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Kalyaan, A., Pinilla, P., Krijt, S., Mulders, G. D., & Banzatti, A. (2021). Linking Outer Disk Pebble Dynamics and Gaps to Inner Disk Water Enrichment. Astrophys. J., 921(1), 84.
Abstract: Millimeter continuum imaging of protoplanetary disks reveals the distribution of solid particles and the presence of substructures (gaps and rings) beyond 5-10 au, while infrared (IR) spectra provide access to abundances of gaseous species at smaller disk radii. Building on recent observational findings of an anti-correlation between the inner disk water luminosity and outer dust disk radius, we aim here at investigating the dynamics of icy solids that drift from the outer disk and sublimate their ice inside the snow line, enriching the water vapor that is observed in the IR. We use a volatile-inclusive disk evolution model to explore a range of conditions (gap location, particle size, disk mass, and alpha viscosity) under which gaps in the outer disk efficiently block the inward drift of icy solids. We find that inner disk vapor enrichment is highly sensitive to the location of a disk gap, yielding for each particle size a radial “sweet spot” that reduces the inner disk vapor enrichment to a minimum. For pebbles of 1-10 mm in size, which carry the most mass, this sweet spot is at 7-15 au, suggesting that inner gaps may have a key role in reducing ice delivery to the inner disk and may not allow the formation of Earths and super-Earths. This highlights the importance of observationally determining the presence and properties of inner gaps in disks. Finally, we argue that the inner water vapor abundance can be used as a proxy for estimating the pebble drift efficiency and mass flux entering the inner disk.
Keywords: PROTOPLANETARY DISC; PLANET FORMATION; BINARY-SYSTEMS; EVOLUTION; VAPOR; PARTICLES; REGIONS; RINGS; GAS; H2O
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Long, F., Ren, B. B., Wallack, N. L., Harsono, D., Herczeg, G. J., Pinilla, P., et al. (2023). A Large Double-ring Disk Around the Taurus M Dwarf J04124068+2438157. Astrophys. J., 949(1), 27.
Abstract: Planet formation imprints signatures on the physical structures of disks. In this paper, we present high-resolution (similar to 50 mas, 8 au) Atacama Large Millimeter/submillimeter Array observations of 1.3 mm dust continuum and CO line emission toward the disk around the M3.5 star 2MASSJ04124068+2438157. The dust disk consists of only two narrow rings at radial distances of 0 47 and 0 78 (similar to 70 and 116 au), with Gaussian sigma widths of 5.6 and 8.5 au, respectively. The width of the outer ring is smaller than the estimated pressure scale height by similar to 25%, suggesting dust trapping in a radial pressure bump. The dust disk size, set by the location of the outermost ring, is significantly larger (by 3 sigma) than other disks with similar millimeter luminosity, which can be explained by an early formation of local pressure bump to stop radial drift of millimeter dust grains. After considering the disk's physical structure and accretion properties, we prefer planet-disk interaction over dead zone or photoevaporation models to explain the observed dust disk morphology. We carry out high-contrast imaging at the L' band using Keck/NIRC2 to search for potential young planets, but do not identify any source above 5 sigma. Within the dust gap between the two rings, we reach a contrast level of similar to 7 mag, constraining the possible planet below similar to 2-4M(Jup). Analyses of the gap/ring properties suggest that an approximately Saturn-mass planet at similar to 90 au is likely responsible for the formation of the outer ring, which can potentially be revealed with JWST.
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Kalyaan, A., Pinilla, P., Krijt, S., Banzatti, A., Rosotti, G., Mulders, G. D., et al. (2023). The Effect of Dust Evolution and Traps on Inner Disk Water Enrichment. Astrophys. J., 954(1), 66.
Abstract: Substructures in protoplanetary disks can act as dust traps that shape the radial distribution of pebbles. By blocking the passage of pebbles, the presence of gaps in disks may have a profound effect on pebble delivery into the inner disk, crucial for the formation of inner planets via pebble accretion. This process can also affect the delivery of volatiles (such as H2O) and their abundance within the water snow line region (within a few au). In this study, we aim to understand what effect the presence of gaps in the outer gas disk may have on water vapor enrichment in the inner disk. Building on previous work, we employ a volatile-inclusive disk evolution model that considers an evolving ice-bearing drifting dust population, sensitive to dust traps, which loses its icy content to sublimation upon reaching the snow line. We find that the vapor abundance in the inner disk is strongly affected by the fragmentation velocity (v( f)) and turbulence, which control how intense vapor enrichment from pebble delivery is, if present, and how long it may last. Generally, for disks with low to moderate turbulence (a = 1 x 10(-3)) and a range of v( f), radial locations and gap depths (especially those of the innermost gaps) can significantly alter enrichment. Shallow inner gaps may continuously leak material from beyond it, despite the presence of additional deep outer gaps. We finally find that for realistic v( f) (=10 m s(-1)), the presence of gaps is more important than planetesimal formation beyond the snow line in regulating pebble and volatile delivery into the inner disk.
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