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