Ghosts I: A new faint very isolated dwarf galaxy at D = 12 ± 2 Mpc

Antonela Monachesi, Eric F. Bell, David J. Radburn-Smith, Roelof S. De Jong, Jeremy Bailin, Julianne J. Dalcanton, Benne W. Holwerda, H. Alyson Ford, David Streich, Marija Vlajić, Daniel B. Zucker

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


We report the discovery of a new faint dwarf galaxy, GHOSTS I, using HST/ACS data from one of our GHOSTS (Galaxy Halos, Outer disks, Substructure, Thick disk, and Star clusters) fields. Its detected individual stars populate an approximately 1 mag range of its luminosity function (LF). Using synthetic color-magnitude diagrams (CMDs) to compare with the galaxy's CMD, we find that the colors and magnitudes of GHOSTS I's individual stars are most consistent with being young helium-burning and asymptotic giant branch stars at a distance of 12 ± 2 Mpc. Morphologically, GHOSTS I appears to be actively forming stars, so we tentatively classify it as a dwarf irregular (dIrr) galaxy, although future Hubble Space Telescope (HST) observations deep enough to resolve a larger magnitude range in its LF are required to make a more secure classification. GHOSTS I's absolute magnitude is , making it one of the least luminous dIrr galaxies known, and its metallicity is lower than [Fe/H] = -1.5 dex. The half-light radius of GHOSTS I is 226 ± 38 pc and its ellipticity is 0.47 ± 0.07, similar to Milky Way and M31 dwarf satellites at comparable luminosity. There are no luminous massive galaxies or galaxy clusters within 4 Mpc from GHOSTS I that could be considered as its host, making it a very isolated dwarf galaxy in the local universe.

Original languageEnglish (US)
Article number179
JournalAstrophysical Journal
Issue number2
StatePublished - Jan 10 2014
Externally publishedYes


  • galaxies: dwarf
  • galaxies: individual (GHOSTS I)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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