LkH$\alpha$ 330: Evidence for dust clearing through resolved submillimeter imaging

TL;DR

This study directly images a large, dust-depleted inner gap in the disk around LkHa 330 using submillimeter observations, confirming the presence of a 40 AU radius gap and supporting models of disk clearing likely caused by gravitational perturbations.

Contribution

First direct imaging of a 40 AU inner gap in LkHa 330's disk, validating indirect SED-based gap detection methods and linking dust clearing to gravitational influences.

Findings

Inner gap of 40 AU radius fully resolved

Less than 1.3 x 10^-6 M_solar of dust inside the gap

Gas remains present in the inner disk

Abstract

Mid-infrared spectrophotometric observations have revealed a small sub-class of circumstellar disks with spectral energy distributions (SEDs) suggestive of large inner gaps with low dust content. However, such data provide only an indirect and model dependent method of finding central holes. We present here the direct characterization of a 40 AU radius inner gap in the disk around LkHa 330 through 340 GHz (880 micron) dust continuum imaging with the Submillimeter Array (SMA). This large gap is fully resolved by the SMA observations and mostly empty of dust with less than 1.3 x 10^-6 M_solar of solid particles inside of 40 AU. Gas (as traced by accretion markers and CO M-band emission) is still present in the inner disk and the outer edge of the gap rises steeply -- features in better agreement with the underlying cause being gravitational perturbation than a more gradual process such as grain growth. Importantly, the good agreement of the spatially resolved data and spectrophometry-based model lends confidence to current interpretations of SEDs with significant dust emission deficits as arising from disks with inner gaps or holes. Further SED-based searches can therefore be expected to yield numerous additional candidates that can be examined at high spatial resolution.