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 $\left(r<20\text{AU}\right)$ 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 Ly$\hat{I}\pm$-pumped H${}_2$. The result shows H${}_2$ emission originating in a ring centered at $\sim$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 $\left({\text{FWHM}}_{broad,H_2}=105\pm 15{\text{km s}}^{-1};{\text{FWHM}}_{narrow,H_2}=43\pm 13{\text{km s}}^{-1}\right)$ is statistically preferred to a single-component Gaussian. We interpret this as tentative evidence for gas emitting from radially separated disk regions $\left(⟨r_{broad,H_2}⟩\sim 0.4\pm 0.1\text{AU};⟨r_{narrow,H_2}⟩\sim 3\pm 2\text{AU}\right)$. The 4.7 $\hat{I}¼$m ${}^{12}$CO emission lines are also well fit by two-component profiles $\left(⟨r_{broad,CO}⟩=0.4\pm 0.1\text{AU};⟨r_{narrow,CO}⟩=15\pm 2\text{AU}\right)$. We combine these results with 10 $\hat{I}¼$m 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.

Accepted for publication in ApJ