lumdist {astrolibR} R Documentation

## Calculate luminosity distance (in Mpc) of an object given its redshift

### Description

Calculate luminosity distance (in Mpc) of an object given its redshift

### Usage

```lumdist(z, h0=70, k, lambda0, omega_m, q0)
```

### Arguments

 `z` redshift, positive scalar or vector `h0` Hubble expansion parameter, in km/s/Mpc (default = 70.0) `k` curvature constant normalized to the closure density (default = 0.0 corresponding to a flat universe) `omega_m` matter density normalized to the closure density (default = 0.3) `lambda0` cosmological constant normalized to the closure density (default = 0.7) `q0` deceleration parameter, scalar (default = 0.55)

### Details

The luminosity distance in the Friedmann-Robertson-Walker model is taken from Carroll et al. (1992, p.511). It uses a closed form (Mattig equation) to compute the distance when the cosmological constant is zero, and otherwise computes the partial integral using the R function integrate. The integration can fail to converge at high redshift for closed universes with non-zero lambda.

No more than two of the four parameters (k, omega_M, lambda0, q0) should be specified. None of them need be specified if the default values are adopted.

### Value

 `lumdist` The result of the function is the luminosity distance (in Mpc) for each input value of z

### Author(s)

Written W. Landsman Raytheon ITSS 2000

R adaptation by Arnab Chakraborty June 2013

### References

Carroll, S. M., Press, W. H. and Turner, E. L., 1992, The cosmological constant, Ann. Rev. Astron. Astrophys., 30, 499-542

### Examples

```# Plot the distance of a galaxy in Mpc as a function of redshift out
#  to z = 5.0, assuming the default cosmology (Omega_m=0.3, Lambda = 0.7,
#  H0 = 70 km/s/Mpc)

z <- seq(0,5,length=51)
plot(z, lumdist(z), type='l', lwd=2, xlab='z', ylab='Distance (Mpc)')

# Now overplot the relation for zero cosmological constant and
# Omega_m=0.3

lines(z,lumdist(z, lambda=0, omega_m=0.3), lty=2, lwd=2)
```

[Package astrolibR version 0.1 Index]