Authors: Roueff, Antoine; Pety, Jerome; Gerin, Maryvonne; Segal, Leontine E.; Goicoechea, Javier R.; Liszt, Harvey S.; Gratier, Pierre; Beslic, Ivana; Einig, Lucas; Gaudel, Mathilde; Orkisz, Jan H.; Palud, Pierre; Santa-Maria, Miriam G.; Magalhaes, Victor de Souza; Zakardjian, Antoine; Bardeau, Sebastien; Bron, Emeric; Chainais, Pierre; Coude, Simon; Demyk, Karine; Guzman, Viviana V.; Hughes, Annie; Languignon, David; Levrier, Francois; Lis, Dariusz C.; Le Bourlot, Jacques; Le Petit, Franck; Peretto, Nicolas; Roueff, Evelyne; Sievers, Albrecht; Thouvenin, Pierre-Antoine

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/06/20

DOI: 10.1051/0004-6361/202449148

Abstract: Context. Robust radiative transfer techniques are requisite for efficiently extracting the physical and chemical information from molecular rotational lines. Aims. We study several hypotheses that enable robust estimations of the column densities and physical conditions when fitting one or two transitions per molecular species. We study the extent to which simplifying assumptions aimed at reducing the complexity of the problem introduce estimation biases and how to detect them. Methods. We focus on the CO and HCO+ isotopologues and analyze maps of a 50 square arcminutes field. We used the RADEX escape probability model to solve the statistical equilibrium equations and compute the emerging line profiles, assuming that all species coexist. Depending on the considered set of species, we also fixed the abundance ratio between some species and explored different values. We proposed a maximum likelihood estimator to infer the physical conditions and considered the effect of both the thermal noise and calibration uncertainty. We analyzed any potential biases induced by model misspecifications by comparing the results on the actual data for several sets of species and confirmed with Monte Carlo simulations. The variance of the estimations and the efficiency of the estimator were studied based on the Cramer-Rao lower bound. Results. Column densities can be estimated with 30% accuracy, while the best estimations of the volume density are found to be within a factor of two. Under the chosen model framework, the peak (CO)-C-12 (1 – 0) is useful for constraining the kinetic temperature. The thermal pressure is better and more robustly estimated than the volume density and kinetic temperature separately. Analyzing CO and HCO+ isotopologues and fitting the full line profile are recommended practices with respect to detecting possible biases. Conclusions. Combining a non-local thermodynamic equilibrium model with a rigorous analysis of the accuracy allows us to obtain an efficient estimator and identify where the model is misspecified. We note that other combinations of molecular lines could be studied in the future.

Authors: Cernicharo, J.; Cabezas, C.; Agundez, M.; Endo, Y.; Tercero, B.; Marcelino, N.; de Vicente, P.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/06/17

DOI: 10.1051/0004-6361/202450801

Abstract: We present the discovery with the QUIJOTE line survey of the cations HC5N+ and HC7N+ in the direction of TMC-1. Seven lines with half-integer quantum numbers from J = 25/2-23/2 to 37/2-35/2 have been assigned to HC5N+ and eight lines from J = 55/2-53/2 to 71/2-69/2 to HC7N+. Both species have inverted (2)Pi ground electronic states with very good estimates for their B-0 and A(SO) constants based on optical observations. The lines with the lowest J of HC5N+ exhibit multiple components due to the hyperfine structure introduced by the H and N nuclei. However, these different components collapse for the higher J. No hyperfine structure is found for any of the lines of HC7N+. The derived effective rotational and distortion constants for HC5N+ are B-eff = 1336.662 +/- 0.001 MHz and D-eff = 27.4 +/- 2.6 Hz, while for HC7N+ they are B-eff = 567.85036 +/- 0.00037 MHz and D-eff = 4.01 +/- 0.19 Hz. From the observed intensities, we derived T-rot = 5.5 +/- 0.5 K and N = (9.9 +/- 1.0) x 10(10) cm(-2) for HC5N+, while we obtained T-rot = 8.5 +/- 0.5 K and N = (2.3 +/- 0.2) x 10(10) cm(-2) for HC7N+. The HC5N/HC5N+, C5N/HC5N+, C5N-/HC5N+, HC7N/HC7N+, HC5N+/HC7N+, and C7N-/HC7N+ abundance ratios are 670 +/- 80, 4.8 +/- 0.8, 1.2 +/- 0.2, 1000 +/- 150, 4.2 +/- 0.5, and 2.2 +/- 0.2, respectively. We have run chemical modelling calculations to investigate the formation and destruction of these new cations. We find that these species are mainly formed through the reactions of H-2 and the cations C5N+ and C7N+, and by the reactions of H+ with HC5N and HC7N, while they are mostly destroyed through a reaction with H-2 and a dissociative recombination with electrons. Based on the underestimation of the abundances of HC5N+ and HC7N+ by the chemical model by a factor similar to 20, we suggest that the rate coefficients currently assumed for the reactions of these cations with H-2 could be too high by the same factor, something that will be worth investigating.

Authors: Cernicharo, J.; Tercero, B.; Agundez, M.; Cabezas, C.; Fuentetaja, R.; Marcelino, N.; de Vicente, P.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/06/07

DOI: 10.1051/0004-6361/202449531

Abstract: We present a study of CH3CH2CCH, CH3CH2CN, CH2CHCCH, and CH2CHCN in TMC-1 using the QUIJOTE line survey. We confirm the presence of CH3CH2CCH in TMC-1, which was previously reported as tentative by our group. From a detailed study of the ethynyl and cyanide derivatives of CH2CH2 and CH3CH3 in TMC-1, we found that the CH2CHCCH/CH2CHCN and CH3CH2CCH/CH3CH2CN abundance ratios are 1.5 +/- 0.1 and 4.8 +/- 0.5, respectively. The derived CH2CHCCH/CH3CH2CCH abundance ratio is 15.3 +/- 0.8, and that of CH2CHCN over CH3CH2CN is 48 +/- 5. All the single substituted isotopologs of vinyl cyanide have been detected, and we found that the first and second carbon substitutions in CH2CHCN provide a C-12/C-13 ratio in line with that found for other three-carbon bearing species such as HCCNC and HNCCC. However, the third C-13 isotopolog, (CH2CHCN)-C-13, presents an increase in its abundance similar to that found for HCCCN. Finally, we observed eight b-type transitions of CH2CHCN, and we find that their intensity cannot be fitted adopting the dipole moment mu(b) derived previously. These transitions involve the same rotational levels as those of the a-type transitions. From their intensity, we obtain mu(b) = 0.80 +/- 0.03 D, which is found to be in between earlier values derived in the laboratory using intensity measurements or the Stark effect. Our chemical model indicates that the abundances of CH3CH2 CCH, CH3CH2CN, CH2CHCCH, and CH2CHCN observed in TMC-1 can be explained in terms of gas-phase reactions.

Authors: Cabezas, C.; Endo, Y.; Rivilla, V. M.; Agundez, M.; Jimenez-Serra, I.; Martin-Pintado, J.; Cernicharo, J.

Journal: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Publication date: 2024/06/06

DOI: 10.1093/mnras/stae1358

Abstract: The presence in the interstellar medium of several imines suggests that other molecules of the same family could be present as well. The propargylimine molecule (HCCCHNH), which arises from CCH substitution on the C atom of methanimine (H2CNH), the simplest imine, has been recently detected in space. Therefore, the analogous CCH derivative substituted on the N atom, known as N-ethynylmethanimine (H2CNCCH), is a good candidate to be observed as well. To allow for its astronomical detection we have investigated its laboratory rotational spectra. The species has been produced by an electric discharge of acetonitrile (CH3CN) and acetylene (HCCH) in argon, and its rotational spectrum between 9 and 40GHz has been characterized using a Balle-Flygare narrow band-type Fourier-transform microwave spectrometer. The spectral analysis allowed us to derive accurate spectroscopic parameters to obtain reliable frequency predictions for astronomical searches in different sources. We searched for H2CNCCH in several molecular clouds, G+0.693-0.027, L483, and TMC-1, but did not detect it. The upper limits to its abundance derived are consistent with a preference of the CCH substitution of H2CNH on the C atom rather than on the N atom, in line with quantum chemical calculations on the reaction between CCH and H2CNH.

Authors: Esposito, Federico; Alonso-Herrero, Almudena; Garcia-Burillo, Santiago; Casasola, Viviana; Combes, Francoise; Dallacasa, Daniele; Davies, Richard; Garcia-Bernete, Ismael; Garcia-Lorenzo, Begona; Munoz, Laura Hermosa; de Arriba, Luis Peralta; Pereira-Santaella, Miguel; Pozzi, Francesca; Almeida, Cristina Ramos; Shimizu, Thomas Taro; Vallini, Livia; Bellocchi, Enrica; Gonzalez-Martin, Omaira; Hicks, Erin K. S.; Honig, Sebastian; Labiano, Alvaro; Levenson, Nancy A.; Ricci, Claudio; Rosario, David J.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/05/28

DOI: 10.1051/0004-6361/202449245

Abstract: We present new optical GTC/MEGARA seeing-limited (0.9 ”) integral-field observations of NGC 5506, together with ALMA observations of the CO(3 – 2) transition at a 0.2 ” (similar to 25 pc) resolution. NGC 5506 is a luminous (bolometric luminosity of similar to 10(44) erg s(-1)) nearby (26 Mpc) Seyfert galaxy, part of the Galaxy Activity, Torus, and Outflow Survey (GATOS). We modelled the CO(3 – 2) kinematics with (3D)BAROLO, revealing a rotating and outflowing cold gas ring within the central 1.2 kpc. We derived an integrated cold molecular gas mass outflow rate for the ring of similar to 8 M-circle dot yr(-1). We fitted the optical emission lines with a maximum of two Gaussian components to separate rotation from non-circular motions. We detected high [OIII]lambda 5007 projected velocities (up to similar to 1000 km s(-1)) at the active galactic nucleus (AGN) position, decreasing with radius to an average similar to 330 km s(-1) around similar to 350 pc. We also modelled the [OIII] gas kinematics with a non-parametric method, estimating the ionisation parameter and electron density in every spaxel, from which we derived an ionised mass outflow rate of 0.076 M-circle dot yr(-1) within the central 1.2 kpc. Regions of high CO(3 – 2) velocity dispersion, extending to projected distances of similar to 350 pc from the AGN, appear to be the result from the interaction of the AGN wind with molecular gas in the galaxy’s disc. Additionally, we find the ionised outflow to spatially correlate with radio and soft X-ray emission in the central kiloparsec. We conclude that the effects of AGN feedback in NGC 5506 manifest as a large-scale ionised wind interacting with the molecular disc, resulting in outflows extending to radial distances of 610 pc.

Authors: Cabezas, C.; Agundez, M.; Endo, Y.; Tercero, B.; Lee, Y. -P.; Marcelino, N.; de Vicente, P.; Cernicharo, J.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/05/27

DOI: 10.1051/0004-6361/202450323

Abstract: We present the detection of cyanothioketene, NCCHCS, in the laboratory and toward TMC-1. This transient species was produced through a discharge of a gas mixture of CH2CHCN and CS2 using argon as carrier gas, and its rotational spectrum between 9 and 40 GHz was characterized using a Balle-Flygare narrowband-type Fourier-transform microwave spectrometer. A total of 21 rotational transitions were detected in the laboratory, all of them exhibiting hyperfine structure induced by the spin of the N nucleus. The spectrum for NCCHCS was predicted in the domain of our line surveys using the derived rotational and distortion constants. The detection in the cold starless core TMC-1 was based on the QUIJOTE(1) line survey performed with the Yebes 40 m radio telescope. Twenty-three lines were detected with K-a = 0, 1, and 2 and J(u) = 9 up to 14. The derived column density is (1.2 +/- 0.1)x10(11) cm(-2) for a rotational temperature of 8.5 +/- 1.0 K. The abundance ratio of thioketene and its cyano derivative, H2CCS/NCCHCS, is 6.5 +/- 1.3. Although ketene is more abundant than thioketene by similar to 15 times, its cyano derivative NCCHCO surprisingly is not detected with a 3 sigma upper level to the column density of 3.0 x 10(10) cm(-2), which results in an abundance ratio H2CCO/NCCHCO > 430. Hence, the chemistry of CN derivatives seems to be more favored for S-bearing than for O-bearing molecules. We carried out chemical modeling calculations and found that the gas-phase neutral-neutral reactions CCN + H2CS and CN + H2CCS could be a source of NCCHCS in TMC-1.

Authors: Pereira-Santaella, Miguel; Garcia-Bernete, Ismael; Gonzalez-Alfonso, Eduardo; Alonso-Herrero, Almudena; Colina, Luis; Garcia-Burillo, Santiago; Rigopoulou, Dimitra; Arribas, Santiago; Perna, Michele

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/05/20

DOI: 10.1051/0004-6361/202449982

Abstract: We report the detection of extended (> 0.5-1 kpc) high-ionization [Mg IV] 4.487 mu m (80 eV) emission in four local luminous infrared galaxies observed with JWST/NIRSpec. Excluding the nucleus and outflow of the Type 1 active galactic nucleus (AGN) in the sample, we find that the [Mg IV] luminosity is well correlated with that of H recombination lines, which mainly trace star-forming clumps in these objects, and that the [Ar VI] 4.530 mu m (75 eV), usually seen in AGN, is undetected. On 100-400 pc scales, the [Mg IV] line profiles are broader (sigma([Mg IV]) = 90 +/- 25 km s(-1)) and shifted (Delta v up to +/- 50 km s(-1)) compared to those of the H recombination lines and lower ionization transitions (e.g., sigma(Hu-12) = 57 +/- 15 km s(-1)). The [Mg IV] kinematics follow the large-scale rotating velocity field of these galaxies, and the broad [Mg IV] profiles are compatible with the broad wings detected in the H recombination lines. Based on these observational results, extended highly ionized gas more turbulent than the ambient interstellar medium, possibly a result of ionizing shocks associated with star formation, is the most likely origin of the [Mg IV] emission. We also computed new grids of photoionization and shock models to investigate where the [Mg IV] line originates. Shocks with velocities of 100-130 km s(-1) reproduce the observed line ratios and the [Mg IV] luminosity agrees with that expected from the mechanical energy released by supernove (SNe) in these regions. Therefore, these models support shocks induced by SNe as the origin of the [Mg IV] line. Future studies on the stellar feedback from SNe will benefit from the [Mg IV] line that is little affected by obscuration and, in the absence of an AGN, can only be produced by shocks due to its high ionization-potential.

Authors: Chown, Ryan; Sidhu, Ameek; Peeters, Els; Tielens, Alexander G. G. M.; Cami, Jan; Berne, Olivier; Habart, Emilie; Alarcon, Felipe; Canin, Amelie; Schroetter, Ilane; Trahin, Boris; Van De Putte, Dries; Abergel, Alain; Bergin, Edwin A.; Bernard-Salas, Jeronimo; Boersma, Christiaan; Bron, Emeric; Cuadrado, Sara; Dartois, Emmanuel; Dicken, Daniel; El-Yajouri, Meriem; Fuente, Asuncion; Goicoechea, Javier R.; Gordon, Karl D.; Issa, Lina; Joblin, Christine; Kannavou, Olga; Khan, Baria; Lacinbala, Ozan; Languignon, David; Le Gal, Romane; Maragkoudakis, Alexandros; Meshaka, Raphael; Okada, Yoko; Onaka, Takashi; Pasquini, Sofia; Pound, Marc W.; Robberto, Massimo; Rollig, Markus; Schefter, Bethany; Schirmer, Thiebaut; Vicente, Silvia; Wolfire, Mark G.; 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; Brunken, Sandra; Buragohain, Mridusmita; Burkhardt, Andrew; Candian, Alessandra; Cazaux, Stephanie; 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; Garcia-Lario, Pedro; Gavilan, Lisseth; Gerin, Maryvonne; Gottlieb, Carl A.; Guillard, Pierre; Gusdorf, Antoine; Hartigan, Patrick; He, Jinhua; Herbst, Eric; Hornekaer, Liv; Jager, Cornelia; Janot-Pacheco, Eduardo; Kaufman, Michael; Kemper, Francisca; Kendrew, Sarah; Kirsanova, Maria S.; Klaassen, Pamela; Kwok, Sun; Labiano, Alvaro; Lai, Thomas S. -Y.; Lee, Timothy J.; Lefloch, Bertrand; Le Petit, Franck; Li, Aigen; Linz, Hendrik; Mackie, Cameron J.; Madden, Suzanne C.; Mascetti, Joelle; 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; Rouille, Gael; 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

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/05/14

DOI: 10.1051/0004-6361/202346662

Abstract: 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 mu m. 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 H-2 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 mu m 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 mu m AIB profile deep in the molecular zone, which belongs to class B-11.2. Furthermore, the observations show that the sub-components that contribute to the 5.75, 7.7, and 11.2 mu m 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 mu m AIB emission from class B-11.2 in the molecular PDR to class A(11.2) 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’.

Authors: Habart, Emilie; Peeters, Els; Berne, Olivier; Trahin, Boris; Canin, Amelie; Chown, Ryan; Sidhu, Ameek; De Putte, Dries Van; Alarcon, Felipe; Schroetter, Ilane; Dartois, Emmanuel; Vicente, Silvia; Abergel, Alain; Bergin, Edwin A.; Bernard-Salas, Jeronimo; Boersma, Christiaan; Bron, Emeric; Cami, Jan; Cuadrado, Sara; Dicken, Daniel; Elyajouri, Meriem; Fuente, Asuncion; Goicoechea, Javier R.; Gordon, Karl D.; Issa, Lina; Joblin, Christine; Kannavou, Olga; Khan, Baria; Lacinbala, Ozan; Languignon, David; Le Gal, Romane; Maragkoudakis, Alexandros; Meshaka, Raphael; Okada, Yoko; Onaka, Takashi; Pasquini, Sofia; Pound, Marc W.; Robberto, Massimo; Rollig, Markus; Schefter, Bethany; Schirmer, Thiebaut; 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; Brunken, Sandra; Buragohain, Mridusmita; Burkhardt, Andrew; Candian, Alessandra; Cazaux, Stephanie; 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; Garcia-Lario, Pedro; Gavilan, Lisseth; Gerin, Maryvonne; Gottlieb, Carl A.; Guillard, Pierre; Gusdorf, Antoine; Hartigan, Patrick; He, Jinhua; Herbst, Eric; Hornekaer, Liv; Jager, Cornelia; Janot-Pacheco, Eduardo; Kaufman, Michael; Kemper, Francisca; Kendrew, Sarah; Kirsanova, Maria S.; Klaassen, Pamela; Kwok, Sun; Labiano, Alvaro; Lai, Thomas S. -Y.; Lee, Timothy J.; Lefloch, Bertrand; Le Petit, Franck; Li, Aigen; Linz, Hendrik; Mackie, Cameron J.; Madden, Suzanne C.; Mascetti, Joelle; 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; Rouille, Gael; 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

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/05/14

DOI: 10.1051/0004-6361/202346747

Abstract: 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 photodissociation 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 similar to 150” and 42” in key gas phase lines (e.g., P alpha a, Br alpha, [FeII] 1.64 mu m, H-2 1-0 S(1) 2.12 mu m, 0-0 S(9) 4.69 mu m), aromatic and aliphatic infrared bands (aromatic infrared bands at 3.3-3.4 mu m, 7.7, and 11.3 mu m), 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 similar to 0.1-1” (similar to 0.0002-0.002 pc or similar to 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 H-0/H-2 DF surface was traced by the H-2 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.

Authors: Peeters, Els; Habart, Emilie; Berne, Olivier; Sidhu, Ameek; Chown, Ryan; Van De Putte, Dries; Trahin, Boris; Schroetter, Ilane; Canin, Amelie; Alarcon, 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, Silvia; Abergel, Alain; Bergin, Edwin A.; Bernard-Salas, Jeronimo; Boersma, Christiaan; Bron, Emeric; Cami, Jan; Cuadrado, Sara; Dicken, Daniel; Elyajouri, Meriem; Fuente, Asuncion; Gordon, Karl D.; Issa, Lina; Joblin, Christine; Kannavou, Olga; Lacinbala, Ozan; Languignon, David; Le Gal, Romane; Meshaka, Raphael; Okada, Yoko; Robberto, Massimo; Roellig, Markus; Schirmer, Thiebaut; 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; Bruenken, Sandra; Buragohain, Mridusmita; Burkhardt, Andrew; Candian, Alessandra; Cazaux, Stephanie; 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; Garcia-Lario, Pedro; Gerin, Maryvonne; Gottlieb, Carl A.; Guillard, Pierre; Gusdorf, Antoine; Hartigan, Patrick; He, Jinhua; Herbst, Eric; Hornekaer, Liv; Jaeger, Cornelia; Janot-Pacheco, Eduardo; Kaufman, Michael; Kendrew, Sarah; Kirsanova, Maria S.; Klaassen, Pamela; Kwok, Sun; Labiano, Alvaro; Lai, Thomas S. -Y.; Lee, Timothy J.; Lefloch, Bertrand; Le Petit, Franck; Li, Aigen; Linz, Hendrik; Mackie, Cameron J.; Madden, Suzanne C.; Mascetti, Joelle; 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; Rouille, Gael; 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

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/05/14

DOI: 10.1051/0004-6361/202348244

Abstract: Context. JWST has taken the sharpest and most sensitive infrared (IR) spectral imaging observations ever of the Orion Bar photodissociation 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” x 25” spatio-spectral mosaic covering 0.975.27 mu m at a spectral resolution R of similar to 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 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 theta(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 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.