期刊
ASTROPHYSICAL JOURNAL LETTERS
卷 914, 期 1, 页码 -出版社
IOP Publishing Ltd
DOI: 10.3847/2041-8213/ac0335
关键词
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资金
- STScI grants [HST GO-15851, 14644, 15695]
- Gruber Science Fellowship
- NASA through Hubble Fellowship - Space Telescope Science Institute under NASA [HST-HF2-51454.001-A, NAS5-26555]
- National Science Foundation [AST-1616710]
- Research Corporation for Science Advancement Cottrell Scholar
- Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through an Emmy Noether Research Group [KR4801/1-1]
- DFG Sachbeihilfe [KR4801/2-1]
- European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program via the ERC Starting Grant MUSTANG [714907]
The distance to NGC 1052-DF2 has been determined to be 22.1+/-1.2 Mpc through 40 orbits of HST ACS data, confirming its proximity to the surface brightness fluctuation distance of the bright elliptical galaxy NGC 1052 and refuting the previous idea that its unusual properties could be explained by a closer distance of 20 Mpc.
The large and diffuse galaxies NGC 1052-DF2 and NGC 1052-DF4 have been found to have very low dark matter content and a population of luminous globular clusters (GCs). Accurate distance measurements are key to interpreting these observations. Recently, the distance to NGC 1052-DF4 was found to be 20.0 +/- 1.6 Mpc by identifying the tip of the red giant branch (TRGB) in 12 orbits of Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) imaging. Here we present 40 orbits of HST ACS data for NGC 1052-DF2 and use these data to measure its TRGB. The TRGB is readily apparent in the color-magnitude diagram. Using a forward model that incorporates photometric uncertainties, we find a TRGB magnitude of m (F814W,TRGB) = 27.67 +/- 0.10 mag. The inferred distance is D (TRGB) = 22.1 +/- 1.2 Mpc, consistent with the previous surface brightness fluctuation distances to the bright elliptical galaxy NGC 1052. The new HST distance rules out the idea that some of NGC 1052-DF2's unusual properties can be explained if it were at similar to 13 Mpc; instead, it implies that the galaxy's GCs are even more luminous than had been derived using the previous distance of 20 Mpc. The distance from NGC 1052-DF2 to NGC 1052-DF4 is well-determined at 2.1 +/- 0.5 Mpc, significantly larger than the virial diameter of NGC 1052. We discuss the implications for formation scenarios of the galaxies and for the external field effect, which has been invoked to explain the intrinsic dynamics of these objects in the context of modified Newtonian dynamics.
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