Astrophys. J., 780, 179 (2014/January-2)
GHOSTS I: a new faint very isolated dwarf galaxy at d = 12±2 mpc.
MONACHESI A., BELL E.F., RADBURN-SMITH D.J., DE JONG R.S., BAILIN J., DALCANTON J.J., HOLWERDA B.W., ALYSON FORD H., STREICH D., VLAJIC M. and ZUCKER D.B.
Abstract (from CDS):
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 Mv ∼ -9.85–0.33+0.4, 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.
galaxies: dwarf - galaxies: individual: GHOSTS I
Table 1: [MBR2014] GHOSTS I N=1.
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