Kinematical determination of the luminosity function in the solar neighborhood

Vicente, B.; Garzon, F.
Highlights of Spanish Astrophysics VI, Proceedings of the IX Scientific Meeting of the Spanish Astronomical Society (SEA), held in Madrid, September 13 - 17, 2010, Eds.: M. R. Zapatero Osorio, J. Gorgas, J. Maíz Apellániz, J. R. Pardo, and A. Gil de Paz., p. 552-552


The luminosity function is not only crucial to know the stellar density distribution in space, and thus to know the structure of the Galaxy; it also allows the determination of the stellar mass function using the mass-luminosity relationship. The luminosity and mass functions are crucial to understand star formation and the evolution of the Milky Way. It is customary to assume that the luminosity function in the solar neighborhood, which can be obtained directly from precise star counts, represents well that of the Galactic disk, if not the whole Milky Way and similar external galaxies. Under this assumption, we simply need to calculate in the solar vicinity and then move it to the disk area of interest. In this regard, the larger the sample used for determining more reliable is the extrapolation to galactic studies. We have determined the luminosity function in the solar neighborhood up to 200 pcs considering the proper motions as distance estimators. We used the parameter ``reduced proper motion'' (Luyten 1938) for calibration of the apparent magnitudes to absolute ones. This calibration must be done with kinematically similar populations, i.e., they share the same velocity distribution. So, prior to calculating the luminosity determination we used the SKY model (Wainscoat et al. 1992) to separate stars with different kinematic evolution in our catalogue. As our kinematical database, we used the CdC-SF Catalogue (Vicente et al. 2010), which has proper motion precision similar to that of Hipparcos but to much fainter magnitudes (V=15). Such a rich data allow getting the luminosity function for distances greater than those identified so far by extending existing results. Have greater distances involved have information of the luminosity function for stars more luminous, since the number of bright stars near the sun is quite low. Also, a larger sample with smaller proper motions produce a luminosity function more adapted to the real Galaxy model due to decrease the correction factor of completeness.