2019ApJ...871L..31S

We report deep, single-dish 21 cm observations of NGC 1052-DF2, taken with the Green Bank Telescope. NGC 1052-DF2, proposed to be lacking in dark matter, is currently classified as an ultra-diffuse galaxy in the NGC 1052 group. We do not detect the galaxy, and derive an upper limit on the H I mass. The galaxy is extremely gas poor, and we find that a 3σ M_HI detection at a distance of 19 Mpc and using a line width of 3.2 km s^–1 would have an upper limit of M_HI,lim< 5.5×10⁵M_☉. At this mass limit, the gas fraction of neutral gas mass to stellar mass is extremely low, at M_H I_/M*_ < 0.0027. This extremely low gas fraction, comparable to Galactic dwarf spheroidals and gas-poor dwarf ellipticals, implies that either the galaxy is within the virial radius of NGC 1052, where its gas has been stripped due to its proximity to the central galaxy, or that NGC 1052-DF2 is at a distance that is large enough to inhibit detection of its gas. We also estimate the upper limit of the H I mass of NGC 1052-DF2 resided at 13 Mpc. This would give an H I mass of M_HI,lim< 2.5×10⁵M_☉, and an H I gas fraction if M_H I_/M*_ < 0.0024, becoming even more extreme for its environment. While the dark matter fraction would be less extreme at this distance, the neutral gas fraction would be unprecedented for an object in a low-density environment.