Galactoseismology: Discovery of Vertical Waves in the Galactic Disk

Details Galactoseismology: Discovery of Vertical Waves in the Galactic Disk Galactoseismology: Discovery of Vertical Waves in the Galactic Disk

2012-03-30

arxiv.org/abs/1203.6861v1

Astronomy and Astrophysics

Astrophysics

Galaxy Astrophysics

10 pages, 5 figures, accepted for publication in the Astrophysical Journal Letters

Scientific paper

We present evidence for a Galactic North-South asymmetry in the number density and bulk velocity of solar neighborhood stars. The number density profile, which is derived from main-sequence stars in the Sloan Digital Sky Survey, shows a (North - South)/(North + South) deficit at |z| ~ 400 pc and an excess at |z| ~ 800 pc. The bulk velocity profile, which is derived from the Sloan Extension for Galactic Understanding and Exploration, shows a gradual trend across the Galactic midplane as well as smaller-scale features. We speculate that the North-South asymmetry, which has the appearance of a wavelike perturbation, is intrinsic to the disk. We explore the physics of this phenomenon through an analysis of the linearized Boltzmann and Poisson equations and through one-dimensional simulations. The perturbation may be excited by the passage of a satellite galaxy or dark matter subhalo through the Galactic disk, in which case we are witnessing a recent disk-heating event.

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