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1. PDRs4All VI: Probing the Photochemical Evolution of PAHs in the Orion Bar Using Machine Learning Techniques

Author

Pasquini, S., Peeters, E., Schefter, B., Khan, B., Sidhu, A., Chown, R., Cami, J., Tielens, A., Alarcon, F., Canin, A., Schroetter, I., Trahin, B., Van De Putte, D., Boersma, C., Dartois, E., Onaka, T., Candian, A., Hartigan, P., Lai, T. S. -Y., Rouille, G., Sales, D. A., Zhang, Y., Habart, E., and Berne, O.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

[Abridged] JWST observations of the Orion Bar have shown the incredible richness of PAH bands and their variation on small scales. We aim to probe the photochemical evolution of PAHs across the key zones of the photodissociation region (PDR) that is the Orion Bar using unsupervised machine learning. We use NIRSpec and MIRI IFU data from the JWST ERS Program PDRs4All. We lever bisecting k-means clustering to generate detailed spatial maps of the spectral variability in several wavelength regions. We discuss the variations in the cluster profiles and connect them to the local physical conditions. We interpret these variations with respect to the key zones: the HII region, the atomic PDR zone, and the three dissociation fronts. The PAH emission exhibits spectral variation that depends strongly on spatial position in the PDR. We find the 8.6um band to behave differently than all other bands which vary systematically with one another. We find uniform variation in the 3.4-3.6um bands and 3.4/3.3 intensity ratio. We attribute the carrier of the 3.4-3.6um bands to a single side group attached to very similarly sized PAHs. Cluster profiles reveal a transition between characteristic profiles classes of the 11.2um feature from the atomic to the molecular PDR zone. We find the carriers of each of the profile classes to be independent, and reason the latter to be PAH clusters existing solely deep in the molecular PDR. Clustering also reveals a connection between the 11.2 and 6.2um bands; and that clusters generated from variation in the 10.9-11.63um region can be used to recover those in the 5.95-6.6um region. Clustering is a powerful tool for characterizing PAH variability on both spatial and spectral scales. For individual bands as well as global spectral behaviours, we find UV-processing to be the most important driver of the evolution of PAHs and their spectral signatures in the Orion Bar., Comment: 28 pages, 20 figures, submitted to A&A

Published
2023
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2. A far-ultraviolet-driven photoevaporation flow observed in a protoplanetary disk.

Author

Berné O, Habart E, Peeters E, Schroetter I, Canin A, Sidhu A, Chown R, Bron E, Haworth TJ, Klaassen P, Trahin B, Van De Putte D, Alarcón F, Zannese M, Abergel A, Bergin EA, Bernard-Salas J, Boersma C, Cami J, Cuadrado S, Dartois E, Dicken D, Elyajouri M, Fuente A, Goicoechea JR, Gordon KD, Issa L, Joblin C, Kannavou O, Khan B, Lacinbala O, Languignon D, Le Gal R, Maragkoudakis A, Meshaka R, Okada Y, Onaka T, Pasquini S, Pound MW, Robberto M, Röllig M, Schefter B, Schirmer T, Simmer T, Tabone B, Tielens AGGM, Vicente S, Wolfire MG, Aleman I, Allamandola L, Auchettl R, Baratta GA, Baruteau C, Bejaoui S, Bera PP, Black JH, Boulanger F, Bouwman J, Brandl B, Brechignac P, Brünken S, Buragohain M, Burkhardt A, Candian A, Cazaux S, Cernicharo J, Chabot M, Chakraborty S, Champion J, Colgan SWJ, Cooke IR, Coutens A, Cox NLJ, Demyk K, Meyer JD, Engrand C, Foschino S, García-Lario P, Gavilan L, Gerin M, Godard M, Gottlieb CA, Guillard P, Gusdorf A, Hartigan P, He J, Herbst E, Hornekaer L, Jäger C, Janot-Pacheco E, Kaufman M, Kemper F, Kendrew S, Kirsanova MS, Knight C, Kwok S, Labiano Á, Lai TS, Lee TJ, Lefloch B, Le Petit F, Li A, Linz H, Mackie CJ, Madden SC, Mascetti J, McGuire BA, Merino P, Micelotta ER, Morse JA, Mulas G, Neelamkodan N, Ohsawa R, Paladini R, Palumbo ME, Pathak A, Pendleton YJ, Petrignani A, Pino T, Puga E, Rangwala N, Rapacioli M, Ricca A, Roman-Duval J, Roueff E, Rouillé G, Salama F, Sales DA, Sandstrom K, Sarre P, Sciamma-O'Brien E, Sellgren K, Shannon MJ, Simonnin A, Shenoy SS, Teyssier D, Thomas RD, Togi A, Verstraete L, Witt AN, Wootten A, Ysard N, Zettergren H, Zhang Y, Zhang ZE, and Zhen J

Abstract

Most low-mass stars form in stellar clusters that also contain massive stars, which are sources of far-ultraviolet (FUV) radiation. Theoretical models predict that this FUV radiation produces photodissociation regions (PDRs) on the surfaces of protoplanetary disks around low-mass stars, which affects planet formation within the disks. We report James Webb Space Telescope and Atacama Large Millimeter Array observations of a FUV-irradiated protoplanetary disk in the Orion Nebula. Emission lines are detected from the PDR; modeling their kinematics and excitation allowed us to constrain the physical conditions within the gas. We quantified the mass-loss rate induced by the FUV irradiation and found that it is sufficient to remove gas from the disk in less than a million years. This is rapid enough to affect giant planet formation in the disk.

Published
2024
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3. Formation of the methyl cation by photochemistry in a protoplanetary disk.

Author

Berné O, Martin-Drumel MA, Schroetter I, Goicoechea JR, Jacovella U, Gans B, Dartois E, Coudert LH, Bergin E, Alarcon F, Cami J, Roueff E, Black JH, Asvany O, Habart E, Peeters E, Canin A, Trahin B, Joblin C, Schlemmer S, Thorwirth S, Cernicharo J, Gerin M, Tielens A, Zannese M, Abergel A, Bernard-Salas J, Boersma C, Bron E, Chown R, Cuadrado S, Dicken D, Elyajouri M, Fuente A, Gordon KD, Issa L, Kannavou O, Khan B, Lacinbala O, Languignon D, Le Gal R, Maragkoudakis A, Meshaka R, Okada Y, Onaka T, Pasquini S, Pound MW, Robberto M, Röllig M, Schefter B, Schirmer T, Sidhu A, Tabone B, Van De Putte D, Vicente S, and Wolfire MG

Abstract

Forty years ago, it was proposed that gas-phase organic chemistry in the interstellar medium can be initiated by the methyl cation CH 3 + (refs. 1-3 ), but so far it has not been observed outside the Solar System 4,5 . Alternative routes involving processes on grain surfaces have been invoked 6,7 . Here we report James Webb Space Telescope observations of CH 3 + in a protoplanetary disk in the Orion star-forming region. We find that gas-phase organic chemistry is activated by ultraviolet irradiation., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Published
2023
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