Dark Galactic Subhalos and the Gaia Snail
Gaia has revealed a clear signal of disequilibrium in the solar neighborhood in the form of a spiral (or snail) feature in the vertical phase-space distribution. We investigate the possibility that this structure emerges from ongoing perturbations by dark $\left(1{0}^{6}{M}_{\odot }-1{0}^{8}\,{M}_{\...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ada963 |
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| author | Daniel Gilman Jo Bovy Neige Frankel Andrew Benson |
| author_facet | Daniel Gilman Jo Bovy Neige Frankel Andrew Benson |
| author_sort | Daniel Gilman |
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| description | Gaia has revealed a clear signal of disequilibrium in the solar neighborhood in the form of a spiral (or snail) feature in the vertical phase-space distribution. We investigate the possibility that this structure emerges from ongoing perturbations by dark $\left(1{0}^{6}{M}_{\odot }-1{0}^{8}\,{M}_{\odot }\right)$ Galactic subhalos. We develop a probabilistic model for generating subhalo orbits based on a semianalytic model of structure formation, and combine this framework with an approximate prescription for calculating the response of the disk to external perturbations. We also develop a phenomenological treatment for the diffusion of phase-space spirals caused by gravitational scattering between stars and giant molecular clouds, a process that erases the kinematic signatures of old ( t ≳ 0.6 Gyr) events. Perturbations caused by dark subhalos are, on average, orders of magnitude weaker than those caused by luminous satellite galaxies, but the ubiquity of dark halos predicted by cold dark matter makes them a more probable source of strong perturbation to the dynamics of the solar neighborhood. Dark subhalos alone do not cause enough disturbance to explain the Gaia snail, but they excite fluctuations of ∼0.1–0.5 km s ^−1 in the mean vertical velocity of stars near the Galactic midplane that should persist to the present day. Subhalos also produce correlations between vertical frequency and orbital angle that could be mistaken as originating from a single past disturbance. Our results motivate investigation of the Milky Way's dark satellites by characterizing their kinematic signatures in phase-space spirals across the Galaxy. |
| format | Article |
| id | doaj-art-2632e37cf5f64ee4a2d0704c48477ec3 |
| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-2632e37cf5f64ee4a2d0704c48477ec32025-02-03T07:27:59ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198012410.3847/1538-4357/ada963Dark Galactic Subhalos and the Gaia SnailDaniel Gilman0https://orcid.org/0000-0002-5116-7287Jo Bovy1https://orcid.org/0000-0001-6855-442XNeige Frankel2https://orcid.org/0000-0002-6411-8695Andrew Benson3https://orcid.org/0000-0001-5501-6008Department of Astronomy and Astrophysics, University of Chicago , Chicago, IL 60637, USA ; gilmanda@uchicago.edu; Brinson Prize Fellow; Department of Astronomy and Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON M5S 3H4, CanadaDepartment of Astronomy and Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON M5S 3H4, CanadaDepartment of Astronomy and Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON M5S 3H4, Canada; Canadian Institute for Theoretical Astrophysics, University of Toronto , 60 St. George Street, Toronto, ON M5S 3H8, CanadaCarnegie Institution for Science , 813 Santa Barbara Street, Pasadena, CA 91101, USAGaia has revealed a clear signal of disequilibrium in the solar neighborhood in the form of a spiral (or snail) feature in the vertical phase-space distribution. We investigate the possibility that this structure emerges from ongoing perturbations by dark $\left(1{0}^{6}{M}_{\odot }-1{0}^{8}\,{M}_{\odot }\right)$ Galactic subhalos. We develop a probabilistic model for generating subhalo orbits based on a semianalytic model of structure formation, and combine this framework with an approximate prescription for calculating the response of the disk to external perturbations. We also develop a phenomenological treatment for the diffusion of phase-space spirals caused by gravitational scattering between stars and giant molecular clouds, a process that erases the kinematic signatures of old ( t ≳ 0.6 Gyr) events. Perturbations caused by dark subhalos are, on average, orders of magnitude weaker than those caused by luminous satellite galaxies, but the ubiquity of dark halos predicted by cold dark matter makes them a more probable source of strong perturbation to the dynamics of the solar neighborhood. Dark subhalos alone do not cause enough disturbance to explain the Gaia snail, but they excite fluctuations of ∼0.1–0.5 km s ^−1 in the mean vertical velocity of stars near the Galactic midplane that should persist to the present day. Subhalos also produce correlations between vertical frequency and orbital angle that could be mistaken as originating from a single past disturbance. Our results motivate investigation of the Milky Way's dark satellites by characterizing their kinematic signatures in phase-space spirals across the Galaxy.https://doi.org/10.3847/1538-4357/ada963Dark matterStellar dynamicsGalaxy stellar disksGaia |
| spellingShingle | Daniel Gilman Jo Bovy Neige Frankel Andrew Benson Dark Galactic Subhalos and the Gaia Snail The Astrophysical Journal Dark matter Stellar dynamics Galaxy stellar disks Gaia |
| title | Dark Galactic Subhalos and the Gaia Snail |
| title_full | Dark Galactic Subhalos and the Gaia Snail |
| title_fullStr | Dark Galactic Subhalos and the Gaia Snail |
| title_full_unstemmed | Dark Galactic Subhalos and the Gaia Snail |
| title_short | Dark Galactic Subhalos and the Gaia Snail |
| title_sort | dark galactic subhalos and the gaia snail |
| topic | Dark matter Stellar dynamics Galaxy stellar disks Gaia |
| url | https://doi.org/10.3847/1538-4357/ada963 |
| work_keys_str_mv | AT danielgilman darkgalacticsubhalosandthegaiasnail AT jobovy darkgalacticsubhalosandthegaiasnail AT neigefrankel darkgalacticsubhalosandthegaiasnail AT andrewbenson darkgalacticsubhalosandthegaiasnail |