TY - JOUR
T1 - A Trio of New Local Group Galaxies with Extreme Properties
AU - McConnachie, Alan W.
AU - Huxor, Avon
AU - Martin, Nicolas F.
AU - Irwin, Mike J.
AU - Chapman, Scott C.
AU - Fahlman, Gregory
AU - Ferguson, Annette M. N.
AU - Ibata, Rodrigo A.
AU - Lewis, Geraint F.
AU - Richer, Harvey
AU - Tanvir, Nial R.
PY - 2008/12/1
Y1 - 2008/12/1
N2 - We report on the discovery of three new dwarf galaxies in the Local
Group. These galaxies are found in new CFHT/MegaPrime g,i imaging of the
southwestern quadrant of M31, extending our extant survey area to
include the majority of the southern hemisphere of M31's halo out to 150
kpc. All these galaxies have stellar populations which appear typical of
dwarf spheroidal (dSph) systems. The first of these galaxies, Andromeda
XVIII, is the most distant Local Group dwarf discovered in recent years,
at ~1.4 Mpc from the Milky Way (~600 kpc from M31). The second galaxy,
Andromeda XIX, a satellite of M31, is the most extended dwarf galaxy
known in the Local Group, with a half-light radius of rh~1.7
kpc. This is approximately an order of magnitude larger than the typical
half-light radius of many Milky Way dSphs, and reinforces the difference
in scale sizes seen between the Milky Way and M31 dSphs (such that the
M31 dwarfs are generally more extended than their Milky Way
counterparts). The third galaxy, Andromeda XX, is one of the faintest
galaxies so far discovered in the vicinity of M31, with an absolute
magnitude of order MV~-6.3. Andromeda XVIII, XIX, and XX
highlight different aspects of, and raise important questions regarding,
the formation and evolution of galaxies at the extreme faint end of the
luminosity function. These findings indicate that we have not yet
sampled the full parameter space occupied by dwarf galaxies, although
this is an essential prerequisite for successfully and consistently
linking these systems to the predicted cosmological dark matter
substructure.
AB - We report on the discovery of three new dwarf galaxies in the Local
Group. These galaxies are found in new CFHT/MegaPrime g,i imaging of the
southwestern quadrant of M31, extending our extant survey area to
include the majority of the southern hemisphere of M31's halo out to 150
kpc. All these galaxies have stellar populations which appear typical of
dwarf spheroidal (dSph) systems. The first of these galaxies, Andromeda
XVIII, is the most distant Local Group dwarf discovered in recent years,
at ~1.4 Mpc from the Milky Way (~600 kpc from M31). The second galaxy,
Andromeda XIX, a satellite of M31, is the most extended dwarf galaxy
known in the Local Group, with a half-light radius of rh~1.7
kpc. This is approximately an order of magnitude larger than the typical
half-light radius of many Milky Way dSphs, and reinforces the difference
in scale sizes seen between the Milky Way and M31 dSphs (such that the
M31 dwarfs are generally more extended than their Milky Way
counterparts). The third galaxy, Andromeda XX, is one of the faintest
galaxies so far discovered in the vicinity of M31, with an absolute
magnitude of order MV~-6.3. Andromeda XVIII, XIX, and XX
highlight different aspects of, and raise important questions regarding,
the formation and evolution of galaxies at the extreme faint end of the
luminosity function. These findings indicate that we have not yet
sampled the full parameter space occupied by dwarf galaxies, although
this is an essential prerequisite for successfully and consistently
linking these systems to the predicted cosmological dark matter
substructure.
UR - http://www.scopus.com/inward/record.url?scp=56849117613&partnerID=8YFLogxK
U2 - 10.1086/591313
DO - 10.1086/591313
M3 - Article
SN - 1538-4357
VL - 688
SP - 1009
EP - 1020
JO - Astrophysical Journal
JF - Astrophysical Journal
ER -