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# File rvsao/Util/velcon.x
# By Doug Mink, Harvard-Smithsonian Center for Astrophysics
# April 30, 1997
# Subroutines to convert between velocity in km/sec and z = dwl/wl
# VEL2Z Convert velocity in km/sec to z = dwl/wl
# VEL2Z1 Convert velocity in km/sec to 1+z
# Z2VEL Convert velocity in z to km/sec
double procedure vel2z1 (velocity)
double velocity # Velocity in km/sec
double c # Velocity of light in km/sec
double z1 # 1+z (unitless)
begin
c = 299792.5
z1 = sqrt ((1.d0 + (velocity / c)) / (1.d0 - velocity / c))
return (z1)
end
double procedure vel2z (velocity)
double velocity # Velocity in km/sec
double c # Velocity of light in km/sec
double z # dwl / wl (unitless)
begin
c = 299792.5
z = vel2z1 (velocity) - 1.d0
return (z)
end
double procedure z2vel (z)
double z # dwl / wl (unitless)
double c # Velocity of light in km/sec
double velocity # Velocity in km/sec
begin
velocity = z12vel (1.d0 + z)
return (velocity)
end
double procedure z12vel (z)
double z # dwl / wl (unitless)
double c # Velocity of light in km/sec
double velocity # Velocity in km/sec
double z12 # (1+z)^2
begin
z12 = z1 * z1
velocity = c * ((z12 - 1.d0) / (z12 + 1.d0))
return (velocity)
end
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