Journal article
The GALAH survey: tracing the Milky Way's formation and evolution through RR Lyrae stars
Monthly notices of the Royal Astronomical Society, Vol.531(1), pp.137-162
06/01/2024
DOI: 10.1093/mnras/stae1149
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 >= 10 Gyr) 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] approximate to -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.
Details
- Title: Subtitle
- The GALAH survey: tracing the Milky Way's formation and evolution through RR Lyrae stars
- Creators
- Valentina D'Orazi - University of Rome Tor VergataNicholas Storm - Australian National UniversityAndrew R. Casey - Australian National UniversityVittorio F. Braga - Australian National UniversityAlice Zocchi - University of ViennaGiuseppe Bono - University of Rome Tor VergataMichele Fabrizio - Astronomical Observatory of RomeChristopher Sneden - Australian National UniversityDavide Massari - Australian National UniversityRiano E. Giribaldi - Université Libre de BruxellesMaria Bergemann - Max Planck Institute for AstronomySimon W. Campbell - ASTRO-3DLuca Casagrande - ARC Centre of Excellence for All-sky AstrophysicsRichard de Grijs - Macquarie UniversityGayandhi De Silva - Macquarie UniversityMaria Lugaro - Konkoly ObservatoryDaniel B. Zucker - Macquarie UniversityAngela Bragaglia - Australian National UniversityDiane Feuillet - Lund UniversityGiuliana Fiorentino - Astronomical Observatory of RomeBrian Chaboyer - Dartmouth CollegeMassimo Dall'Ora - INAF Osserv Astron Capodimonte, Salita Moiariello 16, I-80131 Naples, ItalyMassimo Marengo - Florida State UniversityClara E. Martinez-Vazquez - NSF’s NOIRLabNoriyuki Matsunaga - The University of TokyoMatteo Monelli - Astronomical Observatory of RomeJoseph P. Mullen - Iowa State UniversityDavid Nataf - Johns Hopkins UniversityMaria Tantalo - Astronomical Observatory of RomeFrederic Thevenin - Observatoire de la Côte d’AzurFabio R. Vitello - Istituto di Radioastronomia di BolognaRolf-Peter Kudritzki - University of Hawaii SystemJoss Bland-Hawthorn - SkySven Buder - ASTRO-3DKen Freeman - Australian National UniversityJanez Kos - University of LjubljanaGeraint F. Lewis - University of SydneyKarin Lind - AlbaNovaSarah Martell - ARC Centre of Excellence for All-sky AstrophysicsSanjib Sharma - University of SydneyDennis Stello - UNSW SydneyTomaz Zwitter - University of Ljubljana
- Resource Type
- Journal article
- Publication Details
- Monthly notices of the Royal Astronomical Society, Vol.531(1), pp.137-162
- Publisher
- Oxford Univ Press
- DOI
- 10.1093/mnras/stae1149
- ISSN
- 0035-8711
- eISSN
- 1365-2966
- Number of pages
- 26
- Grant note
- CE170100013 / Australian Research Council Centre of Excellence for All Sky Astrophysics in 3Dimensions(ASTRO3D); Australian Research Council 2022YP5ACE; 2022ARWP9C / European Union-Next Generation EU Spanish Ministry of Science and Innovation(MICINN) through the Spanish State Research Agency, under Severo Ochoa Programe 2020-2023 AYA2020-118778GB-I00 / Spanish Ministry of Economy and Competitiveness (MINECO); Spanish Government TKP2021-NKTA-64 / NKFIH excellence grant 4000142234 / European Space Agency PID2020-118778GB-I00 / Agencia Estatalde Investigacion del Ministerio de Cienciae Innovacion (AEI-MCINN) P1-0188 / Slovenian Research Agency; Slovenian Research Agency - Slovenia DP190102431; DP210101299 / Australian Research Council LP2023-10 / Lendulet Program of the Hungarian Academy of Sciences
- Language
- English
- Date published
- 06/01/2024
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984701729902771
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