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Drozdovsky I.1 and Tikhonov N.2
1Astronomical Institute, St.-Petersburg State
University, Petrodvoretz, 198904, Russia
2Special Astrophysical Observatory, N.Arkhyz, Karachai-Circassian Rep., 357147, Russia
In this paper we present the results of detailed B, V, R, I, and H
study of the isolated nearby blue compact dwarf (BCD) galaxy NGC6789.
Judging from the literature the observed galaxy has not been resolved
into stars up to now. On CCD frames obtained with 6m BTA telescope and
2.5m Nordic telescope the galaxy is well resolved into stars.
Its colour-magnitude diagram confirms two component
(core-halo) galaxy morphology, which consists of two stellar populations
distinct in structure and colour: an inner high surface-brightness
young population within 150 pc from the center of the galaxy,
and a relatively low surface-brightness intermediate-age population
extending out to at least 600 pc.
The distance of the galaxy, estimated from the
tip of the red giant branch (TRGB) is 2.1 Mpc which places
NGC6789 close to the Local Group. Using the colour of the RGB, we estimate
the metallicity of the halo population. Two acceptable results have
been obtained: [Fe/H] = -1.25 dex and [Fe/H] = -0.85 dex.
Key words: nearby galaxies: dwarf galaxies (NGC 6789): distance moduli: star content