Galactic longitude dependent galactic model parameters

We present the Galactic model parameters for thin disc estimated by Sloan Digital Sky Survey (SDSS) data of 14 940 stars with apparent magnitudes 16 < g(o) <= 21 in six intermediate latitude fields in the first Galactic quadrant. Star/galaxy separation was performed by using the SDSS photometric pipeline and the isodensity contours in the (g - r)(o) - (r - i)(o) two colour diagram. The separation of thin disc stars is carried out by the bimodal distribution of stars in the (g - r)o histogram, and the absolute magnitudes were evaluated by a procedure presented in the literature (Bilir, S., Karaali, S., Tuncel, S. 2005. AN 326, 321). Exponential density law fits better to the derived density functions for the absolute magnitude intervals 8 < M(g) <= 9 and 11 < M(g) <= 12, whereas sech/sech(2) laws are more appropriate for absolute magnitude intervals 9 < M(g) <= 10 and 10 < M(g) <= 11. We showed that the scaleheight and scatelength are Galactic longitude dependent. The average values and ranges of the scaleheight and the scalelength are < H > = 220 pc (196 <= H <= 234 pc) and < H > = 1900 pc (1561 <= h <= 2280 pc) respectively. This result would be useful to explain different numerical values claimed for those parameters obtained by different authors for the fields in different directions of the Galaxy. (c) 2006 Elsevier B.V. All rights reserved.