Microlensing optical depth revisited with recent star counts

More reliable constraints on the microlensing optical depth can come from a better understanding of the Galactic model. Based on well-constrained Galactic bulge and disk models constructed from survey observations, such as those from HST, 2MASS, and SDSS, we calculate the microlensing optical depths toward Galactic bulge fields and compare them with recent results from microlensing surveys. We test the Χ² statistics of the microlensing optical depths expected from these models, as well as from previously proposed models, using two types of data: optical depth maps in (l, b) and averaged optical depth over Galactic longitude l as a function of latitude b. From this analysis, we find that the Galactic bulge models from 2MASS and Han & Gould, and model G2 of Stanek et al., show good agreement with the microlensing optical depth profiles for all the microlensing observations, compared with model E2 of Stanek et al. On the other hand, we find that models involving an SDSS disk model produce relatively higher Χ² values. It should be noted that modeled microlensing optical depths diverge at low Galactic latitudes, |b| ≲ 2°. Therefore, we suggest microlensing observations toward regions much closer to the center of the Galaxy to further test the proposed Galactic models, if technically feasible, rather than waiting for a larger data set of microlensing events.