المؤلفون: Van De Putte, Dries, Meshaka, Raphael, Trahin, Boris, Habart, Emilie, Peeters, Els, Berné, Olivier, Alarcón, Felipe, Canin, Amélie, Chown, Ryan, Schroetter, Ilane, Sidhu, Ameek, Boersma, Christiaan, Bron, Emeric, Dartois, Emmanuel, Goicoechea, Javier R., Gordon, Karl D., Onaka, Takashi, Tielens, Alexander G. G. M., Verstraete, Laurent, Wolfire, Mark G., Abergel, Alain, Bergin, Edwin A., Bernard-Salas, Jeronimo, Cami, Jan, Cuadrado, Sara, Dicken, Daniel, Elyajouri, Meriem, Fuente, Asunción, Joblin, Christine, Khan, Baria, Lacinbala, Ozan, Languignon, David, Gal, Romane Le, Maragkoudakis, Alexandros, Okada, Yoko, Pasquini, Sofia, Pound, Marc W., Robberto, Massimo, Röllig, Markus, Schefter, Bethany, Schirmer, Thiébaut, Tabone, Benoit, Vicente, Sílvia, Zannese, Marion, Colgan, Sean W. J., He, Jinhua, Rouillé, Gaël, Togi, Aditya, Aleman, Isabel, 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, 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, Herbst, Eric, Hornekaer, Liv, Issa, Lina, Jäger, Cornelia, Janot-Pacheco, Eduardo, Kannavou, Olga, Kaufman, Michael, Kemper, Francisca, Kendrew, Sarah, Kirsanova, Maria S., Klaassen, Pamela, Kwok, Sun, Labiano, Álvaro, Lai, Thomas S. -Y., Floch, Bertrand Le, Petit, Franck Le, Li, Aigen, Linz, Hendrik, Mackie, Cameron J., Madden, Suzanne C., Mascetti, Joëlle, McGuire, Brett A., Merino, Pablo, Micelotta, Elisabetta R., 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, Rho, Jeonghee, Ricca, Alessandra, Roman-Duval, Julia, Roser, Joseph, Roueff, Evelyne, Salama, Farid, Sales, Dinalva A., Sandstrom, Karin, Sarre, Peter, Sciamma-O'Brien, Ella, Sellgren, Kris, Shenoy, Sachindev S., Teyssier, David, Thomas, Richard D., Witt, Adolf N., Wootten, Alwyn, Ysard, Nathalie, Zettergren, Henning, Zhang, Yong, Zhang, Ziwei E., Zhen, Junfeng

المصدر: A&A 687, A86 (2024)

مصطلحات موضوعية: Astrophysics - Astrophysics of Galaxies

الوصف: Mid-infrared emission features probe the properties of ionized gas, and hot or warm molecular gas. The Orion Bar is a frequently studied photodissociation region (PDR) containing large amounts of gas under these conditions, and was observed with the MIRI IFU aboard JWST as part of the "PDRs4All" program. The resulting IR spectroscopic images of high angular resolution (0.2") reveal a rich observational inventory of mid-IR emission lines, and spatially resolve the substructure of the PDR, with a mosaic cutting perpendicularly across the ionization front and three dissociation fronts. We extracted five spectra that represent the ionized, atomic, and molecular gas layers, and measured the most prominent gas emission lines. An initial analysis summarizes the physical conditions of the gas and the potential of these data. We identified around 100 lines, report an additional 18 lines that remain unidentified, and measured the line intensities and central wavelengths. The H I recombination lines originating from the ionized gas layer bordering the PDR, have intensity ratios that are well matched by emissivity coefficients from H recombination theory, but deviate up to 10% due contamination by He I lines. We report the observed emission lines of various ionization stages of Ne, P, S, Cl, Ar, Fe, and Ni, and show how certain line ratios vary between the five regions. We observe the pure-rotational H$_2$ lines in the vibrational ground state from 0-0 S(1) to 0-0 S(8), and in the first vibrationally excited state from 1-1 S(5) to 1-1 S(9). We derive H$_2$ excitation diagrams, and approximate the excitation with one thermal (~700 K) component representative of an average gas temperature, and one non-thermal component (~2700 K) probing the effect of UV pumping. We compare these results to an existing model for the Orion Bar PDR and highlight the differences with the observations.
Comment: 26 pages, 12 figures, 3 tables. Submitted to A&A, under review (1st revision)

الوصول الحر: http://arxiv.org/abs/2404.03111Test

المؤلفون: 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, Elyajour, Meriem, Fuente, Asuncion, Gordon, Karl D., Issa, Lina, Joblin, Christine, Kannavou, Olga, Lacinbala, Ozan, Languignon, David, Gal, Romane Le, 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, 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, Gerin, Maryvonne, Gottlieb, Carl A., Guillard, Pierre, Gusdorf, Antoine, Hartigan, Patrick, He, Jinhua, Herbst, Eric, Hornekaer, Liv, Jager, 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, Petit, Franck Le, 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

المصدر: A&A 685, A74 (2024)

مصطلحات موضوعية: Astrophysics - Astrophysics of Galaxies

الوصف: (Abridged) We investigate the impact of radiative feedback from massive stars on their natal cloud and focus on the transition from the HII region to the atomic PDR (crossing the ionisation front (IF)), and the subsequent transition to the molecular PDR (crossing the dissociation front (DF)). We use 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 Program. The NIRSpec data reveal a forest of lines including, but not limited to, HeI, HI, and CI recombination lines, ionic lines, OI and NI fluorescence lines, Aromatic Infrared Bands (AIBs including aromatic CH, aliphatic CH, and their CD counterparts), CO2 ice, pure rotational and ro-vibrational lines from H2, and ro-vibrational lines HD, CO, and CH+, most of them 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. We observe numerous smaller scale structures whose typical size decreases with distance from Ori C and IR lines from CI, if solely arising from radiative recombination and cascade, reveal very high gas temperatures consistent with the hot irradiated surface of small-scale dense clumps deep inside the PDR. The H2 lines reveal multiple, prominent filaments which 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. 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.
Comment: 52 pages, 30 figures, submitted to A&A

الوصول الحر: http://arxiv.org/abs/2310.08720Test

المؤلفون: Habart, Emilie, Peeters, Els, Berné, Olivier, Trahin, Boris, Canin, Amélie, Chown, Ryan, Sidhu, Ameek, Van De Putte, Dries, 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, rew, 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

المصدر: A&A 685, A73 (2024)

مصطلحات موضوعية: Astrophysics - Astrophysics of Galaxies

الوصف: The JWST has captured the most detailed and sharpest infrared 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). We investigate the fundamental interaction of far-ultraviolet 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. 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. A complex, structured, and folded DF surface was traced by the H2 lines. This dataset was used to revisit the commonly adopted 2D PDR structure of the Orion Bar. 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.

الوصول الحر: http://arxiv.org/abs/2308.16732Test

المؤلفون: 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, 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, 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, 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

المصدر: A&A 685, A75 (2024)

مصطلحات موضوعية: Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics

الوصف: (Abridged) 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. 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, the atomic PDR, and the HII region. We use JWST NIRSpec IFU and MIRI MRS observations of the Orion Bar from the JWST Early Release Science Program, PDRs4All (ID: 1288). We extract five template spectra to represent the morphology and environment of the Orion Bar PDR. 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. While the spectra are dominated by the well-known AIBs at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 $\mu$m, a wealth of weaker features and sub-components are present. We report trends in the widths and relative strengths of AIBs across the five template spectra. These trends yield valuable insight 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'.
Comment: 25 pages, 10 figures, to appear in A&A

الوصول الحر: http://arxiv.org/abs/2308.16733Test

المؤلفون: Chown, Ryan, Sidhu, Ameek, Peeters, Els, Tielens, A.G.G.M., Cami, Jan, Berné, O., Habart, Emilie, Alarcon, Felipe, Canin, Amelie, Schroetter, Ilane, Trahin, Boris, Van De Putte, Dries, Abergel, Alain, Bergin, E. A., Bernard-Salas, J., Boersma, Christiaan, Bron, E., Cuadrado, S., Dartois, E., Dicken, D., El-Yajouri, Meriem, Fuente, A., Goicoechea, J.R., Gordon, K., Issa, Lina, Joblin, C., Kannavou, Olga, Khan, Baria, Lacinbala, Ozan, Languignon, David, Gal, R. Le, Maragkoudakis, Alexandros, Meshaka, Raphael, Okada, Yoko, Onaka, Takashi, Pasquini, Sofia, Pound, Marc W., Robberto, Massimo, Rollig, M., Schefter, Bethany, Schirmer, Thiébaut, Vicente, S., Wolfire, M.G., Zannese, Marion, Aleman, I., Allamandola, Louis, Auchettl, Rebecca, Baratta, Giuseppe Antonio, Bejaoui, Salma, Bera, Partha P., Black, John H, 1949, Boulanger, F., Bouwman, Jordy, Brandl, B. R., Brechignac, Philippe, Brünken, S., Buragohain, Mridusmita, Burkhardt, Andrew, Candian, Alessandra, Cazaux, S., Cernicharo, Jose, Chabot, Marin, Chakraborty, Shubhadip, Champion, Jason, Colgan, Sean W. J., Cooke, Ilsa R., Coutens, A., Cox, N. L. J., Demyk, K., Meyer, Jennifer Donovan, Foschino, Sacha, Garcia-Lario, P., Gavilan, Lisseth, Gerin, M., Gottlieb, C. A., Guillard, P., Gusdorf, Antoine, Hartigan, Patrick, He, J. H., Herbst, E, Hornekaer, Liv, Jäger, Cornelia, Janot-Pacheco, Eduardo, Kaufman, M., Kemper, F., Kendrew, S., Kirsanova, M. S., Klaassen, Pamela, Kwok, Sun, Labiano, A., Lai, Thomas, Lee, Timothy J., Lefloch, B., Le Petit, Franck, 1975, Li, Aigen, Linz, H., MacKie, Cameron J., Madden, S. C., Mascetti, Joëlle, McGuire, Brett, Merino, Pablo, Micelotta, Elisabetta R., Misselt, K. A., Morse, Jon A., Mulas, Giacomo, Neelamkodan, Naslim, Ohsawa, Ryou, Omont, A.A., Paladini, R., Palumbo, Maria Elisabetta, Pathak, Amit, Pendleton, Yvonne J., Petrignani, Annemieke, Pino, Thomas, Puga, E., Rangwala, Naseem, Rapacioli, Mathias, Ricca, Alessandra, Roman-Duval, J., 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, D., Thomas, Richard D., Togi, Aditya, Verstraete, Laurent, Witt, Adolf N., Wootten, A., Zettergren, H., Zhang, Yong, Zhang, Ziwei E., Zhen, Junfeng

المصدر: Astronomy and Astrophysics. 685

مصطلحات موضوعية: ISM: individual objects: Orion Bar, Infrared: ISM, Astrochemistry, Photon-dominated region (PDR), Techniques: spectroscopic, ISM: molecules

الوصف: 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’.

وصف الملف: electronic

الوصول الحر: https://research.chalmers.se/publication/541303Test
https://research.chalmers.se/publication/541303/file/541303_Fulltext.pdfTest

المؤلفون: Habart, Emilie, Peeters, Els, Berné, O., Trahin, Boris, Canin, Amelie, Chown, Ryan, Sidhu, Ameek, De Putte, Dries Van, Alarcon, Felipe, Schroetter, Ilane, Dartois, E., Vicente, S., Abergel, Alain, Bergin, E. A., Bernard-Salas, J., Boersma, Christiaan, Bron, E., Cami, Jan, Cuadrado, S., Dicken, D., Elyajouri, Meriem, Fuente, A., Goicoechea, J.R., Gordon, K., Issa, Lina, Joblin, C., Kannavou, Olga, Khan, Baria, Lacinbala, Ozan, Languignon, David, Gal, R. Le, Maragkoudakis, Alexandros, Meshaka, Raphael, Okada, Yoko, Onaka, Takashi, Pasquini, Sofia, Pound, Marc W., Robberto, Massimo, Rollig, M., Schefter, Bethany, Schirmer, Thiébaut, Tabone, Benoît, Tielens, A.G.G.M., Wolfire, M.G., Zannese, Marion, Ysard, Nathalie, Miville-Deschênes, Marc Antoine, Aleman, I., Allamandola, Louis, Auchettl, Rebecca, Baratta, Giuseppe Antonio, Bejaoui, Salma, Bera, Partha P., Black, John H, 1949, Boulanger, F., Bouwman, Jordy, Brandl, B. R., Brechignac, Philippe, Brünken, S., Buragohain, Mridusmita, Burkhardt, Andrew, Candian, Alessandra, Cazaux, S., Cernicharo, Jose, Chabot, Marin, Chakraborty, Shubhadip, Champion, Jason, Colgan, Sean W. J., Cooke, Ilsa R., Coutens, A., Cox, N. L. J., Demyk, K., Meyer, Jennifer Donovan, Foschino, Sacha, Garcia-Lario, P., Gavilan, Lisseth, Gerin, M., Gottlieb, C. A., Guillard, P., Gusdorf, Antoine, Hartigan, Patrick, He, J. H., Herbst, E, Hornekaer, Liv, Jäger, Cornelia, Janot-Pacheco, Eduardo, Kaufman, M., Kemper, F., Kendrew, S., Kirsanova, M. S., Klaassen, Pamela, Kwok, Sun, Labiano, A., Lai, Thomas, Lee, Timothy J., Lefloch, B., Le Petit, Franck, 1975, Li, Aigen, Linz, H., MacKie, Cameron J., Madden, S. C., Mascetti, Joëlle, McGuire, Brett, Merino, Pablo, Micelotta, Elisabetta R., Misselt, K. A., Morse, Jon A., Mulas, Giacomo, Neelamkodan, Naslim, Ohsawa, Ryou, Omont, A.A., Paladini, R., Palumbo, Maria Elisabetta, Pathak, Amit, Pendleton, Yvonne J., Petrignani, Annemieke, Pino, Thomas, Puga, E., Rangwala, Naseem, Rapacioli, Mathias, Ricca, Alessandra, Roman-Duval, J., 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, D., Thomas, Richard D., Togi, Aditya, Verstraete, Laurent, Witt, Adolf N., Wootten, A., Zettergren, H., Zhang, Yong, Zhang, Ziwei E., Zhen, Junfeng

المصدر: Astronomy and Astrophysics. 685

مصطلحات موضوعية: photon-dominated region (PDR), ISM: clouds, infrared: ISM

الوصف: 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.

وصف الملف: electronic

الوصول الحر: https://research.chalmers.se/publication/541302Test
https://research.chalmers.se/publication/541302/file/541302_Fulltext.pdfTest

المؤلفون: Peeters, Els, Habart, Emilie, Berné, O., Sidhu, Ameek, Chown, Ryan, Van De Putte, Dries, Trahin, Boris, Schroetter, Ilane, Canin, Amelie, Alarcon, Felipe, Schefter, Bethany, Khan, Baria, Pasquini, Sofia, Tielens, A.G.G.M., Wolfire, M.G., Dartois, E., Goicoechea, J.R., Maragkoudakis, Alexandros, Onaka, Takashi, Pound, Marc W., Vicente, S., Abergel, Alain, Bergin, E. A., Bernard-Salas, J., Boersma, Christiaan, Bron, E., Cami, Jan, Cuadrado, S., Dicken, D., Elyajouri, Meriem, Fuente, A., Gordon, K., Issa, Lina, Joblin, C., Kannavou, Olga, Lacinbala, Ozan, Languignon, David, Gal, R. Le, Meshaka, Raphael, Okada, Yoko, Robberto, Massimo, Rollig, M., Schirmer, Thiébaut-Antoine, 1992, Tabone, Benoît, Zannese, Marion, Aleman, I., Allamandola, Louis, Auchettl, Rebecca, Baratta, Giuseppe Antonio, Bejaoui, Salma, Bera, Partha P., Black, John H, 1949, Boulanger, F., Bouwman, Jordy, Brandl, B. R., Brechignac, Philippe, Brünken, S., Buragohain, Mridusmita, Burkhardt, Andrew, Candian, Alessandra, Cazaux, S., Cernicharo, Jose, Chabot, Marin, Chakraborty, Shubhadip, Champion, Jason, Colgan, Sean W. J., Cooke, Ilsa R., Coutens, A., Cox, N. L. J., Demyk, K., Meyer, Jennifer Donovan, Foschino, Sacha, Garcia-Lario, P., Gerin, M., Gottlieb, C. A., Guillard, P., Gusdorf, Antoine, Hartigan, Patrick, He, J. H., Herbst, E, Hornekaer, Liv, Jäger, Cornelia, Janot-Pacheco, Eduardo, Kaufman, M., Kendrew, S., Kirsanova, M. S., Klaassen, Pamela, Kwok, Sun, Labiano, A., Lai, Thomas, Lee, Timothy J., Lefloch, B., Le Petit, Franck, 1975, Li, Aigen, Linz, H., MacKie, Cameron J., Madden, S. C., Mascetti, Joëlle, McGuire, Brett, Merino, Pablo, Micelotta, Elisabetta R., Misselt, K. A., Morse, Jon A., Mulas, Giacomo, Neelamkodan, Naslim, Ohsawa, Ryou, Paladini, R., Palumbo, Maria Elisabetta, Pathak, Amit, Pendleton, Yvonne J., Petrignani, Annemieke, Pino, Thomas, Puga, E., Rangwala, Naseem, Rapacioli, Mathias, Ricca, Alessandra, Roman-Duval, J., 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, D., Thomas, Richard D., Togi, Aditya, Verstraete, Laurent, Witt, Adolf N., Wootten, A., Ysard, Nathalie, Zettergren, H., Zhang, Yong, Zhang, Ziwei E., Zhen, Junfeng

المصدر: Astronomy and Astrophysics. 685

مصطلحات موضوعية: Infrared: ISM, ISM: individual objects: Orion Bar, Techniques: spectroscopic, HII regions, Photon-dominated region (PDR)

الوصف: 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.

وصف الملف: electronic

الوصول الحر: https://research.chalmers.se/publication/541267Test
https://research.chalmers.se/publication/541267/file/541267_Fulltext.pdfTest

المؤلفون: Berné, Olivier, Habart, Émilie, Peeters, Els, Abergel, Alain, Bergin, Edwin A., Bernard-Salas, Jeronimo, Bron, Emeric, Cami, Jan, Cazaux, Stéphanie, Dartois, Emmanuel, Fuente, Asunción, Goicoechea, Javier R., Gordon, Karl D., Okada, Yoko, Onaka, Takashi, Robberto, Massimo, Röllig, Markus, Tielens, Alexander G. G. M., Vicente, Silvia, Wolfire, Mark G., Alarcon, Felipe, Boersma, C., Canin, Ameélie, Chown, Ryan, Dicken, Daniel, Languignon, David, Gal, Romane Le, Pound, Marc W., Trahin, Boris, Simmer, Thomas, Sidhu, Ameek, Van De Putte, Dries, Cuadrado, Sara, Guilloteau, Claire, Maragkoudakis, Alexandros, Schefter, Bethany R., Schirmer, Thiébaut, Aleman, Isabel, Allamandola, Louis, Auchettl, Rebecca, Baratta, Giuseppe Antonio, Bejaoui, Salma, Bera, Partha P., Bilalbegovic, Goranka, Black, John H., Boulanger, Francois, Bouwman, Jordy, Brandl, Bernhard, Brechignac, Philippe, Brunken, Sandra, Burkhardt, Andrew, Candian, Alessandra, 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, Engrand, Cécile, Foschino, Sacha, Garcıa-Lario, Pedro, Gavilan, Lisseth, Gerin, Maryvonne, Godard, Marie, Gottlieb, Carl A., Guillard, Pierre, Gusdorf, Antoine, Hartigan, Patrick, He, Jinhua, Herbst, Eric, Hornekaer, Liv, Jaeger, Cornelia, Janot-Pacheco, Eduardo, Joblin, Christine, Kaufman, Michael, Kemper, Francisca, Kendrew, Sarah, Kirsanova, Maria S., Klaassen, Pamela, Knight, Collin, Kwok, Sun, Labiano, Alvaro, Lai, Thomas S. -Y., Lee, Timothy J., Lefloch, Bertrand, Petit, Franck Le, 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, Shannon, Matthew J., 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

مصطلحات موضوعية: Astrophysics - Astrophysics of Galaxies

الوصف: Massive stars disrupt their natal molecular cloud material through radiative and mechanical feedback processes. These processes have profound effects on the evolution of interstellar matter in our Galaxy and throughout the Universe, from the era of vigorous star formation at redshifts of 1-3 to the present day. The dominant feedback processes can be probed by observations of the Photo-Dissociation Regions (PDRs) where the far-ultraviolet photons of massive stars create warm regions of gas and dust in the neutral atomic and molecular gas. PDR emission provides a unique tool to study in detail the physical and chemical processes that are relevant for most of the mass in inter- and circumstellar media including diffuse clouds, proto-planetary disks and molecular cloud surfaces, globules, planetary nebulae, and star-forming regions. PDR emission dominates the infrared (IR) spectra of star-forming galaxies. Most of the Galactic and extragalactic observations obtained with the James Webb Space Telescope (JWST) will therefore arise in PDR emission. In this paper we present an Early Release Science program using the MIRI, NIRSpec, and NIRCam instruments dedicated to the observations of an emblematic and nearby PDR: the Orion Bar. These early JWST observations will provide template datasets designed to identify key PDR characteristics in JWST observations. These data will serve to benchmark PDR models and extend them into the JWST era. We also present the Science-Enabling products that we will provide to the community. These template datasets and Science-Enabling products will guide the preparation of future proposals on star-forming regions in our Galaxy and beyond and will facilitate data analysis and interpretation of forthcoming JWST observations.
Comment: Submitted to PASP

الوصول الحر: http://arxiv.org/abs/2201.05112Test

المؤلفون: Cartwright, Richard J., Beddingfield, Chloe B., Nordheim, Tom A., Elder, Catherine M., Castillo-Rogez, Julie C., Neveu, Marc, Bramson, Ali M., Sori, Michael M., Buratti, Bonnie J., Pappalardo, Robert T., Roser, Joseph E., Cohen, Ian J., Leonard, Erin J., Ermakov, Anton I., Showalter, Mark R., Grundy, William M., Turtle, Elizabeth P., Hofstadter, Mark D.

مصطلحات موضوعية: Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics

الوصف: The 27 satellites of Uranus are enigmatic, with dark surfaces coated by material that could be rich in organics. Voyager 2 imaged the southern hemispheres of Uranus' five largest 'classical' moons Miranda, Ariel, Umbriel, Titania, and Oberon, as well as the largest ring moon Puck, but their northern hemispheres were largely unobservable at the time of the flyby and were not imaged. Additionally, no spatially resolved datasets exist for the other 21 known moons, and their surface properties are essentially unknown. Because Voyager 2 was not equipped with a near-infrared mapping spectrometer, our knowledge of the Uranian moons' surface compositions, and the processes that modify them, is limited to disk-integrated datasets collected by ground- and space-based telescopes. Nevertheless, images collected by the Imaging Science System on Voyager 2 and reflectance spectra collected by telescope facilities indicate that the five classical moons are candidate ocean worlds that might currently have, or had, liquid subsurface layers beneath their icy surfaces. To determine whether these moons are ocean worlds, and investigate Uranus' ring moons and irregular satellites, close-up observations and measurements made by instruments onboard a Uranus orbiter are needed.
Comment: Accepted in AAS Planetary Science Journal. arXiv admin note: text overlap with arXiv:2007.07284

الوصول الحر: http://arxiv.org/abs/2105.01164Test

المؤلفون: Cartwright, Richard J., Nordheim, Tom A., Cruikshank, Dale P., Hand, Kevin P., Roser, Joseph E., Grundy, William M., Beddingfield, Chloe B., Emery, Joshua P.

مصطلحات موضوعية: Astrophysics - Earth and Planetary Astrophysics

الوصف: We investigated whether sulfur-bearing species are present on the icy Galilean moon Callisto by analyzing eight near-infrared reflectance spectra collected over a wide range of sub-observer longitudes. We measured the band areas and depths of a 4-micron feature in these spectra, which has been attributed to sulfur dioxide (SO2), as well as carbonates, in previously collected datasets of this moon. All eight spectra we collected display the 4-micron band. The four spectra collected over Callisto's leading hemisphere display significantly stronger 4-micron bands compared to the four trailing hemisphere spectra (> 3-sigma difference). We compared the central wavelength position and shape of Callisto's 4-micron band to laboratory spectra of various sulfur-bearing species and carbonates. Our comparison demonstrates that Callisto's 4-micron band has a spectral signature similar to thermally-altered sulfur, as well as a 4.025 micron feature attributed to disulfanide (HS2). Our analysis therefore supports the presence of S-bearing species on Callisto but is not consistent with the presence of SO2. The significantly stronger 4-micron band detected on Callisto's leading hemisphere could result from collisions with H2S-rich dust grains that originate on Jupiter's retrograde irregular satellites or implantation of magnetospheric S ions that originate from volcanic activity on Io. Alternatively, S-bearing species could be native to Callisto and are exposed by dust collisions and larger impacts that drive regolith overturn, primarily on its leading side.

الوصول الحر: http://arxiv.org/abs/2010.01395Test