The GALAH survey: Tracing the Milky Way's formation and evolution through RR Lyrae stars
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| Format: | Preprint |
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2024
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| author | D'Orazi, Valentina Storm, Nicholas Casey, Andrew R. Braga, Vittorio F. Zocchi, Alice Bono, Giuseppe Fabrizio, Michele Sneden, Christopher Massari, Davide Giribaldi, Riano E. Bergemann, Maria Campbell, Simon W. Casagrande, Luca de Grijs, Richard De Silva, Gayandhi Lugaro, Maria Zucker, Daniel B. Bragaglia, Angela Feuillet, Diane Fiorentino, Giuliana Chaboyer, Brian Dall'Ora, Massimo Marengo, Massimo Martínez-Vázquez, Clara E. Matsunaga, Noriyuki Monelli, Matteo Mullen, Joseph P. Nataf, David Tantalo, Maria Thevenin, Frederic Vitello, Fabio R. Kudritzki, Rolf-Peter Bland-Hawthorn, Joss Buder, Sven Freeman, Ken Kos, Janez Lewis, Geraint F. Lind, Karin Martell, Sarah Sharma, Sanjib Stello, Dennis Zwitter, Tomaž |
| author_facet | D'Orazi, Valentina Storm, Nicholas Casey, Andrew R. Braga, Vittorio F. Zocchi, Alice Bono, Giuseppe Fabrizio, Michele Sneden, Christopher Massari, Davide Giribaldi, Riano E. Bergemann, Maria Campbell, Simon W. Casagrande, Luca de Grijs, Richard De Silva, Gayandhi Lugaro, Maria Zucker, Daniel B. Bragaglia, Angela Feuillet, Diane Fiorentino, Giuliana Chaboyer, Brian Dall'Ora, Massimo Marengo, Massimo Martínez-Vázquez, Clara E. Matsunaga, Noriyuki Monelli, Matteo Mullen, Joseph P. Nataf, David Tantalo, Maria Thevenin, Frederic Vitello, Fabio R. Kudritzki, Rolf-Peter Bland-Hawthorn, Joss Buder, Sven Freeman, Ken Kos, Janez Lewis, Geraint F. Lind, Karin Martell, Sarah Sharma, Sanjib Stello, Dennis Zwitter, Tomaž |
| contents | 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 characterised 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$\ge$10 Gyr) low-mass stars and accurate distance indicators. We exploited Data Release 3 of the GALAH survey to identify 78 field RRLs suitable for chemical analysis. Using synthetic spectra calculations, we determined atmospheric parameters and abundances of Fe, Mg, Ca, Y, and Ba. Most of our stars exhibit halo-like chemical compositions, with an iron peak around [Fe/H]$\approx -$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 characterised by thin disc kinematics and displays sub-solar $α$-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. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2405_04580 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | The GALAH survey: Tracing the Milky Way's formation and evolution through RR Lyrae stars D'Orazi, Valentina Storm, Nicholas Casey, Andrew R. Braga, Vittorio F. Zocchi, Alice Bono, Giuseppe Fabrizio, Michele Sneden, Christopher Massari, Davide Giribaldi, Riano E. Bergemann, Maria Campbell, Simon W. Casagrande, Luca de Grijs, Richard De Silva, Gayandhi Lugaro, Maria Zucker, Daniel B. Bragaglia, Angela Feuillet, Diane Fiorentino, Giuliana Chaboyer, Brian Dall'Ora, Massimo Marengo, Massimo Martínez-Vázquez, Clara E. Matsunaga, Noriyuki Monelli, Matteo Mullen, Joseph P. Nataf, David Tantalo, Maria Thevenin, Frederic Vitello, Fabio R. Kudritzki, Rolf-Peter Bland-Hawthorn, Joss Buder, Sven Freeman, Ken Kos, Janez Lewis, Geraint F. Lind, Karin Martell, Sarah Sharma, Sanjib Stello, Dennis Zwitter, Tomaž Astrophysics of Galaxies Solar and Stellar Astrophysics 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 characterised 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$\ge$10 Gyr) low-mass stars and accurate distance indicators. We exploited Data Release 3 of the GALAH survey to identify 78 field RRLs suitable for chemical analysis. Using synthetic spectra calculations, we determined atmospheric parameters and abundances of Fe, Mg, Ca, Y, and Ba. Most of our stars exhibit halo-like chemical compositions, with an iron peak around [Fe/H]$\approx -$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 characterised by thin disc kinematics and displays sub-solar $α$-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. |
| title | The GALAH survey: Tracing the Milky Way's formation and evolution through RR Lyrae stars |
| topic | Astrophysics of Galaxies Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2405.04580 |