Icarus Revisited: An Ancient, Metal-poor Accreted Stellar Stream in the Disk of the Milky Way
Year: 2024
Type: article
Abstract: 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, P. 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 chemodynamical 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 < [Fe/H] < −0.7 belonging to Icarus and Gaia-Sausage-Enceladus (GSE), respectively. The revised properties of Icarus are: 〈V + V LSR〉 ≃ 171 km s−1, σ V ≃ 37 km s−1, 〈e〉 ≃ 0.36, 〈[Fe/H]〉 ≃ −1.35, 〈[Mg/Fe]〉 ≃ +0.27, 〈[Al/Fe]〉 ≃ −0.13, and 〈[Mn/Fe]〉 ≃ −0.39. From the color–magnitude diagram 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’s stars are consistent with the debris of a dwarf galaxy with a stellar mass of ∼109 M ☉ accreted onto a primordial disk on an initial prograde low-inclination orbit.
Source: The Astrophysical Journal
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: Smithsonian Institution, U.S. Department of Energy, Alfred P. Sloan Foundation, Yale University, Carnegie Institution of Washington, Vanderbilt University, Ohio State University, University of Washington, Johns Hopkins University, Carnegie Mellon University, University of Notre Dame, University of Portsmouth, New Mexico State University, European Space Agency, York University, University of Oxford, Ministério da Ciência, Tecnologia e Inovação, Istituto Nazionale di Astrofisica, Universidad Nacional Autónoma de México, Agencia Nacional de Investigación y Desarrollo, Max-Planck-Institut für Astrophysik, Max-Planck-Institut für Astronomie, Instituto de Astrofísica de Canarias, Office of Science, University of Colorado Boulder, Leibniz-Gemeinschaft, Australian Astronomical Optics-Macquarie, Lawrence Berkeley National Laboratory
OpenAlex ID: W4405591041