153 research outputs found
On the Interpretation of the l-v Features in the Milky Way Galaxy
We model the gas dynamics of barred galaxies using a three-dimensional,
high-resolution, -body+hydrodynamical simulation and apply it to the Milky
Way in an attempt to reproduce both the large-scale structure and the clumpy
morphology observed in Galactic H\emissiontype{I} and CO diagrams. Owing
to including the multi-phase interstellar medium, self-gravity, star-formation
and supernovae feedback, the clumpy morphology, as well as the large-scale
features, in observed diagrams are naturally reproduced. We identify in
our diagrams with a number of not only large-scale peculiar features such
as the '3-kpc arm', '135-km s arm' and 'Connecting arm' but also clumpy
features such as `Bania clumps', and then link these features in a face-on view
of our model. We give suggestions on the real structure of the Milky Way and on
the fate of gas clumps in the central region.Comment: accepted to PAS
Galactic Rotation from Cepheids with Gaia DR2 and Effects of Non-Axisymmetry
We apply a simple axisymmetric disc model to 218 Galactic Cepheids whose
accurate measurements of the distance and velocities are obtained by
cross-matching an existing Cepheids catalogue with the Gaia DR2 data. Our model
fit determines the "local centrifugal speed", defined as the
rotation speed required to balance the local radial gravitational force at
the Sun's location to be km s and the Sun's
azimuthal and radial peculiar motions to be km s
and km s, respectively. These results are obtained
with strong priors on the solar radius, kpc, and Sun's angular
rotation velocity, km s kpc. We
also applied the axisymmetric model to mock data from an N-body/hydrodynamic
simulation of a Milky Way-like galaxy with a bar and spiral arms. We find that
our axisymmetric model fit to the young stars recovers the local centrifugal
speed reasonably well, even in the face of significant non-axisymmetry.
However, the local centrifugal speed determined from our Cepheid sample could
suffer from systematic uncertainty as large as 6 km s.Comment: 13 pages, 8 figures, 2 tables, accepted for publication in MNRA
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