A Tip of the Red Giant Branch Distance to the Dark Matter Deficient Galaxy NGC1052-DF4 from Deep Hubble Space Telescope Data

TL;DR

This study measures the distance to the dark matter deficient galaxy NGC1052-DF4 using deep HST data and the tip of the red giant branch method, confirming its distance and ruling out errors as an explanation for its unusual properties.

Contribution

First TRGB distance measurement to NGC1052-DF4 using deep HST imaging, confirming its distance and supporting its classification as a dark matter deficient galaxy.

Findings

TRGB distance of 20.0 ± 1.6 Mpc to NGC1052-DF4

Distance consistent with previous SBF measurements

Unusual properties not due to distance errors

Abstract

Previous studies have shown that the large, diffuse galaxies NGC1052-DF2 and NGC1052-DF4 both have populations of unusually luminous globular clusters as well as a very low dark matter content. Here we present newly-obtained deep Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) imaging of one of these galaxies, NGC1052-DF4. We use these data to measure the distance of the galaxy from the location of the tip of the red giant branch (TRGB). We find a rapid increase in the number of detected stars fainter than $m_{F814W} \sim 27.3$, which we identify as the onset of the red giant branch. Using a forward modeling approach that takes the photometric uncertainties into account, we find a TRGB magnitude of $m_{F814W,\rm TRGB}=27.47 \pm 0.16$. The inferred distance, including the uncertainty in the absolute calibration, is $D_{\rm TRGB}=20.0 \pm 1.6$ Mpc. The TRGB distance of NGC1052-DF4 is consistent with the previously-determined surface brightness fluctuation distance of $D_{\rm SBF}=18.7\pm 1.7$ Mpc to NGC1052-DF2 and is consistent with the distance of the bright elliptical galaxy NGC1052. We conclude that the unusual properties of these galaxies cannot be explained by distance errors.