Kuiper Belt-like Hot and Cold Populations of Planetesimal Inclinations in the β Pictoris Belt Revealed by ALMA

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 β Pictoris...

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Bibliographic Details
Published in:The Astronomical journal 2019-04, Vol.157 (4), p.135
Main Authors: Matrà, L., Wyatt, M. C., Wilner, D. J., Dent, W. R. F., Marino, S., Kennedy, G. M., Milli, J.
Format: Article
Language:English
Subjects:
Astronomy
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
ASYMMETRY
CARBON MONOXIDE
circumstellar matter
COMPARATIVE EVALUATIONS
DISTRIBUTION
EMISSION
Extrasolar
Extrasolar planets
INCLINATION
Kuiper belt
Kuiper belt: general
PERTURBATION THEORY
Pictoris
planetary systems
PLANETS
Populations
protoplanetary disks
PROTOPLANETS
STARS
stars: individual
submillimeter: planetary systems
Vertical distribution
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Summary: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 β 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 β 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 and 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 β 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 southwest/northeast asymmetry previously reported for millimeter emission. Finally, we consider the origin of the belt's inclination distribution. Secular perturbations from β 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 cannot reproduce the two populations observed. This argues for an alternative or additional scenario, such as planetesimal being born with high inclinations, or the presence of a "β Pic c" planet, potentially migrating outward near the belt's inner edge.
ISSN:0004-6256
1538-3881
1538-3881
DOI:10.3847/1538-3881/ab06c0