A&A 413, 903-912 (2004)
DOI: 10.1051/0004-6361:20034031
The distance to the giant elliptical galaxy NGC 5128
M. RejkubaEuropean Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
(Received 1 July 2003 / Accepted 18 September 2003)
Abstract
The distance to NGC 5128, the central galaxy of
the Centaurus group and the nearest giant elliptical to us,
has been determined
using two independent distance indicators: the
Mira period-luminosity (PL) relation and the luminosity of the tip
of the red giant branch (RGB). The data were taken at two
different locations in the halo of
NGC 5128 with the ISAAC near-IR array on ESO VLT.
From more than 20 hours of observations with ISAAC a very deep
-band luminosity function was constructed. The tip
of the RGB is detected at
mag.
Using an empirical calibration
of the
K-band RGB tip magnitude, and
assuming a mean metallicity of
[M/ H]=-0.4 dex and
reddening of
E(B-V)=0.11, a distance modulus of NGC 5128
of
was derived. The comparison of
the
H-band RGB tip magnitude in NGC 5128 and the Galactic Bulge
implies a distance modulus of NGC 5128 of
in
good agreement with the
K-band RGB tip
measurement.
The inner halo field has larger photometric errors, brighter
completeness limits and a larger number of blends.
Thus the RGB tip feature is not as sharp as in the outer halo field.
The population of stars above the tip of the RGB amounts to 2176 stars
in the outer halo field (Field 1) and 6072 stars in the inner halo
field (Field 2). The large majority of these sources belong to the
asymptotic giant branch (AGB)
population in NGC 5128 with numerous long period variables.
Mira variables were used to
determine the distance of NGC 5128 from a period-luminosity relation
calibrated using the Hipparcos parallaxes and LMC Mira period-luminosity
relation in the
K-band. This is the first Mira period-luminosity relation
outside the Local Group. A distance modulus
of
was derived,
adopting the LMC distance modulus of
.
The mean of the two methods yields a
distance modulus to NGC 5128 of
corresponding to
Mpc.
Key words: galaxies: elliptical and lenticular, cD -- galaxies: stellar content -- stars: fundamental parameters -- galaxies: individual: NGC 5128
SIMBAD Objects
© ESO 2004