Bibcode
Zasowski, G.; Ness, M. K.; García Pérez, A. E.; Martinez-Valpuesta, I.; Johnson, J. A.; Majewski, S. R.
Bibliographical reference
The Astrophysical Journal, Volume 832, Issue 2, article id. 132, 14 pp. (2016).
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12
2016
Journal
Citations
37
Refereed citations
32
Description
Much of the inner Milky Way’s (MW) global rotation and velocity
dispersion patterns can be reproduced by models of secularly evolved,
bar-dominated bulges. More sophisticated constraints, including the
higher moments of the line-of-sight velocity distributions (LOSVDs) and
limits on the chemodynamical substructure, are critical for interpreting
observations of the unresolved inner regions of extragalactic systems
and for placing the MW in context with other galaxies. Here, we use
SDSS-APOGEE data to develop these constraints, by presenting the first
maps of the skewness and kurtosis of the LOSVDs of metal-rich and
metal-poor inner MW stars (divided at [Fe/H] = -0.4), and
comparing the observed patterns to those that are seen both in N-body
models and in extragalactic bars. Despite closely matching the mean
velocity and dispersion, the models do not reproduce the observed
skewness patterns of the LOSVDs in different ways, which demonstrates
that our understanding of the detailed orbital structure of the inner MW
remains an important regime for improvement. We find evidence in the MW
of the skewness-velocity correlation that is used as a diagnostic
of extragalactic bars/bulges. This correlation appears in metal-rich
stars only, providing further evidence for different evolutionary
histories of chemically differentiated populations. We connect these
skewness measurements to previous work on high-velocity
“peaks” in the inner Galaxy, confirming the presence of that
phenomenon, and we quantify the cylindrical rotation of the inner
Galaxy, finding that the latitude-independent rotation vanishes outside
l ˜ 7°. Finally, we evaluate the MW data in the light of
selected extragalactic bar diagnostics and discuss the progress and
challenges in using the MW as a resolved analog of unresolved stellar
populations.