The inclination distribution of the Kuiper belt provides unique constraints on its origin and dynamical evolution , motivating vertically resolved observations of extrasolar planetesimal belts .
We present ALMA observations of millimeter emission in the near edge-on planetesimal belt around \beta Pictoris , finding that the vertical distribution is significantly better described by the sum of two Gaussians compared to a single Gaussian .
This indicates that , as for the Kuiper belt , the inclination distribution of \beta Pic ’ s belt is better described by the sum of dynamically hot and cold populations rather than a single component .
The hot and cold populations have RMS inclinations of 8.9 ^ { +0.7 } _ { -0.5 } and 1.1 ^ { +0.5 } _ { -0.5 } degrees .
We also report that an axisymmetric belt model provides a good fit to new and archival ALMA visibilities , and confirm that the midplane is misaligned with respect to \beta Pic b ’ s orbital plane .
However , we find no significant evidence for either the inner disk tilt observed in scattered light and CO emission or the South-West/North-East ( SW/NE ) asymmetry previously reported for millimeter emission .
Finally , we consider the origin of the belt ’ s inclination distribution .
Secular perturbations from \beta Pic b are unlikely to provide sufficient dynamical heating to explain the hot population throughout the belt ’ s radial extent , and viscous stirring from large bodies within the belt alone can not reproduce the two populations observed .
This argues for an alternative or additional scenario , such as planetesimals being born with high inclinations , or the presence of a ‘ \beta Pic c ’ planet , potentially migrating outwards near the belt ’ s inner edge .