Browsing by Author "Lefloch, Bertrand"

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    Chemical and Physical Characterization of the Isolated Protostellar Source CB68: FAUST IV
    (IOP Publishing, 2022) Imai, Muneaki; Oya, Yoko; Svoboda, Brian; Liu, Hauyu Baobab; Lefloch, Bertrand; Viti, Serena; Zhang, Yichen; Ceccarelli, Cecilia; Codella, Claudio; Chandler, Claire J.; Sakai, Nami; Aikawa, Yuri; Alves, Felipe O.; Balucani, Nadia; Bianchi, Eleonora; Bouvier, Mathilde; Busquet, Gemma; Caselli, Paola; Caux, Emmanuel; Charnley, Steven; Choudhury, Spandan; Cuello, Nicolas; Simone, Marta De; Dulieu, Francois; Durán, Aurora; Evans, Lucy; Favre, Cécile; Fedele, Davide; Feng, Siyi; Fontani, Francesco; Francis, Logan; Hama, Tetsuya; Hanawa, Tomoyuki; Herbst, Eric; Hirano, Shingo; Hirota, Tomoya; Isella, Andrea; Jímenez-Serra, Izaskun; Johnstone, Doug; Kahane, Claudine; Gal, Romane Le; Loinard, Laurent; López-Sepulcre, Ana; Maud, Luke T.; Maureira, María José; Menard, Francois; Mercimek, Seyma; Miotello, Anna; Moellenbrock, George; Mori, Shoji; Murillo, Nadia M.; Nakatani, Riouhei; Nomura, Hideko; Oba, Yasuhiro; O'Donoghue, Ross; Ohashi, Satoshi; Okoda, Yuki; Ospina-Zamudio, Juan; Pineda, Jaime; Podio, Linda; Rimola, Albert; Sakai, Takeshi; Segura-Cox, Dominique; Shirley, Yancy; Taquet, Vianney; Testi, Leonardo; Vastel, Charlotte; Watanabe, Naoki; Watanabe, Yoshimasa; Witzel, Arezu; Xue, Ci; Zhao, Bo; Yamamoto, Satoshi
    The chemical diversity of low-mass protostellar sources has so far been recognized, and environmental effects are invoked as its origin. In this context, observations of isolated protostellar sources without the influence of nearby objects are of particular importance. Here, we report the chemical and physical structures of the low-mass Class 0 protostellar source IRAS 16544−1604 in the Bok globule CB 68, based on 1.3 mm Atacama Large Millimeter/submillimeter Array observations at a spatial resolution of ∼70 au that were conducted as part of the large program FAUST. Three interstellar saturated complex organic molecules (iCOMs), CH3OH, HCOOCH3, and CH3OCH3, are detected toward the protostar. The rotation temperature and the emitting region size for CH3OH are derived to be 131 ± 11 K and ∼10 au, respectively. The detection of iCOMs in close proximity to the protostar indicates that CB 68 harbors a hot corino. The kinematic structure of the C18O, CH3OH, and OCS lines is explained by an infalling–rotating envelope model, and the protostellar mass and the radius of the centrifugal barrier are estimated to be 0.08–0.30 M ⊙ and <30 au, respectively. The small radius of the centrifugal barrier seems to be related to the small emitting region of iCOMs. In addition, we detect emission lines of c-C3H2 and CCH associated with the protostar, revealing a warm carbon-chain chemistry on a 1000 au scale. We therefore find that the chemical structure of CB 68 is described by a hybrid chemistry. The molecular abundances are discussed in comparison with those in other hot corino sources and reported chemical models.
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    Misaligned Rotations of the Envelope, Outflow, and Disks in the Multiple Protostellar System of VLA 1623–2417: FAUST. III
    (IOP Publishing, 2022) Ohashi, Satoshi; Codella, Claudio; Sakai, Nami; Chandler, Claire J.; Ceccarelli, Cecilia; Alves, Felipe; Fedele, Davide; Hanawa, Tomoyuki; Durán, Aurora; Favre, Cécile; López-Sepulcre, Ana; Loinard, Laurent; Mercimek, Seyma; Murillo, Nadia M.; Podio, Linda; Zhang, Yichen; Aikawa, Yuri; Balucani, Nadia; Bianchi, Eleonora; Bouvier, Mathilde; Busquet, Gemma; Caselli, Paola; Caux, Emmanuel; Charnley, Steven; Choudhury, Spandan; Cuello, Nicolas; Simone, Marta De; Dulieu, Francois; Evans, Lucy; Feng, Siyi; Fontani, Francesco; Francis, Logan; Hama, Tetsuya; Herbst, Eric; Hirano, Shingo; Hirota, Tomoya; Imai, Muneaki; Isella, Andrea; Jímenez-Serra, Izaskun; Johnstone, Doug; Kahane, Claudine; Gal, Romane Le; Lefloch, Bertrand; Maud, Luke T.; Maureira, María José; Menard, Francois; Miotello, Anna; Moellenbrock, George; Mori, Shoji; Nakatani, Riouhei; Nomura, Hideko; Oba, Yasuhiro; O'Donoghue, Ross; Okoda, Yuki; Ospina-Zamudio, Juan; Oya, Yoko; Pineda, Jaime; Rimola, Albert; Sakai, Takeshi; Segura-Cox, Dominique; Shirley, Yancy; Svoboda, Brian; Taquet, Vianney; Testi, Leonardo; Vastel, Charlotte; Viti, Serena; Watanabe, Naoki; Watanabe, Yoshimasa; Witzel, Arezu; Xue, Ci; Zhao, Bo; Yamamoto, Satoshi
    We report a study of the low-mass Class 0 multiple system VLA 1623AB in the Ophiuchus star-forming region, using H13CO+ (J = 3–2), CS (J = 5–4), and CCH (N = 3–2) lines as part of the ALMA Large Program FAUST. The analysis of the velocity fields revealed the rotation motion in the envelope and the velocity gradients in the outflows (about 2000 au down to 50 au). We further investigated the rotation of the circumbinary VLA 1623A disk, as well as the VLA 1623B disk. We found that the minor axis of the circumbinary disk of VLA 1623A is misaligned by about 12° with respect to the large-scale outflow and the rotation axis of the envelope. In contrast, the minor axis of the circumbinary disk is parallel to the large-scale magnetic field according to previous dust polarization observations, suggesting that the misalignment may be caused by the different directions of the envelope rotation and the magnetic field. If the velocity gradient of the outflow is caused by rotation, the outflow has a constant angular momentum and the launching radius is estimated to be 5–16 au, although it cannot be ruled out that the velocity gradient is driven by entrainments of the two high-velocity outflows. Furthermore, we detected for the first time a velocity gradient associated with rotation toward the VLA 16293B disk. The velocity gradient is opposite to the one from the large-scale envelope, outflow, and circumbinary disk. The origin of its opposite gradient is also discussed.
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    Multiple chemical tracers finally unveil the intricate NGC 1333 IRAS 4A outflow system. FAUST XVI
    (Oxford University Press, 2024) Chahine, Layal; Ceccarelli, Cecilia; De Simone, Marta; Chandler, Claire J; Codella, Claudio; Podio, Linda; López-Sepulcre, Ana; Sakai, Nami; Loinard, Laurent; Bouvier, Mathilde; Caselli, Paola; Vastel, Charlotte; Bianchi, Eleonora; Cuello, Nicolás; Fontani, Francesco; Johnstone, Doug; Sabatini, Giovanni; Hanawa, Tomoyuki; Zhang, Ziwei E; Aikawa, Yuri; Busquet, Gemma; Caux, Emmanuel; Durán, Aurore; Herbst, Eric; Ménard, François; Segura-Cox, Dominique; Svoboda, Brian; Balucani, Nadia; Charnley, Steven; Dulieu, François; Evans, Lucy; Fedele, Davide; Feng, Siyi; Hama, Tetsuya; Hirota, Tomoya; Isella, Andrea; Jímenez-Serra, Izaskun; Lefloch, Bertrand; Maud, Luke T; Maureira, María José; Miotello, Anna; Moellenbrock, George; Nomura, Hideko; Oba, Yasuhiro; Ohashi, Satoshi; Okoda, Yuki; Oya, Yoko; Pineda, Jaime; Rimola, Albert; Sakai, Takeshi; Shirley, Yancy; Testi, Leonardo; Viti, Serena; Watanabe, Naoki; Watanabe, Yoshimasa; Zhang, Yichen; Yamamoto, Satoshi
    The exploration of outflows in protobinary systems presents a challenging yet crucial endeavour, offering valuable insights into the dynamic interplay between protostars and their evolution. In this study, we examine the morphology and dynamics of jets and outflows within the IRAS 4A protobinary system. This analysis is based on ALMA observations of SiO(5–4), H2CO(30, 3–20, 3), and HDCO(41, 4–31, 3) with a spatial resolution of ∼150 au. Leveraging an astrochemical approach involving the use of diverse tracers beyond traditional ones has enabled the identification of novel features and a comprehensive understanding of the broader outflow dynamics. Our analysis reveals the presence of two jets in the redshifted emission, emanating from IRAS 4A1 and IRAS 4A2, respectively. Furthermore, we identify four distinct outflows in the region for the first time, with each protostar, 4A1 and 4A2, contributing to two of them. We characterize the morphology and orientation of each outflow, challenging previous suggestions of bends in their trajectories. The outflow cavities of IRAS 4A1 exhibit extensions of 10 and 13 arcsec with position angles (PA) of 0° and -12°, respectively, while those of IRAS 4A2 are more extended, spanning 18 and 25 arcsec with PAs of 29° and 26°. We propose that the misalignment of the cavities is due to a jet precession in each protostar, a notion supported by the observation that the more extended cavities of the same source exhibit lower velocities, indicating they may stem from older ejection events.
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    PDRs4All - II. JWST’s NIR and MIR imaging view of the Orion Nebula
    (EDP Sciences, 2024) Habart, Emilie; Peeters, Els; Berné, Olivier; Trahin, Boris; Canin, Amélie; Chown, Ryan; Sidhu, Ameek; Putte, Dries Van De; Alarcón, Felipe; Schroetter, Ilane; Dartois, Emmanuel; Vicente, Sílvia; Abergel, Alain; Bergin, Edwin A.; Bernard-Salas, Jeronimo; Boersma, Christiaan; Bron, Emeric; Cami, Jan; Cuadrado, Sara; Dicken, Daniel; Elyajouri, Meriem; Fuente, Asunción; Goicoechea, Javier R.; Gordon, Karl D.; Issa, Lina; Joblin, Christine; Kannavou, Olga; Khan, Baria; Lacinbala, Ozan; Languignon, David; Gal, Romane Le; Maragkoudakis, Alexandros; Meshaka, Raphael; Okada, Yoko; Onaka, Takashi; Pasquini, Sofia; Pound, Marc W.; Robberto, Massimo; Röllig, Markus; Schefter, Bethany; Schirmer, Thiébaut; Tabone, Benoit; Tielens, Alexander G. G. M.; Wolfire, Mark G.; Zannese, Marion; Ysard, Nathalie; Miville-Deschenes, Marc-Antoine; Aleman, Isabel; Allamandola, Louis; Auchettl, Rebecca; Baratta, Giuseppe Antonio; Bejaoui, Salma; Bera, Partha P.; Black, John H.; Boulanger, Francois; Bouwman, Jordy; Brandl, Bernhard; Brechignac, Philippe; Brünken, Sandra; Buragohain, Mridusmita; Burkhardt, Andrew; Candian, Alessandra; Cazaux, Stéphanie; Cernicharo, Jose; Chabot, Marin; Chakraborty, Shubhadip; Champion, Jason; Colgan, Sean W. J.; Cooke, Ilsa R.; Coutens, Audrey; Cox, Nick L. J.; Demyk, Karine; Meyer, Jennifer Donovan; Foschino, Sacha; García-Lario, Pedro; Gavilan, Lisseth; Gerin, Maryvonne; Gottlieb, Carl A.; Guillard, Pierre; Gusdorf, Antoine; Hartigan, Patrick; He, Jinhua; Herbst, Eric; Hornekaer, Liv; Jäger, Cornelia; Janot-Pacheco, Eduardo; Kaufman, Michael; Kemper, Francisca; Kendrew, Sarah; Kirsanova, Maria S.; Klaassen, Pamela; Kwok, Sun; Labiano, Álvaro; Lai, Thomas S.-Y.; Lee, Timothy J.; Lefloch, Bertrand; Petit, Franck Le; Li, Aigen; Linz, Hendrik; Mackie, Cameron J.; Madden, Suzanne C.; Mascetti, Joëlle; McGuire, Brett A.; Merino, Pablo; Micelotta, Elisabetta R.; Misselt, Karl; Morse, Jon A.; Mulas, Giacomo; Neelamkodan, Naslim; Ohsawa, Ryou; Omont, Alain; Paladini, Roberta; Palumbo, Maria Elisabetta; Pathak, Amit; Pendleton, Yvonne J.; Petrignani, Annemieke; Pino, Thomas; Puga, Elena; Rangwala, Naseem; Rapacioli, Mathias; Ricca, Alessandra; Roman-Duval, Julia; Roser, Joseph; Roueff, Evelyne; Rouillé, Gaël; Salama, Farid; Sales, Dinalva A.; Sandstrom, Karin; Sarre, Peter; Sciamma-O’Brien, Ella; Sellgren, Kris; Shenoy, Sachindev S.; Teyssier, David; Thomas, Richard D.; Togi, Aditya; Verstraete, Laurent; Witt, Adolf N.; Wootten, Alwyn; Zettergren, Henning; Zhang, Yong; Zhang, Ziwei E.; Zhen, Junfeng
    Context. The James Webb Space Telescope (JWST) has captured the most detailed and sharpest infrared (IR) images ever taken of the inner region of the Orion Nebula, the nearest massive star formation region, and a prototypical highly irradiated dense photo-dissociation region (PDR). Aims. We investigate the fundamental interaction of far-ultraviolet (FUV) photons with molecular clouds. The transitions across the ionization front (IF), dissociation front (DF), and the molecular cloud are studied at high-angular resolution. These transitions are relevant to understanding the effects of radiative feedback from massive stars and the dominant physical and chemical processes that lead to the IR emission that JWST will detect in many Galactic and extragalactic environments. Methods. We utilized NIRCam and MIRI to obtain sub-arcsecond images over ~150″ and 42″ in key gas phase lines (e.g., Pa α, Br α, [FeII] 1.64 µm, H2 1−0 S(1) 2.12 µm, 0–0 S(9) 4.69 µm), aromatic and aliphatic infrared bands (aromatic infrared bands at 3.3–3.4 µm, 7.7, and 11.3 µm), dust emission, and scattered light. Their emission are powerful tracers of the IF and DF, FUV radiation field and density distribution. Using NIRSpec observations the fractional contributions of lines, AIBs, and continuum emission to our NIRCam images were estimated. A very good agreement is found for the distribution and intensity of lines and AIBs between the NIRCam and NIRSpec observations. Results. Due to the proximity of the Orion Nebula and the unprecedented angular resolution of JWST, these data reveal that the molecular cloud borders are hyper structured at small angular scales of ~0.1–1″ (~0.0002–0.002 pc or ~40–400 au at 414 pc). A diverse set of features are observed such as ridges, waves, globules and photoevaporated protoplanetary disks. At the PDR atomic to molecular transition, several bright features are detected that are associated with the highly irradiated surroundings of the dense molecular condensations and embedded young star. Toward the Orion Bar PDR, a highly sculpted interface is detected with sharp edges and density increases near the IF and DF. This was predicted by previous modeling studies, but the fronts were unresolved in most tracers. The spatial distribution of the AIBs reveals that the PDR edge is steep and is followed by an extensive warm atomic layer up to the DF with multiple ridges. A complex, structured, and folded H0/H2 DF surface was traced by the H2 lines. This dataset was used to revisit the commonly adopted 2D PDR structure of the Orion Bar as our observations show that a 3D “terraced” geometry is required to explain the JWST observations. JWST provides us with a complete view of the PDR, all the way from the PDR edge to the substructured dense region, and this allowed us to determine, in detail, where the emission of the atomic and molecular lines, aromatic bands, and dust originate. Conclusions. This study offers an unprecedented dataset to benchmark and transform PDR physico-chemical and dynamical models for the JWST era. A fundamental step forward in our understanding of the interaction of FUV photons with molecular clouds and the role of FUV irradiation along the star formation sequence is provided.
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    PDRs4All - III. JWST’s NIR spectroscopic view of the Orion Bar
    (EDP Sciences, 2024) Peeters, Els; Habart, Emilie; Berné, Olivier; Sidhu, Ameek; Chown, Ryan; Putte, Dries Van De; Trahin, Boris; Schroetter, Ilane; Canin, Amélie; Alarcón, Felipe; Schefter, Bethany; Khan, Baria; Pasquini, Sofia; Tielens, Alexander G. G. M.; Wolfire, Mark G.; Dartois, Emmanuel; Goicoechea, Javier R.; Maragkoudakis, Alexandros; Onaka, Takashi; Pound, Marc W.; Vicente, Sílvia; Abergel, Alain; Bergin, Edwin A.; Bernard-Salas, Jeronimo; Boersma, Christiaan; Bron, Emeric; Cami, Jan; Cuadrado, Sara; Dicken, Daniel; Elyajouri, Meriem; Fuente, Asunción; Gordon, Karl D.; Issa, Lina; Joblin, Christine; Kannavou, Olga; Lacinbala, Ozan; Languignon, David; Gal, Romane Le; Meshaka, Raphael; Okada, Yoko; Robberto, Massimo; Röllig, Markus; Schirmer, Thiébaut; Tabone, Benoit; Zannese, Marion; Aleman, Isabel; Allamandola, Louis; Auchettl, Rebecca; Baratta, Giuseppe Antonio; Bejaoui, Salma; Bera, Partha P.; Black, John H.; Boulanger, Francois; Bouwman, Jordy; Brandl, Bernhard; Brechignac, Philippe; Brünken, Sandra; Buragohain, Mridusmita; Burkhardt, Andrew; Candian, Alessandra; Cazaux, Stéphanie; Cernicharo, Jose; Chabot, Marin; Chakraborty, Shubhadip; Champion, Jason; Colgan, Sean W. J.; Cooke, Ilsa R.; Coutens, Audrey; Cox, Nick L. J.; Demyk, Karine; Meyer, Jennifer Donovan; Foschino, Sacha; García-Lario, Pedro; Gerin, Maryvonne; Gottlieb, Carl A.; Guillard, Pierre; Gusdorf, Antoine; Hartigan, Patrick; He, Jinhua; Herbst, Eric; Hornekaer, Liv; Jäger, Cornelia; Janot-Pacheco, Eduardo; Kaufman, Michael; Kendrew, Sarah; Kirsanova, Maria S.; Klaassen, Pamela; Kwok, Sun; Labiano, Álvaro; Lai, Thomas S.-Y.; Lee, Timothy J.; Lefloch, Bertrand; Petit, Franck Le; Li, Aigen; Linz, Hendrik; Mackie, Cameron J.; Madden, Suzanne C.; Mascetti, Joëlle; McGuire, Brett A.; Merino, Pablo; Micelotta, Elisabetta R.; Misselt, Karl; Morse, Jon A.; Mulas, Giacomo; Neelamkodan, Naslim; Ohsawa, Ryou; Paladini, Roberta; Palumbo, Maria Elisabetta; Pathak, Amit; Pendleton, Yvonne J.; Petrignani, Annemieke; Pino, Thomas; Puga, Elena; Rangwala, Naseem; Rapacioli, Mathias; Ricca, Alessandra; Roman-Duval, Julia; Roser, Joseph; Roueff, Evelyne; Rouillé, Gaël; Salama, Farid; Sales, Dinalva A.; Sandstrom, Karin; Sarre, Peter; Sciamma-O’Brien, Ella; Sellgren, Kris; Shenoy, Sachindev S.; Teyssier, David; Thomas, Richard D.; Togi, Aditya; Verstraete, Laurent; Witt, Adolf N.; Wootten, Alwyn; Ysard, Nathalie; Zettergren, Henning; Zhang, Yong; Zhang, Ziwei E.; Zhen, Junfeng
    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 H2 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 H2; 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 θ1 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 H2 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 H2 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.
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    PDRs4All - IV. An embarrassment of riches: Aromatic infrared bands in the Orion Bar
    (EDP Sciences, 2024) Chown, Ryan; Sidhu, Ameek; Peeters, Els; Tielens, Alexander G. G. M.; Cami, Jan; Berné, Olivier; Habart, Emilie; Alarcón, Felipe; Canin, Amélie; Schroetter, Ilane; Trahin, Boris; Putte, Dries Van De; Abergel, Alain; Bergin, Edwin A.; Bernard-Salas, Jeronimo; Boersma, Christiaan; Bron, Emeric; Cuadrado, Sara; Dartois, Emmanuel; Dicken, Daniel; El-Yajouri, Meriem; Fuente, Asunción; Goicoechea, Javier R.; Gordon, Karl D.; Issa, Lina; Joblin, Christine; Kannavou, Olga; Khan, Baria; Lacinbala, Ozan; Languignon, David; Gal, Romane Le; Maragkoudakis, Alexandros; Meshaka, Raphael; Okada, Yoko; Onaka, Takashi; Pasquini, Sofia; Pound, Marc W.; Robberto, Massimo; Röllig, Markus; Schefter, Bethany; Schirmer, Thiébaut; Vicente, Sílvia; Wolfire, Mark G.; Zannese, Marion; Aleman, Isabel; Allamandola, Louis; Auchettl, Rebecca; Baratta, Giuseppe Antonio; Bejaoui, Salma; Bera, Partha P.; Black, John H.; Boulanger, François; Bouwman, Jordy; Brandl, Bernhard; Brechignac, Philippe; Brünken, Sandra; Buragohain, Mridusmita; Burkhardt, Andrew; Candian, Alessandra; Cazaux, Stéphanie; Cernicharo, Jose; Chabot, Marin; Chakraborty, Shubhadip; Champion, Jason; Colgan, Sean W. J.; Cooke, Ilsa R.; Coutens, Audrey; Cox, Nick L. J.; Demyk, Karine; Meyer, Jennifer Donovan; Foschino, Sacha; García-Lario, Pedro; Gavilan, Lisseth; Gerin, Maryvonne; Gottlieb, Carl A.; Guillard, Pierre; Gusdorf, Antoine; Hartigan, Patrick; He, Jinhua; Herbst, Eric; Hornekaer, Liv; Jäger, Cornelia; Janot-Pacheco, Eduardo; Kaufman, Michael; Kemper, Francisca; Kendrew, Sarah; Kirsanova, Maria S.; Klaassen, Pamela; Kwok, Sun; Labiano, Álvaro; Lai, Thomas S.-Y.; Lee, Timothy J.; Lefloch, Bertrand; Petit, Franck Le; Li, Aigen; Linz, Hendrik; Mackie, Cameron J.; Madden, Suzanne C.; Mascetti, Joëlle; McGuire, Brett A.; Merino, Pablo; Micelotta, Elisabetta R.; Misselt, Karl; Morse, Jon A.; Mulas, Giacomo; Neelamkodan, Naslim; Ohsawa, Ryou; Omont, Alain; Paladini, Roberta; Palumbo, Maria Elisabetta; Pathak, Amit; Pendleton, Yvonne J.; Petrignani, Annemieke; Pino, Thomas; Puga, Elena; Rangwala, Naseem; Rapacioli, Mathias; Ricca, Alessandra; Roman-Duval, Julia; Roser, Joseph; Roueff, Evelyne; Rouillé, Gaël; Salama, Farid; Sales, Dinalva A.; Sandstrom, Karin; Sarre, Peter; Sciamma-O’Brien, Ella; Sellgren, Kris; Shenoy, Sachindev S.; Teyssier, David; Thomas, Richard D.; Togi, Aditya; Verstraete, Laurent; Witt, Adolf N.; Wootten, Alwyn; Zettergren, Henning; Zhang, Yong; Zhang, Ziwei E.; Zhen, Junfeng
    Context. Mid-infrared observations of photodissociation regions (PDRs) are dominated by strong emission features called aromatic infrared bands (AIBs). The most prominent AIBs are found at 3.3, 6.2, 7.7, 8.6, and 11.2 µm. The most sensitive, highest-resolution infrared spectral imaging data ever taken of the prototypical PDR, the Orion Bar, have been captured by JWST. These high-quality data allow for an unprecedentedly detailed view of AIBs.Aims. We provide an inventory of the AIBs found in the Orion Bar, along with mid-IR template spectra from five distinct regions in the Bar: the molecular PDR (i.e. the three H2 dissociation fronts), the atomic PDR, and the H II region. Methods. We used JWST NIRSpec IFU and MIRI MRS observations of the Orion Bar from the JWST Early Release Science Program, PDRs4All (ID: 1288). We extracted five template spectra to represent the morphology and environment of the Orion Bar PDR. We investigated and characterised the AIBs in these template spectra. We describe the variations among them here. Results. The superb sensitivity and the spectral and spatial resolution of these JWST observations reveal many details of the AIB emission and enable an improved characterization of their detailed profile shapes and sub-components. The Orion Bar spectra are dominated by the well-known AIBs at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 µm with well-defined profiles. In addition, the spectra display a wealth of weaker features and sub-components. The widths of many AIBs show clear and systematic variations, being narrowest in the atomic PDR template, but showing a clear broadening in the H II region template while the broadest bands are found in the three dissociation front templates. In addition, the relative strengths of AIB (sub-)components vary among the template spectra as well. All AIB profiles are characteristic of class A sources as designated by Peeters (2022, A&A, 390, 1089), except for the 11.2 µm AIB profile deep in the molecular zone, which belongs to class B11.2. Furthermore, the observations show that the sub-components that contribute to the 5.75, 7.7, and 11.2 µm AIBs become much weaker in the PDR surface layers. We attribute this to the presence of small, more labile carriers in the deeper PDR layers that are photolysed away in the harsh radiation field near the surface. The 3.3/11.2 AIB intensity ratio decreases by about 40% between the dissociation fronts and the H II region, indicating a shift in the polycyclic aromatic hydrocarbon (PAH) size distribution to larger PAHs in the PDR surface layers, also likely due to the effects of photochemistry. The observed broadening of the bands in the molecular PDR is consistent with an enhanced importance of smaller PAHs since smaller PAHs attain a higher internal excitation energy at a fixed photon energy. Conclusions. Spectral-imaging observations of the Orion Bar using JWST yield key insights into the photochemical evolution of PAHs, such as the evolution responsible for the shift of 11.2 µm AIB emission from class B11.2 in the molecular PDR to class A11.2 in the PDR surface layers. This photochemical evolution is driven by the increased importance of FUV processing in the PDR surface layers, resulting in a “weeding out” of the weakest links of the PAH family in these layers. For now, these JWST observations are consistent with a model in which the underlying PAH family is composed of a few species: the so-called ‘grandPAHs’.