From ridges in the velocity distribution to wiggles in the rotation curve. (arXiv:1812.11190v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Martinez_Medina_L/0/1/0/all/0/1">Luis A. Martinez-Medina</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pichardo_B/0/1/0/all/0/1">Barbara Pichardo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Peimbert_A/0/1/0/all/0/1">Antonio Peimbert</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Valenzuela_O/0/1/0/all/0/1">Octavio Valenzuela</a>
Just recently, through the Gaia Data Release 2 (DR2), we became aware of the
richness in substructure contained in the kinematics of the Milky Way disk. Of
particular interest is the presence of diagonal ridges covering the stellar
velocity distribution, $V_{phi}-R$; as shown in some studies, it is likely
that these ridges are the signature of phase mixing, of transient spiral arms,
or of the central bar. Here, with a Galactic model containing both: bar and
spirals, we found the same pattern of diagonal ridges extended from the inner
to the outer disk. Interestingly, these ridges in the $V_{phi}-R$ plane
correlate so well with wiggles in the computed rotation curve (RC). Hence,
although the DR2 reveals for the first time such substructures in a wide
spatial coverage with high precision, we notice that we have always seen such
pattern of ridges, but projected into the form of wiggles in the RC. The
separation and amplitude of the wiggles strongly depend on the extension and
layout of ridges in the $V_{phi}-R$ plane. This means that within the RC are
encoded the kinematic state of the disk as well as information about the bar
and spiral arms. The velocity amplitude of the wiggles suggest that similar
features currently observable in external galaxies rotation curves have similar
origin triggered by spiral arms and bars.
Just recently, through the Gaia Data Release 2 (DR2), we became aware of the
richness in substructure contained in the kinematics of the Milky Way disk. Of
particular interest is the presence of diagonal ridges covering the stellar
velocity distribution, $V_{phi}-R$; as shown in some studies, it is likely
that these ridges are the signature of phase mixing, of transient spiral arms,
or of the central bar. Here, with a Galactic model containing both: bar and
spirals, we found the same pattern of diagonal ridges extended from the inner
to the outer disk. Interestingly, these ridges in the $V_{phi}-R$ plane
correlate so well with wiggles in the computed rotation curve (RC). Hence,
although the DR2 reveals for the first time such substructures in a wide
spatial coverage with high precision, we notice that we have always seen such
pattern of ridges, but projected into the form of wiggles in the RC. The
separation and amplitude of the wiggles strongly depend on the extension and
layout of ridges in the $V_{phi}-R$ plane. This means that within the RC are
encoded the kinematic state of the disk as well as information about the bar
and spiral arms. The velocity amplitude of the wiggles suggest that similar
features currently observable in external galaxies rotation curves have similar
origin triggered by spiral arms and bars.
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