cosmoFns (version 1.1-1)

lookbackTime: Cosmic lookback time

Description

Compute cosmic lookback time given z and cosmological parameters

Usage

lookbackTime(z, omega.m = 0.27, omega.lambda = 0.73, H.0 = 71)

Arguments

z

Redshift

omega.m

Omega matter parameter

omega.lambda

Omega lambda parameter

H.0

Hubble constant in km/s/Mpc

Value

Lookback time in Gyr.

Details

Defaults for omega.m, omega.lambda, and omega.m, are from WMAP cosmology; omega.k (curvature term) is computed from relationship between omegas in flat cosmology (omega.k = 0).

References

"Principles of Physical Cosmology," P.J. Peebles, Princeton c. 1993, (5.63); "Distance Measures in Cosmology," Hogg (2000), arXiv:astro-ph/9905116, equation (30); "First-year WMAP observations...", Spergel et al., ApJS 148:175 (2003)

Examples

# NOT RUN {
# lookback time for z = 2
lookbackTime(2)
# Inverse problem, age of Earth (4.6 Gyr) example:
uniroot(function(x) lookbackTime(x) - 4.6, c(0,2))$root
# }