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Deep Imaging of the Very Isolated Dwarf Galaxy NGC 6789

Ignacio Trujillo, Sergio Guerra Arencibia, Ignacio Ruiz Cejudo, Mireia Montes, Miguel R. Alarcon, and Miquel Serra-Ricart

Published November 2025 • © 2025. The Author(s). Published by the American Astronomical Society.
Research Notes of the AAS, Volume 9, Number 11Citation Ignacio Trujillo et al 2025 Res. Notes AAS 9 303DOI 10.3847/2515-5172/ae1cbeAuthorsFiguresReferences

Abstract

We present deep optical imaging of the extremely isolated dwarf galaxy NGC 6789, obtained with the new 2 m Two-meter Twin Telescope at Teide Observatory. Despite its location in the Local Void, NGC 6789 exhibits surprising recent central star formation equivalent to approximately 4% of its total stellar mass. The origin of the gas necessary for this level of star formation remains unknown. Our data reach surface brightness limits of 29.8, 29.4, and 28.9 mag arcsec⁻² in the Sloan g, r, and i filters, respectively, and reveal no evidence of tidal features or merger remnants down to ∼30 mag arcsec⁻² (or equivalently, at a radial distance larger than 1.6 kpc). The galaxy’s undisturbed outer elliptical morphology suggests that its recent central star formation was likely produced by either in-situ residual gas or by the accretion of external pristine gas not associated with a minor merging activity.