paper

The Distance of the Dark Matter Deficient Galaxy NGC1052-DF2

arXiv:1807.06025 · doi:10.3847/2041-8213/aada4d

Abstract

We recently inferred that the galaxy NGC1052-DF2 has little or no dark matter and a rich system of unusual globular clusters. We assumed that the galaxy is a satellite of the luminous elliptical galaxy NGC1052 at ~20 Mpc, on the basis of its surface brightness fluctuations (SBF) distance of Mpc, its radial velocity of ~1800 km/s, and its projected position. Here we analyze the color-magnitude diagram (CMD) of NGC1052-DF2, following the suggestion by Trujillo et al. (2018) that the tip of the red giant branch (TRGB) can be detected in currently available HST data and the galaxy is at ~13 Mpc. Using fully populated galaxy models we show that the CMD is strongly influenced by blends. These blends produce a "phantom" TRGB ~2 times brighter than the true TRGB, which can lead to erroneous distance estimates ~1.4 times smaller than the actual distance. We compare NGC1052-DF2 to model images as well as other galaxies in our HST sample, and show that the large population of unblended RGB stars expected for distances of ~13 Mpc is not detected. We also provide a new distance measurement to NGC1052-DF2 that is free of calibration uncertainties, by anchoring it to a satellite of the megamaser host galaxy NGC4258. From a megamaser-TRGB-SBF distance ladder we obtain Mpc, consistent with our previous measurement and with the distance to the elliptical galaxy NGC1052.

arXiv commentAccepted for publication in ApJ Letters. The key point of the paper is made in Figure 2. All data and models are available upon request. Minor changes compared to V1 make the paper more of a stand-alone analysis and less of a response to Trujillo et al. (2018). Also see the independent analysis of Blakeslee & Cantiello (arXiv:1808.02176)

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