The Three Dwarf Spheroidal Galaxies in our Sample:

Sculptor Dwarf Spheroidal Galaxy:

The Sculptor dSph galaxy was discovered by Shapley in 1938 (Shapley 1938, Harvard Bull., 908, 1), and Baade &
Hubble (1939) noted its similarity to a globular cluster, except for size and distance. Sculptor was found to contain a
very rich population of RR Lyrae variable stars (Thackeray 1950), clearly indicating that its stellar population contains
a globular cluster age component. Various studies of evolved stars have shown Sculptor to contain a small number
(eight) of intermediate-age carbon stars (e.g. Frogel et al. 1982; Azzopardi, Lequeux & Westerlund 1986), well-known
indicators of metal-poor intermediate-age stellar populations (e.g. Aaronson et al. 1984) and possibly also anomalous
Cepheids (Norris & Bessel 1978). Recent follow-up studies of the carbon stars (Groenewegen) suggest that 7 of these
stars are actually CH stars.  There is thus very little evidence for significant metal-poor intermediate-age stellar
populations in Sculptor.  Sculptor does show tantalizing evidence on its horizontal branch (HB) for an unusual
enrichment history (Majewski et al. 1999; Hurley-Keller, Mateo, & Grebel 1999) at the oldest times.

Carignan et al. (1998) found evidence for small amounts of HI gas in and around Sculptor. This has recently been found
to be part of a large scale complex, presumably Galactic HVC and unlikely to be associated to Sculptor  (L. Young).

The first attempt to piece together an accurate star formation history determined from a CMD reaching down to globular
cluster age main-sequence turn-offs was made by Da Costa (1984). He determined that the bulk of the stellar population
of Sculptor is likely to be 2-3 Gyr younger than a typical globular cluster, such as M92. He also noted that the intrinsic
width of the RGB was probably caused by a 0.5-dex, spread in abundance ([Fe/H] from  -2.1 to -1.6), and a population
of 'blue stragglers' (in globular cluster terminology), which could be interpreted as main-sequence turn-off stars as young
as 5 Gyr old, or they could be the results of stellar mergers. Kaluzny et al. (1995) made a careful study of the central
region of Sculptor and found no main-sequence stars (m(v)<21), ruling out any star formation over the last 2 Gyr.

Using Wide Field Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST), Monkiewicz et al. (1999) have
made the deepest CMD of Sculptor to date; although they cover a tiny fraction of the entire galaxy, they detected stars
several magnitudes below the oldest possible main-sequence turn-offs. Their accurate photometry in this region allowed
them to conclude that the mean age of Sculptor is similar to that of a globular cluster, but that there was probably a spread
in age during this epoch of at least 4 Gyr.

There has been CaT study of 44 RGB stars in Sculptor (Tolstoy et al. 2001) using VLT/FORS1 and there are 8 VLT/UVES
high resolution spectra  (5 from Shetrone et al. 2003;  Tolstoy et al. 2003 and 3 from Geisler et al. 2003).

Fornax Dwarf Spheroidal Galaxy:

The discovery of Fornax was presented in the same paper as the discovery of Sculptor (Shapley 1938, Harvard Bull., 908, 1),
and they make an interesting pair for comparison. Qualitatively they look very similar, although Fornax is larger and more
metal-rich in the mean, and has 5 globular clusters, whereas Sculptor has none. Also, looking in detail at the star formation
histories of Sculptor and Fornax, it is clear that they have followed very different evolutionary paths. Sculptor is dominated by
older stellar populations, whereas Fornax appears to have been forming stars quite actively until 2 Gyr ago, and to be
dominated by a 4-7 Gyr old population, and has evidence for only a small number of globular cluster age stars in its field
population.

Fornax contains a large number of RR Lyrae and Mira variables and carbon stars, as well as one anomalous Cepheid, one
planetary nebula and five globular clusters (Da Costa 1998, in Stellar Astrophysics for the Local Group). Young (1999)
looked for neutral hydrogen, and found none. The best estimate for the mean abundance of the bulk of the stars in Fornax
comes from the intrinsic width of the RGB, and is [Fe/H]  = -1.4 with a spread of about 0.15 dex (Buonanno et al. 1985). It
is quite hard to disentangle age from metallicity effects on the RGB because Fornax has such a long-lasting and complex star
formation history.

The extended sequence of main-sequence turn-offs in the Fornax CMD indicates a long history of star formation (e.g.,
Beauchamp et al. 1995; Stetson, Hesser & Smecker-Hane 1998; Buonanno et al. 1999), which has only recently ceased. The
luminosity of the brightest blue stars shows that Fornax cannot contain any stars younger than 100 Myr (Stetson et al. 1998).

The presence of numerous (120) carbon stars with a wide range of bolometric luminosities indicates a significant mass
dispersion among the progenitors, and hence a significant age spread in the range ago (e.g. Aaronson & Mould 1980, 1985;
Azzopardi et al. 1999, in The Stellar Content of Local Group Galaxies). This is supported by a well-populated
intermediate-age subgiant branch and a red clump, which require a significant population with an age of  2-8 Gyr. Recently,
an HST study sampling the main-sequence turn-offs of the intermediate-age and old populations in the centre of Fornax was
carried out by Buonanno et al. (1999).  They found evidence for a highly variable star formation history starting at the
epoch of globular cluster formation (~15 Gyr ago) and continuing until 0.5 Gyr ago. Their detailed analysis did not take
account of metallicity variations with age, which must be present, and which will probably make their ages roughly 30% too
young, in the mean. An ancient population is uneqivocally present, as demonstrated by detection of a red horizontal branch,
slightly fainter than the red clump, and of RR Lyrae variables (Stetson et al. 1998). There is also a weak, blue horizontal
branch, so Fornax clearly must an old, metal-poor component although perhaps not as extensive as might be infered from
having a globular cluster population.

There has been a CaT study of 33 field RGB stars in Fornax (Tolstoy et al. 2001) and 117  by (Pont et al. 2004)  both studies
using VLT/FORS1. There spectra for 3 stars with VLT/UVES from Shetrone et al. 2003;  Tolstoy et al. 2003. There has also
been an abundance study of individual stars in the globular clusters around Fornax (Letarte, Jablonka, Hill, Tolstoy &
Francois, in prep). Early results to be seen Tolstoy 2003.

Sextans Dwarf Spheroidal Galaxy:

Sextans was discovered using automatic techniques on large scale surveys of APM plates by Irwin et al. 1990. It is of extremely
low surface brightnes and extremely extended so that it is barely identifiable in a visual inspection of the plates.

Suntzeff et al. 1993 made a CaT survey of RGB stars in Sextans, finding 43 members (and 36 field stars). They found that
Sextans has an intrinsic velocity dispersion of 6.2 +/- 0.9 km/s based on 33 stars. The mean metallicity of Sextans stars was
found to be [Fe/H]= -2. with an intrinsic star to star dispersion of 0.2 dex. Hargreaves et al. 1994 also made a dynamical study
of Sextans and observed 26 RGB stars, obtaining high quality spectra for 21 of them. They found similar dispersion and
systemic velocity to previous surveys. They found no sign of rotation about any axis within the errors of the measurements, the
formally derived value around the minor axis being 0.4 km/s at 300 pc from the axis. It is possible that binary stars may be
making a significant contribution to the velocity distribution or that Sextans may be being tidally disrupted. If further work
eliminates both these possibilities then, assuming isotropy in the velocity dispersion and dynamical equilibrium, the core
mass-to- light ratio is 124 (+85-60) Msun/Lsun and the total mass-to-light ratio is 121 (+84-58) Msun/Lsun, implying the
presence of large quantities of dark matter. In a survey for variable stars Mateo, Fischer & Krzeminski (1995) report the
presence of 44 variables: 36 RR Lyr star, 6 anomalous Cepheids, one long-period red variable.  They use them to derive an
accurate distance modulus of 19.67 +/- 0.15  (86kpc) and a metallicity, [Fe/H] = -1.6 +/- 0.2. Their deep wide field CMDs
reveal the presence of a metal-poor population containing stars as young as 2-4 Gyr, consistent with the presence of anomalous
Cepheids in the galaxy. This young population may represent as much as 25% of the total stellar content of Sextans.

Shetrone, Côté & Sargent 2001 took KECK/HIRES spectra of  5 RGB stars in Sextans.