Context :

Aims : To better understand our Galaxy , we investigate the pertinency of describing the system of nearby disk stars in terms of a two-components Schwarzschild velocity distribution.Using the proper motion and parallax information of Hipparcos database , we determine the parameters characterizing the local stellar velocity field of a sample of 22000 disk stars .
The sample we use is essentially the same as the one described by the criteria adopted to study the LSR and the stream motion of the nearby stellar population .

Methods : The selected data is modeled with a two component Schwarzschild velocity distribution whose parameters were determined by a least-square regression .
The celestial sphere was divided into 72 equal area regions used to determine the parameters minimizing the final velocity distribution function .

Results : We verify that the results are not significantly different for the early type stars from the classical treatment using a single Gaussian population distribution .
For late type stars in the subgiant branch , in contrast , we verify that the two-component model gives a much more satisfactory representation .
Our results indicate for each spectral class the presence of these late type stars of a low velocity dispersion population , with \sigma _ { u } \simeq 20 { km . s } ^ { -1 } coexisting with a high velocity dispersion population having \sigma _ { u } \simeq 40 { km . s } ^ { -1 } .
Both populations belong to the disk with scale heights of 120 { pc } and 220 { pc } , respectively , relative to the Galactic disk .

Conclusions :