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THE Gaia-ESO Survey : Metal-rich bananas in the bulge

Williams, Angus A.; Evans, N. W.; Molloy, Matthew; Kordopatis, Georges; Smith, M. C.; Shen, J.; Gilmore, G.; Randich, S.; Bensby, T. LU and Francois, P., et al. (2016) In Astrophysical Journal Letters 824(2).
Abstract

We analyze the kinematics of ∼2000 giant stars in the direction of the Galactic bulge, extracted from the Gaia-ESO survey in the region -10° ≲ l≲ 10° and -11° ≲ b ≲ -3°. We find distinct kinematic trends in the metal-rich ([M H] > 0) and metal-poor ([M H] <0) stars in the data. The velocity dispersion of the metal-rich stars drops steeply with latitude, compared to a flat profile in the metal-poor stars, as has been seen previously. We argue that the metal-rich stars in this region are mostly on orbits that support the boxy-peanut shape of the bulge, which naturally explains the drop in their velocity dispersion profile with latitude. The metal-rich stars also exhibit peaky features in their line of sight velocity histograms,... (More)

We analyze the kinematics of ∼2000 giant stars in the direction of the Galactic bulge, extracted from the Gaia-ESO survey in the region -10° ≲ l≲ 10° and -11° ≲ b ≲ -3°. We find distinct kinematic trends in the metal-rich ([M H] > 0) and metal-poor ([M H] <0) stars in the data. The velocity dispersion of the metal-rich stars drops steeply with latitude, compared to a flat profile in the metal-poor stars, as has been seen previously. We argue that the metal-rich stars in this region are mostly on orbits that support the boxy-peanut shape of the bulge, which naturally explains the drop in their velocity dispersion profile with latitude. The metal-rich stars also exhibit peaky features in their line of sight velocity histograms, particularly along the minor axis of the bulge. We propose that these features are due to stars on resonant orbits supporting the boxy-peanut bulge. This conjecture is strengthened through the comparison of the minor axis data with the velocity histograms of resonant orbits generated in simulations of buckled bars. The "banana" or 2:1:2 orbits provide strongly bimodal histograms with narrow velocity peaks that resemble the Gaia-ESO metal-rich data.

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publication status
published
subject
keywords
galaxies: general, galaxies: kinematics and dynamics, Galaxy: bulge
in
Astrophysical Journal Letters
volume
824
issue
2
publisher
University of Chicago Press
external identifiers
  • Scopus:84976444253
ISSN
2041-8205
DOI
10.3847/2041-8205/824/2/L29
language
English
LU publication?
yes
id
9c568909-138e-4124-9f9c-00d413f2d720
date added to LUP
2016-08-17 14:22:09
date last changed
2016-10-27 13:02:29
@misc{9c568909-138e-4124-9f9c-00d413f2d720,
  abstract     = {<p>We analyze the kinematics of ∼2000 giant stars in the direction of the Galactic bulge, extracted from the Gaia-ESO survey in the region -10° ≲ l≲ 10° and -11° ≲ b ≲ -3°. We find distinct kinematic trends in the metal-rich ([M H] &gt; 0) and metal-poor ([M H] &lt;0) stars in the data. The velocity dispersion of the metal-rich stars drops steeply with latitude, compared to a flat profile in the metal-poor stars, as has been seen previously. We argue that the metal-rich stars in this region are mostly on orbits that support the boxy-peanut shape of the bulge, which naturally explains the drop in their velocity dispersion profile with latitude. The metal-rich stars also exhibit peaky features in their line of sight velocity histograms, particularly along the minor axis of the bulge. We propose that these features are due to stars on resonant orbits supporting the boxy-peanut bulge. This conjecture is strengthened through the comparison of the minor axis data with the velocity histograms of resonant orbits generated in simulations of buckled bars. The "banana" or 2:1:2 orbits provide strongly bimodal histograms with narrow velocity peaks that resemble the Gaia-ESO metal-rich data.</p>},
  author       = {Williams, Angus A. and Evans, N. W. and Molloy, Matthew and Kordopatis, Georges and Smith, M. C. and Shen, J. and Gilmore, G. and Randich, S. and Bensby, T. and Francois, P. and Koposov, S. E. and Recio-Blanco, A. and Bayo, A. and Carraro, G. and Casey, A. and Costado, T. and Franciosini, E. and Hourihane, A. and Laverny, P. De and Lewis, J. and Lind, K. and Magrini, L. and Monaco, L. and Morbidelli, L. and Sacco, G. G. and Worley, C. and Zaggia, S. and Mikolaitis, },
  issn         = {2041-8205},
  keyword      = {galaxies: general,galaxies: kinematics and dynamics,Galaxy: bulge},
  language     = {eng},
  month        = {06},
  number       = {2},
  publisher    = {ARRAY(0x9666718)},
  series       = {Astrophysical Journal Letters},
  title        = {THE Gaia-ESO Survey : Metal-rich bananas in the bulge},
  url          = {http://dx.doi.org/10.3847/2041-8205/824/2/L29},
  volume       = {824},
  year         = {2016},
}