PDRs4All

Astronomy and Astrophysics, vol. 699, pp. L13

Abstract

Most protoplanetary disks experience a phase in which they are subjected to strong ultraviolet radiation from nearby massive stars. This UV radiation can substantially alter their chemistry by producing numerous radicals and molecular ions. In this Letter we present a detailed analysis of the JWST-NIRSpec spectrum of the d203-506 obtained as part of the PDRs4All Early Release Science program. Using state-of-the-art spectroscopic data, we searched for species using a multi-molecule fitting tool, PAHTAT MOL , which we developed for this purpose. Based on this analysis, we report the clear detection of ro-vibrational emission of the CH radical and the likely detection of the H 3 + molecular ion, with estimated abundances of a few times 10 −7 and approximately 10 −8 , respectively. The presence of CH is predicted by gas-phase models and is well explained by hydrocarbon photochemistry. Interstellar H 3 + is usually formed through reactions of H 2 with H 3 + originating from cosmic ray ionization of H 2 . However, recent theoretical studies suggest that H 3 + also forms through far-UV (FUV)-driven chemistry in strongly irradiated ( G 0 > 10 3 ), dense ( n H > 10 6 cm −3 ) gas. The latter is favored as an explanation for the presence of hot H 3 + ( T ex ≳ 1000 K) in the outer disk layers of d203-506, coinciding with the emission of FUV-pumped H 2 and other photodissociation region (PDR) species, such as CH + , CH 3 + , and OH. Our detection of infrared emission from vibrationally excited H 3 + and CH raises questions about their excitation mechanisms and underscores that FUV radiation can have a profound impact on the chemistry of planet-forming disks. They also demonstrate the power of JWST to push the limit of the detection of elusive species in protoplanetary disks.

Authors 22

1. Ilane Schroetter

   Centre National de la Recherche Scientifique · Université Toulouse III - Paul Sabatier · Institut de Recherche en Astrophysique et Planétologie

   Affiliation as printed

   Institut de Recherche en Astrophysique et Planétologie , Université Toulouse III -Paul Sabatier , CNRS , CNES , 9 Av. du colonel Roche , 31028 Toulouse Cedex 04 , France

2. Olivier Berné

   Centre National de la Recherche Scientifique · Université Toulouse III - Paul Sabatier · Institut de Recherche en Astrophysique et Planétologie

   Affiliation as printed

   Institut de Recherche en Astrophysique et Planétologie , Université Toulouse III -Paul Sabatier , CNRS , CNES , 9 Av. du colonel Roche , 31028 Toulouse Cedex 04 , France

3. Javier R. Goicoechea

   Consejo Superior de Investigaciones Científicas · Instituto de Física Fundamental

   Affiliation as printed

   Instituto de Física Fundamental (CSIC) . Calle Serrano 121-123 , 28006 , Madrid , Spain

4. Octavio Roncero

   Consejo Superior de Investigaciones Científicas · Instituto de Física Fundamental

   Affiliation as printed

   Instituto de Física Fundamental (CSIC) . Calle Serrano 121-123 , 28006 , Madrid , Spain

5. Felipe Alarcón

   University of Milan

   Affiliation as printed

   Dipartimento di Fisica , Università degli Studi di Milano , Via Celoria 16 , 20133 Milano , Italy

6. Paul Amiot

   Centre National de la Recherche Scientifique · Université Toulouse III - Paul Sabatier · Institut de Recherche en Astrophysique et Planétologie

   Affiliation as printed

   Institut de Recherche en Astrophysique et Planétologie , Université Toulouse III -Paul Sabatier , CNRS , CNES , 9 Av. du colonel Roche , 31028 Toulouse Cedex 04 , France

7. Oskar Asvany

   University of Cologne

   Affiliation as printed

   I. Physikalisches Institut , Universität zu Köln , Zülpicher Str.77 , D- 50937 Köln , Germany

8. Christiaan Boersma

   Ames Research Center

   Affiliation as printed

   NASA Ames Research Center , MS 245-6 , Moffett Field , CA 94035- 1000 , USA

9. Sandra Brünken

   Radboud University Nijmegen · HFML-FELIX

   Affiliation as printed

   HFML-FELIX , Toernooiveld 7 , 6525ED Nijmegen , the Netherlands

   Institute for Molecules and Materials , Radboud University , Heyen- daalseweg 135 , 6525AJ Nijmegen , the Netherlands

10. J. Cami
11. L. H. Coudert

    Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut des Sciences Moléculaires d'Orsay

    Affiliation as printed

    Institut des Sciences Moléculaires d'Orsay , CNRS , Université Paris- Saclay , 91405 Orsay , France

12. Emmanuel Dartois

    Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut des Sciences Moléculaires d'Orsay

    Affiliation as printed

    Institut des Sciences Moléculaires d'Orsay , CNRS , Université Paris- Saclay , 91405 Orsay , France

13. Asunción Fuente

    Centro de Astrobiología

    Affiliation as printed

    Centro de Astrobiología (CAB) , CSIC-INTA , Ctra. de Ajalvir , km 4 , Torrejón de Ardoz , 28850 Madrid , Spain

14. Bérenger Gans

    Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut des Sciences Moléculaires d'Orsay

    Affiliation as printed

    Institut des Sciences Moléculaires d'Orsay , CNRS , Université Paris- Saclay , 91405 Orsay , France

15. Antoine Gusdorf

    Centre National de la Recherche Scientifique · Université Paris Cité · Université Paris Sciences et Lettres · Observatoire de Paris · École Normale Supérieure - PSL · Sorbonne Université · Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères · Laboratoire de Physique de l'Ecole Normale Supérieure

    Affiliation as printed

    Laboratoire de Physique de l'École normale supérieure , ENS , Uni- versité PSL , CNRS , Sorbonne Université , Université Paris Cité , 75005 Paris , France

    Observatoire de Paris , Université PSL , Sorbonne Université , LERMA , CNRS UMR 8112 , 75014 Paris , France

16. Ugo Jacovella

    Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut des Sciences Moléculaires d'Orsay

    Affiliation as printed

    Institut des Sciences Moléculaires d'Orsay , CNRS , Université Paris- Saclay , 91405 Orsay , France

17. Marie‐Aline Martin‐Drumel

    Centre National de la Recherche Scientifique · Université Paris-Saclay · Sorbonne Université · Institut des Sciences Moléculaires d'Orsay

    Affiliation as printed

    CNRS , Sorbonne Universités , 92190 Meudon , France

    Institut des Sciences Moléculaires d'Orsay , CNRS , Université Paris- Saclay , 91405 Orsay , France

18. Takashi Onaka

    The University of Tokyo

    Affiliation as printed

    Department of Astronomy , Graduate School of Science , The Uni- versity of Tokyo , Tokyo 113-0033 , Japan

19. E. Peeters
20. E. Roueff

    Université Paris Sciences et Lettres · Observatoire de Paris · Laboratoire d'Étude de l'Univers et des Phénomènes Extrêmes

    Affiliation as printed

    LUX , UMR 8262 , Observatoire de Paris , PSL Research University ,

21. Alexander G. G. M. Tielens Aachen Leiden Observatory

    Leiden University · Leiden Observatory · University of Maryland, College Park

    Affiliation as printed

    Astronomy Department , University of Maryland , College Park , MD 20742 , USA

    Leiden Observatory , Leiden University , P.O. Box 9513 , 2300 RA Leiden , The Netherlands

22. Marion Zannese

    Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut d'Astrophysique Spatiale

    Affiliation as printed

    Institut d'Astrophysique Spatiale , Université Paris-Saclay , Centre National de la Recherche Scientifique , 91405 Orsay , France