Advanced

An abundance study of red-giant-branch stars in the Hercules dwarf spheroidal galaxy

Adén, Daniel LU ; Eriksson, K.; Feltzing, Sofia LU ; Grebel, E. K.; Koch, A. and Wilkinson, M. I. (2011) In Astronomy & Astrophysics 525.
Abstract
Context. Dwarf spheroidal galaxies are some of the most metal-poor, and least luminous objects known. Detailed elemental abundance analysis of stars in these faint objects is key to our understanding of star formation and chemical enrichment in the early universe, and may provide useful information on how larger galaxies form. Aims. Our aim is to provide a determination of [Fe/H] and [Ca/H] for confirmed red-giant branch member stars of the Hercules dwarf spheroidal galaxy. Based on this we explore the ages of the prevailing stellar populations in Hercules, and the enrichment history from supernovae. Additionally, we aim to provide a new simple metallicity calibration for Stromgren photometry for metal-poor, red giant branch stars.... (More)
Context. Dwarf spheroidal galaxies are some of the most metal-poor, and least luminous objects known. Detailed elemental abundance analysis of stars in these faint objects is key to our understanding of star formation and chemical enrichment in the early universe, and may provide useful information on how larger galaxies form. Aims. Our aim is to provide a determination of [Fe/H] and [Ca/H] for confirmed red-giant branch member stars of the Hercules dwarf spheroidal galaxy. Based on this we explore the ages of the prevailing stellar populations in Hercules, and the enrichment history from supernovae. Additionally, we aim to provide a new simple metallicity calibration for Stromgren photometry for metal-poor, red giant branch stars. Methods. High-resolution, multi-fibre spectroscopy and Stromgren photometry are combined to provide as much information on the stars as possible. From this we derive abundances by solving the radiative transfer equations through marcs model atmospheres. Results. We find that the red-giant branch stars of the Hercules dSph galaxy are more metal-poor than estimated in our previous study that was based on photometry alone. From this, we derive a new metallicity calibration for the Stromgren photometry. Additionally, we find an abundance trend such that [Ca/Fe] is higher for more metal-poor stars, and lower for more metal-rich stars, with a spread of about 0.8 dex. The [Ca/Fe] trend suggests an early rapid chemical enrichment through supernovae of type II, followed by a phase of slow star formation dominated by enrichment through supernovae of type Ia. A comparison with isochrones indicates that the red giants in Hercules are older than 10 Gyr. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
stars: abundances, galaxies: individual: Hercules, galaxies: dwarf, galaxies: evolution
in
Astronomy & Astrophysics
volume
525
publisher
EDP Sciences
external identifiers
  • wos:000285193700058
  • scopus:78650115650
ISSN
0004-6361
DOI
10.1051/0004-6361/201014963
language
English
LU publication?
yes
id
4eccda50-e4f6-4837-ae07-da923827a842 (old id 1773899)
date added to LUP
2011-02-01 10:21:07
date last changed
2017-01-01 06:32:31
@article{4eccda50-e4f6-4837-ae07-da923827a842,
  abstract     = {Context. Dwarf spheroidal galaxies are some of the most metal-poor, and least luminous objects known. Detailed elemental abundance analysis of stars in these faint objects is key to our understanding of star formation and chemical enrichment in the early universe, and may provide useful information on how larger galaxies form. Aims. Our aim is to provide a determination of [Fe/H] and [Ca/H] for confirmed red-giant branch member stars of the Hercules dwarf spheroidal galaxy. Based on this we explore the ages of the prevailing stellar populations in Hercules, and the enrichment history from supernovae. Additionally, we aim to provide a new simple metallicity calibration for Stromgren photometry for metal-poor, red giant branch stars. Methods. High-resolution, multi-fibre spectroscopy and Stromgren photometry are combined to provide as much information on the stars as possible. From this we derive abundances by solving the radiative transfer equations through marcs model atmospheres. Results. We find that the red-giant branch stars of the Hercules dSph galaxy are more metal-poor than estimated in our previous study that was based on photometry alone. From this, we derive a new metallicity calibration for the Stromgren photometry. Additionally, we find an abundance trend such that [Ca/Fe] is higher for more metal-poor stars, and lower for more metal-rich stars, with a spread of about 0.8 dex. The [Ca/Fe] trend suggests an early rapid chemical enrichment through supernovae of type II, followed by a phase of slow star formation dominated by enrichment through supernovae of type Ia. A comparison with isochrones indicates that the red giants in Hercules are older than 10 Gyr.},
  articleno    = {A153},
  author       = {Adén, Daniel and Eriksson, K. and Feltzing, Sofia and Grebel, E. K. and Koch, A. and Wilkinson, M. I.},
  issn         = {0004-6361},
  keyword      = {stars: abundances,galaxies: individual: Hercules,galaxies: dwarf,galaxies: evolution},
  language     = {eng},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {An abundance study of red-giant-branch stars in the Hercules dwarf spheroidal galaxy},
  url          = {http://dx.doi.org/10.1051/0004-6361/201014963},
  volume       = {525},
  year         = {2011},
}