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arXiv · 2107.10907

The small boxy/peanut structure of the Milky Way traced by old stars

Marcin Semczuk·Walter Dehnen·Ralph Schoenrich·E. Athanassoula
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Abstract

We analyse the positions of RR Lyrae stars in the central region of the Milky Way. In addition to the overall bar shape detected previously, we find evidence for a peanut shaped structure, in form of overdensities near $\ell=-2$ deg and $1$ deg at $b\sim-3.5$ deg. The corresponding physical distance between the two peaks of the peanut is $\sim0.7$ kpc, significantly shorter than that found from near-IR images (3.3 kpc) and red-clump stars. Qualitatively this is expected from `fractionation' of bar orbits, which we demonstrate to be matched in a simulation of an inside-out growing disc subsequently forming a bar.

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Marcin Semczuk, Walter Dehnen, Ralph Schoenrich, E. Athanassoula. 2021-11-11. The small boxy/peanut structure of the Milky Way traced by old stars. https://doi.org/10.1093/mnras%2Fstab3294

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