English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Lyman-$\alpha$ (Ly$\alpha$) is the strongest emission line in UV spectra fromT-Tauri stars. Due to its resonant nature, Ly$\alpha$ emission carriesinformation about the physical properties of the H I medium via the scatteringprocess. This work presents spatially resolved Ly$\alpha$ emission across aprotoplanetary disk in the iconic face-on T-Tauri star TW Hya, observed withHST-STIS at spatial offsets 0$''$, $\pm 0.2''$, and $\pm 0.4''$. Tocomprehensively interpret these Ly$\alpha$ spectra, we utilize a 3D Monte-Carloradiative transfer simulation in a wind-disk geometry. Successfully reproducingthe observed spectra requires scattering contributions from both the wind andthe H I disk. We constrain the properties of the wind, the H I column density($\sim 10^{20} \rm cm^{-2}$) and the outflow velocity ($\sim 200 \rm kms^{-1}$). To reproduce the observed spatial distribution of Ly$\alpha$, we findthat the wind must cover the H I disk when viewed face-on. Furthermore, toexplore the effect of Ly$\alpha$ radiative transfer in T-Tauri stars, wecompute the radiation field within the scattering medium and reveal that thewind reflection causes more Ly$\alpha$ photons to penetrate the disk. We alsoshow the dependence between the disk inclination angle and the spatiallyresolved Ly$\alpha$ spectra. Understanding the role of Ly$\alpha$ emission inT-Tauri stars is pivotal for decoding the complex interactions between thewinds, protoplanetary disks, and surrounding environments, which cansignificantly impact the chemistry in the protoplanetary disk. Our observationand modeling of spatially resolved Ly$\alpha$ show the necessity of spatiallyresolved Ly$\alpha$ observation of a broad range of targets.

First Detection and Modeling of Spatially Resolved Ly$\alpha$ in TW Hya