The realm of Aurora. Density distribution of metal-poor giants in the heart of the Galaxy
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| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Preprint |
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2024
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| _version_ | 1866910677497544704 |
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| author | Kurbatov, Evgeny P. Belokurov, Vasily Koposov, Sergey Kravtsov, Andrey Davies, Elliot Y. Brown, Anthony G. A. Cantat-Gaudin, Tristan Castro-Ginard, Alfred Casey, Andrew R. Drimmel, Ronald Fouesneau, Morgan Khanna, Shourya Rix, Hans-Walter Wallace, Alex |
| author_facet | Kurbatov, Evgeny P. Belokurov, Vasily Koposov, Sergey Kravtsov, Andrey Davies, Elliot Y. Brown, Anthony G. A. Cantat-Gaudin, Tristan Castro-Ginard, Alfred Casey, Andrew R. Drimmel, Ronald Fouesneau, Morgan Khanna, Shourya Rix, Hans-Walter Wallace, Alex |
| contents | The innermost portions of the Milky Way's stellar halo have avoided scrutiny until recently. The lack of wide-area survey data, made it difficult to reconstruct an uninterrupted view of the density distribution of the metal-poor stars inside the Solar radius. In this study, we utilize red giant branch (RGB) stars from Gaia, with metallicities estimated using spectro-photometry from Gaia Data Release 3. Accounting for Gaia's selection function, we examine the spatial distribution of metal-poor ([M/H]<-1.3) RGB stars, from the Galactic centre (r~1 kpc) out to beyond the Solar radius (r~18 kpc). Our best-fitting single-component cored power-law model shows a vertical flattening of ~0.5 and a slope -3.4, consistent with previous studies. Motivated by the mounting evidence for two distinct stellar populations in the inner halo, we additionally test a range of two-component models. One of the components models the tidal debris from the Gaia Sausage/Enceladus merger, while the other captures the Aurora population -- stars that predate the Galactic disk formation. Our best-fit two-component model suggests that both populations contribute equally around the Solar radius, but Aurora dominates the inner halo with a steeper power-law index of -4.5, in agreement with the nitrogen-rich star distribution measured by Horta et al. (2021). |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2410_22250 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | The realm of Aurora. Density distribution of metal-poor giants in the heart of the Galaxy Kurbatov, Evgeny P. Belokurov, Vasily Koposov, Sergey Kravtsov, Andrey Davies, Elliot Y. Brown, Anthony G. A. Cantat-Gaudin, Tristan Castro-Ginard, Alfred Casey, Andrew R. Drimmel, Ronald Fouesneau, Morgan Khanna, Shourya Rix, Hans-Walter Wallace, Alex Astrophysics of Galaxies The innermost portions of the Milky Way's stellar halo have avoided scrutiny until recently. The lack of wide-area survey data, made it difficult to reconstruct an uninterrupted view of the density distribution of the metal-poor stars inside the Solar radius. In this study, we utilize red giant branch (RGB) stars from Gaia, with metallicities estimated using spectro-photometry from Gaia Data Release 3. Accounting for Gaia's selection function, we examine the spatial distribution of metal-poor ([M/H]<-1.3) RGB stars, from the Galactic centre (r~1 kpc) out to beyond the Solar radius (r~18 kpc). Our best-fitting single-component cored power-law model shows a vertical flattening of ~0.5 and a slope -3.4, consistent with previous studies. Motivated by the mounting evidence for two distinct stellar populations in the inner halo, we additionally test a range of two-component models. One of the components models the tidal debris from the Gaia Sausage/Enceladus merger, while the other captures the Aurora population -- stars that predate the Galactic disk formation. Our best-fit two-component model suggests that both populations contribute equally around the Solar radius, but Aurora dominates the inner halo with a steeper power-law index of -4.5, in agreement with the nitrogen-rich star distribution measured by Horta et al. (2021). |
| title | The realm of Aurora. Density distribution of metal-poor giants in the heart of the Galaxy |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2410.22250 |