KDG 218, a Nearby Ultra-Diffuse Galaxy

I. D. Karachentsev; L. N. Makarova; M. E. Sharina; V. E. Karachentseva

doi:10.1134/S1990341317040022

paper

KDG 218, a Nearby Ultra-Diffuse Galaxy

arXiv:1711.06074 · doi:10.1134/S1990341317040022

Abstract

We present properties of the low-surface-brightness galaxy KDG 218 observed with the HST/ACS. The galaxy has a half-light (effective) diameter of $a_{e} = 4 7^{''}$ and a central surface brightness of $S B_{V} (0) = 24. 4^{m} / s q^{''}$ . The galaxy remains unresolved with the HST/ACS, which implies its distance of { $D > 13.1$ Mpc} and linear effective diameter of $A_{e} > 3.0$ kpc. We notice that KDG 218 is most likely associated with a galaxy group around the massive lenticular NGC 4958 galaxy at approximately $22$ Mpc, or with the Virgo Southern Extension filament at approximately $16.5$ Mpc. At these distances, the galaxy is classified as an ultra-diffuse galaxy (UDG) similar to those found in the Virgo, Fornax, and Coma clusters. We also present a sample of 15 UDG candidates in the Local Volume. These sample galaxies have the following mean parameters: $⟨ D ⟩ = 5.1$ Mpc, $⟨ A_{e} ⟩ = 4.8$ kpc, and $⟨ S B_{B} (e)⟩ = 27. 4^{m} / s q^{''}$ . All the local UDG candidates reside near massive galaxies located in the regions with the mean stellar mass density (within 1 Mpc) about 50 times greater than the average cosmic density. The local fraction of UDGs does not exceed 1.5% of the Local Volume population. We notice that the presented sample of local UDGs is a heterogeneous one containing irregular, transition, and tidal types, as well as objects consisting of an old stellar population.

arXiv comment14 pages, 4 figures, 3 tables, published in the Astrophysical Bulletin

KDG 218, a Nearby Ultra-Diffuse Galaxy

Abstract

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