C2D Spitzer-IRS spectra of disks around T Tauri stars. II. PAH emission features

By V. Geers, Jean Augereau, K. Pontoppidan, C. Dullemond, R. Visser, J. Kessler-Silacci, N. Evans II, E. F. Dishoeck, G. Blake, A. Boogert and 3 more. 2006

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Aims. We search for Polycyclic Aromatic Hydrocarbon (PAH) features towards young low-mass (T Tauri) stars and compare them with surveys of intermediate mass (Herbig Ae/Be) stars. The presence and strength of the PAH features are interpreted with disk radiative transfer models exploring the PAH feature dependence on the incident UV radiation, PAH abundance and disk parameters. Methods. Spitzer Space Telescope 5-35 mu m spectra of 54 pre-main sequence stars with disks were obtained, consisting of 38 T Tauri, 7 Herbig Ae/Be and 9 stars with unknown spectral type. Results. Compact PAH emission is detected towards at least 8 sources of which 5 are Herbig Ae/Be stars. The 11.2 mu m PAH feature is detected in all of these sources, as is the 6.2 mu m PAH feature for the 4 sources for which short wavelength data are available. However, the 7.7 and 8.6 mu m features appear strongly in only 1 of these 4 sources. Based on the 11.2 mu m feature, PAH emission is observed towards at least 3 T Tauri stars, with 14 tentative detections, resulting in a lower limit to the PAH detection rate of 8%. The lowest mass source with PAH emission in our sample is T Cha with a spectral type G8. All 4 sources in our sample with evidence for dust holes in their inner disk show PAH emission, increasing the feature/continuum ratio. Typical 11.2 mu m line intensities are an order of magnitude lower than those observed for the more massive Herbig Ae/Be stars. Measured line fluxes indicate PAH abundances that are factors of 10-100 lower than standard interstellar values. Conversely, PAH features from disks exposed to stars with T(eff)

Subfields: Astronomy and Astrophysics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/0516390a590a167dd7bf96db0711cf1bd1413b65

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Citations in the corpus

Gas density drops inside dust cavities of transitional disks around young stars observed with ALMA (2015, background): “We include PAHs since many of our observed sources show PAH features (Brown et al. 2007; Geers et al. 2006) but at a low abundance of 0.1% of the ISM abundance.”
Survival of molecular gas in cavities of transition disks - I. CO (2013, background): “As we make no attempt to model the infrared features of PAHs (see Visser et al. 2007; Geers et al. 2006), the choice of purely neutral PAHs does not affect our results.”
Cold Disks: Spitzer Spectroscopy of Disks around Young Stars with Large Gaps (2007, background): “Such emission is uncommon in the c2d sample, with only∼10% displaying PAH features (Geers et al. 2006; see their Fig.”
Dynamics of Protoplanetary Disks (2010, background): “Observationally, PAH spectral features are detected in only a small fraction of T Tauri stars (Geers et al. 2006, Oliveira et al. 2010).”