TY - JOUR
T1 - New stellar velocity substructures from Gaia DR3 proper motions
AU - Mikkola, Daniel
AU - McMillan, Paul J.
AU - Hobbs, David
PY - 2023/2/1
Y1 - 2023/2/1
N2 - Local stellar motions are expected, and have been shown, to include signatures of the Galaxy’s past dynamical evolution. These are typically divided into the disc, which shows the dynamical effects of spiral arms and the bar, and the stellar halo, with structures thought to be debris from past mergers. We use Gaia Data Release 3 to select large samples of these populations without limiting them to sources with radial velocities. We apply a penalized maximum likelihood method to these samples to determine the full 3D velocity distribution in Cartesian (U, V, and W) or spherical (vr, vφ, and vθ) coordinates. We find that the disc population is dominated by four moving groups and also detect a new moving group at (U, V) = (−10, −15) km s−1 which we call MMH-0. For the stellar halo, we isolate the accreted component with cuts in transverse velocity and the colour–magnitude diagram. In this component, we find several known structures believed to be caused by past mergers, particularly one around (vr, vφ, vθ) = (−150, −300, and −100) km s−1 appears more prominent than previously claimed. Furthermore, we also identify two new structures near (vr, vφ, and vθ) = (225, 25, and 325) km s−1 and (0, 150, and −125) km s−1, which we refer to as MMH-1 and MMH-2, respectively. These results give new insights into local stellar motions and shows the potential of using samples that are not limited to stars with measured line-of-sight velocities, which is key to providing large samples of stars, necessary for future studies.
AB - Local stellar motions are expected, and have been shown, to include signatures of the Galaxy’s past dynamical evolution. These are typically divided into the disc, which shows the dynamical effects of spiral arms and the bar, and the stellar halo, with structures thought to be debris from past mergers. We use Gaia Data Release 3 to select large samples of these populations without limiting them to sources with radial velocities. We apply a penalized maximum likelihood method to these samples to determine the full 3D velocity distribution in Cartesian (U, V, and W) or spherical (vr, vφ, and vθ) coordinates. We find that the disc population is dominated by four moving groups and also detect a new moving group at (U, V) = (−10, −15) km s−1 which we call MMH-0. For the stellar halo, we isolate the accreted component with cuts in transverse velocity and the colour–magnitude diagram. In this component, we find several known structures believed to be caused by past mergers, particularly one around (vr, vφ, vθ) = (−150, −300, and −100) km s−1 appears more prominent than previously claimed. Furthermore, we also identify two new structures near (vr, vφ, and vθ) = (225, 25, and 325) km s−1 and (0, 150, and −125) km s−1, which we refer to as MMH-1 and MMH-2, respectively. These results give new insights into local stellar motions and shows the potential of using samples that are not limited to stars with measured line-of-sight velocities, which is key to providing large samples of stars, necessary for future studies.
KW - Galaxy: kinematics and dynamics
KW - Galaxy: Solar neighbourhood
KW - Galaxy: structure
KW - methods: data analysis
KW - methods: statistical
KW - stars: kinematics and dynamics
U2 - 10.1093/mnras/stac3649
DO - 10.1093/mnras/stac3649
M3 - Article
AN - SCOPUS:85159158875
SN - 0035-8711
VL - 519
SP - 1989
EP - 2003
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -