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Programme of the Galactic meridian: Star counts and galactic models. 1. Distributions of stellar magnitudes and colours
Author(s) -
Andruk V.,
Kharchenko N.,
Schilbach E.,
Scholz R.D.
Publication year - 1995
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.2103160605
Subject(s) - physics , astrophysics , astronomy , galaxy , stars , thick disk , thin disk , star count , disc , extinction (optical mineralogy) , galaxy formation and evolution , t tauri star , halo , k type main sequence star , optics
A comparison of observed stellar distributions with a three‐component model of the Galaxy is presented. The analysis is based on photometric and photoelectric data obtained along the main Galactic meridian and in two fields near the North Galactic pole (programme MEGA). The assumed model considers the Galaxy as composed of the disk (main sequence and disk red giants), the thick disk and spheroid populations. To model the observed colour distribution, we distinguish main sequence stars and disk red giants as the disk subsystem; white dwarfs, subdwarfs and intermediate giants as the thick disk subsystem; extreme subdwarfs, spheroid giants and horizontal branch stars as the spheroid subsystem. A statistical relation between the apparent and absolute magnitudes of stars which make the maximum contribution to the star counts for a given disk subsystem is derived. In order to achieve the best agreement between the model and observations, we fit the values of the ‘dip’ ( aw ) of the disk luminosity function, the correction to the absolute magnitude of disk red giants (Δ M V RG ) and the expression for interstellar extinction. As the main result, we obtained aw = 0.6 (logarithmic scale) and Δ M V RG = 0.5 mag; the interstellar extinction has to be taken into account by the modified Sandage law.