A resolved and asymmetric ring of PAHs within the young circumstellar disk of IRS 48

Abstract

For one decade, the spectral-type and age of the $\rho$ Oph object IRS-48 were subject to debates and mysteries. Modelling its disk with mid-infrared to millimeter observations led to various explanations to account for the complex intricacy of dust-holes and gas-depleted regions. We present multi-epoch high-angular-resolution interferometric near-infrared data of spatially-resolved emissions in its first 15AU, known to have very strong Polycyclic Aromatic Hydrocarbon (PAH) emissions within this dust-depleted region. We make use of new Sparse-Aperture-Masking data to instruct a revised radiative-transfer model where SED fluxes and interferometry are jointly fitted. Neutral and ionized PAH, Very Small Grains (VSG) and classical silicates are incorporated into the model; new stellar parameters and extinction laws are explored. A bright (42L${}_{\odot }$) central-star with A${}_v$=12.5mag and R${}_v$=6.5 requires less near-infrared excess: the inner-most disk at $\approx$1AU is incompatible with the data. The revised stellar parameters place this system on a 4 Myr evolutionary track, 4 times younger than previous estimations, in better agreement with the surrounding $\rho$ Oph region and disk-lifetimes observations. The disk-structure converges to a classical-grains outer-disk from 55AU combined with a fully resolved VSG\&PAH-ring, at 11-26 AU. We find two over-luminosities in the PAH-ring at color-temperatures consistent with the radiative transfer simulations; one follows a Keplerian circular orbit at 14AU. We show a depletion of a factor $\approx$5 of classical dust grains compared to VSG\&PAH: the IRS-48 disk is nearly void of dust-grains in the first 55 AU. A 3.5M${}_{Jup}$ planet on a 40AU orbit qualitatively explains the new disk-structure.

References in corpus (17)

• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• Ring shaped dust accumulation in transition disks
• Monte Carlo radiative transfer in protoplanetary disks
• Photoevaporation of protoplanetary discs I: hydrodynamic models
• The Disk Around CoKu Tau/4: Circumbinary, not Transitional
• Mapping the Shores of the Brown Dwarf Desert I.: Upper Scorpius
• Dos and don'ts of reduced chi-squared
• Line Emission from Gas in Optically Thick Dust Disks around Young Stars
• 2MASS wide field extinction maps: II. The Ophiuchus and the Lupus cloud complexe
• The nature of the Class I population in Ophiuchus as revealed through gas and dust mapping
• Spatially extended PAHs in circumstellar disks around T Tauri and Herbig Ae stars
• Spitzer-IRS spectra of disks around T Tauri stars II. PAH emission features
• On the origin of the X-ray emission from Herbig Ae/Be stars
• Spatial separation of small and large grains in the transitional disk around the young star IRS 48
• SEEDS Adaptive Optics Imaging of the Asymmetric Transition Disk Oph IRS 48 in Scattered Light
• Constraining the structure of the transition disk HD 135344B (SAO 206462) by simultaneous modeling of multiwavelength gas and dust observations
• Testing the companion hypothesis for the origin of the X-ray emission from intermediate-mass main-sequence stars

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• A major asymmetric ice trap in a planet-forming disk IV. Nitric oxide gas and a lack of CN tracing sublimating ices and a C/O ratio $<1$
• Tiny Grains Shining Bright in the Gaps of Herbig Ae Transitional Discs
• The Circumbinary Disc of HD 34700A II. Analysis of a strong dust asymmetry