The Water and Ammonia Content in the Proto-planetary Disk of V883 Ori

John Tobin, Merel L. R. van 't Hoff, Margot Leemker, Ewine F. van Dishoeck, Teresa Paneque-Carreno, Kenji Furuya, Daniel Harsono, Magnus V. Persson, Ilse Cleeves, Patrick D. Sheehan, Lucas Cieza

Water is a fundamental molecule in the star and planet formation process, essential for catalyzing the growth of solid material and the formation of planetesimals within disks. However, the water snowline and the HDO/H2O ratio within proto-planetary disks have not been well-characterized because most water is frozen-out onto dust grains and the water snowline radii are <10 au. The sun-like protostar V883 Ori (M*=1.3 Msun), is undergoing an accretion burst, increasing its luminosity to ~200 Lsun and the observations suggested that its water snowline is 40-120~au in radius and the full dust disk radius is ~200 au. Here we report the direct detection of gas phase water (HDO and H218O) from the disk of V883 Ori using ALMA Bands 5 and 6 at a resolution of ~0.1" (40 au). We measure a midplane water snowline radius of 55 au, comparable to the scale of the Kuiper Belt, and water is detected out to ~160 au radii in the disk upper layers. We then measure the HDO/H2O ratio of the disk to be (2.15 +/- 0.55)x10-3. This ratio is comparable to protostellar envelopes, comets, and exceeds that of Earth's oceans by 3.3σ. We further analyze the non-detection of Ammonia toward V883 Ori from a deep search with the VLA and analyze this in the context of the now known water abundance. We conclude that disks directly inherit water from the star-forming cloud and this water becomes incorporated into large icy bodies, like comets, without significant chemical alteration.