zang {astrolibR}R Documentation

Determine the angular size of an object as a function of redshift

Description

Determine the angular size of an object as a function of redshift

Usage

zang(dl, z, h0, k, lambda0, omega_m, q0)

Arguments

dl

linear size of the object, in kpc, scalar or vector

z

redshift, 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)

lambda0

cosmological constant normalized to the closure density (default = 0.7)

omega_m

matter density normalized to the closure density (default = 0.3)

q0

deceleration parameter, scalar corresponding to

-R*(R'')/(R')^2

(default = -0.55)

Details

This function requires an input size in kpc and returns an angular size in arc seconds.

Default cosmology has a Hubble constant of 70 km/s/Mpc, Omega (matter)=0.3 and a normalized cosmological constant Lambda = 0.7. However these values can be changed by the user. Note that

Omega_m + lambda0 + k = 1

and

q0 = 0.5*omega_m - lambda0

.

Value

angsiz

angular size of the object at the given redshift, in arc seconds, scalar or vector

Author(s)

Written J. Hill STX 1988

R adaptation by Arnab Chakraborty June 2013

See Also

lumdist

Examples

# What would be the angular size of galaxy of diameter 50 kpc at a redshift
#      of 1.5 in an open universe with Lambda = 0 and Omega (matter) = 0.3.
#      Assume the default Hubble constant value of 70 km/s/Mpc.
# Result: 6.58 arc seconds
      
zang(50, 1.5, lambda = 0, omega_m = 0.3)

# Plot the angular size of a 50 kpc diameter galaxy as a function of 
#      redshift for the default cosmology (Lambda = 0.7, Omega_m=0.3) up to 
#      z = 0.5

# zseq = seq(0.01,0.5,length=50)
# plot(zseq, zang(50.0,zseq),xlab='z',ylab='Angular Size (arcsec)')

[Package astrolibR version 0.1 Index]