We study the use of parallax microlensing to separate the effects of the mass function of dark massive halo objects ( MHOs or ‘ machos ’ ) on the one hand and their spatial distribution and kinematics on the other .
This disentanglement is supposed to allow a much better determination of the two than could be achieved entirely on the basis of the durations of events .
We restrict our treatment to the same class of power-law spherical models for the halo of MHOs studied in a previous paper [ ] .
Whereas the duration-based error in the average MHO mass , \bar { \mu } \equiv \bar { M } / M _ { \odot } exceeds ( at N = 100 events ) \bar { \mu } by a factor of 2 or more , parallax microlensing remarkably brings it down to 15-20 % of \bar { \mu } , regardless of the shape of the mass function .
In addition , the slope \alpha of the mass function , dn / d \mu \propto \mu ^ { \alpha } , can be inferred relatively accurately ( \sigma _ { \alpha } < 0.4 ) for a broader range , -3 < \alpha < 0 .
The improvement in the inference of the halo structure is also significant : the index \gamma of the density profile ( \rho \sim R ^ { - \gamma } ) can be obtained with the error \sigma _ { \gamma } < 0.4 .
While in a typical situation the errors for the parameters specifying the velocity dispersion profile are of about the same magnitude as the parameters , virtually all the uncertainty is ‘ concentrated ’ in linear combinations of the parameters that may have little influence on the profile and thus allow its reasonably accurate inference .