The Stellar Content and Distance to the Nearby Blue Compact Dwarf Galaxy NGC6789.

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

Abstract:

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

 
• 1. Introduction.
• 2. Observations and reductions.
• 3. The Results.
  • Colour-magnitude diagram.
  • 3.2. Metallicity.
  • 3.3. Distance.
  • 3.4. Integrated Light.
• 4. Concluding remarks.
• References