The Delegate Survey: KOALA/AAOmega-IFU spectroscopy of three nearby dwarf galaxies
Abstract
Assessing the cosmological typicality of the Local Group is crucial for establishing whether its dwarf galaxy population is representative. To this end, the Delegate Survey targets dwarf galaxies in Local Group analogues for systematic comparison. As a pilot study for the Delegate Survey, we obtained integral-field spectra of three dwarf galaxies, GAMA 79098, GAMA 569709, and HIPASS J1159-19 S2, in two nearby galaxy groups using the KOALA instrument on the AAT. The galaxies were mapped at a spatial sampling of 1.25 arcsec per spaxel, providing two-dimensional spectral coverage of both the stellar and ionised gas components. Using continuum and emission-line maps, we investigate the ionisation structure, star-forming properties, metallicity, star formation histories, and velocity fields of each system. GAMA 79098 exhibits properties closely analogous to the SMC, with ongoing star formation superimposed on an old stellar population and moderate rotational support. GAMA 569709 resembles transition-type Local Group (LG) dwarfs such as NGC 147 and NGC 185, showing predominantly an old stellar population. HIPASS J1159-19 S2 is dominated by young stars and intense star-forming complexes, consistent with a dynamically young, gas-rich galaxy group environment. The two GAMA dwarfs follow the LG stellar mass-metallicity relation within uncertainties, while HIPASS J1159-19 S2 appears approximately 0.5 dex more metal-rich for its stellar mass. Overall, the structural, chemical, and kinematic properties of these dwarfs overlap substantially with analogous LG dwarfs.
Versions
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BibTeX
@misc{ko2026delegate,
title = {{The Delegate Survey: KOALA/AAOmega-IFU spectroscopy of three nearby dwarf galaxies}},
author = {Kyungdo Ko and Helmut Jerjen and Sarah M. Sweet and Ángel R. López-Sánchez and Simon Deeley and Caroline Foster and Holger Baumgardt and Pratyush Kumar Das and Adebusola Alabi},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.18319},
eprint = {2609.18319},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.18319},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The Delegate Survey: KOALA/AAOmega-IFU spectroscopy of three nearby dwarf galaxies
AU - Kyungdo Ko
AU - Helmut Jerjen
AU - Sarah M. Sweet
AU - Ángel R. López-Sánchez
AU - Simon Deeley
AU - Caroline Foster
AU - Holger Baumgardt
AU - Pratyush Kumar Das
AU - Adebusola Alabi
PY - 2026
DA - 2026/09/16
PB - arXiv
DO - 10.48550/arxiv.2609.18319
UR - https://arxiv.org/abs/2609.18319
AB - Assessing the cosmological typicality of the Local Group is crucial for establishing whether its dwarf galaxy population is representative. To this end, the Delegate Survey targets dwarf galaxies in Local Group analogues for systematic comparison. As a pilot study for the Delegate Survey, we obtained integral-field spectra of three dwarf galaxies, GAMA 79098, GAMA 569709, and HIPASS J1159-19 S2, in two nearby galaxy groups using the KOALA instrument on the AAT. The galaxies were mapped at a spatial sampling of 1.25 arcsec per spaxel, providing two-dimensional spectral coverage of both the stellar and ionised gas components. Using continuum and emission-line maps, we investigate the ionisation structure, star-forming properties, metallicity, star formation histories, and velocity fields of each system. GAMA 79098 exhibits properties closely analogous to the SMC, with ongoing star formation superimposed on an old stellar population and moderate rotational support. GAMA 569709 resembles transition-type Local Group (LG) dwarfs such as NGC 147 and NGC 185, showing predominantly an old stellar population. HIPASS J1159-19 S2 is dominated by young stars and intense star-forming complexes, consistent with a dynamically young, gas-rich galaxy group environment. The two GAMA dwarfs follow the LG stellar mass-metallicity relation within uncertainties, while HIPASS J1159-19 S2 appears approximately 0.5 dex more metal-rich for its stellar mass. Overall, the structural, chemical, and kinematic properties of these dwarfs overlap substantially with analogous LG dwarfs.
ER -