PAHs and the Universe

Description

Driven by ground-based, airborne, and IRAS observations, the PAH hypothesis was first formulated in the mid-eighties : the widespreas emission features in the 3-13 µm range are due to UV-pumped, IR fluorescence by large Polycyclic Aromatic Hydrocarbon molecules. These molecules are a ubiquitous component of the insterstellar medium both in local galaxies as well as out to redshifts of ~3 and probably beyond, play an important role in its physical and chemical characteristics, and form a key link between small hydrocarbon species and large carbonaceous grains.

This book gathers contributions that reflect the evolution of the field over the last 25 years, taking advantage of IR space missions - ISO, Spitzer and AKARI - and of dedicated experimental and quantum-chemical studies. We have now reached a stage where we can develop these mid-infrared features as diagnostic tools to study star formation processes, protoplanetary disks as well as galaxy assemblage in the early Universe. The current Herschel/Planck area opens the possibility to better characterize the mid-IR carriers through their contribution to the far-IR and mm emissions. Still, much effort is required before we will fully understand the formation and nature of interstellar PAHs and their role in the Universe. Physical chemists can play an important role in driving this field. This book aims at discussing the state-of-the-art of the PAH hypothesis and to chart the future in this interdisciplinary field. It highlights the various aspects of interstellar PAHs:
- Rich IR spectra of interstellar PAHs
- PAHs and star formation in the near and far Universe
- The lifecycle of PAHs in space
- PAHs in regions of planet formation
- PAHs and carbonaceous grains & Solar system materials.

Sujets

• Sciences expérimentales
• Astronomie et astrophysique
• Astronomie
• Astrophysique
• Space Science
• Sciences et techniques
• Astronomy
• Science
• Physique
• Physical attractiveness

Informations

• Publié par: EDP Sciences
• Date de parution: 01 juillet 2011
• Nombre de lectures: 0
• EAN13: 9782759824823
• Langue: English
• Poids de l'ouvrage: 29 Mo

Extrait

EAS Publications Series, Volume 46, 2011

PAHs and the Universe: A Symposium to th Celebrate the 25 Anniversary of the PAH Hypothesis

Toulouse, France 31 May - 04 June, 2010

Edited by:C. Joblin and A.G.G.M. Tielens

17 avenue du Hoggar, PA de Courtabœuf, B.P. 112, 91944 Les Ulis cedex A, France

First pages of all issues in the series and full-text articles in PDF format are available to registered users at: http://www.eas-journal.org

Sponsors

Centre National de la Recherche Scientifique (CNRS-INSU, INP, INC) Université Toulouse III - Paul Sabatier (UPS) CentreNationald’ É tudesSpatiales(CNES) Région Midi-Pyrénées Ministère de l’Enseignement Supérieur et de la Recherche European Space Agency (ESA) IRSAMC-UPS Réseau de Chimie Théorique Département de la Haute Garonne

Scientific Organizing Committee V. Bierbaum, University of Boulder, USA L. d’Hendecourt, IAS, Paris, France T. Geballe, Gemini Observatory, Hawaii, USA K. Gordon, STScI, Baltimore, USA T. Henning, MPIA, Heidelberg, Germany E. Herbst, Ohio State University, USA C. Joblin (co-chair), CESR, Toulouse, France R. Kennicutt, University of Cambridge, USA D. Lutz, MPE, Garching, Germany T. Onaka, University of Tokyo, Japan J.-L. Puget, IAS, Paris, France F. Salama, NASA ARC, USA S. Schlemmer, University of Cologne, Germany F. Spiegelman, LCPQ, Toulouse, France A. Tielens (co-chair), Leiden Observatory, The Netherlands

Cover Figure New light on and from PAHs: From Orion to Le Pont de Toulouse. Image credits: Orion as seen by Spitzer, NASA/JPL-Caltech/S.T. Megeath (University of Toledo, Ohio); Toulouse, L. Montier. Indexed in:ADS, Current Contents Proceedings – Engineering & Physical Sciences, ISTP r /ISI Proceedings, ISTP/ISI CDROM Proceedings. ISBN 978-2-7598-0624-9 EDP Sciences Les Ulis ISSN 1633-4760 e-ISSN 1638-1963

This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broad-casting, reproduction on microfilms or in other ways, and storage in data banks. Duplication of this publication or parts thereof is only permitted under the provisions of the French Copyright law of March 11, 1957. Violations fall under the prosecution act of the French Copyright Law.  c EAS, EDP Sciences 2011 Printed in UK

Foreword

Some twenty five years ago, driven by ground-based, airborne, and IRAS ob- servations, the PAH hypothesis was first formulated to explain the strong emis- sion features that dominate the mid-infrared spectra of most bright astronomical sources. In this hypothesis, the well-known infrared emission features – at 3.3, 6.2, 7.7, 8.6, and 11.2μm – were attributed to large (<50 C-atom) Polycyclic Aromatic Hydrocarbon (PAH) molecules that are pumped by the strong far- ultraviolet photon flux from nearby stars. Since then, spectroscopy using the Short Wavelength Spectrometer and ISOCAM on the Infrared Space Observatory launched by the European Space Agency in 1995, the InfraRed Spectrograph on the Spitzer Space Telescope launched by NASA in 2005 and the InfraRed Camera onboard the Japanese AKARI satellite launched in 2006 have revealed the richness of the interstellar infrared emission spectrum and the variations therein. These spectral variations reflect variations in the molecular characteristics of the PAH family, reflecting the local physical and chemical conditions of the emitting re- gions. Parallel to these observational developments, experimental and theoretical studies of the physical and chemical properties of astrophysically relevant PAHs have really taken off. Such studies aim at elucidating the intrinsic infrared, visible, and ultraviolet properties of large PAH molecules and their dependence on molec- ular characteristics. In addition, dedicated experiments are performed to study the origin, evolution, and chemical role of PAHs in the interstellar medium. It is clear that this field has really taken off and the PAH hypothesis has evolved into the reigning paradigm. Observations have shown that PAH molecules are abundant and ubiquitous in the interstellar medium. Conversely, PAHs may also be a dominant “force” in the interstellar medium, dominating the photoelectric heating of interstellar gas and may be important for the ionization balance inside dense molecular cloud cores. While much progress has been made, still more remains to be discovered including the role of derivative species such as nitrogenated PAHs, PAH clusters and PAH complexes with metals, and the relationship between PAH molecules and carbona- ceous grains including Hydrogenated Amorphous Carbon and diamond. PAHs may also provide a catalytic surface for the formation of, for example, molecular hy- drogen. Furthermore, photolysis of PAH related species may provide a source of small hydrocarbons particularly in regions rich in UV photons. We are now reaching a stage where we can start to use the observations of the IR emission spectrum as diagnostic tools to determine the physical conditions in the emitting regions of, in particular, regions of star and planet formation. Be- cause the IR emission features dominate the IR spectrum of regions of massive star formation, these bands are also often used as proxies to determine the importance of star formation on galactic scales. Specifically, the importance of star forma- tion versus AGN activity for the luminosity source of (Ultra)Luminous InfraRed Galaxies is based upon a quantitative interpretation of the observed PAH emis- sion from galactic nuclei. At this moment, the Herschel and Planck ESA space missions are geared towards probing the low frequency bending modes of PAHs

IV

and the rotational transitions of this spinning dust component. The James Webb Space Telescope and the Stratospheric Observatory for Infrared Astronomy, and the possible SPICA mission will provide in the coming years spectral imaging at high resolution and increased sensitivity. The future for the PAH universe looks bright. We considered it therefore timely to organize a scientific meeting “PAHs and the th universe: A Symposium to celebrate the 25 anniversary of the PAH hypothesis” with the goal to bring together experts in the area of astronomical observations, laboratory studies, and astronomical modeling of interstellar PAHs to discuss the state-of-the-art and to chart the future. Moreover, and more importantly, two of the pioneers of the interstellar PAH hypothesis – Lou Allamandola and Alain Léger – are reaching a milestone in their life – they soon will be 65 years young - and this meeting provided a good occasion to celebrate their accomplishments in opening up and driving this field. The symposium was hosted in Toulouse (France) by the CESR and LCPQ th (University of Toulouse and CNRS), May 31 through June 4 , 2010. We are very grateful for their hospitality and want to acknowledge the hard work by the local organizing committee that was instrumental in making this sympo- sium such a resounding success. This symposium would not have been possible without the generous financial support by INSU-CNRS, Université Paul Sabatier (UPS), CNES, Région Midi-Pyrénées, Ministère de l’Enseignement Supérieur et de la Recherche, ESA, IRSAMC-UPS, INC-CNRS, Réseau de chimie théorique, INP-CNRS, and Département de la Haute Garonne. We would like to thank the Scientific Organizing Committee for the well-conceived scientific program, which highlighted all aspects of interstellar PAHs. We also thank the participants for the reviews, contributed papers, and poster papers and the stimulating discus- sions. The PAH symposium was attended by some 130 scientists from 18 different countries and 5 continents, all united in their quest for the molecular Universe. This is the first time in 25 years that a symposium was organized on this important topic and we felt that this warranted the publication of proceedings. The goal of the proceedings paralleled those of the symposium: to publish a lasting legacy of this meeting summarizing the field and charting the future. We have asked the reviewers to write review chapters at a graduate level pedagogical fashion to yield a reference text for years to come. In addition, these proceedings include the contributed papers, which provide a cross cut of the field as it is today. In reading these papers, we have been impressed by the hard work and care with which they were written. A symposium and its proceedings are only as good as the participants and speakers make it and, from that perspective, this meeting was top-notch.

Mountain View & Toulouse Xander Tielens & Christine Joblin

December 9, 2010

DOI: 10.1051/eas/1146000

ACKE ALATA ALLAMANDOLA ALVARO GALUE

BAOUCHE BARTHEL BASIRE BEARPARK BECKER BERNARD BERNE BIENNIER BIERBAUM BLANCHET BOERSMA BOGGIO-PASQUA BOULANGER BOUWMAN BRECHIGNAC BRYSON

CALZETTI CAMI CANDIAN CARPENTIER CERNICHARO CHANDRASEKARAN CHERCHNEFF CONTRERAS COUPEAUD COX

D’HENDECOURT DALLE ORE DARTOIS DEDONDER DEMYK DOPFER DRAINE

ELLINGER

FERAUD FRIHA

GADALLAH GADEA GADALLAH

List of Participants

Bram Ivan Louis Hector

SAOUD Robert Marie Michael Luann Jean-Philippe Olivier Ludovic Veronica Valérie Christiaan Martial Franc¸ois Jordy Philippe Kathryn

Daniela Jan Alessandra Yvain Jose Vijayanand Isabelle Cesar Anne Nick

Louis Cristina Emmanuel Claude Karine Otto Bruce

Yves

Géraldine Hela

Kamel Florent Xavier Kamel

Instit. Astronomy, K.U. Leuven, Belgium Centre Laser, Univ. Paris Sud 11, France NASA Ames Research Center, CA, USA FOM Rijnhuizen, The Netherlands

Paris Observatory, France Instit. Phys. Chem., KIT, Karlsruhe, Germany ISMO, Univ. Paris Sud/CNRS, France Imperial College London, UK Johns Hopkins Univ., Baltimore, USA CESR, Univ. Toulouse/CNRS, France Leiden Observatory, The Netherlands IPR, Univ. Rennes 1/CNRS, France Univ. Colorado, Boulder, USA LCAR-IRSAMC, Univ. Toulouse/CNRS, France NASA Ames Research Center, CA, USA LCPQ, Univ. Toulouse/CNRS, France IAS, Univ. Paris Sud/CNRS, France Leiden Observatory, The Netherlands ISMO, Univ. Paris Sud/CNRS, France NASA Ames Research Center, CA, USA

Astronomy Dept., Univ. Massachusetts, USA Univ. Western Ontario & SETI Instit., Canada University of Nottingham, UK Max-Planck-Instit. Astron., Jena, Germany Centro de Astrobiologia INTA-CSIC, Spain ISM, Univ. Bordeaux 1/CNRS, France Universitaet Basel, Switzerland NASA Ames Research Center, CA, USA CESR, Univ. Toulouse/CNRS, France Instit. Astronomy, K.U. Leuven, Belgium

IAS, Univ. Paris Sud/CNRS, France SETI Institute/ NASA Ames, CA, USA IAS, Univ. Paris Sud/CNRS, France CNRS/Univ. Paris-Sud 11, France CESR, Univ. Toulouse/CNRS, France TU Berlin, Germany Princeton University, USA

LCT - Univ. Pierre et Marie Curie/ CNRS, France

ISMO, Univ. Paris Sud/CNRS, France ISMO, Univ. Paris Sud/CNRS, France

University of Jena, Germany LCPQ, Univ. Toulouse/CNRS, France University of Jena, Germany

VI

GADEA GALLIANO GEBALLE GEPPERT GIARD GODARD GORDON GUENNOUN

HAMMONDS HANNACHI HARAGUCHI HEBDEN HELTON HERBST HOLM HONY HORNEKAER HUNT

IGLESIAS-GROTH IVANOVSKAYA

J Ä GER JOALLAND JOBLIN JØRGENSEN JOUVET

KAMP KANEDA KAZMIERCZAK KIM KLÆRKE KRELOWSKI

LAGACHE LAWICKI LE BOURLOT LE PADELLEC LE PAGE LEE LEGER LI

MAHADEVAPPA MARBLE MASCETTI MASON MAURETTE MAYER MENNELLA MISSELT

Florent Xavier Frédéric Tom Wolf Martin Marie Karl Zohra

Mark Yacine Kentaro Kerry L. Andrew Eric Anne I. S. Sacha Liv Leslie

Susana Viktoria

Cornelia Baptiste Christine Bjarke Christophe

Inga Hidehiro Maja Ji Hoon Benedikte Jacek

Guilaine Arkadiusz Jacques Arnaud Valéry Timothy Alain Aigen

Naganathappa Andy Joëlle Rachel Michel Paul Vito Karl

LCPQ, Univ. Toulouse/CNRS, France AIM, CEA/Saclay, France Gemini Observatory, Hawaii, USA Stockholm University, Sweden CESR, Univ. Toulouse/CNRS, France IAS, Univ. Paris Sud/CNRS, France Space Telescope Science Instit., Baltimore, USA ISM, Univ. Bordeaux 1/CNRS, France

University of Nottingham, UK ISM, Univ. Bordeaux 1/CNRS, France Nagoya University, Japan University of Manchester, UK University of Minnesota, Minneapolis, USA Ohio State University, Columbus, USA Stockholm University, Sweden AIM, CEA/Saclay, France Aarhus University, Denmark INAF-Osserv. Astrof. Arcetri, Italy

Instit. Astrof ¡sica de Canarias, Spain ISMO, Univ. Paris Sud/CNRS, France

Friedrich Schiller Univ., Jena, Germany CESR/LCPQ - Univ. Toulouse/CNRS, France CESR, Univ. Toulouse/CNRS, France Aarhus University, Denmark ISMO, Univ. Paris Sud/CNRS, France

Kapteyn Astron. Instit., Groningen, The Netherlands Nagoya University, Japan Nicolaus Copernicus Univ., Torun, Poland Seoul National Univ., Republic of Korea Aarhus University, Denmark Nicolaus Copernicus Univ., Torun, Poland

IAS, Univ. Paris Sud/CNRS, France CIMAP - GANIL, France Univ. Paris-Diderot, Paris 7 & Obs. Paris, France CESR, Univ. Toulouse/CNRS, France Univ. Colorado, Boulder, USA NASA Ames Research Center, CA, USA IAS, Univ. Paris Sud/CNRS, France University of Missouri, Columbia, USA

Swami Ramanand Teerth Marathwada Univ., India Steward Observatory, Tucson, USA ISM, Univ. Bordeaux 1/CNRS, France Gemini Observatory, Hawaii, USA CSNSM, Univ. Paris Sud/CNRS, France Chemistry Dep., Univ. Ottawa, Canada INAF-Osserv. Astron. Capodimonte, Italy Steward Observatory, Tucson, USA

MONTILLAUD MULAS

NILSSON

O’DOWD OHSAWA OKADA OMONT ONAKA OOMENS OTAGURO

PARNEIX PATHAK PAUZAT PEETERS PILLERI PINO PUGET

RAPACIOLI RASTOGI RHO RICKETTS RISTORCELLI ROUILLE ROUSSEAU

SAKON SALAMA SALES SANDSTROM SARRE SELLGREN SHENOY SIEBENMORGEN SIMON SMITH SMOLDERS SNOW SPIEGELMAN STEGLICH

TALBI TEILLET-BILLY THROWER TIELENS

VERSTRAETE

WALKER WOODS

Julien Giacomo

Louis

Matt Ryou Yoko Alain Takashi Jos Jacqueline

Pascal Amit Franc¸oise Els Paolo Thomas Jean-Loup

Mathias Shantanu Jeonghee Claire Isabelle Gaël Patrick

Itsuki Farid Dinalva Aires Karin Peter Kris Sachindev Ralf Aude Erin Kristof Theodore Fernand Mathias

Dahbia Dominique John Alexander

Laurent

Mark Paul

CESR, Univ. Toulouse/CNRS, France INAF - Osserv. Astron. Cagliari, Italy

Aarhus University, Denmark

VII

Columbia University, New York, USA Grad. School of Science, Univ. Tokyo, Japan I. Physik. Institut, Univ. Köln, Germany IAP, Univ. Pierre et Marie Curie/CNRS, France University of Tokyo, Japan FOM Rijnhuizen, The Netherlands Western Ontario Univ., London, Canada

ISMO, Univ. Paris Sud/CNRS, France Indian Instit. Astrophysics, Bangalore, India LCT - Univ. Pierre et Marie Curie/ CNRS, France Univ. Western Ontario & SETI Instit., Canada CESR, Univ. Toulouse/CNRS, France ISMO, Univ. Paris Sud/CNRS, France IAS, Univ. Paris Sud/CNRS, France

LCPQ, Univ. Toulouse/CNRS, France Physics Dept., DDU Gorakhpur Univ., India California Institute of Technology, USA NASA Ames Research Center, CA, USA CESR, Univ. Toulouse/CNRS, France Universität Jena, Germany CIMAP - GANIL, France

University of Tokyo, Japan NASA Ames Research Center, CA, USA Univer. Federal Rio Grande do Sul, Porto Alegre, Brazil Max-Planck-Instit. Astron., Heidelberg, Germany University of Nottingham, UK Ohio State University, Columbus, USA NASA Ames Research Center, CA, USA ESO, Garching. Germany LCPQ, Univ. Toulouse/CNRS, France NASA Ames Research Center, CA, USA Instit. Astronomy, K.U. Leuven, Belgium Univ. Colorado, Boulder, USA LCPQ, Univ. Toulouse/CNRS, France Universität Jena, Germany

GRAAL, Univ. Montpellier 2/CNRS, France ISMO, Univ. Paris Sud/CNRS, France Aarhus University, Denmark Leiden Observatory, The Netherlands

IAS, Univ. Paris Sud/CNRS, France

Manly Astrophysics, Australia University of Manchester, UK

Contents

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

List of participants . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction

25 Years of PAH Hypothesis A.G.G.M. Tielens . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . .

Rich IR Spectra of Interstellar PAHs

Astronomical Observations of the PAH Emission Bands E. Peeters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Astronomical Models of PAHs and Dust B.T. Draine . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Dialectics of the PAH Abundance Trend with Metallicity F. Galliano . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The Shape of Mid-IR PAH Bands in the Universe O. Berné, P. Pilleri and C. Joblin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

AKARI Near-Infrared Spectroscopy of 3 Micron PAH and 4 Micron PAD Features T. Onaka, I. Sakon, R. Ohsawa, T. Shimonishi, Y. Okada, M. Tanaka and H. Kaneda . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . .

Laboratory Infrared Spectroscopy of PAHs J. Oomens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Computational IR Spectroscopy for PAHs: From the Early Years to the Present Status F. Pauzat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Modeling the Anharmonic Infrared Emission Spectra of PAHs: Application to the Pyrene Cation M. Basire, P. Parneix, T. Pino, Ph. Bréchignac and F. Calvo . . . . . . . .

Laboratory Spectroscopy of Protonated PAH Molecules Relevant For Interstellar Chemistry O. Dopfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The NASA Ames PAH IR Spectroscopic Database and the far-IR C. Boersma, L.J. Allamandola, C.W. Bauschlicher, Jr., A. Ricca, J. Cami, E. Peeters, F. Sánchez de Armas, G. Puerta Saborido, A.L. Mattioda and D.M. Hudgins . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .

Analyzing Astronomical Observations with the NASA Ames PAH Database J. Cami . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Search for far-IR PAH Bands with Herschel: Modelling and Observational Approaches C. Joblin, G. Mulas, G. Malloci and E. Bergin & the HEXOS consortium . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

PAHs and Star Formation in the Near and Far Universe

Polycyclic Aromatic Hydrocarbons as Star Formation Rate Indicators D. Calzetti . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

PAHs and the ISM in Metal-Poor Starbursts L.K. Hunt, Y.I. Izotov, M. Sauvage and T.X. Thuan . . . . . . . . . . . . . . . .

Introduction to AMUSES: AKARI Survey with a Window of Opportunity J.H. Kim, M. Im, H.M. Lee, M.G. Lee and the AMUSES team . . . . . .

The Lifecycle of PAHs in Space

PAH Evolution in the Harsh Environment of the ISM H. Kaneda, T. Onaka, I. Sakon, D. Ishihara, A. Mouri, M. Yamagishi and A. Yasuda . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .

PAH and Dust Processing in Supernova Remnants J. Rho, M. Andersen, A. Tappe, W.T. Reach, J.P. Bernard and J. Hewitt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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The Formation of Polycyclic Aromatic Hydrocarbons in Evolved Circumstellar Environments I. Cherchneff . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Insights into the Condensation of PAHs in the Envelope of IRC +10216 L. Biennier, H. Sabbah, S.J. Klippenstein, V. Chandrasekaran, I.R. Sims and B.R. Rowe . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . .

Formation and Evolution of Circumstellar and Interstellar PAHs: A Laboratory Study C.S. Contreras, C.L. Ricketts and F. Salama . . . . . . . . . . . . . . . . . . . . . . . .

Confirmation of C 60 in the Reflection Nebula NGC 7023 K. Sellgren, M.W. Werner, J.G. Ingalls, J.D.T. Smith, T.M. Carleton and C. Joblin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The Spitzer Surveys of the Small Magellanic Cloud: Insights into the Life-Cycle of Polycyclic Aromatic Hydrocarbons K.M. Sandstrom, A.D. Bolatto, B.T. Draine, C. Bot and S. Stanimirovic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

PAH-related Very Small Grains in Photodissociation Regions: Implications from Molecular Simulations M. Rapacioli, F. Spiegelman, B. Joalland, A. Simon, A. Mirtschink, C. Joblin, J. Montillaud, O. Berné and D. Talbi . . . . . . . . . . . . . . . . . . . .

The Formation of Benzene in Dense Environments P.M. Woods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Experimental Studies of the Dissociative Recombination Processes + + for the C 6 D and C 6 D Ions 6 7 M. Hamberg, E. Vigren, R.D. Thomas, V. Zhaunerchyk, M. Zhang, S. Trippel, M. Kaminska, I. Kashperka, M. af Ugglas, A. Källberg, A. Simonsson, A. Paál, J. Semaniak, M. Larsson and W.D. Geppert

VUV Photochemistry of PAHs Trapped in Interstellar Water Ice J. Bouwman, H.M. Cuppen, L.J. Allamandola and H. Linnartz . . . . . .

PAHs in Regions of Planet Formation

Observations of Hydrocarbon Emission in Disks Around Young Stars B. Acke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Evolution of PAHs in Protoplanetary Disks I. Kamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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