text: """Plot velocity distributions of Galactic sources."""
  import numpy as np
  import matplotlib.pyplot as plt
  from gammapy.astro.population import velocity_distributions
  from gammapy.utils.distributions import normalize
  
  # TODO: use Quantity
  v_min, v_max = 10, 3000  # km / s
  v = np.linspace(v_min, v_max, 200)
  
  for key in velocity_distributions:
      model = velocity_distributions[key]()
      label = model.__class__.__name__
      plt.plot(v, normalize(model, v_min, v_max)(v), linestyle='-', label=label)
  
  plt.xlim(v_min, v_max)
  plt.ylim(0, 0.004)
  plt.xlabel('Velocity [km/s]')
  plt.ylabel('Probability Density [(km / s)^-1]')
  plt.semilogx()
  plt.legend(prop={'size': 10})
  plt.show()
  