reduces our uncertainty since before the CMB age estimate. The WMAP age constraint can also be shown to provide a stringent {\it lower bound} on the equation of state of dark energy. A precise value of this lower bound would require a global analysis of the WMAP parameter constraints. However, making conservative assumptions about allowed parameter ranges and correlations one derives a lower bound of $ w > -1.22$. Combining this with the WMAP-quoted upper limit on $w$ thus gives roughly symmetric 95% confidence range $w =-1 \pm 0.22$.