The Draco dwarf galaxy in the near-infrared
1
SUPA, School of Physics, University of Edinburgh, IfA, Blackford Hill, Edinburgh EH9 3HJ, UK e-mail: mrc@roe.ac.uk
2
Sterrewacht Leiden, Niels Bohrweg 2, 2333 RA Leiden, The Netherlands e-mail: habing@strw.leidenuniv.nl
Received:
4
May
2005
Accepted:
11
July
2005
With the William Herschel Telescope in La Palma we made
IJK s observations of an area of about
of the Local Group galaxy Draco.
This allows us to describe Draco's late-type stellar population
across the whole galaxy at a photometric level 2 mag deeper than
the 2MASS survey. We detected the red giant branch (RGB) and measured
the magnitude of the tip of the RGB in the three bands. From that
in the I band we obtain a distance modulus of 
, in excellent
agreement with a measurement from RR Lyrae stars. The peak of the
histogram at different 
suggests that Draco has a mean 
while
fiducial RGB tracks of Galactic globular clusters indicate a mean
where the error corresponds to the spread
around the mean value. There are significant differences between
the colour–magnitude diagrams of stars in the inner, medium and
outer areas of the galaxy. A metal poor (
)
intermediate-age population (about 1.6 Gyr old) is clearly
present and emerges in particular between 
and
from the centre of the galaxy. A few additional
carbon star candidates have been identified from both their
location in the colour–magnitude diagram and from an indication of
variability. The large scale distribution of late-type stars is
smooth but irregular in shape; this points at a variation of
inclination with radius.
Key words: stars: late-type / stars: distances / galaxies: Local Group / galaxies: photometry / infrared: stars / stars: carbon
© ESO, 2005