Probing Inner-Edge of Dead Zones in Protoplanetary Disks with ALMA and Next Generation Very Large Array

TL;DR

This paper evaluates the capabilities of ALMA and ngVLA telescopes to observe dust concentrations at the inner edges of dead zones in protoplanetary disks around Herbig stars, crucial for understanding rocky planet formation.

Contribution

It demonstrates that ngVLA can effectively detect dust concentrations at the dead-zone inner edge, surpassing ALMA's resolution limits, and proposes observational strategies for identifying potential rocky planet formation sites.

Findings

ngVLA can detect dust concentrations with 10-hour integrations at 3, 7 mm, and 1 cm wavelengths.

ALMA's resolution limits prevent resolving the dust concentration at the dead-zone inner edge.

Flux density measurements at VLA wavelengths can identify disks with potential dust rings.

Abstract

The discovery of substructures in protoplanetary disks with ALMA has provided us key insights on the formation of planets. However, observational constraints on the formation of rocky planets have been still sparse, especially because of the limited spatial resolution. The inner edge of so-called dead zone is one of the preferential sites of rocky planet formation. We investigate the capabilities of ALMA and ngVLA for observing a dust concentration expected at the inner edge of the dead-zone around a Herbig star. Herbig Ae/Be stars are useful laboratories for exploring the evolution of rocky grains in protoplanetary disks because of their high luminosity which pushes the dead-zone inner edge outward. We find that, thanks to its unprecedented angular resolution and sensitivity, ngVLA can detect the dust concentration at the dead-zone inner edge, with a reasonable integration time of 10 hrs at $\lambda=3,7$ mm and 1 cm. The dust concentration is expected to be optically thick at the ALMA wavelengths and cannot be spatially resolved due to its limited resolution. On the other hand, the flux density from the inner disk regions ($\sim$3--4 au) observed with current VLA is higher for disks with a dust ring, and hence would be a useful indicator that help us choose potential candidates of disks having a dust concentration at the inner most region. With these observations we can characterize the process of dust concentration in the innermost disk regions, where rocky planets can form.