A UV-to-NIR Study of Molecular Gas in the Dust Cavity around RY Lupi

Abstract

We present a study of molecular gas in the inner disk (r < 20 au) around RY Lupi, with spectra from HST-COS, HST-STIS, and VLT-CRIRES. We model the radial distribution of flux from hot gas in a surface layer between r = 0.1–10 au, as traced by Lyα-pumped H_2. The result shows H_2 emission originating in a ring centered at ~3 au that declines within r < 0.1 au, which is consistent with the behavior of disks with dust cavities. An analysis of the H_2 line shapes shows that a two-component Gaussian profile (FWHM_(broad,H_2) = 105 ± 15 km s^(-1); FWHM_(narrow,H_2) = 43 ± 13 km s^(-1)) is statistically preferred to a single-component Gaussian. We interpret this as tentative evidence for gas emitting from radially separated disk regions (〈r_(broad,H_2)〉~ 0.4 ± 0.1 au;〈r_(narrow_H_2)〉 ~ 3 ± 2 au). The 4.7 μm ^(12)CO emission lines are also well fit by two-component profiles (〈r_(broad,CO)〉= 0.4 ± 0.1 au;〈r_(narrow,CO)〉 = 15 ± 2 au). We combine these results with 10 μm observations to form a picture of gapped structure within the mm-imaged dust cavity, providing the first such overview of the inner regions of a young disk. The HST SED of RY Lupi is available online for use in modeling efforts.

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