Connecting HL Tau to the Observed Exoplanet Sample

Abstract

The Atacama Large Millimeter/submilimeter Array (ALMA) recently revealed a set of nearly concentric gaps in the protoplanetary disk surrounding the young star HL Tau. If these are carved by forming gas giants, this provides the first set of orbital initial conditions for planets as they emerge from their birth disks. Using N-body integrations, we have followed the evolution of the system for 5 Gyr to explore the possible outcomes. We find that HL Tau initial conditions scaled down to the size of typically observed exoplanet orbits naturally produce several populations in the observed exoplanet sample. First, for a plausible range of planetary masses, we can match the observed eccentricity distribution of dynamically excited radial velocity giant planets with eccentricities $>$ 0.2. Second, we roughly obtain the observed rate of hot Jupiters around FGK stars. Finally, we obtain a large efficiency of planetary ejections of $\approx 2$ per HL Tau-like system, but the small fraction of stars observed to host giant planets makes it hard to match the rate of free-floating planets inferred from microlensing observations. In view of upcoming GAIA results, we also provide predictions for the expected mutual inclination distribution, which is significantly broader than the absolute inclination distributions typically considered by previous studies.

Accepted in MNRAS. 11 pages

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Cited by in corpus (9)

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• Secular transport during disk dispersal: the case of Kepler-419
• Radial migration of gap-opening planets in protoplanetary disks. II. The case of a planet pair
• Stability Constrained Characterization of Multiplanet Systems
• Primordial Dusty Rings and Episodic Outbursts in Protoplanetary Discs
• On the Origin of Banded Structure in Dusty Protoplanetary Discs: HL Tau and TW Hya
• Architecture of three-planet systems predicted from the observed protoplanetary disk of HL Tau
• Longterm Stability of Planetary Systems formed from a Transitional Disk