Authors: Massalkhi, S.; Agundez, M.; Fonfria, J. P.; Pardo, J. R.; Velilla-Prieto, L.; Cernicharo, J.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/07/09

DOI: 10.1051/0004-6361/202450188

Abstract: Circumstellar envelopes around asymptotic giant branch (AGB) stars contain a rich diversity of molecules, whose spatial distribution is regulated by different chemical and physical processes. In the outer circumstellar layers, all molecules are efficiently destroyed due to interactions with interstellar ultraviolet photons. Here we aim to carry out a coherent and uniform characterization of the radial extent of three molecules (SiO, CS, and SiS) in envelopes around O- and C-rich AGB stars, and to study their dependence on mass-loss rate. To this end, we observed a reduced sample of seven M-type and seven C-type AGB envelopes in multiple lines of SiO, CS, and SiS with the Yebes 40 m and IRAM 30 m telescopes. The selected sources cover a wide range of mass-loss rates, from similar to 10(-7) M-circle dot yr(-1) to a few times 10(-5) M-circle dot yr(-1), and the observed lines cover a wide range of upper-level energies, from 2 K to 130 K. We carried out excitation and radiative transfer calculations over a wide parameter space in order to characterize the abundance and radial extent of each molecule. A chi(2) analysis indicates that the abundance is usually well constrained while the radial extent is in some cases more difficult to constrain. Our results indicate that the radial extent of the molecules considered here increases with increasing envelope density, in agreement with previous observational findings. At high envelope densities of (M) over dot/upsilon(infinity) > 10(-6) M-circle dot yr(-1) km(-1) s, SiO, CS, and SiS show a similar radial extent, while at low envelope densities of (M) over dot/upsilon(infinity) < 10(-7) M-circle dot yr(-1) km(-1) s, differences in radial extent appear among the three molecules, in agreement with theoretical expectations based on destruction due to photodissociation. At low envelope densities, we find a sequence of increasing radial extent, SiS -> CS -> SiO. We also find a tentative dependence of the radial extent on the chemical type (O- or C-rich) of the star for SiO and CS. Interferometric observations and further investigation of the photodissociation of SiO, CS, and SiS should provide clarification of the situation in regards to the relative photodissociation radii of SiO, CS, and SiS in AGB envelopes and their dependence on envelope density and C/O ratio.

Authors: Rigopoulou, D.; Donnan, F. R.; Garcia-Bernete, I; Pereira-Santaella, M.; Alonso-Herrero, A.; Davies, R.; Hunt, L. K.; Roche, P. F.; Shimizu, T.

Journal: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Publication date: 2024/07/09

DOI: 10.1093/mnras/stae1535

Abstract: We present a systematic study of mid-infrared spectra of galaxies including star-forming galaxies and active galactic nuclei observed with JWST MIRI-MRS and NIRSpec-IFU. We focus on the relative variations of the 3.3, 6.2, 7.7, 11.3, 12.7, and 17 $mu$m polycyclic aromatic hydrocarbon (PAH) features within spatially resolved regions of galaxies including NGC 3256, NGC 7469, VV 114, II Zw96, and NGC 5728. Using theoretical PAH models and extending our earlier work, we introduce a new PAH diagnostic involving the 17 $mu$m PAH feature. To determine the drivers of PAH band variations in galaxies, we compare observed PAH spectral bands to predictions from theoretical PAH models. We consider extinction, dehydrogenation, and PAH size and charge as possible drivers of PAH band variations. We find a surprising uniformity in PAH size distribution among the spatially resolved regions of the galaxies studied here, with no evidence for preferential destruction of the smallest grains, contrary to earlier findings. Neither extinction nor dehydrogenation play a crucial role in setting the observed PAH bands. Instead, we find that PAH charge plays a significant role in PAH inter-band variations. We find a tight relation between PAH charge and the intensity of the radiation field as traced by the [Ne iii]$/$[Ne ii] maps. In agreement with recent JWST results, we find a predominance of neutral PAH molecules in the nuclei of active galaxies and their outflows. Ionized PAHs are the dominant population in star-forming galaxies. We discuss the implications of our findings for the use of PAHs as ISM tracers in high redshift galaxies.

Authors: Hacar, A.; Socci, A.; Bonanomi, F.; Petry, D.; Tafalla, M.; Harsono, D.; Forbrich, J.; Alves, J.; Grossschedl, J.; Goicoechea, J. R.; Pety, J.; Burkert, A.; Li, G. X.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/07/05

DOI: 10.1051/0004-6361/202348565

Abstract: Context. Recent molecular surveys have revealed the rich gas organization of sonic-like filaments at small scales (so-called fibers) in all types of environments prior to the formation of low- and high-mass stars. These fibers form at the end of the turbulent cascade and are identified as the fine substructure within the hierarchical nature of the gas in the interstellar medium (ISM). Aims. Isolated fibers provide the subsonic conditions for the formation of low-mass stars. This paper introduces the Emergence of high-mass stars in complex fiber networks (EMERGE) project, which investigates whether complex fiber arrangements (networks) can also explain the origin of high-mass stars and clusters. Methods. We analyzed the EMERGE Early ALMA Survey including seven star-forming regions in Orion (OMC-1,2,3, and 4 South, LDN 1641N, NGC 2023, and the Flame Nebula) that were homogeneously surveyed in three molecular lines (N2H+ J = 1-0, HNC J = 1-0, and HC3N J = 10-9) and in the 3mm continuum using a combination of interferometric ALMA mosaics and IRAM-30m single-dish (SD) maps, together with a series of Herschel, Spitzer, and WISE archival data. We also developed a systematic data reduction framework allowing the massive data processing of ALMA observations. Results. We obtained independent continuum maps and spectral cubes for all our targets and molecular lines at different (SD and interferometric) resolutions, and we explored multiple data combination techniques. Based on our low-resolution (SD) observations (30 ” or similar to 12 000 au), we describe the global properties of our sample, which covers a wide range of physical conditions, including low- (OMC-4 South and NGC 2023), intermediate (OMC-2, OMC-3, and LDN 1641N), and high-mass (OMC-1 and Flame Nebula) star-forming regions in different evolutionary stages. The comparison between our single-dish maps and ancillary YSO catalogs denotes N2H+ (1-0) as the best proxy for the dense, star-forming gas in our targets, which show a constant star formation efficiency and a fast time evolution of less than or similar to 1 Myr. While apparently clumpy and filamentary in our SD data, all targets show a much more complex fibrous substructure at the enhanced resolution of our combined ALMA+IRAM-30m maps (4.” 5 or similar to 2000 au). A large number of filamentary features at subparsec scales are clearly recognized in the high-density gas (greater than or similar to 10(5) cm(-3)) that is traced by N2H+ (1-0) directly connected to the formation of individual protostars. Surprisingly, this complex gas organization appears to extend farther into the more diffuse gas (similar to 10(3)-10(4) cm(-3)) traced by HNC (1-0). Conclusions. This paper presents the EMERGE Early ALMA Survey, which includes a first data release of continuum maps and spectral products for this project that are to be analysed in future papers of this series. A first look at these results illustrates the need of advanced data combination techniques between high-resolution interferometric (ALMA) and high-sensitivity, low-resolution single-dish (IRAM-30 m) datasets to investigate the intrinsic multiscale, gas structure of the ISM.

Authors: Van De Putte, Dries; Meshaka, Raphael; Trahin, Boris; Habart, Emilie; Peeters, Els; Berne, Olivier; Alarcon, Felipe; Canin, Amelie; 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, Asuncion; Joblin, Christine; Khan, Baria; Lacinbala, Ozan; Languignon, David; Le Gal, Romane; Maragkoudakis, Alexandros; Okada, Yoko; Pasquini, Sofia; Pound, Marc W.; Robberto, Massimo; Rollig, Markus; Schefter, Bethany; Schirmer, Thiebaut; Tabone, Benoit; Vicente, Silvia; Zannese, Marion; Colgan, Sean W. J.; He, Jinhua; Rouille, Gael; 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; Brunken, Sandra; Buragohain, Mridusmita; Burkhardt, Andrew; Candian, Alessandra; Cazaux, Stephanie; Cernicharo, Jose; Chabot, Marin; Chakraborty, Shubhadip; Champion, Jason; 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; Herbst, Eric; Hornekaer, Liv; Issa, Lina; Jager, Cornelia; Janot-Pacheco, Eduardo; Kannavou, Olga; Kaufman, Michael; Kemper, Francisca; Kendrew, Sarah; Kirsanova, Maria S.; Klaassen, Pamela; Kwok, Sun; Labiano, Alvaro; Lai, Thomas S. -Y.; Le Floch, Bertrand; Le Petit, Franck; Li, Aigen; Linz, Hendrik; Mackie, Cameron J.; Madden, Suzanne C.; Mascetti, Joelle; 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

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/07/02

DOI: 10.1051/0004-6361/202449295

Abstract: Context. Mid-infrared emission features are important probes of the properties of ionized gas and hot or warm molecular gas, which are difficult to probe at other wavelengths. The Orion Bar photodissociation region (PDR) is a bright, nearby, and frequently studied target containing large amounts of gas under these conditions. Under the PDRs4All Early Release Science Program for JWST, a part of the Orion Bar was observed with MIRI integral field unit (IFU) spectroscopy, and these high-sensitivity IR spectroscopic images of very high angular resolution (0.2 ”) provide a rich observational inventory of the mid-infrared (MIR) emission lines, while resolving the H II region, the ionization front, and multiple dissociation fronts. Aims. We list, identify, and measure the most prominent gas emission lines in the Orion Bar using the new MIRI IFU data. An initial analysis summarizes the physical conditions of the gas and demonstrates the potential of these new data and future IFU observations with JWST. Methods. The MIRI IFU mosaic spatially resolves the substructure of the PDR, its footprint cutting perpendicularly across the ionization front and three dissociation fronts. We performed an up-to-date data reduction, and extracted five spectra that represent the ionized, atomic, and molecular gas layers. We identified the observed lines through a comparison with theoretical line lists derived from atomic data and simulated PDR models. The identified species and transitions are summarized in the main table of this work, with measurements of the line intensities and central wavelengths. Results. We identified around 100 lines and report an additional 18 lines that remain unidentified. The majority consists of H I recombination lines arising from the ionized gas layer bordering the PDR. The H I line ratios are well matched by emissivity coefficients from H recombination theory, but deviate by up to 10% because of contamination by He I lines. We report the observed emission lines of various ionization stages of Ne, P, S, Cl, Ar, Fe, and Ni. We show how the Ne III/Ne II, S IV/S III, and Ar III/Ar II ratios trace the conditions in the ionized layer bordering the PDR, while Fe III/Fe II and Ni III/Ni II exhibit a different behavior, as there are significant contributions to Fe II and Ni II from the neutral PDR gas. 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 for the three observed dissociation fronts, the rotational excitation can be approximated with one thermal (similar to 700 K) component representative of an average gas temperature, and one nonthermal component (similar to 2700 K) probing the effect of UV pumping. We compare these results to an existing model of the Orion Bar PDR, and find that the predicted excitation matches the data qualitatively, while adjustments to the parameters of the PDR model are required to reproduce the intensity of the 0-0 S (6) to S (8) lines.

Authors: Fuente, Asuncion; Roueff, Evelyne; Le Petit, Franck; Le Bourlot, Jacques; Bron, Emeric; Wolfire, Mark G.; Babb, James F.; Yan, Pei-Gen; Onaka, Takashi; Black, John H.; Schroetter, Ilane; Van De Putte, Dries; Sidhu, Ameek; Canin, Amelie; Trahin, Boris; Alarcon, Felipe; Chown, Ryan; Kannavou, Olga; Berne, Olivier; Habart, Emilie; Peeters, Els; Goicoechea, Javier R.; Zannese, Marion; Meshaka, Raphael; Okada, Yoko; Roellig, Markus; Le Gal, Romane; Sales, Dinalva A.; Palumbo, Maria Elisabetta; Baratta, Giuseppe Antonio; Madden, Suzanne C.; Neelamkodan, Naslim; Zhang, Ziwei E.; Stancil, P. C.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/07/02

DOI: 10.1051/0004-6361/202449229

Abstract: Context. One of the main problems in astrochemistry is determining the amount of sulfur in volatiles and refractories in the interstellar medium. The detection of the main sulfur reservoirs (icy H2S and atomic gas) has been challenging, and estimates are based on the reliability of models to account for the abundances of species containing less than 1% of the total sulfur. The high sensitivity of the James Webb Space Telescope provides an unprecedented opportunity to estimate the sulfur abundance through the observation of the [S I] 25.249 mu m line. Aims. Our aim is to determine the amount of sulfur in the ionized and warm molecular phases toward the Orion Bar as a template to investigate sulfur depletion in the transition between the ionized gas and the molecular cloud in HII regions. Methods. We used the [S III] 18.7 mu m, [S IV] 10.5 mu m, and [S 1] 25.249 mu m lines to estimate the amount of sulfur in the ionized and molecular gas along the Orion Bar. For the theoretical part, we used an upgraded version of the Meudon photodissociation region (PDR) code to model the observations. New inelastic collision rates of neutral atomic sulfur with ortho-and para- molecular hydrogen were calculated to predict the line intensities. Results. The [S III] 18.7 mu m and [S IV] 10.5 mu m lines are detected over the imaged region with a shallow increase (by a factor of 4) toward the HII region. This suggests that their emissions are partially coming from the Orion Veil. We estimate a moderate sulfur depletion, by a factor of similar to 2, in the ionized gas. The corrugated interface between the molecular and atomic phases gives rise to several edge-on dissociation fronts we refer to as DF1, DF2, and DF3. The [S 1] 25.249 mu m line is only detected toward DF2 and DF3, the dissociation fronts located farthest from the HII region. This is the first ever detection of the [S 1] 25.249 mu m line in a PDR. The detailed modeling of DF3 using the Meudon PDR code shows that the emission of the [S 1] 25.249 mu m line is coming from warm (>40 K) molecular gas located at A(V) similar to 1-5 mag from the ionization front. Moreover, the intensity of the [S 1] 25.249 mu m line is only accounted for if we assume the presence of undepleted sulfur. Conclusions. Our data show that sulfur remains undepleted along the ionic, atomic, and molecular gas in the Orion Bar. This is consistent with recent findings that suggest that sulfur depletion is low in massive star-forming regions because of the interaction of the UV photons coming from the newly formed stars with the interstellar matter.