Letter to the Editor

Observing the linked depletion of dust and CO gas at 0.1–10 au in disks of intermediate-mass stars

¹ Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721, USA
e-mail: banzatti@lpl.arizona.edu
² Universidad Autonónoma de Madrid, Dpto. Física Teórica, Facultad de Ciencias, Campus de Cantoblanco, 28049 Madrid, Spain
³ Institute of Astronomy, Madingley Rd, Cambridge CB3 0HA, UK
⁴ Unidad Mixta Internacional Franco-Chilena de Astronomía, CNRS/INSU UMI 3386 and Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
⁵ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
⁶ Department of Physics & Astronomy, 118 Kinard Laboratory, Clemson University, Clemson, SC, USA
⁷ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁸ University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822-0345, USA

Received: 3 October 2017
Accepted: 26 November 2017

Abstract

We report on the discovery of correlations between dust and CO gas tracers of the 0.1–10 au region in planet-forming disks around young intermediate-mass stars. The abundance of refractory elements on stellar photospheres decreases as the location of hot CO gas emission recedes to larger disk radii, and as the near-infrared excess emission from hot dust in the inner disk decreases. The linked behavior between these observables demonstrates that the recession of infrared CO emission to larger disk radii traces an inner disk region where dust is being depleted. We also find that Herbig disk cavities have either low (~5–10%) or high (~20–35%) near-infrared excess, a dichotomy that has not been captured by the classic definition of “pre-transitional” disks.