TY - JOUR
T1 - Ghosts I
T2 - A new faint very isolated dwarf galaxy at D = 12 ± 2 Mpc
AU - Monachesi, Antonela
AU - Bell, Eric F.
AU - Radburn-Smith, David J.
AU - De Jong, Roelof S.
AU - Bailin, Jeremy
AU - Dalcanton, Julianne J.
AU - Holwerda, Benne W.
AU - Alyson Ford, H.
AU - Streich, David
AU - Vlajić, Marija
AU - Zucker, Daniel B.
PY - 2014/1/10
Y1 - 2014/1/10
N2 - 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.
AB - 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.
KW - galaxies: dwarf
KW - galaxies: individual (GHOSTS I)
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U2 - 10.1088/0004-637X/780/2/179
DO - 10.1088/0004-637X/780/2/179
M3 - Article
AN - SCOPUS:84891274916
SN - 0004-637X
VL - 780
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 179
ER -