open access publication

Article, 2024

PDRs4All

Astronomy & Astrophysics, ISSN 0004-6361, 1432-0746, Volume 685, Page a74, 10.1051/0004-6361/202348244

Contributors

Peeters, Els 0000-0002-2541-1602 (Corresponding author) [1] [2] Habart, Emilie 0000-0001-9136-8043 [3] Berné, Olivier 0000-0002-1686-8395 [4] Sidhu, Ameek 0000-0003-3771-4990 [2] Chown, Ryan 0000-0001-8241-7704 [2] Van De Putte, Dries 0000-0002-5895-8268 [5] Trahin, Boris 0000-0001-5875-5340 [3] Schroetter, Ilane 0000-0002-1099-7401 [4] Canin, Amélie 0000-0002-7830-6363 [4] Alarcón, Felipe 0000-0002-2692-7862 [6] Schefter, Bethany R 0000-0001-5080-8030 [2] Khan, Baria [2] Pasquini, Sofia [2] Tielens, Alexander Godfried Gerardus Maria 0000-0003-0306-0028 [7] [8] Wolfire, Mark G [7] Dartois, Emmanuel 0000-0003-1197-7143 [9] Goicoechea, Javier R 0000-0001-7046-4319 [10] Maragkoudakis, Alexandros 0000-0003-2552-3871 [11] Onaka, Takashi 0000-0002-8234-6747 [12] [13] Pound, Marc W 0000-0002-7269-342X [7] Vicente, Sílvia M 0000-0001-8973-0752 [14] Abergel, Alain [3] Bergin, Edwin A [6] Bernard-Salas, Jeronimo [15] [16] Boersma, Christiaan [11] Bron, Emeric E [17] Cami, Jan 0000-0002-2666-9234 [1] [2] Cuadrado, Sara 0000-0002-7393-1813 [10] Dicken, Daniel 0000-0003-0589-5969 [18] Elyajouri, Meriem 0000-0002-6086-2337 [3] Fuente, Asunción 0000-0001-6317-6343 [19] Gordon, Karl D 0000-0001-5340-6774 [5] [20] Issa, Lina [4] Joblin, Christine 0000-0003-1561-6118 [4] Kannavou, Olga [3] Lacinbala, Ozan 0000-0002-5263-7922 [21] Languignon, David [17] Le Gal, Romane 0000-0003-1837-3772 [22] [23] Meshaka, Raphael [3] [17] Okada, Yoko [24] Robberto, Massimo 0000-0002-9573-3199 [5] [25] Röllig, Markus [26] [27] Schirmer, Thiébaut [3] [28] Tabone, Benoît 0000-0002-1103-3225 [3] Zannese, Marion 0009-0002-6069-0907 [3] Aleman, Isabel Regina Guerra 0000-0002-7989-9041 [29] [30] Allamandola, Louis John 0000-0002-6049-4079 [11] [31] Auchettl, Rebecca [32] Baratta, Giuseppe Antonio 0000-0002-3688-160X [33] Bejaoui, Salma 0000-0001-8646-9464 [11] Bera, Partha Pratim 0000-0003-0843-3209 [11] [31] Black, John H 0000-0001-7221-7207 [28] Boulanger, Francois [34] Bouwman, Jordy 0000-0003-4757-2500 [35] [36] Brandl, Bernhard R 0000-0001-9737-169X [8] [37] Bréchignac, Philippe [9] Brünken, Sandra 0000-0001-7175-4828 [38] Buragohain, Mridusmita 0000-0002-5436-9845 [39] Burkhardt, Andrew [40] Candian, Alessandra 0000-0002-5431-4449 [41] Cazaux, Stéphanie [37] Cernicharo, José 0000-0002-3518-2524 [10] Chabot, Marin [42] Chakraborty, Shubhadip [43] [44] Champion, Jason [4] Colgan, Sean W J 0000-0001-6275-7437 [11] Cooke, Ilsa R 0000-0002-0850-7426 [45] Coutens, Audrey 0000-0003-1805-3920 [4] Cox, Nick L J [15] [16] Demyk, Karine [4] Meyer, Jennifer Donovan 0000-0002-3106-7676 [46] Foschino, Sacha 0000-0003-2455-2355 [4] García-Lario, Pedro 0000-0003-4039-8212 [47] Gerin, Maryvonne [48] Gottlieb, Carl A 0000-0003-2845-5317 [49] Guillard, Pierre 0000-0002-2421-1350 [50] [51] [52] Gusdorf, Antoine [34] [48] Hartigan, Patrick [53] He, Jinhua [54] [55] [56] Herbst, Eric [57] Hornekær, Liv Haahr [58] Jäger, Cornelia [59] Janot-Pacheco, Eduardo [30] Kaufman, Michael [60] Kendrew, Sarah 0000-0002-7612-0469 [5] Kirsanova, Maria S 0000-0003-4338-9055 [61] Klaassen, Pamela D 0000-0001-9443-0463 [18] Kwok, Sun [45] Labiano, Alvaro 0000-0002-0690-8824 [47] Lai, Thomas S-Y 0000-0001-8490-6632 [62] Lee, Timothy J [11] Lefloch, Bertrand [63] Le Petit, Franck [17] Li, Aigen [64] Linz, Hendrik 0000-0002-8115-8437 [65] Mackie, Cameron J [66] [67] Madden, Suzanne C 0000-0003-3229-2899 [68] Mascetti, Joe Lle 0000-0002-8585-9118 [69] Mcguire, Brett A 0000-0003-1254-4817 [46] [70] Merino, Pablo 0000-0002-0267-4020 [71] Micelotta, Elisabetta R 0000-0002-6555-5109 [72] Misselt, Karl [73] Morse, Jon A [74] Mulas, Giacomo 0000-0003-0602-6669 [4] [75] Neelamkodan, Naslim 0000-0001-8901-7287 [76] Ohsawa, Ryou 0000-0001-5797-6010 [77] Paladini, Roberta 0000-0002-5158-243X [62] Palumbo, Maria Elisabetta 0000-0002-9122-491X [33] Pathak, Amit [78] Pendleton, Yvonne J 0000-0001-8102-2903 [79] Petrignani, Annemieke 0000-0002-6116-5867 [41] Pino, Thomas [9] Puga, Elena [5] Rangwala, Naseem [11] Rapacioli, Mathias 0000-0003-2394-6694 [80] Ricca, Alessandra 0000-0002-3141-0630 [1] [11] Roman-Duval, Julia Christine 0000-0001-6326-7069 [5] Roser, Joseph E 0000-0002-1806-3494 [1] [11] Roueff, Evelyne M 0000-0002-4949-8562 [17] Rouillé, Gaël 0000-0002-4016-1461 [59] Salama, Farid 0000-0002-6064-4401 [11] Sales, Dinalva Aires De 0000-0002-3496-5711 [81] Sandstrom, Karin M 0000-0002-4378-8534 [82] Sarre, Peter [83] Sciamma-O'Brien, Ella M 0000-0002-1883-552X [11] Sellgren, Kris [84] Shenoy, Sachindev S 0000-0003-0281-7383 [85] Teyssier, David [47] Thomas, Richard D [86] Togi, Aditya [87] Verstraete, Laurent [3] Witt, Adolf N 0000-0003-0760-4483 [88] Wootten, Alwyn [46] Ysard, Nathalie 0000-0003-1037-4121 [3] Zettergren, Henning 0000-0002-2493-4161 [86] Zhang, Yong 0000-0002-1086-7922 [89] Zhang, Ziwei E [90] Zhen, Junfeng [91]

Affiliations

  1. [1] Search for Extraterrestrial Intelligence
    2. [NORA names: United States; America, North; OECD];
  2. [2] Western University
    3. [NORA names: Canada; America, North; OECD];
  3. [3] Institut d'Astrophysique Spatiale
    4. [NORA names: France; Europe, EU; OECD];
  4. [4] Research Institute in Astrophysics and Planetology
    5. [NORA names: France; Europe, EU; OECD];
  5. [5] Space Telescope Science Institute
    6. [NORA names: United States; America, North; OECD];

Abstract

Context . JWST has taken the sharpest and most sensitive infrared (IR) spectral imaging observations ever of the Orion Bar photodis-sociation region (PDR), which is part of the nearest massive star-forming region the Orion Nebula, and often considered to be the ‘prototypical’ strongly illuminated PDR. Aims . We investigate the impact of radiative feedback from massive stars on their natal cloud and focus on the transition from the H II region to the atomic PDR – crossing the ionisation front (IF) –, and the subsequent transition to the molecular PDR – crossing the dissociation front (DF). Given the prevalence of PDRs in the interstellar medium and their dominant contribution to IR radiation, understanding the response of the PDR gas to far-ultraviolet (FUV) photons and the associated physical and chemical processes is fundamental to our understanding of star and planet formation and for the interpretation of any unresolved PDR as seen by JWST. Methods . We used high-resolution near-IR integral field spectroscopic data from NIRSpec on JWST to observe the Orion Bar PDR as part of the PDRs4All JWST Early Release Science programme. We constructed a 3″ × 25″’ spatio-spectral mosaic covering 0.97– 5.27 μm at a spectral resolution R of ~2700 and an angular resolution of 0.075″–0.173″. To study the properties of key regions captured in this mosaic, we extracted five template spectra in apertures centred on the three H 2 dissociation fronts, the atomic PDR, and the H II region. This wealth of detailed spatial-spectral information was analysed in terms of variations in the physical conditions-incident UV field, density, and temperature – of the PDR gas. Results . The NIRSpec data reveal a forest of lines including, but not limited to, He I , H I , and C I recombination lines; ionic lines (e.g. Fe III and Fe II ); O I and N I fluorescence lines; aromatic infrared bands (AIBs, including aromatic CH, aliphatic CH, and their CD counterparts); pure rotational and ro-vibrational lines from H 2 ; and ro-vibrational lines from HD, CO, and CH + , with most of them having been detected for the first time towards a PDR. Their spatial distribution resolves the H and He ionisation structure in the Huygens region, gives insight into the geometry of the Bar, and confirms the large-scale stratification of PDRs. In addition, we observed numerous smaller-scale structures whose typical size decreases with distance from θ 1 Ori C and IR lines from C I , if solely arising from radiative recombination and cascade, reveal very high gas temperatures (a few 1000 K) consistent with the hot irradiated surface of small-scale dense clumps inside the PDR. The morphology of the Bar, in particular that of the H 2 lines, reveals multiple prominent filaments that exhibit different characteristics. This leaves the impression of a ‘terraced’ transition from the predominantly atomic surface region to the CO-rich molecular zone deeper in. We attribute the different characteristics of the H 2 filaments to their varying depth into the PDR and, in some cases, not reaching the C + /C/CO transition. These observations thus reveal what local conditions are required to drive the physical and chemical processes needed to explain the different characteristics of the DFs and the photochemical evolution of the AIB carriers. Conclusions . This study showcases the discovery space created by JWST to further our understanding of the impact radiation from young stars has on their natal molecular cloud and proto-planetary disk, which touches on star and planet formation as well as galaxy evolution.

Keywords

AIB, C-I, CH, CO, H 2 lines, H II regions, H-Y, HD, Huygens, Huygens region, IR lines, IR radiation, JWST, NIRSPEC, NIRSPEC data, O I, Ori, Ori C, Orion, Orion Nebula, PDR, UV field, angular resolution, aperture, aromatic infrared bands, band, bar, carriers, cascade, cases, characteristics, chemical, chemical processes, cloud, clumps, conditions, data, dense clumps, density, depth, discovery, discovery space, disk, dissociation, dissociation front, distance, distribution, evolution, far-ultraviolet, feedback, field, filaments, forest, forest of lines, formation, front, galaxies, galaxy evolution, gas, gas temperature, geometry, imaging observations, impact, impact radiation, impression, information, infrared, infrared bands, integral field spectroscopic data, interpretation, interstellar medium, ionic lines, ionisation, ionisation front, ionisation structure, large-scale stratification, lines, local conditions, massive star-forming regions, massive stars, medium, molecular clouds, molecular zone, morphology, mosaicism, natal cloud, natal molecular cloud, nearest, nearest massive star-forming regions, nebula, observations, photochemical evolution, planet, planet formation, prevalence, process, programme, properties, proto-planetary disks, radiation, radiative feedback, radiative recombination, recombination, region, resolution, resolution R, response, ro-vibrational lines, science programmes, sensitive infrared, sharpest, size, smaller-scale structures, space, spatial distribution, spatial-spectral information, spatio-spectral, spectra, spectral imaging observations, spectral resolution R, spectroscopic data, star-forming regions, stars, structure, study, surface region, temperature, template, template spectra, transition, typical size, variation, wealth, young stars, zone

Funders

  • Institut National des Sciences de l'Univers
  • Russian Science Foundation
  • National Aeronautics and Space Administration
  • Science and Engineering Research Board
  • Ministry of Economy, Industry and Competitiveness
  • Chinese Academy of Sciences
  • Atomic Energy and Alternative Energies Commission
  • Natural Sciences and Engineering Research Council
  • Canadian Space Agency
  • Japan Society for the Promotion of Science
  • Deutsche Forschungsgemeinschaft
  • Swedish Research Council
  • United Arab Emirates University
  • Thermo Fisher Scientific (United States)
  • European Commission

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