# Imaging a Central Ionized Component, a Narrow Ring, and the CO Snowline in the Multi-Gapped Disk of HD 169142

## TL;DR

This study uses high-resolution VLA observations to analyze the structure of the HD 169142 disk, revealing multiple gaps, a narrow ring, and an ionized central component, linking disk features to planet formation processes.

## Contribution

First high-resolution VLA imaging of HD 169142 disk revealing detailed gap and ring structures and their relation to the CO snowline and potential planet formation.

## Key findings

- Narrow ring at 25 au with asymmetric morphology.
- Detection of gaps at 45 au and 85 au, with the outer gap near the CO snowline.
- Identification of a central ionized gas source likely from free-free emission.

## Abstract

We report Very Large Array observations at 7 mm, 9 mm, and 3 cm toward the pre-transitional disk of the Herbig Ae star HD 169142. These observations have allowed us to study the mm emission of this disk with the highest angular resolution so far ($0\rlap."12\times0\rlap."09$, or 14 au$\times$11 au, at 7 mm). Our 7 and 9 mm images show a narrow ring of emission at a radius of $\sim25$ au tracing the outer edge of the inner gap. This ring presents an asymmetric morphology that could be produced by dynamical interactions between the disk and forming planets. Additionally, the azimuthally averaged radial intensity profiles of the 7 and 9 mm images confirm the presence of the previously reported gap at $\sim45$ au, and reveal a new gap at $\sim85$ au. We analyzed archival DCO$^+$(3-2) and C$^{18}$O(2-1) ALMA observations, showing that the CO snowline is located very close to this third outer gap. This suggests that growth and accumulation of large dust grains close to the CO snowline could be the mechanism responsible for this proposed outer gap. Finally, a compact source of emission is detected at 7 mm, 9 mm, and 3 cm toward the center of the disk. Its flux density and spectral index indicate that it is dominated by free-free emission from ionized gas, which could be associated with either the photoionization of the inner disk, an independent object, or an ionized jet.