Authors: Agundez, M.; Marcelino, N.; Tercero, B.; Cernicharo, J.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2023/09/13

DOI: 10.1051/0004-6361/202347524

Abstract: We report the detection of large hydrocarbon cycles toward several cold dense clouds. We observed four sources (L1495B, Lupus-1A, L483, and L1527) in the Q band (31-50 GHz) using the Yebes 40 m radiotelescope. Using the line stack technique, we find statistically significant evidence of benzonitrile (C6H5CN) in L1495B, Lupus-1A, and L483 at levels of 31.8s, 15.0s, and 17.2s, respectively, while there is no hint of C6H5CN in the fourth source, L1527. The column densities derived are in the range (1.7-3.8) x 10(11) cm-2, which is somewhat below the value derived toward the cold dense cloud TMC-1. When we simultaneously analyze all the benzonitrile abundances derived toward cold clouds in this study and in the literature, a clear trend emerges in that the higher the abundance of HC7N, the more abundant C6H5CN is. This indicates that aromatic cycles are especially favored in those interstellar clouds where long carbon chains are abundant, which suggests that the chemical processes that are responsible for the formation of linear carbon chains are also behind the synthesis of aromatic rings. We also searched for cycles other than benzonitrile, and found evidence of indene (C9H8), cyclopentadiene (C5H6), and 1-cyano cyclopentadiene (1-C5H5CN) at levels of 9.3s, 7.5s, and 8.4s, respectively, toward L1495B, which shows the strongest signal from C6H5CN. The relative abundances between the various cycles detected in L1495B are consistent – within a factor of three – with those previously found in TMC-1. It is therefore likely that not only C(6)H(5)CNbut also other large aromatic cycles are abundant in clouds rich in carbon chains.

Authors: Agundez, M.; Marcelino, N.; Tercero, B.; Jimenez-Serra, I.; Cernicharo, J.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2023/09/13

DOI: 10.1051/0004-6361/202347077

Abstract: We present new observations of molecular anions with the Yebes 40 m and IRAM 30 m telescopes toward the cold, dense clouds TMC-1 CP, Lupus-1A, L1527, L483, L1495B, and L1544. We report the first detections of C3N- and C5N- in Lupus-1A as well as C4H- and C6H- in L483. In addition, we detected new lines of C6H- toward the six targeted sources, of C4H- toward TMC-1 CP, Lupus-1A, and L1527, and of C8H- and C3N- in TMC-1 CP. Excitation calculations using recently computed collision rate coefficients indicate that the lines of anions accessible to radiotelescopes run from subthermally excited to thermalized as the size of the anion increases, with the degree of departure from thermalization depending on the H-2 volume density and the line frequency. We noticed that the collision rate coefficients available for the radical C6H are not sufficient to explain various observational facts, thereby calling for the collision data for this species to be revisited. The observations presented here, together with observational data from the literature, have been used to model the excitation of interstellar anions and to constrain their abundances. In general, the anion-to-neutral ratios derived here agree with the literature values, when available, within 50% (by a factor of two at most), except for the C4H-/C4H ratio, which shows higher differences due to a revision of the dipole moment of C4H. From the set of anion-to-neutral abundance ratios derived two conclusions can be drawn. First, the C6H-/C6H ratio shows a tentative trend whereby it increases with increasing H-2 density, as we would expect on the basis of theoretical grounds. Second, the assertion that the higher the molecular size, the higher the anion-to-neutral ratio is incontestable; furthermore, this supports a formation mechanism based on radiative electron attachment. Nonetheless, the calculated rate coefficients for electron attachment to the medium size species C4H and C3N are probably too high and too low, respectively, by more than one order of magnitude.

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

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2023/09/04

DOI: 10.1051/0004-6361/202346498

Abstract: Continuing Q-band (31-50 GHz) integrations on IRC +10216 with the Yebes 40m telescope have now reached sub-millikelvin noise with hundreds of new lines arising above an average 3 sigma detection limit of 0.71mK (as low as 0.45mK in the lower frequency end). The recent discovery of the C7N- anion and the relatively large abundance of the HC9N member of the cyanopolyyne family opens the door for searching in the data for harmonically related series of lines belonging to singlet species, with intensities close to the detection limit, that could belong to heavier anions. One such series has been found with rotational quantum numbers from J = 52 – 51 up to J = 74 – 73, with at least 15 distinguishable features clearly detected as isolated or partly blended. There are two main candidates for the carriers of the series: C9N- and/or C10H-, for which our high-level-of-theory ab initio calculations predict a quite compatible rotational constant of similar to 300 MHz. In this paper we discuss, based on our ab initio calculations and also on chemical models, which of these two candidates is the most likely carrier. There is more evidence for the C10H- candidate. It would be, to date, the heaviest anion discovered in space through a series of detected individual lines.

Authors: Haworth, Thomas J.; Reiter, Megan; O’Dell, C. Robert; Zeidler, Peter; Berne, Olivier; Manara, Carlo F.; Ballabio, Giulia; Kim, Jinyoung S.; Bally, John; Goicoechea, Javier R.; Aru, Mari-Liis; Gupta, Aashish; Miotello, Anna

Journal: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Publication date: 2023/09/01

DOI: 10.1093/mnras/stad2581

Abstract: We present Very Large Telescope/Multi-Unit Spectroscopic Explorer Narrow Field Mode observations of a pair of disc-bearing young stellar objects towards the Orion Bar: 203-504 and 203-506. Both of these discs are subject to external photoevaporation, where winds are launched from their outer regions due to environmental irradiation. Intriguingly, despite having projected separation from one another of only 1.65 arcsec(660 au at 400 pc), 203-504 has a classic teardrop shaped ‘proplyd’ morphology pointing towards theta(2) Ori A (indicating irradiation by the EUV of that star, rather than theta(1) Ori C) but 203-506 has no ionization front, indicating it is not irradiated by stellar EUV at all. However, 203-506 does sho w [C I ] 8727 angstrom and [O I ] 6300 angstrom in emission, indicating irradiation by stellar FUV. This explicitly demonstrates the importance of FUV irradiation in driving mass loss from discs. We conclude that shielding of 203-506 from EUV is most likely due to its position on the observers side of an ionized layer lying in the foreground of the Huygens Region. We demonstrate that the outflow HH 519, previously thought to be emanating from 203-504 is actually an irradiated cloud edge and identify a new compact outflow from that object approximately along our line of sight with a velocity similar to 130 km s(-1).

Authors: Hashimoto, T.; Alvarez-Marquez, J.; Fudamoto, Y.; Colina, L.; Inoue, A. K.; Nakazato, Y.; Ceverino, D.; Yoshida, N.; Costantin, L.; Sugahara, Y.; Gomez, A. Crespo; Blanco-Prieto, C.; Mawatari, K.; Arribas, S.; Marques-Chaves, R.; Pereira-Santaella, M.; Bakx, T. J. L. C.; Hagimoto, M.; Hashigaya, T.; Matsuo, H.; Tamura, Y.; Usui, M.; Ren, Y. W.

Journal: ASTROPHYSICAL JOURNAL LETTERS

Publication date: 2023/09/01

DOI: 10.3847/2041-8213/acf57c

Abstract: The protoclusters in the epoch of reionization, traced by galaxy overdensity regions, are ideal laboratories for studying the process of stellar assembly and cosmic reionization. We present the spectroscopic confirmation of the core of the most distant protocluster at z = 7.88, A2744-z7p9OD, with the James Webb Space Telescope NIRSpec integral field unit spectroscopy. The core region includes as many as four galaxies detected in [O III] 4960 and 5008 angstrom in a small area of similar to 3 ” x 3 ”, corresponding to similar to 11 x 11 kpc, after the lensing magnification correction. Three member galaxies are also tentatively detected in dust continuum in Atacama Large Millimeter/submillimeter Array Band 6, which is consistent with their red ultraviolet continuum slopes, beta similar to -1.3. The member galaxies have stellar masses in the range of log(M-*/M-circle dot) similar to 7.6-9.2 and star formation rates of similar to 3-50 M-circle dot yr(-1), showing a diversity in their properties. FirstLight cosmological simulations reproduce the physical properties of the member galaxies including the stellar mass, [O III] luminosity, and dust-to-stellar mass ratio, and predict that the member galaxies are on the verge of merging in a few to several tens of Myr to become a large galaxy with M-* similar to 6 x 10(9)M(circle dot). The presence of a multiple merger and evolved galaxies in the core region of A2744-z7p9OD indicates that environmental effects are already at work 650 Myr after the Big Bang.

Authors: Rocha, Carlos M. R.; Roncero, Octavio; Bulut, Niyazi; Zuchowski, Piotr; Navarro-Almaida, David; Fuente, Asuncion; Wakelam, Valentine; Loison, Jean-Christophe; Roueff, Evelyne; Goicoechea, Javier R.; Esplugues, Gisela; Beitia-Antero, Leire; Caselli, Paola; Lattanzi, Valerio; Pineda, Jaime; Le Gal, Romane; Rodriguez-Baras, Marina; Riviere-Marichalar, Pablo

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2023/09/01

DOI: 10.1051/0004-6361/202346967

Abstract: Context. Carbon monosulphide (CS) is among the few sulphur-bearing species that have been widely observed in all environments, including in the most extreme, such as diffuse clouds. Moreover, CS has been widely used as a tracer of the gas density in the interstellar medium in our Galaxy and external galaxies. Therefore, a complete understanding of its chemistry in all environments is of paramount importance for the study of interstellar matter. Aims. Our group is revising the rates of the main formation and destruction mechanisms of CS. In particular, we focus on those involving open-shell species for which the classical capture model might not be sufficiently accurate. In this paper, we revise the rates of reactions CH + S -> CS + H and C-2 + S -> CS + C. These reactions are important CS formation routes in some environments such as dark and diffuse warm gas. Methods. We performed ab initio calculations to characterize the main features of all the electronic states correlating to the open shell reactants. For CH+S, we calculated the full potential energy surfaces (PESs) for the lowest doublet states and the reaction rate constant with a quasi-classical method. For C-2+S, the reaction can only take place through the three lower triplet states, which all present deep insertion wells. A detailed study of the long-range interactions for these triplet states allowed us to apply a statistic adiabatic method to determine the rate constants. Results. Our detailed theoretical study of the CH + S -> CS + H reaction shows that its rate is nearly independent of the temperature in a range of 10-500 K, with an almost constant value of 5.5 x 10(-11) cm(3) s(-1) at temperatures above 100 K. This is a factor of about 2-3 lower than the value obtained with the capture model. The rate of the reaction C-2 + S -> CS + C does depend on the temperature, and takes values close to 2.0 x 10(-10) cm(3) s-(1) at low temperatures, which increase to similar to 5.0 x 10(-10) cm(3) s(-1) for temperatures higher than 200 K. In this case, our detailed modeling – taking into account the electronic and spin states – provides a rate that is higher than the one currently used by factor of approximately 2. Conclusions. These reactions were selected based on their inclusion of open-shell species with many degenerate electronic states, and, unexpectedly, the results obtained in the present detailed calculations provide values that differ by a factor of about 2-3 from the simpler classical capture method. We updated the sulphur network with these new rates and compare our results in the prototypical case of TMC1 (CP). We find a reasonable agreement between model predictions and observations with a sulphur depletion factor of 20 relative to the sulphur cosmic abundance. However, it is not possible to fit the abundances of all sulphur-bearing molecules better than a factor of 10 at the same chemical time.

Authors: Silva, W. G. D. P.; Cernicharo, J.; Schlemmer, S.; Marcelino, N.; Loison, J. -c.; Agundez, M.; Gupta, D.; Wakelam, V.; Thorwirth, S.; Cabezas, C.; Tercero, B.; Domenech, J. L.; Fuentetaja, R.; Kim, W. -j.; de Vicente, P.; Asvany, O.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2023/08/21

DOI: 10.1051/0004-6361/202347174e

Abstract: