zang {astrolibR} | R Documentation |
Determine the angular size of an object as a function of redshift
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
Omega_m + lambda0 + k = 1
and
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
# 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)')