Gaia kinematics reveal a complex lopsided and twisted Galactic disc warp. (arXiv:1812.07576v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Romero_Gomez_M/0/1/0/all/0/1">M. Romero-Gómez</a> (ICCUB-IEEC), <a href="http://arxiv.org/find/astro-ph/1/au:+Mateu_C/0/1/0/all/0/1">C. Mateu</a> (CIDA & U. República, Uruguay), <a href="http://arxiv.org/find/astro-ph/1/au:+Aguilar_L/0/1/0/all/0/1">L. Aguilar</a> (IA-UNAM), <a href="http://arxiv.org/find/astro-ph/1/au:+Figueras_F/0/1/0/all/0/1">F. Figueras</a> (ICCUB-IEEC), <a href="http://arxiv.org/find/astro-ph/1/au:+Castro_Ginard_A/0/1/0/all/0/1">A. Castro-Ginard</a> (ICCUB-IEEC)
There are few warp kinematic models able to characterise both structure and
kinematics. These models are needed to shed some light to the lopsidedness and
twisting of the stellar warp already seen in gas and dust. We use the vertical
information from the Gaia Data Release 2 up to G=20 mag to study the structure
of the Galactic warp, the related vertical motions and the relation with age.
We analyse two populations up to galactocentric distances of R=16 kpc, a young
bright sample formed by OB stars and an older one of Red Giant Branch stars. We
use two methods (ngc PCM and LonKin) based on the Gaia observables, together
with 2D maps of positions and proper motions in the Galactic plane. We indeed
confirm the age dependency of the Galactic warp, both in positions and
kinematics, being the height of the Galactic warp ~ 0.2 kpc for the OB sample
and ~1.0 kpc for the Red Giant Branch at R=14 kpc. Both methods find that the
onset radius is 12
Sun-anticentre line towards galactic azimuths ~180-200 deg increasingly with
radius. Also, the RGB sample reveals a slightly lopsided stellar warp with
|Z(down)|- |Z(up)|~250 pc. The line of maximum of proper motions in latitude is
systematically offset from the line-of-nodes estimated from the spatial data,
which our warp models predict as a kinematic signature of lopsidedness. We also
show a prominent wave-like pattern of a bending mode different in the OB and
RGB samples. Both positions and kinematics also reveal substructures that might
not be related to the large scale Galactic warp or to the bending mode. GaiaDR2
reveals a high degree of complexity that triggers the need for complex
kinematic models, flexible enough to combine wave-like patterns and an S-shaped
lopsided and twisted warp [abridged].
There are few warp kinematic models able to characterise both structure and
kinematics. These models are needed to shed some light to the lopsidedness and
twisting of the stellar warp already seen in gas and dust. We use the vertical
information from the Gaia Data Release 2 up to G=20 mag to study the structure
of the Galactic warp, the related vertical motions and the relation with age.
We analyse two populations up to galactocentric distances of R=16 kpc, a young
bright sample formed by OB stars and an older one of Red Giant Branch stars. We
use two methods (ngc PCM and LonKin) based on the Gaia observables, together
with 2D maps of positions and proper motions in the Galactic plane. We indeed
confirm the age dependency of the Galactic warp, both in positions and
kinematics, being the height of the Galactic warp ~ 0.2 kpc for the OB sample
and ~1.0 kpc for the Red Giant Branch at R=14 kpc. Both methods find that the
onset radius is 12<R<13 kpc for the OB sample and 10<R<11 kpc for the RGB. From
the RGB sample, we find from R>10 kpc the line-of-nodes twists away from the
Sun-anticentre line towards galactic azimuths ~180-200 deg increasingly with
radius. Also, the RGB sample reveals a slightly lopsided stellar warp with
|Z(down)|- |Z(up)|~250 pc. The line of maximum of proper motions in latitude is
systematically offset from the line-of-nodes estimated from the spatial data,
which our warp models predict as a kinematic signature of lopsidedness. We also
show a prominent wave-like pattern of a bending mode different in the OB and
RGB samples. Both positions and kinematics also reveal substructures that might
not be related to the large scale Galactic warp or to the bending mode. GaiaDR2
reveals a high degree of complexity that triggers the need for complex
kinematic models, flexible enough to combine wave-like patterns and an S-shaped
lopsided and twisted warp [abridged].
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