J/A+A/648/A108 Heavy-elements heritage of the falling sky (Recio-Blanco+, 2021)
Heavy-elements heritage of the falling sky.
Recio-Blanco A., Fernandez-Alvar E., de Laverny P., Antoja T., Helmi A.,
Crida A.
<Astron. Astrophys. 648, A108 (2021)>
=2021A&A...648A.108R 2021A&A...648A.108R (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Clusters, globular ; Stars, nearby ; Abundances
Keywords: Galaxy: abundances - Galaxy: halo - Galaxy: stellar content -
Galaxy: formation
Abstract:
A fundamental element of galaxy formation is the accretion of mass
through mergers of satellites or gas. Recent dynamical analyses based
on Gaia data have revealed major accretion events in the history of
the Milky Way. Nevertheless, our understanding of the primordial
Galaxy is hindered because the bona fide identification of the most
metal-poor and correspondingly oldest accreted stars remains
challenging.
Galactic archaeology needs a new accretion diagnostic to understand
primordial stellar populations. Contrary to α-elements,
neutron-capture elements present unexplained large abundance spreads
for low-metallicity stars, which could result from a mixture of
formation sites.
We analysed the abundances of yttrium, europium, magnesium, and iron
in MilkyWay satellite galaxies, field halo stars, and globular
clusters. The chemical information was complemented by orbital
parameters based on Gaia data. In particular, we considered the
average inclination of the orbits.
The [Y/Eu] abundance behaviour with respect to the [Mg/Fe] turnovers
for satellite galaxies of various masses reveals that
higher-luminosity systems, for which the [Mg/Fe] abundance declines at
higher metallicities, present enhanced [Y/Eu] abundances, particularly
in the [Fe/H] regime between -2.25dex and -1.25dex. In addition, the
analysis has uncovered a chemo-dynamical correlation for both globular
clusters and field stars of the Galactic halo, accounting for about
half of the [Y/Eu] abundance spread. In particular, [Y/Eu]
under-abundances typical of protracted chemical evolutions are
preferentially observed in polar-like orbits, pointing to a possible
anisotropy in the accretion processes.
Our results strongly suggest that the observed [Y/Eu] abundance spread
in the Milky Way halo could result from a mixture of systems with
different masses. They also highlight that both nature and nurture are
relevant to the formation of the Milky Way since its primordial
epochs, thereby opening new pathways for chemical diagnostics of the
build-up of our Galaxy.
Description:
Sample of chemical abundances and orbital parameters used in the
paper. It comprises several samples of objects: globular clusters and
field stars, from the Milky Way. We made use of abundances of
europium, yttrium, and [Mg/Fe], collected from multiple literature
works (see Column 1 of this Table 2, but also Table 1 of the paper,
not in electronic form). Field stars abundances come from two
different compilations: a photometric selection of metal-poor stars
(Roederer et al., 2014AJ....147..136R 2014AJ....147..136R, Cat. J/AJ/147/136) and a study
of heavy-element abundances for high-alpha and low-alpha stars at
intermediate metallicity (Fishlock et al., 2017MNRAS.466.4672F 2017MNRAS.466.4672F).
Globular cluster abundances come for a compilation of literature works
used in Recio-Blanco (2018A&A...620A.194R 2018A&A...620A.194R). For a description of the
orbital inclination estimates see Section 3 in the paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 54 61 Chemical abundances and orbital parameters
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See also:
J/AJ/147/136 : Stars of very low metal abundance. VI. Abundances
(Roederer+, 2014)
J/MNRAS/484/2832 : Proper motions of Milky Way globular clusters
(Vasiliev, 2019)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Ref References code (1)
14- 25 A12 --- Object Target name
27- 31 F5.2 [-] [Fe/H] Iron abundance
33- 36 F4.2 [-] [alpha/Fe] ?=9.99 alpha element abundance with respect
to iron
38- 42 F5.2 [-] [Y/Fe] Yttrium abundance with respect to iron
44- 48 F5.2 [-] [Eu/Fe] Europium abundance with respect to iron
50- 54 F5.1 deg Incl Orbital inclination
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Note (1): References code as follows:
F2017 = Fishlock et al., 2017MNRAS.466.4672F 2017MNRAS.466.4672F
R2018 = Recio-Blanco, 2018A&A...620A.194R 2018A&A...620A.194R
R2014 = Roederer et al., 2014AJ....147..136R 2014AJ....147..136R, Cat. J/AJ/147/136
V2018 = Vasiliev, 2019MNRAS.484.2832V 2019MNRAS.484.2832V, Cat, J/MNRAS/484/2832
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Acknowledgements:
Alejandra Recio-Blanco, alejandra.recio-blanco(at)oca.eu
(End) A. Recio-Blanco [Observatoire Cote d'Azur], P. Vannier [CDS] 19-Apr-2021