zang: Determine the angular size of an object as a function of...
In astrolibR: Astronomy Users Library

Description Usage Arguments Details Value Author(s) See Also Examples

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

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

`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)

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

1	Omega_m + lambda0 + k = 1

and

1	q0 = 0.5*omega_m - lambda0

angsiz

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

Written J. Hill STX 1988

R adaptation by Arnab Chakraborty June 2013

lumdist

# 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)')