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:
https://lup.lub.lu.se/record/1773899
- author
- Adén, Daniel
LU
; Eriksson, K.
; Feltzing, Sofia
LU
; Grebel, E. K.
; Koch, A.
and Wilkinson, M. I.
- organization
- publishing date
- 2011
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- stars: abundances, galaxies: individual: Hercules, galaxies: dwarf, galaxies: evolution
- in
- Astronomy & Astrophysics
- volume
- 525
- article number
- A153
- 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
- 2016-04-01 14:59:21
- date last changed
- 2024-01-10 11:04:36
@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.}},
author = {{Adén, Daniel and Eriksson, K. and Feltzing, Sofia and Grebel, E. K. and Koch, A. and Wilkinson, M. I.}},
issn = {{0004-6361}},
keywords = {{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}},
doi = {{10.1051/0004-6361/201014963}},
volume = {{525}},
year = {{2011}},
}