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Chemical characterization of the inner Galactic bulge : North-South symmetry

Nandakumar, G. LU ; Ryde, N. LU ; Schultheis, M.; Thorsbro, B. LU ; Jönsson, H. LU ; Barklem, P. S.; Rich, R. M. and Fragkoudi, F. (2018) In Monthly Notices of the Royal Astronomical Society 478(4). p.4374-4389
Abstract

While the number of stars in the Galactic bulge with detailed chemical abundance measurements is increasing rapidly, the inner Galactic bulge (|b| < 2°) remains poorly studied, due to heavy interstellar absorption and photometric crowding. We have carried out a high-resolution IR spectroscopic study of 72 M giants in the inner bulge using the CRIRES (ESO/VLT) facility. Our spectra cover the wavelength range of 2.0818-2.1444 μm with the resolution of R ~ 50 000 and have signal-to-noise ratio of 50:100. Our stars are located along the bulge minor axis at l = 0°, b= ±0°, ±1°, ±2°, and +3°. Our sample was analysed in a homogeneous way using the most current K-band line list. We clearly detect a bimodal metallicity distribution function... (More)

While the number of stars in the Galactic bulge with detailed chemical abundance measurements is increasing rapidly, the inner Galactic bulge (|b| < 2°) remains poorly studied, due to heavy interstellar absorption and photometric crowding. We have carried out a high-resolution IR spectroscopic study of 72 M giants in the inner bulge using the CRIRES (ESO/VLT) facility. Our spectra cover the wavelength range of 2.0818-2.1444 μm with the resolution of R ~ 50 000 and have signal-to-noise ratio of 50:100. Our stars are located along the bulge minor axis at l = 0°, b= ±0°, ±1°, ±2°, and +3°. Our sample was analysed in a homogeneous way using the most current K-band line list. We clearly detect a bimodal metallicity distribution function with a metal-rich peak at ~ +0.3 dex and a metal-poor peak at ~ -0.5 dex and no stars with [Fe/H] > +0.6 dex. The Galactic Centre field reveals in contrast a mainly metal-rich population with a mean metallicity of +0.3 dex. We derived [Mg/Fe] and [Si/Fe] abundances that are consistent with trends from the outer bulge. We confirm for the supersolar metallicity stars the decreasing trend in [Mg/Fe] and [Si/Fe] as expected from chemical evolution models. With the caveat of a relatively small sample, we do not find significant differences in the chemical abundances between the Northern and the Southern fields; hence, the evidence is consistent with symmetry in chemistry between North and South.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Galaxy: bulge, Stars: abundances, Stars: late-type
in
Monthly Notices of the Royal Astronomical Society
volume
478
issue
4
pages
16 pages
publisher
Oxford University Press (OUP)
external identifiers
  • scopus:85050822268
ISSN
0035-8711
DOI
10.1093/mnras/sty1255
language
English
LU publication?
yes
id
5e78f73c-5457-4640-bd1c-88c6cc3d4503
date added to LUP
2018-08-15 15:08:11
date last changed
2019-02-20 11:24:13
@article{5e78f73c-5457-4640-bd1c-88c6cc3d4503,
  abstract     = {<p>While the number of stars in the Galactic bulge with detailed chemical abundance measurements is increasing rapidly, the inner Galactic bulge (|b| &lt; 2°) remains poorly studied, due to heavy interstellar absorption and photometric crowding. We have carried out a high-resolution IR spectroscopic study of 72 M giants in the inner bulge using the CRIRES (ESO/VLT) facility. Our spectra cover the wavelength range of 2.0818-2.1444 μm with the resolution of R ~ 50 000 and have signal-to-noise ratio of 50:100. Our stars are located along the bulge minor axis at l = 0°, b= ±0°, ±1°, ±2°, and +3°. Our sample was analysed in a homogeneous way using the most current K-band line list. We clearly detect a bimodal metallicity distribution function with a metal-rich peak at ~ +0.3 dex and a metal-poor peak at ~ -0.5 dex and no stars with [Fe/H] &gt; +0.6 dex. The Galactic Centre field reveals in contrast a mainly metal-rich population with a mean metallicity of +0.3 dex. We derived [Mg/Fe] and [Si/Fe] abundances that are consistent with trends from the outer bulge. We confirm for the supersolar metallicity stars the decreasing trend in [Mg/Fe] and [Si/Fe] as expected from chemical evolution models. With the caveat of a relatively small sample, we do not find significant differences in the chemical abundances between the Northern and the Southern fields; hence, the evidence is consistent with symmetry in chemistry between North and South.</p>},
  author       = {Nandakumar, G. and Ryde, N. and Schultheis, M. and Thorsbro, B. and Jönsson, H. and Barklem, P. S. and Rich, R. M. and Fragkoudi, F.},
  issn         = {0035-8711},
  keyword      = {Galaxy: bulge,Stars: abundances,Stars: late-type},
  language     = {eng},
  month        = {08},
  number       = {4},
  pages        = {4374--4389},
  publisher    = {Oxford University Press (OUP)},
  series       = {Monthly Notices of the Royal Astronomical Society},
  title        = {Chemical characterization of the inner Galactic bulge : North-South symmetry},
  url          = {http://dx.doi.org/10.1093/mnras/sty1255},
  volume       = {478},
  year         = {2018},
}