Mid-infrared Multi-wavelength Imaging of Ophiuchus\,IRS\,48\,Transitional Disk

TL;DR

This study presents detailed mid-infrared imaging of the Ophiuchus IRS 48 transitional disk, revealing asymmetric features and temperature estimates that inform disk structure and shadowing effects relevant to planet formation.

Contribution

First mid-infrared multi-wavelength images of IRS 48 reveal disk asymmetry and temperature, supporting models of inner-outer disk alignment and shadowing effects.

Findings

Asymmetric double peaks in Q-band images indicate disk asymmetry.

Dust temperature at peaks is approximately 135 K, not responsible for asymmetry.

Inner disk shadowing influences outer disk morphology.

Abstract

Transitional disks around the Herbig Ae/Be stars are fascinating targets in the contexts of disk evolution and also planet formation. Oph IRS 48 is one of such Herbig Ae stars, which shows an inner dust cavity and azimuthally lopsided large dust distribution. We present new images of Oph IRS 48 at eight mid-infrared (MIR) wavelengths from 8.59 to 24.6\,$\mu {\rm m}$ taken with the COMICS mounted on the 8.2\,m Subaru Telescope. The N-band (7 to 13\,$\mu {\rm m}$) images show that the flux distribution is centrally peaked with a slight spatial extent, while the Q-band (17 to 25\,$\mu {\rm m}$) images show asymmetric double peaks (east and west). Using 18.8 and 24.6\,$\mu$m images, we derived the dust temperature at both east and west peaks to be 135$\pm$22 K. Thus, the asymmetry may not be attributed to a difference in the temperature. % thus other reason is necessary to explain the asymmetry of east and west peaks in Q-band. Comparing our results with previous modeling works, we conclude that the inner disk is aligned to the outer disk. A shadow casted by the optically thick inner disk has a great influence on the morphology of MIR thermal emission from the outer disk.