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C2D Spitzer-IRS spectra of disks around T Tauri stars

Geers, V. C. and Augereau, J.-C. and Pontoppidan, K. M. and Dullemond, C. P. and Visser, R. and Kessler-Silacci, J. E. and Evans, N. J., II and van Dishoeck, E. F. and Blake, G. A. and Boogert, A. C. A. and Brown, J. M. and Lahuis, F. and Merín, B. (2006) C2D Spitzer-IRS spectra of disks around T Tauri stars. Astronomy and Astrophysics, 459 (2). pp. 545-556. ISSN 0004-6361. doi:10.1051/0004-6361:20064830.

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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 µm 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 µm PAH feature is detected in all of these sources, as is the 6.2 µm PAH feature for the 4 sources for which short wavelength data are available. However, the 7.7 and 8.6 µm features appear strongly in only 1 of these 4 sources. Based on the 11.2 µm 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 µm 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) ≤ 4200 K without enhanced UV are predicted to be below the current detection limit, even for high PAH abundances. Disk modeling shows that the 6.2 and 11.2 µm features are the best PAH tracers for T Tauri stars, whereas the 7.7 and 8.6 µm bands have low feature over continuum ratios due to the strongly rising silicate emission.

Item Type:Article
Related URLs:
URLURL TypeDescription
Pontoppidan, K. M.0000-0001-7552-1562
Visser, R.0000-0003-1775-5461
Evans, N. J., II0000-0001-5175-1777
van Dishoeck, E. F.0000-0001-7591-1907
Blake, G. A.0000-0003-0787-1610
Additional Information:© ESO 2006. Received 9 January 2006 / Accepted 22 August 2006. Support for this work, part of the Spitzer Legacy Science Program, was provided by NASA through contracts 1224608, 1230779 and 1256316 issued by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. Astrochemistry in Leiden is supported by a NWO Spinoza grant and a NOVA grant, and by the European Research Training Network “The Origin of Planetary Systems" (PLANETS, contract number HPRN-CT-2002-00308). B. Merín acknowledges funding from the “Fundación Ramón Areces (Spain). The authors wish to thank Louis Allamandola and Andrew Mattioda for discussions and new opacities and Emilie Habart for comparisons with her models.
Funding AgencyGrant Number
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)UNSPECIFIED
Nederlandse Onderzoekschool voor de Astronomie (NOVA)UNSPECIFIED
European Research Training NetworkHPRN-CT-2002-00308
Fundación Ramón ArecesUNSPECIFIED
Subject Keywords:stars: pre-main sequence; planetary systems: protoplanetary disks; circumstellar matter; astrochemistry; ISM: molecules
Issue or Number:2
Record Number:CaltechAUTHORS:GEEaanda06
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13771
Deposited By: Tony Diaz
Deposited On:25 Jun 2009 17:21
Last Modified:08 Nov 2021 22:40

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