Authors: Garcia-Bernete, I.; Alonso-Herrero, A.; Rigopoulou, D.; Pereira-Santaella, M.; Shimizu, T.; Davies, R.; Donnan, F. R.; Roche, P. F.; Gonzalez-Martin, O.; Ramos Almeida, C.; Bellocchi, E.; Boorman, P.; Combes, F.; Efstathiou, A.; Esparza-Arredondo, D.; Garcia-Burillo, S.; Gonzalez-Alfonso, E.; Hicks, E. K. S.; Honig, S.; Labiano, A.; Levenson, N. A.; Lopez-Rodriguez, E.; Ricci, C.; Packham, C.; Rouan, D.; Stalevski, M.; Ward, M. J.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2023/12/25

DOI: 10.1051/0004-6361/202348266

Abstract: We present the first results of the Galaxy Activity, Torus, and Outflow Survey (GATOS), a project aimed at understanding the properties of the dusty molecular tori and their connection to the host galaxy in nearby Seyfert galaxies. Our project expands the range of active galactic nuclei (AGN) luminosities and Eddington ratios covered by previous surveys of Seyferts conducted by the Atacama Large Millimeter Array (ALMA), allowing us to study the gas feeding and feedback cycle in a combined sample of 19 Seyferts. We used ALMA to obtain new images of the emission of molecular gas and dust using the CO(3-2) and HCO+(4-3) lines as well as their underlying continuum emission at 870 mu m with high spatial resolutions (0.1 ” similar to 7 – 13 pc) in the circumnuclear disks (CND) of ten nearby (D < 28 Mpc) Seyfert galaxies selected from an ultra-hard X-ray survey. Our new ALMA observations detect 870 mu m continuum and CO line emission from spatially resolved disks located around the AGN in all the sources. The bulk of the 870 mu m continuum flux can be accounted for by thermal emission from dust in the majority of the targets. For most of the sources, the disks show a preponderant orientation perpendicular to the AGN wind axes, as expected for dusty molecular tori. The median diameters and molecular gas masses of the tori are similar to 42 pc and similar to 6 x 10(5) M-circle dot, respectively. We also detected the emission of the 4-3 line of HCO+ in four GATOS targets. The order of magnitude differences found in the CO/HCO+ ratios within our combined sample point to a very different density radial stratification inside the dusty molecular tori of these Seyferts. We find a positive correlation between the line-of-sight gas column densities responsible for the absorption of X-rays and the molecular gas column densities derived from CO toward the AGN in our sources. Furthermore, the median values of both column densities are similar. This suggests that the neutral gas line-of-sight column densities of the dusty molecular tori imaged by ALMA significantly contribute to the obscuration of X-rays. The radial distributions of molecular gas in the CND of our combined sample show signs of nuclear-scale molecular gas deficits. We also detect molecular outflows in the sources that show the most extreme nuclear-scale gas deficits in our sample. These observations find for the first time supporting evidence that the imprint of AGN feedback is more extreme in higher luminosity and/or higher Eddington ratio Seyfert galaxies.

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

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2023/12/11

DOI: 10.1051/0004-6361/202348495

Abstract: In this work, we present the detection of twelve doublets with quantum numbers of N = 12-11 to N = 17-16 of the nu(11)(mu(2)Sigma) vibrationally excited state of C6H towards TMC-1. This marks the first time that an excited vibrational state of a molecule has been detected in a cold starless core. The data are part of the QUIJOTE line survey gathered with the Yebes 40m radio telescope. The line intensities have been aptly reproduced with a rotational temperature of 6.2 +/- 0.4 K and a column density of (1.2 +/- 0.2)x10(11) cm(-2). We also analysed the ground state transitions of C6H, detecting fourteen lines with quantum numbers of J = 23/2-21/2 to J = 35/2 for each of the two 2 pi 3/2 and 2 pi 1/2 ladders. It is not possible to model the intensities of all the transitions of the ground state simultaneously using a single column density. We considered the two ladders as two different species and found that the rotational temperature is the same for both ladders, Trot(2 pi 3/2)=Trot(2 pi 1/2)=6.2 +/- 0.2, achieving a result that is comparable to that of the nu 11(2 mu sigma) state. The derived column densities are N(2 pi 3/2) = (6.2 +/- 0.3)x1012 cm-2 and N(2 pi 1/2) = (8.0 +/- 0.4)x1010 cm-2. The fraction of C6H molecules in its 2 pi 3/2, 2 pi 1/2, and nu 11(mu 2 sigma) states is 96.8%, 1.3%, and 1.9%, respectively. Finally, we report that this vibrational mode has also been detected towards the cold cores Lupus-1A and L1495B, as well as the low-mass star forming cores L1527 and L483, with fractions of C6H molecules in this mode of 3.8%, 4.1%, 14.8%, and 6%, respectively.

Authors: Changala, P. Bryan; Chen, Ning L.; Le, Hai L.; Gans, Berenger; Steenbakkers, Kim; Salomon, Thomas; Bonah, Luis; Schroetter, Ilane; Canin, Amelie; Martin-Drumel, Marie-Aline; Jacovella, Ugo; Dartois, Emmanuel; Boye-Peronne, Severine; Alcaraz, Christian; Asvany, Oskar; Brunken, Sandra; Thorwirth, Sven; Schlemmer, Stephan; Goicoechea, Javier R.; Rouille, Gael; Sidhu, Ameek; Chown, Ryan; van de Putte, Dries; Trahin, Boris; Alarcon, Felipe; Berne, Olivier; Habart, Emilie; Peeters, Els

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2023/12/05

DOI: 10.1051/0004-6361/202347765

Abstract: Context. The methyl cation (CH3+) has recently been discovered in the interstellar medium through the detection of 7 mu m (1400 cm(-1)) features toward the d203-506 protoplanetary disk by the JWST. Line-by-line spectroscopic assignments of these features, however, were unsuccessful due to complex intramolecular perturbations preventing a determination of the excitation and abundance of the species in that source. Aims. Comprehensive rovibrational assignments guided by theoretical and experimental laboratory techniques provide insight into the excitation mechanisms and chemistry of CH3+ in d203-506. Methods. The rovibrational structure of CH3+ was studied theoretically by a combination of coupled-cluster electronic structure theory and (quasi-)variational nuclear motion calculations. Two experimental techniques were used to confirm the rovibrational structure of CH3+ : (1) infrared leak-out spectroscopy of the methyl cation, and (2) rotationally resolved photoelectron spectroscopy of the methyl radical (CH3). In (1), CH3+ ions, produced by the electron impact dissociative ionization of methane, were injected into a 22-pole ion trap where they were probed by the pulses of infrared radiation from the FELIX free electron laser. In (2), neutral CH3, produced by CH3NO2 pyrolysis in a molecular beam, was probed by pulsed-field ionization zero-kinetic-energy photoelectron spectroscopy. Results. The quantum chemical calculations performed in this study have enabled a comprehensive spectroscopic assignment of the nu(+)(2) 2 and nu(+)(4) bands of CH3+ detected by the JWST. The resulting spectroscopic constants and derived Einstein A coefficients fully reproduce both the infrared and photoelectron spectra and permit the rotational temperature of CH3+ (T = 660 +/- 80 K) in d203-506 to be derived. A beam-averaged column density of CH3+ in this protoplanetary disk is also estimated.

Authors: Tiwari, M.; Kievit, R.; Kabanovic, S.; Bonne, L.; Falasca, F.; Guevara, C.; Higgins, R.; Justen, M.; Karim, R.; Kavak, U.; Pabst, C.; Pound, M. W.; Schneider, N.; Simon, R.; Stutzki, J.; Wolfire, M.; Tielens, A. G. G. M.

Journal: ASTROPHYSICAL JOURNAL

Publication date: 2023/12/01

DOI: 10.3847/1538-4357/ad003c

Abstract: We explore the potential of the Gaussian mixture model (GMM), an unsupervised machine-learning method, to identify coherent physical structures in the interstellar medium. The implementation we present can be used on any kind of spatially and spectrally resolved data set. We provide a step-by-step guide to use these models on different sources and data sets. Following the guide, we run the models on NGC 1977, RCW 120, and RCW 49 using the [C ii] 158 mu m mapping observations from the SOFIA telescope. We find that the models identified six, four, and five velocity coherent physical structures in NGC 1977, RCW 120, and RCW 49, respectively, which are validated by analyzing the observed spectra toward these structures and by comparison to earlier findings. In this work we demonstrate that GMM is a powerful tool that can better automate the process of spatial and spectral analysis to interpret mapping observations.

Authors: Santa-Maria, M. G.; Goicoechea, J. R.; Pety, J.; Gerin, M.; Orkisz, J. H.; Le Petit, F.; Einig, L.; Palud, P.; Magalhaes, V. de Souza; Beslic, I.; Segal, L.; Bardeau, S.; Bron, E.; Chainais, P.; Chanussot, J.; Gratier, P.; Guzman, V. V.; Hughes, A.; Languignon, D.; Levrier, F.; Lis, D. C.; Liszt, H. S.; Le Bourlot, J.; Oya, Y.; Oberg, K.; Peretto, N.; Roueff, E.; Roueff, A.; Sievers, A.; Thouvenin, P. -A.; Yamamoto, S.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2023/10/30

DOI: 10.1051/0004-6361/202346598

Abstract: Context. Massive stars form within dense clumps inside giant molecular clouds (GMCs). Finding appropriate chemical tracers of the dense gas (n(H-2) > several 10(4) cm(-)3 or A(V) > 8 mag) and linking their line luminosity with the star formation rate is of critical importance. Aims. Our aim is to determine the origin and physical conditions of the HCN-emitting gas and study their relation to those of other molecules. Methods. In the context of the IRAM 30m ORION-B large program, we present 5 deg(2) (similar to 250 pc(2)) HCN, HNC, HCO+, and CO J = 1-0 maps of the Orion B GMC, complemented with existing wide-field [CI] 492 GHz maps, as well as new pointed observations of rotationally excited HCN, HNC, H13CN, and (HNC)-C-13 lines. We compare the observed HCN line intensities with radiative transfer models including line overlap effects and electron excitation. Furthermore, we study the HCN/HNC isomeric abundance ratio with updated photochemical models. Results. We spectroscopically resolve the HCN J = 1-0 hyperfine structure (HFS) components (and partially resolved J = 2-1 and 3-2 components). We detect anomalous HFS line intensity (and line width) ratios almost everywhere in the cloud. About 70% of the total HCN J = 1-0 luminosity, L'(HCN J = 1-0) = 110Kkm s(-1) pc(-2), arises from AV < 8 mag. The HCN/CO J = 1-0 line intensity ratio, widely used as a tracer of the dense gas fraction, shows a bimodal behavior with an inflection point at AV less than or similar to 3 mag typical of translucent gas and illuminated cloud edges. We find that most of the HCN J = 1-0 emission arises from extended gas with n(H-2) less than or similar to 10(4) cm(-3), and even lower density gas if the ionization fraction is chi(e) >= 10(-5) and electron excitation dominates. This result contrasts with the prevailing view of HCN J = 1-0 emission as a tracer of dense gas and explains the low-AV branch of the HCN/CO J =1-0 intensity ratio distribution. Indeed, the highest HCN/CO ratios (similar to 0.1) at A(V) < 3 mag correspond to regions of high [C I] 492 GHz/CO J =1-0 intensity ratios (>1) characteristic of low-density photodissociation regions. The low surface brightness (. 1 Kkm s-1) and extended HCN and HCO+ J = 1-0 emission scale with IFIR – a proxy of the stellar far-ultraviolet (FUV) radiation field – in a similar way. Together with CO J = 1-0, these lines respond to increasing I-FIR up to G(0) similar or equal to 20. On the other hand, the bright HCN J = 1-0 emission (> 6 Kkm s(-1)) from dense gas in star-forming clumps weakly responds to IFIR once the FUV field becomes too intense (G(0) > 1500). In contrast, HNC J = 1-0 and [CI] 492 GHz lines weakly respond to I-FIR for all G(0). The different power law scalings (produced by different chemistries, densities, and line excitation regimes) in a single but spatially resolved GMC resemble the variety of Kennicutt-Schmidt law indexes found in galaxy averages. Conclusions. Given the widespread and extended nature of the [CI] 492 GHz emission, as well as its spatial correlation with that of HCO+, HCN, and (CO)-C-13 J = 1-0 lines (in this order), we argue that the edges of GMCs are porous to FUV radiation from nearby massive stars. Enhanced FUV radiation favors the formation and excitation of HCN on large scales, not only in dense star-forming clumps, and it leads to a relatively low value of the dense gas mass to total luminosity ratio, alpha (HCN) = 29 M-circle dot/(K km s(-1)pc(2)) in Orion B. As a corollary for extragalactic studies, we conclude that high HCN/CO J = 1-0 line intensity ratios do not always imply the presence of dense gas, which may be better traced by HNC than by HCN.

Authors: Palud, Pierre; Einig, Lucas; Le Petit, Franck; Bron, Emeric; Chainais, Pierre; Chanussot, Jocelyn; Pety, Jerome; Thouvenin, Pierre-Antoine; Languignon, David; Beslic, Ivana; Santa-Maria, Miriam G.; Orkisz, Jan H.; Segal, Leontine E.; Zakardjian, Antoine; Bardeau, Sebastien; Gerin, Maryvonne; Goicoechea, Javier R.; Gratier, Pierre; Guzman, Viviana V.; Hughes, Annie; Levrier, Francois; Liszt, Harvey S.; Le Bourlot, Jacques; Roueff, Antoine; Sievers, Albrecht

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2023/10/25

DOI: 10.1051/0004-6361/202347074

Abstract: Context. The interpretation of observations of atomic and molecular tracers in the galactic and extragalactic interstellar medium (ISM) requires comparisons with state-of-the-art astrophysical models to infer some physical conditions. Usually, ISM models are too timeconsuming for such inference procedures, as they call for numerous model evaluations. As a result, they are often replaced by an interpolation of a grid of precomputed models.Aims. We propose a new general method to derive faster, lighter, and more accurate approximations of the model from a grid of precomputed models for use in inference procedures.Methods. These emulators are defined with artificial neural networks (ANNs) with adapted architectures and are fitted using regression strategies instead of interpolation methods. The specificities inherent in ISM models need to be addressed to design and train adequate ANNs. Indeed, such models often predict numerous observables (e.g., line intensities) from just a few input physical parameters and can yield outliers due to numerical instabilities or physical bistabilities and multistabilities. We propose applying five strategies to address these characteristics: (1) an outlier removal procedure; (2) a clustering method that yields homogeneous subsets of lines that are simpler to predict with different ANNs; (3) a dimension reduction technique that enables us to adequately size the network architecture; (4) the physical inputs are augmented with a polynomial transform to ease the learning of nonlinearities; and (5) a dense architecture to ease the learning of simpler relations between line intensities and physical parameters.Results. We compare the proposed ANNs with four standard classes of interpolation methods, nearest-neighbor, linear, spline, and radial basis function (RBF), to emulate a representative ISM numerical model known as the Meudon PDR code. Combinations of the proposed strategies produce networks that outperform all interpolation methods in terms of accuracy by a factor of 2 in terms of the average error (reaching 4.5% on the Meudon PDR code) and a factor of 3 for the worst-case errors (33%). These networks are also 1000 times faster than accurate interpolation methods and require ten to forty times less memory.Conclusions. This work will enable efficient inferences on wide-field multiline observations of the ISM.