J/MNRAS/531/137 GALAH DR3 RR Lyrae abundances (D'Orazi+, 2024)
The GALAH survey:
tracing the Milky Way's formation and evolution through RR Lyrae stars.
D'Orazi V., Storm N., Casey A.R., Braga V.F., Zocchi A., Bono G.,
Fabrizio M., Sneden C., Massari D., Giribaldi R.E., Bergemann M.,
Campbell S.W., Casagrande L., de Grijs R., De Silva G., Lugaro M.,
Zucker D.B., Bragaglia A., Feuillet D., Fiorentino G., Chaboyer B.,
Dall'Ora M., Marengo M., Martinez-Vazquez C.E., Matsunaga N., Monelli M.,
Mullen J.P., Nataf D., Tantalo M., Thevenin F., Vitello F.R.,
Kudritzki R.-P., Bland-Hawthorn J., Buder S., Freeman K., Kos J.,
Lewis G.F., Lind K., Martell S., Sharma S., Stello S., Zwitter T.
<Mon. Not. R. Astron. Soc. 531, 137-162 (2024)>
=2024MNRAS.531..137D 2024MNRAS.531..137D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Abundances ; Optical
Keywords: stars: abundances - stars: Population II -
stars: variables: RR Lyrae - Galaxy: abundances - Galaxy: disc -
Galaxy: halo
Abstract:
Stellar mergers and accretion events have been crucial in shaping the
evolution of the Milky Way (MW). These events have been dynamically
identified and chemically characterized using red giants and
main-sequence stars. RR Lyrae (RRL) variables can play a crucial role
in tracing the early formation of the MW since they are ubiquitous,
old (t≥10Gyr) low-mass stars and accurate distance indicators. We
exploited Data Release 3 of the GALAH survey to identify 78 field RRLs
suitable for chemical analysis. Using synthetic spectra calculations,
we determined atmospheric parameters and abundances of Fe, Mg, Ca, Y,
and Ba. Most of our stars exhibit halo-like chemical compositions,
with an iron peak around [Fe/H]~-1.40, and enhanced Ca and Mg content.
Notably, we discovered a metal-rich tail, with [Fe/H] values ranging
from ∼1 to approximately solar metallicity. This sub-group includes
almost 1/4 of the sample, it is characterized by thin disc kinematics
and displays sub- solar alpha-element abundances, marginally
consistent with the majority of the MW stars. Surprisingly, they
differ distinctly from typical MW disc stars in terms of the s-process
elements Y and Ba. We took advantage of similar data available in the
literature and built a total sample of 535 field RRLs for which we
estimated kinematical and dynamical properties. We found that metal-
rich RRLs (1/3 of the sample) likely represent an old component of the
MW thin disc. We also detected RRLs with retrograde orbits and
provided preliminary associations with the Gaia-Sausage-Enceladus,
Helmi, Sequoia, Sagittarius, and Thamnos stellar streams.
Description:
We performed a detailed abundance analysis of 78 RRLs through
high-resolution spectra collected within the DR3 of the GALAH survey.
We used a fully consistent NLTE approach to derive spectroscopic
parameters and abundances for Fe, Ca, Mg, Y, and Ba.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 109 78 Atmospheric parameters and abundances
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See also:
J/MNRAS/506/150 : The GALAH+ Survey DR3 (Buder+, 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 15 I15 --- GALAH GALAH identifier
17- 20 I4 K Teff Effective temperature
22- 24 I3 K e_Teff Effective temperature error
26- 29 F4.2 [cm/s2] logg Surface gravity
31- 34 F4.2 [cm/s2] e_logg Surface gravity
36- 39 F4.2 km/s Vmic Micro-turbulence velocity
41- 44 F4.2 km/s e_Vmic Micro-turbulence velocity error
46- 50 F5.2 --- [Fe/H] Abundance [Fe/H]
52- 55 F4.2 --- e_[Fe/H] Error on [Fe/H]
57- 61 F5.2 --- [Mg/Fe] ? Abundance [Mg/Fe]
63- 65 F3.1 --- e_[Mg/Fe] ? Error on [Mg/Fe]
67- 71 F5.2 --- [Ca/Fe] ? Abundance [Ca/Fe]
73- 76 F4.2 --- e_[Ca/Fe] ? Error on [Ca/Fe]
78- 82 F5.2 --- [Si/Fe] ? Abundance [Si/Fe]
84- 87 F4.2 --- e_[Si/Fe] ? Error on [Si/Fe]
89- 93 F5.2 --- [Y/Fe] ? Abundance [Y/Fe]
95- 98 F4.2 --- e_[Y/Fe] ? Error on [Y/Fe]
100-104 F5.2 --- [Ba/Fe] ? Abundance [Ba/Fe]
106-109 F4.2 --- e_[Ba/Fe] ? Error on [Ba/Fe]
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Acknowledgements:
Valentina D'Orazi, vdorazi(at)roma2.infn.it
(End) Patricia Vannier [CDS] 21-May-2024