The large-scale kinematics of young stars in the Milky Way disc: first results from SDSS-V
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arXiv
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| Natura: | Preprint |
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2025
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| author | Zari, Eleonora Villaseñor, Jaime Kounkel, Marina Rix, Hans-Walter Frankel, Neige Tkachenko, Andrew Khoperskov, Sergey D'Onghia, Elena Roman-Lopes, Alexandre Román-Zúñiga, Carlos Stringfellow, Guy S. Tan, Jonathan C. Wofford, Aida Bizyaev, Dmitry Donor, John Fernández-Trincado, José G. Morrison, Sean Pan, Kaike Sanchez, Sebastian F. Saydjari, Andrew |
| author_facet | Zari, Eleonora Villaseñor, Jaime Kounkel, Marina Rix, Hans-Walter Frankel, Neige Tkachenko, Andrew Khoperskov, Sergey D'Onghia, Elena Roman-Lopes, Alexandre Román-Zúñiga, Carlos Stringfellow, Guy S. Tan, Jonathan C. Wofford, Aida Bizyaev, Dmitry Donor, John Fernández-Trincado, José G. Morrison, Sean Pan, Kaike Sanchez, Sebastian F. Saydjari, Andrew |
| contents | We present a first large-scale kinematic map of $\sim$50,000 young OB stars ($T_{\rm eff} \geq 10,000$ K), based on BOSS spectroscopy from the Milky Way Mapper OB program in the ongoing Sloan Digital Sky Survey V (SDSS-V). Using photogeometric distances, line-of-sight velocities and Gaia DR3 proper motions, we map 3D Galactocentric velocities across the Galactic plane to $\sim$5 kpc from the Sun, with a focus on radial motions ($v_R$). Our results reveal mean radial motion with amplitudes of $\pm 30$ km/s that are coherent on kiloparsec scales, alternating between inward and outward motions. These $\bar{v}_R$ amplitudes are considerably higher than those observed for older, red giant populations. These kinematic patterns show only a weak correlation with spiral arm over-densities. Age estimates, derived from MIST isochrones, indicate that 85% of the sample is younger than $\sim300$ Myr and that the youngest stars ($\le 30$ Myr) align well with density enhancements. The age-dependent $\bar{v}_R$ in Auriga makes it plausible that younger stars exhibits different velocity variations than older giants. The origin of the radial velocity features remains uncertain, and may result from a combination of factors, including spiral arm dynamics, the Galactic bar, resonant interactions, or phase mixing following a perturbation. The present analysis is based on approximately one-third of the full target sample. The completed survey will enable a more comprehensive investigation of these features and a detailed dynamical interpretation. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_10387 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The large-scale kinematics of young stars in the Milky Way disc: first results from SDSS-V Zari, Eleonora Villaseñor, Jaime Kounkel, Marina Rix, Hans-Walter Frankel, Neige Tkachenko, Andrew Khoperskov, Sergey D'Onghia, Elena Roman-Lopes, Alexandre Román-Zúñiga, Carlos Stringfellow, Guy S. Tan, Jonathan C. Wofford, Aida Bizyaev, Dmitry Donor, John Fernández-Trincado, José G. Morrison, Sean Pan, Kaike Sanchez, Sebastian F. Saydjari, Andrew Astrophysics of Galaxies We present a first large-scale kinematic map of $\sim$50,000 young OB stars ($T_{\rm eff} \geq 10,000$ K), based on BOSS spectroscopy from the Milky Way Mapper OB program in the ongoing Sloan Digital Sky Survey V (SDSS-V). Using photogeometric distances, line-of-sight velocities and Gaia DR3 proper motions, we map 3D Galactocentric velocities across the Galactic plane to $\sim$5 kpc from the Sun, with a focus on radial motions ($v_R$). Our results reveal mean radial motion with amplitudes of $\pm 30$ km/s that are coherent on kiloparsec scales, alternating between inward and outward motions. These $\bar{v}_R$ amplitudes are considerably higher than those observed for older, red giant populations. These kinematic patterns show only a weak correlation with spiral arm over-densities. Age estimates, derived from MIST isochrones, indicate that 85% of the sample is younger than $\sim300$ Myr and that the youngest stars ($\le 30$ Myr) align well with density enhancements. The age-dependent $\bar{v}_R$ in Auriga makes it plausible that younger stars exhibits different velocity variations than older giants. The origin of the radial velocity features remains uncertain, and may result from a combination of factors, including spiral arm dynamics, the Galactic bar, resonant interactions, or phase mixing following a perturbation. The present analysis is based on approximately one-third of the full target sample. The completed survey will enable a more comprehensive investigation of these features and a detailed dynamical interpretation. |
| title | The large-scale kinematics of young stars in the Milky Way disc: first results from SDSS-V |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2509.10387 |