Icarus revisited: An Ancient, Metal-poor Accreted Stellar Stream in the Disk of the Milky Way
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arXiv
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| Natura: | Preprint |
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2024
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| _version_ | 1866910652860203008 |
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| author | Fiorentin, Paola Re Spagna, Alessandro Lattanzi, Mario G. Cignoni, Michele Vitali, Sara |
| author_facet | Fiorentin, Paola Re Spagna, Alessandro Lattanzi, Mario G. Cignoni, Michele Vitali, Sara |
| contents | The search for accreted satellites in the Galactic disk is a challenging task, to which Gaia plays a crucial role in synergy with ground-based spectroscopic surveys. In 2021, Re Fiorentin et al. discovered five substructures with disk kinematics including Icarus. To gain more insight into the origin of Icarus as a remnant of a dwarf galaxy rather than a signature of secular processes of disk formation, we complement astrometric Gaia DR3 data with spectroscopy from APOGEE DR17 and GALAH DR3, and explore the chemo-dynamical distributions within 3 kpc of the Sun. We select 622 stars in the accreted/unevolved regions of [Mg/Mn]-[Al/Fe] and [Mg/Fe]-[Fe/H], where we identify 81 and 376 stars with $-2<{\rm[Fe/H]}<-0.7$ belonging to Icarus and Gaia-Sausage-Enceladus (GSE), respectively. The revised properties of Icarus are: $\langle V+V_{\rm LSR}\rangle\simeq171~\rm{km~s}^{-1}$, $σ_{V}\simeq37\rm{km~s}^{-1}$, $\langle e\rangle\simeq0.36$, $\langle{\rm[Fe/H]}\rangle\simeq-1.35$, $\langle{\rm[Mg/Fe]}\rangle\simeq+0.27$, $\langle{\rm[Al/Fe]}\rangle\simeq-0.13$, and $\langle{\rm[Mn/Fe]}\rangle\simeq-0.39$. From the CMD of its members, Icarus appears older than 12 Gyr. Such age and dynamical properties are reminiscent of the metal-weak thick disk. However, detailed chemical analysis in the diagnostic spaces [Ni/Fe]-[(C+N)/O], [Y/Eu]-[Fe/H], [Eu/Mg]-[Fe/H], [Ba/Y]-[Fe/H], and [Ba/Mg]-[Mg/H] evidences that Icarus and GSE occupy the accreted region, well separated from the bulk of in situ disk stars. Updated comparisons with N-body simulations confirm that Icarus' stars are consistent with the debris of a dwarf galaxy with a stellar mass of $\sim~10^9~M_\odot$ accreted onto a primordial disk on an initial prograde low-inclination orbit. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2410_12581 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Icarus revisited: An Ancient, Metal-poor Accreted Stellar Stream in the Disk of the Milky Way Fiorentin, Paola Re Spagna, Alessandro Lattanzi, Mario G. Cignoni, Michele Vitali, Sara Astrophysics of Galaxies The search for accreted satellites in the Galactic disk is a challenging task, to which Gaia plays a crucial role in synergy with ground-based spectroscopic surveys. In 2021, Re Fiorentin et al. discovered five substructures with disk kinematics including Icarus. To gain more insight into the origin of Icarus as a remnant of a dwarf galaxy rather than a signature of secular processes of disk formation, we complement astrometric Gaia DR3 data with spectroscopy from APOGEE DR17 and GALAH DR3, and explore the chemo-dynamical distributions within 3 kpc of the Sun. We select 622 stars in the accreted/unevolved regions of [Mg/Mn]-[Al/Fe] and [Mg/Fe]-[Fe/H], where we identify 81 and 376 stars with $-2<{\rm[Fe/H]}<-0.7$ belonging to Icarus and Gaia-Sausage-Enceladus (GSE), respectively. The revised properties of Icarus are: $\langle V+V_{\rm LSR}\rangle\simeq171~\rm{km~s}^{-1}$, $σ_{V}\simeq37\rm{km~s}^{-1}$, $\langle e\rangle\simeq0.36$, $\langle{\rm[Fe/H]}\rangle\simeq-1.35$, $\langle{\rm[Mg/Fe]}\rangle\simeq+0.27$, $\langle{\rm[Al/Fe]}\rangle\simeq-0.13$, and $\langle{\rm[Mn/Fe]}\rangle\simeq-0.39$. From the CMD of its members, Icarus appears older than 12 Gyr. Such age and dynamical properties are reminiscent of the metal-weak thick disk. However, detailed chemical analysis in the diagnostic spaces [Ni/Fe]-[(C+N)/O], [Y/Eu]-[Fe/H], [Eu/Mg]-[Fe/H], [Ba/Y]-[Fe/H], and [Ba/Mg]-[Mg/H] evidences that Icarus and GSE occupy the accreted region, well separated from the bulk of in situ disk stars. Updated comparisons with N-body simulations confirm that Icarus' stars are consistent with the debris of a dwarf galaxy with a stellar mass of $\sim~10^9~M_\odot$ accreted onto a primordial disk on an initial prograde low-inclination orbit. |
| title | Icarus revisited: An Ancient, Metal-poor Accreted Stellar Stream in the Disk of the Milky Way |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2410.12581 |