# lumdist: Calculate luminosity distance (in Mpc) of an object given its... In astrolibR: Astronomy Users Library

## Description

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

## Usage

 `1` ```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

 ``` 1 2 3 4 5 6 7 8 9 10 11``` ```# 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) ```

### Example output ```
```

astrolibR documentation built on May 2, 2019, 3:26 a.m.