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tokens: UFD1. There are 12 resolved stars brighter than I = 28.5 mag in the net CMDs (Figures 2 (c) and (d)). The number of field contaminants with I 28.5 mag in the area covered by the UFD field is estimated to be 4.8 ± 0.3, while there are 15 stars in the area of UFD. Thus, the net number of the member stars in the area of the UFD is estimated to be 10 ± 4, which is consistent with the number derived after CMD decontamination. Eight of the 12 stars have a narrow range of colors with , showing a vertical sequence, while three of them show much redder colors than the others. Therefore, these eight stars are considered to show the RGB of Fornax UFD1, while three redder stars are probably foreground or background sources. Because of the small sample of the RGB stars in the CMD, it is not easy to derive an accurate distance to Fornax UFD1. We estimate approximately the distance to this UFD, assuming that the mean magnitude of the two brightest blue RGB stars in the CMD corresponds to the magnitude of the TRGB. The mean magnitude and color of these two stars are I = 27.38 ±0.14 mag and . This magnitude value is 0.24 mag fainter than the value of Virgo UFD1, I = 27.14 ±0.04 mag (Jang Lee 2014 ; see the lower panels in Figure 2 ). Applying the TRGB calibration in Jang Lee ( 2017 ) to this TRGB magnitude, we derive a value for the distance to Fornax UFD1, d = 19.0 ± 1.3 Mpc (). This value is consistent with the distance to NGC 1316. This shows that Fornax UFD1 is likely to belong to Fornax. In Figure 2 , we overlaid 12 Gyr isochrones for[ α /Fe] = 0.2 (Fabrizio et al. 2015 ) and [Fe/H] = −2.4 to −0.4 in the Dartmouth model (Dotter et al. 2008 ), which were shifted according to the distance and foreground reddening for Fornax UFD1. Although the number of stars is small, the RGB of UFD1 is, on average, bluer and narrower compared with the RGB of NGC 1316 in the control field. This shows that the mean metallicity of this new UFD is much lower than that of the NGC 1316 halo. The CMD of these RGB stars is matched roughly by the RGB part of the isochrones for low metallicity. It is noted that the RGB of Fornax UFD1 is even bluer than the RGB of the lowest metallicity with [Fe/H] ≈ −2.4. We estimate roughly the mean metallicity of the RGB stars to be [Fe/H] ≈ −2.4 ± 0.4. 3.3. Basic Parameters of Fornax UFD1 We constructed radial profiles of surface brightness and cumulative integrated magnitude of Fornax UFD1 using IRAF/ELLIPSE, as plotted in Figures 3 (a) and (b). We masked out cosmic rays and background galaxies in the original image and ran the ELLIPSE task adopting a smoothing option of 3 × 3 pixel binning. The radial profiles of surface brightness in Figure 3 show a flat core in the inner region at r 1′′ and decline rapidly in the outer region, showing that this UFD is a dynamically relaxed system like typical old star clusters. The radial profiles of surface brightness for r 4′′ are fitted well by a Sérsic law (Sérsic 1963 ) with an index n = 0.54 ± 0.06 for