Mass inventory of the giant-planet formation zone in a solar nebula analog

Abstract

The initial mass distribution in the solar nebula is a critical input to planet formation models that seek to reproduce today's Solar System. Traditionally, constraints on the gas mass distribution are derived from observations of the dust emission from disks, but this approach suffers from large uncertainties in grain growth and gas-to-dust ratio. On the other hand, previous observations of gas tracers only probe surface layers above the bulk mass reservoir. Here we present the first partially spatially resolved observations of the ${}^{13}$C${}^{18}$O J=3-2 line emission in the closest protoplanetary disk, TW Hya, a gas tracer that probes the bulk mass distribution. Combining it with the C${}^{18}$O J=3-2 emission and the previously detected HD J=1-0 flux, we directly constrain the mid-plane temperature and optical depths of gas and dust emission. We report a gas mass distribution of 13${}_{-5}^{+8}\times$(R/20.5AU)${}^{-0.9_{-0.3}^{+0.4}}$ g cm${}^{-2}$ in the expected formation zone of gas and ice giants (5-21AU). We find the total gas/millimeter-sized dust mass ratio is 140 in this region, suggesting that at least 2.4M_earth of dust aggregates have grown to >centimeter sizes (and perhaps much larger). The radial distribution of gas mass is consistent with a self-similar viscous disk profile but much flatter than the posterior extrapolation of mass distribution in our own and extrasolar planetary systems.

Definitive version of the manuscript is published in Nature Astronomy, 10.1038/s41550-017-0130. This is the authors' version

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Cited by in corpus (10)

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• Protoplanetary disc `isochrones' and the evolution of discs in the $\dot{M}-M_{\mathrm{d}}$ plane
• CO emission tracing a warp or radial flow within $\lesssim$ 100 au in the HD 100546 protoplanetary disk
• A dust and gas cavity in the disc around CQ Tau revealed by ALMA
• DCO${}^{+}$, DCN and N${}_2$D${}^{+}$ reveal three different deuteration regimes in the disk around the Herbig Ae star HD163296
• Gas mass tracers in protoplanetary disks: CO is still the best
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• CO diffusion and desorption kinetics in CO${}_2$ ices