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The usage of Stromgren photometry in studies of local group dwarf spheroidal galaxies - Application to Draco: a new catalogue of Draco members and a study of the metallicity distribution function and radial gradients

Faria, Daniel LU ; Feltzing, Sofia LU ; Lundström, Ingemar LU ; Gilmore, G.; Wahlgren, Glenn LU ; Ardeberg, Arne LU and Linde, Peter LU (2007) In Astronomy & Astrophysics 465(2). p.28-357
Abstract
Aims. In this paper we demonstrate how Stromgren uvby photometry can be efficiently used to: 1. identify red giant branch stars that are members in a dwarf spheroidal galaxy; 2. derive age-independent metallicities for the same stars and quantify the associated errors. Methods. Stromgren uvby photometry in a 11 x 22 arcmin field centered on the Draco dwarf spheroidal galaxy was obtained using the Isaac Newton Telescope on La Palma. Members of the Draco dSph galaxy were identified using the surface gravity sensitive c(1) index which discriminates between red giant and dwarf stars. Thus enabling us to distinguish the (red giant branch) members of the dwarf spheroidal galaxy from the foreground dwarf stars in our galaxy. The method is... (More)
Aims. In this paper we demonstrate how Stromgren uvby photometry can be efficiently used to: 1. identify red giant branch stars that are members in a dwarf spheroidal galaxy; 2. derive age-independent metallicities for the same stars and quantify the associated errors. Methods. Stromgren uvby photometry in a 11 x 22 arcmin field centered on the Draco dwarf spheroidal galaxy was obtained using the Isaac Newton Telescope on La Palma. Members of the Draco dSph galaxy were identified using the surface gravity sensitive c(1) index which discriminates between red giant and dwarf stars. Thus enabling us to distinguish the (red giant branch) members of the dwarf spheroidal galaxy from the foreground dwarf stars in our galaxy. The method is evaluated through a comparison of our membership list with membership classifications in the literature based on radial velocities and proper motions. The metallicity sensitive m(1) index was used to derive individual and age-independent metallicities for the members of the Draco dSph galaxy. The derived metallicities are compared to studies based on high resolution spectroscopy and the agreement is found to be very good. Results. We present metallicities for 169 members of the red giant branch in the Draco dwarf spheroidal galaxy (the largest sample to date). The metallicity distribution function for the Draco dSph galaxy shows a mean [Fe/H] = -1.74 dex with a spread of 0.24 dex. The correlation between metallicity and colour for the stars on the red giant branch is consistent with a dominant old, and coeval population. There is a possible spatial population gradient over the field with the most metal-rich stars being more centrally concentrated than the metal-poor stars. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
galaxies :, galaxies : individual : Draco dSph, galaxies : dwarf, photometry, galaxies : stellar content, individual : UGC 10822, Local Group
in
Astronomy & Astrophysics
volume
465
issue
2
pages
28 - 357
publisher
EDP Sciences
external identifiers
  • wos:000245107900006
  • scopus:34147142483
ISSN
0004-6361
DOI
10.1051/0004-6361:20065244
language
English
LU publication?
yes
id
1d968055-a280-48ed-8016-3b2147f8f4a6 (old id 669957)
date added to LUP
2007-12-10 11:18:01
date last changed
2017-08-13 04:14:35
@article{1d968055-a280-48ed-8016-3b2147f8f4a6,
  abstract     = {Aims. In this paper we demonstrate how Stromgren uvby photometry can be efficiently used to: 1. identify red giant branch stars that are members in a dwarf spheroidal galaxy; 2. derive age-independent metallicities for the same stars and quantify the associated errors. Methods. Stromgren uvby photometry in a 11 x 22 arcmin field centered on the Draco dwarf spheroidal galaxy was obtained using the Isaac Newton Telescope on La Palma. Members of the Draco dSph galaxy were identified using the surface gravity sensitive c(1) index which discriminates between red giant and dwarf stars. Thus enabling us to distinguish the (red giant branch) members of the dwarf spheroidal galaxy from the foreground dwarf stars in our galaxy. The method is evaluated through a comparison of our membership list with membership classifications in the literature based on radial velocities and proper motions. The metallicity sensitive m(1) index was used to derive individual and age-independent metallicities for the members of the Draco dSph galaxy. The derived metallicities are compared to studies based on high resolution spectroscopy and the agreement is found to be very good. Results. We present metallicities for 169 members of the red giant branch in the Draco dwarf spheroidal galaxy (the largest sample to date). The metallicity distribution function for the Draco dSph galaxy shows a mean [Fe/H] = -1.74 dex with a spread of 0.24 dex. The correlation between metallicity and colour for the stars on the red giant branch is consistent with a dominant old, and coeval population. There is a possible spatial population gradient over the field with the most metal-rich stars being more centrally concentrated than the metal-poor stars.},
  author       = {Faria, Daniel and Feltzing, Sofia and Lundström, Ingemar and Gilmore, G. and Wahlgren, Glenn and Ardeberg, Arne and Linde, Peter},
  issn         = {0004-6361},
  keyword      = {galaxies :,galaxies : individual : Draco dSph,galaxies : dwarf,photometry,galaxies : stellar content,individual : UGC 10822,Local Group},
  language     = {eng},
  number       = {2},
  pages        = {28--357},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {The usage of Stromgren photometry in studies of local group dwarf spheroidal galaxies - Application to Draco: a new catalogue of Draco members and a study of the metallicity distribution function and radial gradients},
  url          = {http://dx.doi.org/10.1051/0004-6361:20065244},
  volume       = {465},
  year         = {2007},
}