2007A&A...467.1025G


Query : 2007A&A...467.1025G

2007A&A...467.1025G - Astronomy and Astrophysics, volume 467, 1025-1036 (2007/6-1)

Near-infrared observations of the Fornax dwarf galaxy. I. The red giant branch.

GULLIEUSZIK M., HELD E.V., RIZZI L., SAVIANE I., MOMANY Y. and ORTOLANI S.

Abstract (from CDS):

We present a study of the evolved stellar populations in the dwarf spheroidal galaxy Fornax based on wide-area near-infrared observations, aimed at obtaining new independent estimates of its distance and metallicity distribution. Assessing the reliability of near-infrared methods is most important in view of future space- and ground-based deep near-infrared imaging of resolved stellar systems. We have obtained JHK imaging photometry of the stellar populations in Fornax. The observations cover an 18.5x18.5arcmin2 central area with a mosaic of SOFI images at the ESO NTT. Our data sample all the red giant branch (RGB) for the whole area. Deeeper observations reaching the red clump of helium-burning stars have also been obtained for a 4.5x4.5arcmin2 region. Near-infrared photometry led to measurements of the distance to Fornax based on the K-band location of the RGB tip and the red clump. Once corrected for the mean age of the stellar populations in the galaxy, the derived distance modulus is (m-M)0=20.74±0.11, corresponding to a distance of 141Kpc, in good agreement with estimates from optical data. We have obtained a photometric estimate of the mean metallicity of red giant stars in Fornax from their (J-K) and (V-K) colors, using several methods. The effect of the age-metallicity degeneracy on the combined optical-infrared colors is shown to be less important than for optical or infrared colors alone. By taking age effects into account, we have derived a distribution function of global metallicity [M/H] from optical-infrared colors of individual stars. Our photometric Metallicity Distribution Function covers the range -2.0<[M/H]←0.6, with a main peak at [M/H]≃-0.9 and a long tail of metal-poor stars, and less metal-rich stars than derived by recent spectroscopy. If metallicities from CaII triplet lines are correct, this result confirms a scenario of enhanced metal enrichment in the last 1-4Gyr.

Abstract Copyright:

Journal keyword(s): galaxies: dwarf - galaxies: individual: Fornax - Local Group - galaxies: stellar content

VizieR on-line data: <Available at CDS (J/A+A/467/1025): table2.dat table3.dat>

Nomenclature: Table 2: [GHR2007] Shallow NNNNN (Nos 1-11377). Table 3: [GHR2007] Deep NNNN (Nos 1-1894).

Status at CDS : All or part of tables of objects will not be ingested in SIMBAD.

Simbad objects: 16

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Number of rows : 16
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 NGC 104 GlC 00 24 05.359 -72 04 53.20     4.09     ~ 3889 0
2 NGC 288 GlC 00 52 45.24 -26 34 57.4   10 8.13     ~ 1038 0
3 NGC 362 GlC 01 03 14.26 -70 50 55.6     6.58     ~ 1074 0
4 NAME Fornax Dwarf Spheroidal G 02 39 59.3 -34 26 57   9.02 7.4     ~ 1729 1
5 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 17261 1
6 M 68 GlC 12 39 27.98 -26 44 38.6     7.96     ~ 991 0
7 M 4 GlC 16 23 35.22 -26 31 32.7           ~ 1841 0
8 M 107 GlC 16 32 31.86 -13 03 13.6           ~ 783 0
9 M 13 GlC 16 41 41.634 +36 27 40.75     5.8     ~ 2183 0
10 NGC 6528 GlC 18 04 49.61 -30 03 20.8   12.12 10.65     ~ 523 0
11 NGC 6553 GlC 18 09 15.68 -25 54 27.9   9.08       ~ 599 0
12 NGC 6624 GlC 18 23 40.51 -30 21 39.7           ~ 880 1
13 M 55 GlC 19 39 59.71 -30 57 53.1     6.49     ~ 852 0
14 M 15 GlC 21 29 58.33 +12 10 01.2           ~ 3127 0
15 NAME Local Group GrG ~ ~           ~ 8310 0
16 NAME Galactic Bulge reg ~ ~           ~ 4252 0

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