Hubble Space Telescope Imaging of Isolated Local Volume Dwarfs GALFA-Dw3 and Dw4

Understand

We present observations of the dwarf galaxies GALFA Dw3 and GALFA Dw4 with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST).

• These galaxies were initially discovered as optical counterparts to compact HI clouds in the GALFA survey.
• Both objects resolve into stellar populations which display an old red giant branch, younger helium burning, and massive main sequence stars.
• We use the tip of the red giant branch method to determine the distance to each galaxy, finding distances of 7.61$_{-0.29}^{+0.28}$ Mpc and 3.10$_{-0.17}^{+0.16}$ Mpc, respectively.