Gas and Dust Toward DG Tau B and VV CrA

TL;DR

This study investigates molecular absorption and disk properties in DG Tau B and VV CrA using Spitzer IRS, near-IR spectroscopy, and mid-IR imaging, revealing low organic molecule abundances and disk grain growth.

Contribution

It provides new insights into the molecular composition and dust properties of edge-on disks, highlighting the importance of line-of-sight effects and disk geometry.

Findings

CO₂ is the only gas absorption detected toward DG Tau B.

Low organic molecule abundances suggest limited gas absorption detection.

Evidence of significant grain growth and settling in DG Tau B's disk.

Abstract

We present findings for DG Tau B and VV CrA, two of the objects observed in our Spitzer IRS project to search for molecular absorption in edge-on disks, along with near-IR spectroscopy of the CO fundamental transitions and mid-IR imaging. While the only gas absorption seen in the Spitzer IRS spectrum toward DG Tau B is CO$_{2}$, we use gas abundances and gas/ice ratios to argue that we are probing regions of the disk that have low organic molecule abundances. This implies the rarity of detecting molecular absorption toward even edge-on disks with Spitzer IRS is a result of high dependence on the line of sight. We also argue the disk around DG Tau B shows high amounts of grain growth and settling. For VV CrA, we use the silicate absorption feature to estimate a dust extinction, and model the disk with a spectral energy distribution fitting tool to give evidence in support of the disk geometry presented by Smith et al. (2009) where the Primary disk is the main source of extinction toward the infrared companion.