A new model for the luminosity distribution in the inner Milky Way is found , using a non-parametric penalized maximum-likelihood algorithm to deproject a dereddened COBE/DIRBE L-band map of the inner Galaxy .
The model is also constrained by the apparent magnitude ( line-of-sight ) distributions of clump giant stars in certain bulge fields .
An important new feature is the inclusion of a spiral arm model in the disk .

Spiral arms make the model appear broader on the sky , thus our bar is more elongated than in previous eight-fold symmetric models .
They also lead to a smoother disk model interior to the Sun .
The bar length is \approx 3.5 { kpc } and its axis ratios are 1 : ( 0.3-0.4 ) :0.3 , independent of whether the spiral arm model is 4-armed or 2-armed .
The larger elongation in the plane makes it possible to reproduce the observed clump giant distributions as well .
With only the surface brightness data a small model degeneracy is found even for fixed orientation of the bar , amounting to about \pm 0.1 uncertainty in the in-plane axial ratio .
Including the clump giant data removes most of this degeneracy and also places additional constraints on the bar ’ s orientation angle .
We estimate 15 \deg \mathrel { \hbox to 0.0 pt { \lower 3.0 pt \hbox { $ \mathchar 536 $ } \hss } \raise 2. % 0 pt \hbox { $ \mathchar 316 $ } } \varphi _ { bar } \mathrel { \hbox to 0.0 pt { \lower 3.0 % pt \hbox { $ \mathchar 536 $ } \hss } \raise 2.0 pt \hbox { $ \mathchar 316 $ } } 30 \deg , with the best models obtained for 20 \deg \mathrel { \hbox to 0.0 pt { \lower 3.0 pt \hbox { $ \mathchar 536 $ } \hss } \raise 2. % 0 pt \hbox { $ \mathchar 316 $ } } \varphi _ { bar } \mathrel { \hbox to 0.0 pt { \lower 3.0 % pt \hbox { $ \mathchar 536 $ } \hss } \raise 2.0 pt \hbox { $ \mathchar 316 $ } } 25 \deg .

We use our reference model to predict a microlensing optical depth map towards the bulge , normalising its mass by the observed terminal velocity curve .
For clump giant sources at ( l,b ) = ( 3.9 \deg, - 3.8 \deg ) we find \tau _ { -6 } \equiv \tau / 10 ^ { -6 } = 1.27 , within 1.8 \sigma of the new MACHO measurement given by Popowski et al .
The value for all sources at ( l,b ) = ( 2.68 \deg, - 3.35 \deg ) is \tau _ { -6 } = 1.1 , still > 3 \sigma away from the published MACHO DIA value .
The dispersion of these \tau _ { -6 } values within our models is \simeq 10 \% .
Because the distribution of sources is well-fit by the NIR model , increasing the predicted optical depths by > 20 \% will be difficult .
Thus the high value of the measured clump giant optical depth argues for a near-maximal disk in the Milky Way .