Sagittarius dSph 3D structure from Gaia DR2 and Machine Learning
Three-dimensional rendering of the core of the Sagittarius dSph galaxy
(Sgr) using the Gaia second data release (DR2) and machine
learning techniques. The full phase-space, i.e. 3D positions and
kinematics, was derived for more than 1.2 x 105 member
stars in Sgr by combining their proper motions with distances from
3300 RR-Lyrae stars and line-of-sight velocities of more than 2000
spectroscopically observed stars covering the core of the galaxy. The
Cartesian grid is aligned to the Galactocentric frame with the disk of
the Milky Way (MW) contained in the X-Y plane, and the
Sun is located at (X, Y, Z) = (-8.29, 0, 0)
kpc. The color shade indicates stellar density. The orange arrow shows
the bulk velocity of the center-of-mass (COM) and the blue arrow
indicates the internal angular momentum of Sgr. Black cones of
different size mark the the error-weighted mean direction and speed of
the stars, upon subtraction of the COM velocity, measured within
3-dimensional Voronoi cells of ~500 stars each. The direction
towards the MW center is shown by a white dashed line.
The image can be rotated and zoomed using standard gestures, depending
on your operating system (e.g. slide two fingers up or down to zoom in and
out, click and drag to rotate, etc.), or using the menu at the top of
the figure (much slower and not recommended).
More information on this result and the underlying analysis can be
found in del Pino et al. (2020, ApJ in press).