What can we learn about protoplanetary disks from analysis of mid-infrared carbonaceous dust emission?

Abstract

In this Paper we analyze the mid-infrared (mid-IR) emission of very small dust particles in a sample of 12 protoplanetary disks to see how they are connected to interstellar dust particles and to investigate the possibility that their emission can be used as a probe of the physical conditions and evolution of the disk. We define a basis made of three mid-IR template spectra PAH${}^0$, PAH${}^{+}$ and VSGs that were derived from the analysis of reflection nebulae, and an additional PAH${}^x$ spectrum that was introduced by Joblin et al. (2008) for the analysis of the spectra of planetary nebulae. From the optimization of the fit of 12 star+disk spectra, using a linear combination of the 4 template spectra, we found that an additional small grain component with a broad feature at 8.3 $\mu$m is needed. We find that the fraction of VSG emission in disks decreases with increasing stellar temperature. VSGs appear to be destroyed by UV photons at the surface of disks, thus releasing free PAH molecules, which are eventually ionized as it is observed in photodissociation regions. On the opposite, we observe that the fraction of PAH${}^x$ increases with increasing star temperature except in the case of B stars where they are absent. We argue that this is compatible with the identification of PAH${}^x$ as large ionized PAHs, most likely emitting in regions of the disk that are close to the star. Finally, we provide a UV-dependant scheme to explain the evolution of PAHs and VSGs in protoplanetary disks. We show that A stars modify the size spectrum of PAHs and VSGs in favor of large PAHs while B stars destroy even the largest PAHs up to large radii in the disk. These results allow us to put new constrains on the properties of two sources: IRS 48 and "Gomez's Hamburger" which are poorly characterized.

arXiv commentAccepted for publication in A&A

References in corpus (27)

• Dust Grain Size Distributions and Extinction in the Milky Way, LMC, and SMC
• Interstellar Dust Grains
• The Infrared Spectrograph on the Spitzer Space Telescope
• The rich 6 to 9 um spectrum of interstellar PAHs
• ISO spectroscopy of circumstellar dust in 14 Herbig Ae/Be systems: towards an understanding of dust processing
• The profiles of the 3 to 12 $\mu$m PAH features
• ISO spectroscopy of disks around Herbig Ae/Be stars
• Spectral Mapping Reconstruction of Extended Sources
• Analysis of the emission of very small dust particles from Spitzer spectro-imagery data using blind signal separation methods
• Cold Disks: Spitzer Spectroscopy of Disks around Young Stars with Large Gaps
• The unusual hydrocarbon emission from the early carbon star HD 100764: The connection between aromatics and aliphatics
• Formation and destruction of polycyclic aromatic hydrocarbon clusters in the interstellar medium
• Spitzer/IRAC and ISOCAM/CVF insights on the origin of the Near to Mid-IR Galactic diffuse emission
• Mid-infrared spectra of PAH emission in Herbig AeBe stars
• PAH chemistry and IR emission from circumstellar disks
• Spitzer-IRS spectra of disks around T Tauri stars II. PAH emission features
• Study of the properties and spectral energy distributions of the Herbig AeBe stars HD 34282 and HD 141569
• PAHs in Circumstellar Disks around Herbig Ae/Be stars
• Spatial separation of small and large grains in the transitional disk around the young star IRS 48
• Chemistry and line emission from evolving Herbig Ae disks
• Modeling the Infrared Emission from the HD 141569A Disk
• A Keplerian disk around the Herbig Ae star HD 34282
• A Keplerian Disk around the Herbig Ae star HD169142
• Carriers of the mid-IR emission bands in PNe reanalysed. Evidence of a link between circumstellar and interstellar aromatic dust
• Mid-InfraRed imaging of the circumstellar dust around three Herbig Ae stars : HD135344, CQTau, HD163296
• A double-lined spectroscopic orbit for the young star HD 34700
• Young Stellar Groups Around Herbig Ae/Be Stars: A Low-Mass YSO Census

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• The warm gas atmosphere of the HD 100546 disk seen by Herschel (Evidence of a gas-rich, carbon-poor atmosphere?)
• Evaporating Very Small Grains as tracers of the UV radiation field in Photo-dissociation Regions
• Circumstellar disks around Herbig Be stars
• PDRs4All: A JWST Early Release Science Program on radiative feedback from massive stars
• Polycyclic aromatic hydrocarbon ionization as a tracer of gas flows through protoplanetary disk gaps
• Polycyclic Aromatic Hydrocarbon in Protoplanetary Disks around Herbig Ae/Be and T Tauri Stars
• Unusual PAH Emission in Nearby Early-Type Galaxies: A Signature of an Intermediate Age Stellar Population?
• The JWST Early Release Science Program for the Direct Imaging & Spectroscopy of Exoplanetary Systems
• Mid-infrared PAH and H2 emission as a probe of physical conditions in extreme PDRs
• Observational Evidence Linking Interstellar UV Absorption to PAH Molecules
• Long-term multi-wavelength studies of GRS 1915+105 I. A high-energy and mid-infrared focus with RXTE, INTEGRAL, and Spitzer
• Interferometric Evidence for Quantum Heated Particles in the Inner Region of Protoplanetary Disks around Herbig Stars
• Massive young disks around Herbig Ae stars
• Dust and Polycyclic Aromatic Hydrocarbon in the HD 34700 Debris Disk
• Evolution of PAHs in protoplanetary disks
• The physical conditions in Gomez's Hamburger (IRAS 18059-3211), a pre-MS rotating disk
• Very Large Telescope observations of Gomez's Hamburger: Insights into a young protoplanet candidate