Vertical evolution of exocometary gas – I. How vertical diffusion shortens the CO lifetime
نویسندگان
چکیده
Bright debris discs can contain large amounts of CO gas. This gas was thought to be a protoplanetary remnant until it recently shown that could released in collisions volatile-rich solids. As is released, interstellar UV radiation photodissociates producing CI, which shield allowing mass accumulate. However, this picture challenged because CI inefficient at shielding if and are vertically mixed. Here, we study for the first time vertical evolution determine how mixing affects efficiency by CI. We present 1D model accounts release, photodissociation, ionisation, viscous evolution, due turbulent diffusion. find surface density high diffusion weak ($\alpha_{\rm v}/\alpha<[H/r]^2$) above midplane, forming an optically thick layer shields underneath. Conversely, strong v}/\alpha>[H/r]^2$) become well mixed, shortening lifetime. Moreover, also limit amount dust settling. High-resolution ALMA observations resolve distribution thus constrain shielding. scale heights may not good probes mean molecular weight, composition, Finally, show lifetime might long enough spread interior planetesimal belt where produced.
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ژورنال
عنوان ژورنال: Monthly Notices of the Royal Astronomical Society
سال: 2022
ISSN: ['0035-8711', '1365-8711', '1365-2966']
DOI: https://doi.org/10.1093/mnras/stac1756