For instance, fitting model isochrones
in the color-magnitude space allowed
us to establish the age and metallicity
of the underlying stellar population; it
also isolated those stars giving us an
opportunity to perform a structural
analysis of each object by obtaining
half-light radius and ellipticity. From
this we could fit the radial profile to un-
derstand how the stars are distributed.
We further obtained a stellar luminosi-
ty function, which helped us to explore
the possibilities of mass segregation.
DES 1 and Eri III:
A Comparative Review
The sketch in Figure 4 shows the workflow
from image to data products. For the cases of
DES 1 and Eri III, this process worked excep-
tionally well revealing that the fundamental
properties of the two stellar populations are
remarkably similar. They have essentially the
same metallicity ([Fe/H] DES 1 = -2.38 vs. [Fe/H]
= -2.40 dex) and mean alpha abundance
Eri III
([α/Fe] ≈ +0.2 dex for both), along with com-
parable ages (11.2 billion years (Gyr) vs. 12.5
Gyr).
Structurally, DES 1 and Eri III also share simi-
lar properties: ellipticity (0.41 DES 1 vs. 0.44 Eri III );
position angle (112° DES 1 vs. 109° Eri III ); and Eri
III is about 1.5 times larger than DES 1 and
slightly more luminous (M V, DES 1 = -2.07 vs. M V,
= -1.42).
Er iIII
When it comes to their location in the Milky
Way halo, they are projected onto the trailing
filaments of neutral hydrogen gas from the
Figure 3.
Color-magnitude
diagrams for DES 1, Eri
III, and Tuc V (from left to
right, respectively). The
rectangular outline within
each frame shows the
window of the discovery
photometry. The data
are based on GMOS-S
photometry, which trace
the stellar populations
in these ultra-faint
dwarf candidates 3-4
magnitudes deeper than
before.
Figure 4.
Sample work flow, from
image to data products,
for Eri III.
April 2018
GeminiFocus
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