Observed kinematics of the Milky Way nuclear stellar disk region
arxiv(2024)
摘要
The nuclear region of the Milky Way is believed to host a nuclear stellar
disk, co-spatial with the gaseous central molecular zone. Previous kinematical
studies detected faster rotation for the stars belonging to the nuclear stellar
disk, compared to the surrounding regions. We analyze the rotation velocity of
stars at the nuclear stellar disk, and compare them with its analog in a few
control fields just outside this region. We limit our analysis to stars in the
red clump of the color magnitude diagram, in order to be able to relate their
mean de-reddened luminosity with distance along the line of sight. We used a
proper motion catalog, obtained from point spread function photometry on VVV
images, to construct maps of the transverse velocity for these stars. We
complemented our analysis with radial velocities from the 17th data release of
the APOGEE survey. We find that the main difference between the nuclear stellar
disk region and its surroundings is that at the former we see only stars moving
eastward, which we believe are located in front of the Galactic center. On the
contrary, in every other direction, we see the brightest red clump stars moving
eastward, and the faintest ones moving westward, as expected for a rotating
disk. We interpret these observations as being produced by the central
molecular zone, hiding stars behind itself. What we observe is compatible with
being produced by just the absence of the component at the back, without
requiring the presence of a cold, fast rotating disk. This component is also
not clearly detected in the newest release of the APOGEE catalog. In other
words, we find no clear signature of the nuclear stellar disk as a distinct
kinematical component.
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