Astrophys. J., 852, 68-68 (2018/January-2)
On the nature of ultra-faint dwarf galaxy candidates. I. DES1, Eridanus III, and Tucana V.
CONN B.C., JERJEN H., KIM D. and SCHIRMER M.
Abstract (from CDS):
We use deep Gemini/GMOS-S g, r photometry to study the three ultra-faint dwarf galaxy candidates DES1, Eridanus III (Eri III), and Tucana V (Tuc V). Their total luminosities, MV(DES1) = -1.42 ± 0.50 and MV(Eri III) = -2.07 ± 0.50, and mean metallicities, [Fe/H]=-2.38–0.19+0.21 and [Fe/H]=-2.40–0.12+0.19, are consistent with them being ultra-faint dwarf galaxies, as they fall just outside the 1σ confidence band of the luminosity-metallicity relation for Milky Way satellite galaxies. However, their positions in the size-luminosity relation suggest that they are star clusters. Interestingly, DES1 and Eri III are at relatively large Galactocentric distances, with DES1 located at DGC=74±4 kpc and Eri III at DGC=91±4 kpc. In projection, both objects are in the tail of gaseous filaments trailing the Magellanic Clouds and have similar 3D separations from the Small Magellanic Cloud (SMC): ΔDSMC,DES1=31.7 kpc and ΔDSMC,EriIII=41.0 kpc, respectively. It is plausible that these stellar systems are metal-poor SMC satellites. Tuc V represents an interesting phenomenon in its own right. Our deep photometry at the nominal position of Tuc V reveals a low-level excess of stars at various locations across the GMOS field without a well-defined center. An SMC Northern Overdensity-like isochrone would be an adequate match to the Tuc V color-magnitude diagram, and the proximity to the SMC (12.°1; ΔDSMC,TucV=13 kpc) suggests that Tuc V is either a chance grouping of stars related to the SMC halo or a star cluster in an advanced stage of dissolution.
© 2018. The American Astronomical Society. All rights reserved.
galaxies: dwarf - Galaxy: halo - globular clusters: general - Hertzsprung-Russell and C-M diagrams - Local Group - Local Group
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