Astronomy and Astrophysics, volume 476, 279-289 (2007/12-2)
Spatially extended polycyclic aromatic hydrocarbons in circumstellar disks around T Tauri and Herbig Ae stars.
GEERS V.C., VAN DISHOECK E.F., VISSER R., PONTOPPIDAN K.M., AUGEREAU J.-C., HABART E. and LAGRANGE A.M.
Abstract (from CDS):
Our aim is to determine the presence and location of the emission from polycyclic aromatic hydrocarbons (PAHs) towards low and intermediate mass young stars with disks using large aperture telescopes. VLT-VISIR N-band spectra and VLT-ISAAC and VLT-NACO L-band spectra of 29 sources are presented, spectrally resolving the 3.3, 8.6, 11.2, and 12.6µm PAH features. Spatial-extent profiles of the features and the continuum emission have been derived and used to associate the PAH emission with the disks. The results are discussed in the context of recent PAH-emission disk models. The 3.3, 8.6, and 11.2µm PAH features are detected toward a small fraction of the T Tauri stars, with typical upper limits between 1x10–15 and 5x10–17W/m2. All 11.2µm detections from a previous Spitzer survey are confirmed with (tentative) 3.3µm detections, and both the 8.6 and the 11.2µm features are detected in all PAH sources. For 6 detections, the spatial extent of the PAH features is confined to scales typically smaller than 0.12-0.34'', consistent with the radii of 12-60AU disks at their distances (typically 150pc). For 3 additional sources, WL 16, HD 100546, and TY CrA, one or more of the PAH features are more extended than the hot dust continuum of the disk, whereas for Oph IRS 48, the size of the resolved PAH emission is confirmed as smaller than for the large grains. For HD 100546, the 3.3µm emission is confined to a small radial extent of 12±3AU, most likely associated with the outer rim of the gap in this disk. Gaps with radii out to 10-30AU may also affect the observed PAH extent for other sources. For both Herbig Ae and T Tauri stars, the small measured extents of the 8.6 and 11.2µm features are consistent with larger (≥100 carbon atoms) PAHs.
stars: pre-main sequence - planetary systems: protoplanetary disks - circumstellar matter - astrochemistry
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