Galactic structure from the Spacelab infrared telescope. II, Luminosity models of the Milky Way

The three-dimensional luminosity distribution of the Milky Way has been determined from a 2.4 μm map of the northern Galactic plane. The radial surface brightness profile of the disk has an exponential scale length of 3.0 kpc (assuming R 0 =8 kpc). The vertical distribution of light follows the law exp (−|z|/h z ) more closely than a canonical sech 2 profile. In the solar neighborhood, the scale height h z is ∼247 pc (assuming R 0 =8 kpc), in agreement with star counts perpendicular to the galactic plane. The scale height is not constant with radius but decreases to ∼165 pc at R=5 kpc.