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A photometric and spectroscopic study of the new dwarf spheroidal galaxy in Hercules. Metallicity, velocities and a clean list of RGB members

Adén, Daniel LU ; Feltzing, Sofia LU ; Koch, A.; Wilkinson, M.I.; Grebel, E.K.; Lundström, Ingemar LU ; Gilmore, G.F.; Zucker, D.B.; Belukurov, V. and Evans, N.W., et al. (2009) In Astronomy & Astrophysics 506(3). p.1147-1168
Abstract
Our aim is to provide as clean and as complete a sample as possible of red giant branch stars that are members of the Hercules dSph galaxy. With this sample we explore the velocity dispersion and the metallicity of the system. Stromgren photometry and multi-fibre spectroscopy are combined to provide information about the evolutionary state of the stars (via the Stromgren c_1 index) and their radial velocities. Based on this information we have selected a clean sample of red giant branch stars, and show that foreground contamination by Milky Way dwarf stars can greatly distort the results. Our final sample consists of 28 red giant branch stars in the Hercules dSph galaxy. Based on these stars we find a mean photometric metallicity of -2.35... (More)
Our aim is to provide as clean and as complete a sample as possible of red giant branch stars that are members of the Hercules dSph galaxy. With this sample we explore the velocity dispersion and the metallicity of the system. Stromgren photometry and multi-fibre spectroscopy are combined to provide information about the evolutionary state of the stars (via the Stromgren c_1 index) and their radial velocities. Based on this information we have selected a clean sample of red giant branch stars, and show that foreground contamination by Milky Way dwarf stars can greatly distort the results. Our final sample consists of 28 red giant branch stars in the Hercules dSph galaxy. Based on these stars we find a mean photometric metallicity of -2.35 dex which is consistent with previous studies. We find evidence for an abundance spread. Using those stars for which we have determined radial velocities we find a systemic velocity of 45.2 km/s with a dispersion of 3.72 km/s, this is lower than values found in the literature. Furthermore we identify the horizontal branch and estimate the mean magnitude of the horizontal branch of the Hercules dSph galaxy to be V_0=21.17, which corresponds to a distance of 147 kpc. We have shown that a proper cleaning of the sample results in a smaller value for the velocity dispersion of the system. This has implications for galaxy properties derived from such velocity dispersions. (Less)
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type
Contribution to journal
publication status
published
subject
keywords
galaxies: fundamental parameters, galaxies: dwarf, galaxies:, individual: Hercules, galaxies: kinematics and dynamics, photometry
in
Astronomy & Astrophysics
volume
506
issue
3
pages
1147 - 1168
publisher
EDP Sciences
external identifiers
  • wos:000271514900011
  • scopus:70449449671
ISSN
0004-6361
DOI
10.1051/0004-6361/200912718
language
English
LU publication?
yes
id
cd7f6436-d9fa-4b73-9bab-8888707ef33f (old id 1468045)
alternative location
http://arxiv.org/abs/0908.3489
date added to LUP
2009-08-26 16:13:29
date last changed
2017-03-19 03:43:49
@article{cd7f6436-d9fa-4b73-9bab-8888707ef33f,
  abstract     = {Our aim is to provide as clean and as complete a sample as possible of red giant branch stars that are members of the Hercules dSph galaxy. With this sample we explore the velocity dispersion and the metallicity of the system. Stromgren photometry and multi-fibre spectroscopy are combined to provide information about the evolutionary state of the stars (via the Stromgren c_1 index) and their radial velocities. Based on this information we have selected a clean sample of red giant branch stars, and show that foreground contamination by Milky Way dwarf stars can greatly distort the results. Our final sample consists of 28 red giant branch stars in the Hercules dSph galaxy. Based on these stars we find a mean photometric metallicity of -2.35 dex which is consistent with previous studies. We find evidence for an abundance spread. Using those stars for which we have determined radial velocities we find a systemic velocity of 45.2 km/s with a dispersion of 3.72 km/s, this is lower than values found in the literature. Furthermore we identify the horizontal branch and estimate the mean magnitude of the horizontal branch of the Hercules dSph galaxy to be V_0=21.17, which corresponds to a distance of 147 kpc. We have shown that a proper cleaning of the sample results in a smaller value for the velocity dispersion of the system. This has implications for galaxy properties derived from such velocity dispersions.},
  author       = {Adén, Daniel and Feltzing, Sofia and Koch, A. and Wilkinson, M.I. and Grebel, E.K. and Lundström, Ingemar and Gilmore, G.F. and Zucker, D.B. and Belukurov, V. and Evans, N.W. and Faria, Daniel},
  issn         = {0004-6361},
  keyword      = {galaxies: fundamental parameters,galaxies: dwarf,galaxies:,individual: Hercules,galaxies: kinematics and dynamics,photometry},
  language     = {eng},
  number       = {3},
  pages        = {1147--1168},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {A photometric and spectroscopic study of the new dwarf spheroidal galaxy in Hercules. Metallicity, velocities and a clean list of RGB members},
  url          = {http://dx.doi.org/10.1051/0004-6361/200912718},
  volume       = {506},
  year         = {2009},
}