DDO68-C: HST confirms yet another companion of the isolated dwarf galaxy DDO 68

Matteo Correnti; Francesca Annibali; Michele Bellazzini; Mariarosa Marinelli; Alessandra Aloisi; Michele Cignoni; Monica Tosi; Raffaele Pascale; John M. Cannon; Lila Schisgal; Leslie K. Hunt; Elena Sacchi; Sangmo T. Sohn

arXiv · 2502.18171

DDO68-C: HST confirms yet another companion of the isolated dwarf galaxy DDO 68

Matteo Correnti·Francesca Annibali·Michele Bellazzini·Mariarosa Marinelli·Alessandra Aloisi·Michele Cignoni·Monica Tosi·Raffaele Pascale·John M. Cannon·Lila Schisgal·Leslie K. Hunt·Elena Sacchi·Sangmo T. Sohn

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Abstract

We present the results of deep Hubble Space Telescope photometry of the dwarf galaxy DDO 68-C, proposed as possibly associated with the isolated peculiar dwarf DDO 68. The new data resolve for the first time the stars of DDO 68-C down to well below the tip of the Red Giant Branch (RGB), revealing a low mass (M$_{*}$ $\sim$ 1.5 $\times$ 10$^7$ M$_{\odot}$) star forming galaxy with a backbone of old stars. By means of a fully homogeneous analysis and using the RGB tip as a standard candle, we find that DDO 68 and DDO 68-C lie at the same distance from us, within the uncertainties (D = 12.6 $\pm$ 0.3 Mpc and D = 12.7 $\pm$ 0.4 Mpc, respectively), thus confirming that the two dwarfs are physically associated. While paired dwarf galaxies with mutual projected distance similar to DDO 68 and DDO 68-C are not exceptional in the Lynx-Cancer Void where they live, DDO 68 remains a unicum as, in addition to the newly confirmed companion, it records the evidence of at least two other satellites.

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Matteo Correnti, Francesca Annibali, Michele Bellazzini, Mariarosa Marinelli, Alessandra Aloisi, Michele Cignoni, Monica Tosi, Raffaele Pascale, John M. Cannon, Lila Schisgal, Leslie K. Hunt, Elena Sacchi, Sangmo T. Sohn. 2025-02-25. DDO68-C: HST confirms yet another companion of the isolated dwarf galaxy DDO 68. https://arxiv.org/abs/2502.18171

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