Title:Galaxy model by using infrared star counts

Abstract:
Most of the first quantitative models for the structure of the Galaxy used the star counts method to explore 
the relevant parameters as a whole. Some of the most important models are due to Bahcall & Soneira 
(1980), the Besançon group (Robin & Crezé (1986)), Wainscoat et al. (1992), Ortiz & Lépine (1993), 
among others. The data used suffered, however, of incomplete photometric coverage and poor spatial 
coverage. Even the IRAS survey, carried out in 1980’s over the whole sky in wavelengths between 12 
and 100 μm, suffers of completeness problems for weak sources due to moderate sensitivity and low 
spatial resolution. The advent of large area detectors in the near infrared, in 1990’s, allowed the 
realization of large scale surveys like 2MASS and DENIS. These surveys covered a magnitude range 
between 4 and 14 on J, H, Ks and I bands with complete spatial coverage and adequate photometric 
quality. These surveys were consolidated in public databases which can be queried easily, producing 
quantitative results for the comparison with galactic structure models. Taking as a starting point the Ortiz & 
Lépine star counts model, elaborated on the pre 2MASS era, we made comparisons between the 
predictions and the observed counts that are summarized in this work. We describe the systematics of 
building a grid in the sky, the model assumptions, how it works and possible paths for improvements. We 
also summarize a possible way of exploring the most important parameters with an algorithm that is 
adequate for large amounts of data and large number of parameters.