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Near-Infrared Spectroscopy of Interstellar Dust

Published online by Cambridge University Press:  30 March 2011

F. Boulanger
Affiliation:
Institut d’Astrophysique Spatiale (IAS), UMR 8617, CNRS & Université Paris-Sud 11, Bâtiment 121, 91405 Orsay Cedex, France
T. Onaka
Affiliation:
Department of Astronomy, University of Tokyo, Tokyo 113-0033, Japan
P. Pilleri
Affiliation:
Université de Toulouse, UPS, CESR, 9 avenue du colonel Roche, 31028 Toulouse, France CNRS, UMR 5187, 31028 Toulouse, France
C. Joblin
Affiliation:
Université de Toulouse, UPS, CESR, 9 avenue du colonel Roche, 31028 Toulouse, France CNRS, UMR 5187, 31028 Toulouse, France

Abstract

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Near infrared observations of reflection nebulae have set the historical ground for thediscovery of interstellar PAHs, but since, space observations have focused on their mid-IRfeatures, and data shortward of 5   μm have remained scarce. TheSpitzer/IRAC images in the 3.6 and 4.5   μm channels do show that thenear-IR emission from small dust particles is ubiquitous across the Galaxy, but provide nospectroscopic information. To investigate the nature of this near-IR dust emission, wehave obtained AKARI spectroscopic observations, over the 2.5−5   μmspectral range, for a set of archetype PDRs mapped with the Spitzer spectrometer at mid-IRwavelengths. These AKARI data supplement earlier observations with the SWS ISOspectrometer, in providing the gain in sensitivity needed to observe low excitationsources, and the spatial information required to spatially correlate near-IR spectroscopicsignatures with physical conditions and observed changes in mid-IR spectra. This paperpresents the first results of the data analysis, in relation to two open questions oninterstellar PAHs. (1) Is there an evolutionary link from aliphatic carbon dust to PAHs?(2) What is the origin of the near-IR dust continuum? The AKARI spectra display featureslongward of the main 3.29   μm PAH feature, and continuum emission. Theintensity ratio between the features ascribed to aliphatic CH bonds and the3.29   μm aromatic band, varies spatially in a way that may beinterpreted as evidence for aromatization of the smallest dust particles byphoto-processing. The continuum displays a striking step-increase across the3.29   μm feature. We also present a spectrum of a photodissociationregion with a feature at 4.65   μm, which has been speculated to berelated to the CD stretch in aliphatic hydrocarbon side-groups on PAHs.

Type
Research Article
Copyright
© EAS, EDP Sciences 2011

References

Allamandola, L.J., Tielens, A., & Barker, J.R., 1989, ApJS, 71, 733 CrossRef
Berné, O., Joblin, C., Deville, Y., et al., 2007, A&A, 469, 575
Bernstein, M.P., Sandford, S.A., & Allamandola, L.J., 1996, ApJ, 472, L127 CrossRef
DeFrees, D.J., Miller, M.D., Talbi, D., et al., 1993, ApJ, 408, 530
Draine, B.T., 2004, in Astrophysics in the Far Ultraviolet [Astro-ph/0410310]
Draine, B.T., & Li, A., 2007, ApJ, 657, 810 CrossRef
Flagey, N., Boulanger, F.,Verstraete, L., et al., 2006, A&A, 453, 969
Geballe, T.R., Tielens, A.G.G.M., Allamandola, L.J., et al., 1989, ApJ, 341, 278 CrossRef
Joblin, C., Tielens, A.G.G.M., Allamandola, L.J., & Geballe, T.R., 1996, ApJ, 458, 610 CrossRef
Jones, A.P., Tielens, A.G.G.M., & Hollenbach, D.J., 1996, ApJ, 469, 740 CrossRef
Léger, A., & Puget, J.L., 1984, A&A, 137, L5 PubMed
Léger, d Hendecourt, L., & Boissel, P., 1988, PhRvL, 60, 921L
Linsky, J., Draine, B.T., Moos, H.W., et al., 2006, ApJ, 647, 1106 CrossRef
Ohyama, Y., Onaka, T., Matsuhara, H., et al., 2007, PASJ, 59, S411
Peeters, E., Allamandola, L.J., Bauschlicher, C.W., et al., 2004, ApJ, 604, 252 CrossRef
Rapacioli, M., Joblin, C., & Boissel, P., 2005, A&A, 429, 193
Rapacioli, M., Calvo, F., Joblin, C., et al., 2006, A&A, 460, 519
Sellgren, K., Werner, M.W., & Dinerstein, H.L., 1983, ApJ, 271, L13 CrossRef
van Diedenhoven, B., Peeters, E., Van Kerckhoven, C., et al., 2004, ApJ, 611, 928 CrossRef
Verstraete, L., Pech, C., Moutou, C., et al., 2001, A&A, 372, 981