Compact Hydrogen Sulfide Emission Indicates Sulfur-bearing Ice Sublimation in the Inner Disk of HD 163296

2026/04/13 by Yoshihide Yamato, Yuri Aikawa, Kenji Furuya +8 · 1 voice
Physics and Astronomy · #astro-ph.EP #astro-ph.SR

paper · pdf · doi:10.3847/1538-4357/ae5f95

Abstract

The sulfur chemistry in protoplanetary disks directly affects the composition and potential habitability of nascent planets, but its volatile inventory remains highly uncertain. Here, we present deep Atacama Large Millimeter/submillimeter Array (ALMA) observations of hydrogen sulfide (H₂S) along with SO and SO₂ in the disk around HD 163296 at an angular resolution of ≈0. ^′′3 (or ≈30 au). We detect unresolved, compact emission of H₂S and SO (and tentatively SO₂) at the disk center with a broad line width of ∼40 km s^-1, suggesting that the emission is originating from the innermost regions. By fitting line profiles with a geometrically-thin Keplerian-rotating disk model, we constrain the emitting radii and gas temperatures of these molecules to be ≈3-5 au and \gtrsim90-120 K, respectively, consistent with sublimation of sulfur-bearing molecules along with water ice in the inner warm region. While the higher or comparable column density of H₂S with respect to SO and SO₂ indicates that H₂S is an important volatile sulfur reservoir in the disk, the limited constraints mean that we cannot rule out significantly depleted volatile sulfur as also commonly inferred in other planet-forming disks. Further observations are needed to better constrain disk sulfur inventory, unravel how sulfur compounds are reprocessed in disks, and shed light on the nature of less-volatile species, such as salts and sulfide minerals, which may occupy a significant portion of sulfur budget.

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Discussions

• Compact Hydrogen Sulfide Emission Indicates Sulfur-bearing Ice Sublimation in the Inner Disk of HD 163296 Yamato et al. arXiv (ApJ) arxiv.org/abs/2604.11408 [bsky, 1 points, 0 comments]