In [1]:

    

using DiskJockey.constants


    

In [2]:

    

lam0 = lam0s["12CO3-2"] # microns
# lam0 = lam0s["13CO2-1"]
# lam0 = lam0s["12CO2-1"]


    

    
Out[2]:





866.9633734040698

In [3]:

    

c_kms


    

    
Out[3]:





299792.458

In [4]:

    

function wl_to_vel(wl)
    
    return c_kms * (wl - lam0)/lam0
end

function vel_to_wl(vel)
    beta = vel/c_kms # relativistic Doppler formula
    return lam0 * sqrt((1. - beta) / (1. + beta)) # [microns]
end


    

    
Out[4]:





vel_to_wl (generic function with 1 method)

In [5]:

    

# Wavelengths in the data set are
vmin = wl_to_vel(866.950)
vmax = wl_to_vel(866.996)
println("Velocities range from $vmin to $vmax and span ", vmax - vmin, " km/s")
println("Midpoint is ", (vmax + vmin)/2)


    

    




Velocities range from -4.624469499965454 to 11.282146040012217 and span 15.906615539977672 km/s
Midpoint is 3.328838270023381

In [18]:

    

# LSR velocities in Output image span from 2.38 kms to 9.18 km/s.
println(9.18 - 2.38)


    

    




6.8

In [12]:

    

wl_to_vel(867.)


    

    
Out[12]:





12.66533000001882

In [13]:

    

vel_to_wl(12.6653)


    

    
Out[13]:





866.9267476685413

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