Examinando por Autor "Caselli, P."

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Restringido
ALMA–IRDC – II. First high-angular resolution measurements of the 14N/15N ratio in a large sample of infrared-dark cloud cores
(Oxford Academics: Oxford University Press, 2021-03-22) Fontani, F.; Barnes, A. T.; Caselli, P.; Henshaw, J. D.; Cosentino, G.; Jiménez Serra, I.; Tan, J. C.; Pineda, J. E.; Law, C. Y.; European Research Council (ERC); Agencia Estatal de Investigación (AEI)
The 14N/15N ratio in molecules exhibits a large variation in star-forming regions, especially when measured from N2H+ isotopologues. However, there are only a few studies performed at high-angular resolution. We present the first interferometric survey of the 14N/15N ratio in N2H+ obtained with Atacama Large Millimeter Array observations towards four infrared-dark clouds harbouring 3 mm continuum cores associated with different physical properties. We detect N15NH+ (1–0) in ∼20−40 per cent of the cores, depending on the host cloud. The 14N/15N values measured towards the millimetre continuum cores range from a minimum of ∼80 up to a maximum of ∼400. The spread of values is narrower than that found in any previous single-dish survey of high-mass star-forming regions and than that obtained using the total power data only. This suggests that the 14N/15N ratio is on average higher in the diffuse gaseous envelope of the cores and stresses the need for high-angular resolution maps to measure correctly the 14N/15N ratio in dense cores embedded in IRDCs. The average 14N/15N ratio of ∼210 is also lower than the interstellar value at the Galactocentric distance of the clouds (∼300–330), although the sensitivity of our observations does not allow us to unveil 14N/15N ratios higher than ∼400. No clear trend is found between the 14N/15N ratio and the core physical properties. We find only a tentative positive trend between 14N/15N and H2 column density. However, firmer conclusions can be drawn only with higher sensitivity measurements.
Restringido
ALMA–IRDC: dense gas mass distribution from cloud to core scales
(Oxford Academics: Oxford University Press, 2021-03-22) Barnes, A. T.; Henshaw, J. D.; Fontani, F.; Pineda, J. E.; Cosentino, G.; Tan, J. C.; Caselli, P.; Jiménez Serra, I.; Law, C. Y.; Avison, A.; Bigiel, F.; Feng, S.; Kong, S.; Longmore, S. N.; Moser, L.; Parker, R. J.; Sánchez Monge, Á.; Wang, K.; European Research Council (ERC); Agencia Estatal de Investigación (AEI); Deutsche Forschungsgemeinschaft (DFG); East Asia Core Observatories Association (EACOA); National Natural Science Foundation of China (NSFC); National Key Research and Development Program of China; Peking University; Avison, A. [0000-0002-2562-8609]
Infrared dark clouds (IRDCs) are potential hosts of the elusive early phases of high mass star formation (HMSF). Here, we conduct an in-depth analysis of the fragmentation properties of a sample of 10 IRDCs, which have been highlighted as some of the best candidates to study HMSF within the Milky Way. To do so, we have obtained a set of large mosaics covering these IRDCs with Atacama Large Millimeter/submillimeter Array (ALMA) at Band 3 (or 3 mm). These observations have a high angular resolution (∼3 arcsec; ∼0.05 pc), and high continuum and spectral line sensitivity (∼0.15 mJy beam−1 and ∼0.2 K per 0.1 km s−1 channel at the N2H+ (1 − 0) transition). From the dust continuum emission, we identify 96 cores ranging from low to high mass (M = 3.4−50.9 M⊙) that are gravitationally bound (αvir = 0.3−1.3) and which would require magnetic field strengths of B = 0.3−1.0 mG to be in virial equilibrium. We combine these results with a homogenized catalogue of literature cores to recover the hierarchical structure within these clouds over four orders of magnitude in spatial scale (0.01–10 pc). Using supplementary observations at an even higher angular resolution, we find that the smallest fragments (<0.02 pc) within this hierarchy do not currently have the mass and/or the density required to form high-mass stars. None the less, the new ALMA observations presented in this paper have facilitated the identification of 19 (6 quiescent and 13 star-forming) cores that retain >16 M⊙ without further fragmentation. These high-mass cores contain trans-sonic non-thermal motions, are kinematically sub-virial, and require moderate magnetic field strengths for support against collapse. The identification of these potential sites of HMSF represents a key step in allowing us to test the predictions from high-mass star and cluster formation theories.
Acceso Abierto
Evolutionary view through the starless cores in Taurus Deuteration in TMC 1-C and TMC 1-CP
(EDP Sciences, 2021-06-15) Navarro Almaida, D.; Fuente, A.; Majumdar, L.; Wakelam, V.; Caselli, P.; Rivière Marichalar, P.; Treviño Morales, S. P.; Cazaux, S.; Jiménez Serra, I.; Kramer, C.; Chacón Tanarro, A.; Kirk, J. M.; Ward Thompson, D.; Tafalla, M.; Centre National D'Etudes Spatiales (CNES); Agencia Estatal de Investigación (AEI); European Research Council (ERC); Navarro Almaida, D. [0000-0002-8499-7447]; Fuente, A. [0000-0001-6317-6343]; Wakelam, V. [0000-0001-9676-2605]; Caselli, P. [0000-0003-1481-7911]; Rivière Marichalar, P. [0000-0003-0969-8137]; Treviño Morales, S. P. [0000-0002-4033-2881]; Ward Thompson, D. [0000-0003-1140-2761]; Jiménez Serra, I. [0000-0003-4493-8714]; Tafalla, M. [0000-0002-2569-1253]
Context. The chemical and physical evolution of starless and pre-stellar cores are of paramount importance to understanding the process of star formation. The Taurus Molecular Cloud cores TMC 1-C and TMC 1-CP share similar initial conditions and provide an excellent opportunity to understand the evolution of the pre-stellar core phase. Aims. We investigated the evolutionary stage of starless cores based on observations towards the prototypical dark cores TMC 1-C and TMC 1-CP. Methods. We mapped the prototypical dark cores TMC 1-C and TMC 1-CP in the CS 3 → 2, C34S 3 → 2, 13CS 2 → 1, DCN 1 → 0, DCN 2 → 1, DNC 1 → 0, DNC 2 → 1, DN13C 1 → 0, DN13C 2 → 1, N2H+ 1 → 0, and N2D+ 1 → 0 transitions. We performed a multi-transitional study of CS and its isotopologs, DCN, and DNC lines to characterize the physical and chemical properties of these cores. We studied their chemistry using the state-of-the-art gas-grain chemical code NAUTILUS and pseudo time-dependent models to determine their evolutionary stage. Results. The central nH volume density, the N2H+ column density, and the abundances of deuterated species are higher in TMC 1-C than in TMC 1-CP, yielding a higher N2H+ deuterium fraction in TMC 1-C, thus indicating a later evolutionary stage for TMC 1-C. The chemical modeling with pseudo time-dependent models and their radiative transfer are in agreement with this statement, allowing us to estimate a collapse timescale of ~1 Myr for TMC 1-C. Models with a younger collapse scenario or a collapse slowed down by a magnetic support are found to more closely reproduce the observations towards TMC 1-CP. Conclusions. Observational diagnostics seem to indicate that TMC 1-C is in a later evolutionary stage than TMC 1-CP, with a chemical age ~1 Myr. TMC 1-C shows signs of being an evolved core at the onset of star formation, while TMC 1-CP appears to be in an earlier evolutionary stage due to a more recent formation or, alternatively, a collapse slowed down by a magnetic support.
Restringido
FAUST I. The hot corino at the heart of the prototypical Class I protostar L1551 IRS5.
(Oxford Academics: Oxford University Press, 2020-07-21) Bianchi, S.; Chandler, C. J.; Ceccarelli, C.; Codella, C.; Sakai, N.; López Sepulcre, A.; Maud, L. T.; Moellenbrock, G.; Svoboda, B.; Watanabe, Y.; Sakai, T.; Ménard, F.; Aikawa, Y.; Alves, F.; Balucani, N.; Bouvier, M.; Caselli, P.; Caux, E.; Charnley, S.; Choudhury, S.; De Simone, M.; Dulieu, F.; Durán, A.; Evans, L.; Favre, C.; Fedele, D.; Feng, S.; Fontani, F.; Francis, L.; Hama, T.; Hanawa, T.; Herbst, E.; Hirota, T.; Imai, M.; Isella, A.; Jiménez Serra, I.; Johnstone, D.; Kahane, C.; Lefloch, B.; Loinard, L.; Maureira, M. J.; Mercimek, S.; Miotello, A.; Mori, S.; Nakatani, R.; Nomura, H.; Oba, Y.; Ohashi, S.; Okoda, Y.; Ospina Zamudio, J.; Oya, Y.; Pineda, J.; Podio, L.; Rimola, A.; Segura Cox, D.; Shirley, Y.; Taquet, V.; Testi, L.; Vastel, C.; Viti, S.; Watanabe, N.; Witzel, A.; Xue, C.; Zhao, B.; Zhang, Y.; Yamamoto, S.; European Research Council (ERC); Japan Society for the Promotion of Science (KAKENHI); Agencia Estatal de Investigación (AEI); Universidad Nacional Autónoma de México (UNAM); Agence Nationale de la Recherche (ANR); Balucani, N. [0000-0001-5121-5683]; De Oliveira Alves, F. [0000-0002-7945-064X]; Hama, T. [0000-0002-4991-4044]; Ohashi, S. [0000-0002-9661-7958]; Johnstone, D. [0000-0002-6773-459X]; Watanabe, Y. [0000-0002-9668-3592]; Ceccarelli, C. [0000-0001-9664-6292]; Pineda, J. [0000-0002-3972-1978]; Fedele, D. [0000-0001-6156-0034]; Mercimek, S. [0000-0002-0742-7934]; Xue, C. [0000-0003-2760-2119]; Sakai, N. [0000-0002-3297-4497]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The study of hot corinos in solar-like protostars has been so far mostly limited to the Class 0 phase, hampering our understanding of their origin and evolution. In addition, recent evidence suggests that planet formation starts already during Class I phase, which therefore represents a crucial step in the future planetary system chemical composition. Hence, the study of hot corinos in Class I protostars has become of paramount importance. Here, we report the discovery of a hot corino towards the prototypical Class I protostar L1551 IRS5, obtained within the ALMA (Atacama Large Millimeter/submillimeter Array) Large Program FAUST (Fifty AU STudy of the chemistry in the disc/envelope system of solar-like protostars). We detected several lines from methanol and its isotopologues (13CH3OH and CH2DOH), methyl formate, and ethanol. Lines are bright towards the north component of the IRS5 binary system, and a possible second hot corino may be associated with the south component. The methanol lines' non-LTE analysis constrains the gas temperature (∼100 K), density (≥1.5 × 108 cm−3), and emitting size (∼10 au in radius). All CH3OH and 13CH3OH lines are optically thick, preventing a reliable measure of the deuteration. The methyl formate and ethanol relative abundances are compatible with those measured in Class 0 hot corinos. Thus, based on this work, little chemical evolution from Class 0 to I hot corinos occurs.
Acceso Abierto
FAUST. II. Discovery of a Secondary Outflow in IRAS 15398−3359: Variability in Outflow Direction during the Earliest Stage of Star Formation?
(The Institute of Physics (IOP), 2021-03-22) Okoda, Y.; Oya, Y.; Francis, L.; Johnstone, D.; Inutsuka, S. I.; Ceccarelli, C.; Codella, C.; Chandler, C. J.; Sakai, N.; Aikawa, Y.; Alves, F.; Balucani, N.; Bianchi, E.; Bouvier, M.; Caselli, P.; Caux, E.; Charnley, S.; Choudhury, S.; De Simone, M.; Dulieu, F.; Durán, A.; Evans, L.; Favre, C.; Fedele, D.; Feng, S.; Fontani, F.; Hama, T.; Hanawa, T.; Herbst, E.; Hirota, T.; Imai, M.; Isella, A.; Jiménez Serra, I.; Kahane, C.; Lefloch, B.; Loinard, L.; López Sepulcre, A.; Maud, L. T.; Maureira, M. J.; Ménard, F.; Mercimek, S.; Miotello, A.; Moellenbrock, G.; Mori, S.; Murillo, Nadia M.; Nakatani, R.; Nomura, H.; Oba, Y.; O´Donoghue, R.; Ohashi, S.; Ospina Zamudio, J.; Pineda, J. E.; Podio, L.; Rimola, A.; Sakai, T.; Segura Cox, D.; Shirley, Y.; Svoboda, B.; Taquet, V.; Testi, L.; Vastel, C.; Viti, S.; Watanabe, N.; Watanabe, Y.; Witzel, A.; Xue, C.; Zhang, Y.; Zhao, B.; Yamamoto, S.; European Research Council (ERC); Agencia Estatal de Investigación (AEI); Japan Society for the Promotion of Science (JSPS); Okoda, Y. [0000-0003-3655-5270]; Oya, Y. [0000-0002-0197-8751]; Francis, L. [0000-0001-8822-6327]; Johnstone, D. [0000-0002-6773-459X]; Inutsuka, S. I. [0000-0003-4366-6518]; Ceccarelli, C. [0000-0001-9664-6292]; Codella, C. [0000-0003-1514-3074]; Chandler, C. [0000-0002-7570-5596]; Sakai, N. [0000-0002-3297-4497]; Aikawa, Y. [0000-0003-3283-6884]; Alves, F. [0000-0002-7945-064X]; Balucani, N. [0000-0001-5121-5683]; Bianchi, E. [0000-0001-9249-7082]; Bouvier, M. [0000-0003-0167-0746]; Caselli, P. [0000-0003-1481-7911]; De Simone, M. [0000-0001-5659-0140]; Feng, S. [0000-0002-4707-8409]; Fontani, F. [0000-0003-0348-3418]; Hama, T. [0000-0002-4991-4044]; Hanawa, T. [0000-0002-7538-581X]; Herbst, E. [0000-0002-4649-2536]; Hirota, T. [0000-0003-1659-095X]; Imai, M. [0000-0002-5342-6262]; Isella, A. [0000-0001-8061-2207]; Jiménez Serra, I. [0000-0003-4493-8714]; Kahane, C. [0000-0003-1691-4686]; Loinard, L. [0000-0002-5635-3345]; López Sepulcre, A. [0000-0002-6729-3640]; Maud, L. T. [0000-0002-7675-3565]; Maureira, M. J. [0000-0002-7026-8163]; Menard, F. [0000-0002-1637-7393]; Miotello, A. [0000-0002-7997-2528]; Moellenbrock, G. [0000-0002-3296-8134]; Oba, Y. [0000-0002-6852-3604]; Ohashi, S. [0000-0002-9661-7958]; Pineda, J. E. [0000-0002-3972-1978]; Rimola, A. [0000-0002-9637-4554]; Sakai, T. [0000-0003-4521-7492]; Segura Cox, D. [0000-0003-3172-6763]; Svoboda, B. [0000-0002-8502-6431]; Taquet, V. [0000-0003-0407-7489]
We have observed the very low-mass Class 0 protostar IRAS 15398−3359 at scales ranging from 50 to 1800 au, as part of the Atacama Large Millimeter/Submillimeter Array Large Program FAUST. We uncover a linear feature, visible in H2CO, SO, and C18O line emission, which extends from the source in a direction almost perpendicular to the known active outflow. Molecular line emission from H2CO, SO, SiO, and CH3OH further reveals an arc-like structure connected to the outer end of the linear feature and separated from the protostar, IRAS 15398−3359, by 1200 au. The arc-like structure is blueshifted with respect to the systemic velocity. A velocity gradient of 1.2 km s−1 over 1200 au along the linear feature seen in the H2CO emission connects the protostar and the arc-like structure kinematically. SO, SiO, and CH3OH are known to trace shocks, and we interpret the arc-like structure as a relic shock region produced by an outflow previously launched by IRAS 15398−3359. The velocity gradient along the linear structure can be explained as relic outflow motion. The origins of the newly observed arc-like structure and extended linear feature are discussed in relation to turbulent motions within the protostellar core and episodic accretion events during the earliest stage of protostellar evolution.
Acceso Abierto
First survey of HCNH+ in high-mass star-forming cloud cores
(EDP Sciences, 2021-07-23) Fontani, F.; Colzi, L.; Redaelli, E.; Sipilä, O.; Caselli, P.; Agencia Estatal de Investigación (AEI); European Commission (EC); Comunidad de Madrid
Context. Most stars in the Galaxy, including the Sun, were born in high-mass star-forming regions. It is hence important to study the chemical processes in these regions to better understand the chemical heritage of the Solar System and most of the stellar systems in the Galaxy. Aims. The molecular ion HCNH+ is thought to be a crucial species in ion-neutral astrochemical reactions, but so far it has been detected only in a handful of star-forming regions, and hence its chemistry is poorly known. Methods. We observed with the IRAM 30 m Telescope 26 high-mass star-forming cores in different evolutionary stages in the J = 3−2 rotational transition of HCNH+. Results. We report the detection of HCNH+ in 16 out of 26 targets. This represents the largest sample of sources detected in this molecular ion to date. The fractional abundances of HCNH+ with respect to H2, [HCNH+], are in the range 0.9−14 × 10−11, and the highest values are found towards cold starless cores, for which [HCNH+] is of the order of 10−10. The abundance ratios [HCNH+]/[HCN] and [HCNH+]/[HCO+] are both ≤0.01 for all objects except for four starless cores, which are well above this threshold. These sources have the lowest gas temperatures and average H2 volume density values in the sample. Based on this observational difference, we ran two chemical models, ‘cold’ and ‘warm’, which attempt to match the average physical properties of the cold(er) starless cores and the warm(er) targets as closely as possible. The reactions occurring in the latter case are investigated in this work for the first time. Our predictions indicate that in the warm model HCNH+ is mainly produced by reactions with HCN and HCO+, while in the cold model the main progenitor species of HCNH+ are HCN+ and HNC+. Conclusions. The observational results indicate, and the model predictions confirm, that the chemistry of HCNH+ is different in cold–early and warm–evolved cores, and the abundance ratios [HCNH+]/[HCN] and [HCNH+]/[HCO+] can be useful astrochemical tools to discriminate between different evolutionary phases in the process of star formation.
Acceso Abierto
Gas phase Elemental abundances in Molecular cloudS (GEMS) II. On the quest for the sulphur reservoir in molecular clouds: the H2S case
(EDP Sciences, 2020-05-12) Navarro Almaida, D.; Le Gal, R.; Fuente, A.; Rivière Marichalar, P.; Wakelam, V.; Cazaux, S.; Caselli, P.; Laas, J. C.; Alonso Albi, T.; Loison, J. C.; Gerin, M.; Kramer, C.; Roueff, E.; Bachiller, R.; Commerçon, B.; Friesen, R.; García Burillo, S.; Goicoechea, J. R.; Giuliano, B. M.; Jiménez Serra, I.; Kirk, J. M.; Lattanzi, V.; Malinen, J.; Marcelino, N.; Martín Doménech, R.; Muñoz Caro, G. M.; Pineda, J.; Tercero, B.; Treviño Morales, S. P.; Roncero, O.; Tafalla, M.; Ward Thompson, D.; European Research Council (ERC); European Commission (EC); Agencia Estatal de Investigación (AEI); Navarro Almaida, D. [0000-0002-8499-7447]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. Sulphur is one of the most abundant elements in the Universe. Surprisingly, sulphuretted molecules are not as abundant as expected in the interstellar medium and the identity of the main sulphur reservoir is still an open question. Aims. Our goal is to investigate the H2S chemistry in dark clouds, as this stable molecule is a potential sulphur reservoir. Methods. Using millimeter observations of CS, SO, H2S, and their isotopologues, we determine the physical conditions and H2S abundances along the cores TMC 1-C, TMC 1-CP, and Barnard 1b. The gas-grain model NAUTILUS is used to model the sulphur chemistry and explore the impact of photo-desorption and chemical desorption on the H2S abundance. Results. Our modeling shows that chemical desorption is the main source of gas-phase H2S in dark cores. The measured H2S abundance can only be fitted if we assume that the chemical desorption rate decreases by more than a factor of 10 when nH > 2 × 104. This change in the desorption rate is consistent with the formation of thick H2O and CO ice mantles on grain surfaces. The observed SO and H2S abundances are in good agreement with our predictions adopting an undepleted value of the sulphur abundance. However, the CS abundance is overestimated by a factor of 5-10. Along the three cores, atomic S is predicted to be the main sulphur reservoir. Conclusions. The gaseous H2S abundance is well reproduced, assuming undepleted sulphur abundance and chemical desorption as the main source of H2S. The behavior of the observed H2S abundance suggests a changing desorption efficiency, which would probe the snowline in these cold cores. Our model, however, highly overestimates the observed gas-phase CS abundance. Given the uncertainty in the sulphur chemistry, we can only conclude that our data are consistent with a cosmic elemental S abundance with an uncertainty of a factor of 10.
Acceso Abierto
Gas phase Elemental abundances in Molecular cloudS (GEMS) III. Unlocking the CS chemistry: the CS+O reaction
(EDP Sciences, 2021-02-02) Bulut, N.; Roncero, O.; Aguado, A.; Loison, J. C.; Navarro Almaida, D.; Wakelam, V.; Fuente, A.; Roueff, E.; Le Gal, R.; Caselli, P.; Gerin, M.; Hickson, K. M.; Spezzano, S.; Riviére Marichalar, P.; Alonso Albi, T.; Bachiller, R.; Jiménez Serra, I.; Kramer, C.; Tercero, B.; Rodríguez Baras, M.; García Burillo, S.; Goicoechea, J. R.; Treviño Morales, S. P.; Esplugues, G.; Cazaux, S.; Commercon, B.; Laas, J. C.; Kirk, J.; Lattanzi, V.; Martín Doménech, R.; Muñoz Caro, G. M.; Pineda, J. E.; Ward Thompson, D.; Tafalla, M.; Marcelino, N.; Malinen, J.; Friesen, R.; Giuliano, B. M.; Agúndez, Marcelino; Hacar, A.; Agencia Estatal de Investigación (AEI); Marcelino, N. [0000-0001-7236-4047]; Roncero, O. [0000-0002-8871-4846]; Pineda, J. [0000-0002-3972-1978]; Agundez, M. [0000-0003-3248-3564]; Tafalla, M. [0000-0002-2569-1253]
Context. Carbon monosulphide (CS) is among the most abundant gas-phase S-bearing molecules in cold dark molecular clouds. It is easily observable with several transitions in the millimeter wavelength range, and has been widely used as a tracer of the gas density in the interstellar medium in our Galaxy and external galaxies. However, chemical models fail to account for the observed CS abundances when assuming the cosmic value for the elemental abundance of sulfur. Aims. The CS+O → CO + S reaction has been proposed as a relevant CS destruction mechanism at low temperatures, and could explain the discrepancy between models and observations. Its reaction rate has been experimentally measured at temperatures of 150−400 K, but the extrapolation to lower temperatures is doubtful. Our goal is to calculate the CS+O reaction rate at temperatures <150 K which are prevailing in the interstellar medium. Methods. We performed ab initio calculations to obtain the three lowest potential energy surfaces (PES) of the CS+O system. These PESs are used to study the reaction dynamics, using several methods (classical, quantum, and semiclassical) to eventually calculate the CS + O thermal reaction rates. In order to check the accuracy of our calculations, we compare the results of our theoretical calculations for T ~ 150−400 K with those obtained in the laboratory. Results. Our detailed theoretical study on the CS+O reaction, which is in agreement with the experimental data obtained at 150–400 K, demonstrates the reliability of our approach. After a careful analysis at lower temperatures, we find that the rate constant at 10 K is negligible, below 10−15 cm3 s−1, which is consistent with the extrapolation of experimental data using the Arrhenius expression. Conclusions. We use the updated chemical network to model the sulfur chemistry in Taurus Molecular Cloud 1 (TMC 1) based on molecular abundances determined from Gas phase Elemental abundances in Molecular CloudS (GEMS) project observations. In our model, we take into account the expected decrease of the cosmic ray ionization rate, ζH2, along the cloud. The abundance of CS is still overestimated when assuming the cosmic value for the sulfur abundance.
Acceso Abierto
Propargylimine in the laboratory and in space: millimetre-wave spectroscopy and its first detection in the ISM
(EDP Sciences, 2020-08-20) Bizzocchi, L.; Prudenzano, D.; Rivilla, V. M.; Pietropolli Charmet, A.; Giuliano, B. M.; Caselli, P.; Martín Pintado, J.; Jiménez Serra, I.; Martín, S.; Requena Torres, M. A.; Rico Villas, F.; Guillemin, J. C.; Centre National D'Etudes Spatiales (CNES); European Research Council (ERC); Agencia Estatal de Investigación (AEI); Rico Villas, F. [0000-0002-5351-3497]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. Small imines containing up to three carbon atoms are present in the interstellar medium (ISM). As alkynyl compounds are abundant in this medium, propargylimine (2-propyn-1-imine, HC ≡C−CH =NH) thus represents a promising candidate for a new interstellar detection. Aims. The goal of the present work is to perform a comprehensive laboratory investigation of the rotational spectrum of propargylimine in its ground vibrational state in order to obtain a highly precise set of rest frequencies and to search for it in space. Methods. The rotational spectra of E and Z geometrical isomers of propargylimine have been recorded in the laboratory in the 83–500 GHz frequency interval. The measurements have been performed using a source-modulation millimetre-wave spectrometer equipped with a pyrolysis system for the production of unstable species. High-level ab initio calculations were performed to assist the analysis and to obtain reliable estimates for an extended set of spectroscopic quantities. We searched for propargylimine at 3 mm and 2 mm in the spectral survey of the quiescent giant molecular cloud G+0.693-0.027 located in the central molecular zone, close to the Galactic centre. Results. About 1000 rotational transitions have been recorded for the E- and Z-propargylimine, in the laboratory. These new data have enabled the determination of a very accurate set of spectroscopic parameters including rotational, quartic, and sextic centrifugal distortion constants. The improved spectral data allowed us to perform a successful search for this new imine in the G+0.693-0.027 molecular cloud. Eighteen lines of Z-propargylimine were detected at level >2.5σ, resulting in a column-density estimate of N = (0.24 ± 0.02) × 1014 cm−2. An upper limit was retrieved for the higher energy E isomer, which was not detected in the data. The fractional abundance (with respect to H2) derived for Z-propargylimine is 1.8 × 10−10. We discuss the possible formation routes by comparing the derived abundance with those measured in the source for possible chemical precursors.
Acceso Abierto
Seeds of Life in Space (SOLIS) VI. Chemical evolution of sulfuretted species along the outflows driven by the low-mass protostellar binary NGC 1333-IRAS4A
(EDP Sciences, 2020-05-15) Taquet, V.; Codella, C.; De Simone, M.; López Sepulcre, A.; Pineda, J. E.; Segura Cox, D.; Ceccarelli, C.; Caselli, P.; Gusdorf, A.; Persson, M. V.; Alves, F.; Caux, E.; Favre, C.; Fontani, F.; Neri, R.; Oya, Y.; Sakai, N.; Vastel, C.; Yamamoto, S.; Bachiller, R.; Balucani, N.; Bianchi, E.; Bizzocchi, L.; Chacón Tanarro, A.; Dulieu, F.; Enrique Romero, J.; Feng, S.; Holdship, J.; Lefloch, B.; Al Edhari, A. J.; Jiménez Serra, I.; Kahane, C.; Lattanzi, V.; Ospina Zamudio, J.; Podio, L.; Punanova, A.; Rimola, A.; Sims, I. R.; Spezzano, S.; Testi, L.; Theulé, P.; Ugliengo, P.; Vasyunin, A. I.; Vazart, F.; Viti, S.; Witzel, A.; Agence Nationale de la Recherche (ANR); European Research Council (ERC); Ceccarelli, C. [0000-0001-9664-6292]; Balucani, N. [0000-0001-5121-5683]; Rimola, A. [0000-0002-9637-4554]; Al Edhari, A. J. [0000-0003-4089-841X]; De Oliveira Alves, F. [0000-0002-7945-064X]; Lefloch, B. [0000-0002-9397-3826]; Persson, M. V. [0000-0002-1100-5734]; Bachiller, R. [0000-0002-5331-5386]; Pineda, J. [0000-0002-3972-1978]; Segura Cox, D. [0000-0003-3172-6763]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. Low-mass protostars drive powerful molecular outflows that can be observed with millimetre and submillimetre telescopes. Various sulfuretted species are known to be bright in shocks and could be used to infer the physical and chemical conditions throughout the observed outflows. Aims. The evolution of sulfur chemistry is studied along the outflows driven by the NGC 1333-IRAS4A protobinary system located in the Perseus cloud to constrain the physical and chemical processes at work in shocks. Methods. We observed various transitions from OCS, CS, SO, and SO2 towards NGC 1333-IRAS4A in the 1.3, 2, and 3 mm bands using the IRAM NOrthern Extended Millimeter Array and we interpreted the observations through the use of the Paris-Durham shock model. Results. The targeted species clearly show different spatial emission along the two outflows driven by IRAS4A. OCS is brighter on small and large scales along the south outflow driven by IRAS4A1, whereas SO2 is detected rather along the outflow driven by IRAS4A2 that is extended along the north east–south west direction. SO is detected at extremely high radial velocity up to + 25 km s−1 relative to the source velocity, clearly allowing us to distinguish the two outflows on small scales. Column density ratio maps estimated from a rotational diagram analysis allowed us to confirm a clear gradient of the OCS/SO2 column density ratio between the IRAS4A1 and IRAS4A2 outflows. Analysis assuming non Local Thermodynamic Equilibrium of four SO2 transitions towards several SiO emission peaks suggests that the observed gas should be associated with densities higher than 105 cm−3 and relatively warm (T > 100 K) temperatures in most cases. Conclusions. The observed chemical differentiation between the two outflows of the IRAS4A system could be explained by a different chemical history. The outflow driven by IRAS4A1 is likely younger and more enriched in species initially formed in interstellar ices, such as OCS, and recently sputtered into the shock gas. In contrast, the longer and likely older outflow triggered by IRAS4A2 is more enriched in species that have a gas phase origin, such as SO2.
Acceso Abierto
Seeds of Life in Space (SOLIS) VII. Discovery of a cold dense methanol blob toward the L1521F VeLLO system.
(EDP Sciences, 2020-04-02) Favre, C.; Vastel, C.; Jiménez Serra, I.; Quénard, D.; Caselli, P.; Ceccarelli, C.; Chacón Tanarro, A.; Fontani, F.; Holdship, J.; Oya, Y.; Punanova, A.; Saki, N.; Spezzano, S.; Yamamoto, S.; Neri, R.; López Sepulcre, A.; Alves, F.; Bachiller, R.; Balucani, N.; Bianchi, E.; Bizzocchi, L.; Codella, C.; Caux, E.; De Simone, M.; Enrique Romero, J.; Dulieu, F.; Feng, S.; Al Edhari, A. J.; Lefloch, B.; Ospina Zamudio, J.; Pineda, J.; Podio, L.; Rimola, A.; Segura Cox, D.; Sims, I. R.; Taquet, V.; Testi, L.; Theulé, P.; Ugliengo, P.; Vasyunin, A. I.; Vazart, F.; Viti, S.; Witzel, A.; Agence Nationale de la Recherche (ANR); Spanish FEDER; Russian Science Foundation (RSF); European Research Council (ERC); Agencia Estatal de Investigación (AEI); Al Edhari, A. J. [0000-0003-4089-841X]; Rimola, A. [0000-0002-9637-4554]; Balucani, N. [0000-0001-5121-5683]; Ceccarelli, C. [0000-0001-9664-6292]; De Oliveira Alves, F. [0000-0002-7945-064X]; Pineda, J. E. [0000-0002-3972-1978]; Segura Cox, D. [0000-0003-3172-6763]; Bachiller, R. [0000-0002-5331-5386]; Fontani, F. [0000-0003-0348-3418]; Sakai, N. [0000-0002-3297-4497]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Aims. The Seeds Of Life In Space IRAM/NOEMA large program aims at studying a set of crucial complex organic molecules in a sample of sources with a well-known physical structure that covers the various phases of solar-type star formation. One representative object of the transition from the prestellar core to the protostar phases has been observed toward the very low luminosity object (VeLLO) L1521F. This type of source is important to study to link prestellar cores and Class 0 sources and also to constrain the chemical evolution during the process of star formation. Methods. Two frequency windows (81.6–82.6 GHz and 96.65–97.65 GHz) were used to observe the emission from several complex organics toward the L1521F VeLLO. These setups cover transitions of ketene (H2CCO), propyne (CH3CCH), formamide (NH2CHO), methoxy (CH3O), methanol (CH3OH), dimethyl ether (CH3OCH3), and methyl formate (HCOOCH3). Results. Only two transitions of methanol (A+, E2) have been detected in the narrow window centered at 96.7 GHz (with an upper limit on E1) in a very compact emission blob (~7′′ corresponding to ~1000 au) toward the northeast of the L1521F protostar. The CS 2–1 transition is also detected within the WideX bandwidth. Consistently with what has been found in prestellar cores, the methanol emission appears ~1000 au away from the dust peak. The location of the methanol blob coincides with one of the filaments that have previously been reported in the literature. The excitation temperature of the gas inferred from methanol is (10 ± 2) K, while the H2 gas density (estimated from the detected CS 2–1 emission and previous CS 5–4 ALMA observations) is a factor >25 higher than the density in the surrounding environment (n(H2) ≥ 107 cm−3). Conclusions. Based on its compactness, low excitation temperature, and high gas density, we suggest that the methanol emission detected with NOEMA is (i) either a cold and dense shock-induced blob that formed recently (≤ a few hundred years) by infalling gas or (ii) a cold and dense fragment that may just have been formed as a result of the intense gas dynamics within the L1521F VeLLO system.
Acceso Abierto
Singly and doubly deuterated formaldehyde in massive star-forming regions
(EDP Sciences, 2021-09-07) Zahorecz, S.; Jiménez Serra, I.; Testi, L.; Immer, K.; Fontani, F.; Caselli, P.; Wang, K.; Onishi, T.; European Research Council (ERC); Agencia Estatal de Investigación (AEI); National Natural Science Foundation of China (NSFC); National Key Research and Development Program of China (NKRDPC); Zahorecz, S. [0000-0001-6149-1278]
Context. Deuterated molecules are good tracers of the evolutionary stage of star-forming cores. During the star formation process, deuterated molecules are expected to be enhanced in cold, dense pre-stellar cores and to deplete after protostellar birth. Aims. In this paper, we study the deuteration fraction of formaldehyde in high-mass star-forming cores at different evolutionary stages to investigate whether the deuteration fraction of formaldehyde can be used as an evolutionary tracer. Methods. Using the APEX SEPIA Band 5 receiver, we extended our pilot study of the J = 3 →2 rotational lines of HDCO and D2CO to eleven high-mass star-forming regions that host objects at different evolutionary stages. High-resolution follow-up observations of eight objects in ALMA Band 6 were performed to reveal the size of the H2CO emission and to give an estimate of the deuteration fractions HDCO/H2CO and D2CO/HDCO at scales of ~6″ (0.04–0.15 pc at the distance of our targets). Results. Our observations show that singly and doubly deuterated H2CO are detected towards high-mass protostellar objects (HMPOs) and ultracompact H II regions (UC H II regions), and the deuteration fraction of H2CO is also found to decrease by an order of magnitude from the earlier HMPO phases to the latest evolutionary stage (UC H II), from ~0.13 to ~0.01. We have not detected HDCO and D2CO emission from the youngest sources (i.e. high-mass starless cores or HMSCs). Conclusions. Our extended study supports the results of the previous pilot study: the deuteration fraction of formaldehyde decreases with the evolutionary stage, but higher sensitivity observations are needed to provide more stringent constraints on the D/H ratio during the HMSC phase. The calculated upper limits for the HMSC sources are high, so the trend between HMSC and HMPO phases cannot be constrained.
Restringido
SiO emission as a probe of cloud–cloud collisions in infrared dark clouds
(Oxford Academics: Oxford University Press, 2020-09-25) Cosentino, R.; Jiménez Serra, I.; Henshaw, J. D.; Caselli, P.; Viti, S.; Barnes, A. T.; Tan, T. C.; Fontani, F.; Wu, B.; European Research Council (ERC); Ministerio de Economía y Competitividad (MINECO); Henshaw, J. [0000-0001-9656-7682]; Fontani, F. [0000-0003-0348-3418]; Barnes, A. [0000-0003-0410-4504]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Infrared dark clouds (IRDCs) are very dense and highly extincted regions that host the initial conditions of star and stellar cluster formation. It is crucial to study the kinematics and molecular content of IRDCs to test their formation mechanism and ultimately characterize these initial conditions. We have obtained high-sensitivity Silicon Monoxide, SiO(2–1), emission maps towards the six IRDCs, G018.82–00.28, G019.27+00.07, G028.53–00.25, G028.67+00.13, G038.95–00.47, and G053.11+00.05 (cloud A, B, D, E, I, and J, respectively), using the 30-m antenna at the Instituto de Radioastronomía Millimétrica (IRAM30m). We have investigated the SiO spatial distribution and kinematic structure across the six clouds to look for signatures of cloud–cloud collision events that may have formed the IRDCs and triggered star formation within them. Towards clouds A, B, D, I, and J, we detect spatially compact SiO emission with broad-line profiles that are spatially coincident with massive cores. Towards the IRDCs A and I, we report an additional SiO component that shows narrow-line profiles and that is widespread across quiescent regions. Finally, we do not detect any significant SiO emission towards cloud E. We suggest that the broad and compact SiO emission detected towards the clouds is likely associated with ongoing star formation activity within the IRDCs. However, the additional narrow and widespread SiO emission detected towards cloud A and I may have originated from the collision between the IRDCs and flows of molecular gas pushed towards the clouds by nearby H II regions.
Acceso Abierto
The Chemical Structure of Young High-mass Star-forming Clumps. II. Parsec-scale CO Depletion and Deuterium Fraction of HCO+
(The Institute of Physics (IOP), 2020-10-01) Feng, S.; Li, D.; Caselli, P.; Du, F.; Lin, Y.; Sipilä, O.; Beuther, H.; Sanhueza, P.; Tatematsu, K.; Liu, Y.; Zhang, Q.; Wang, Y.; Hogge, T.; Jiménez Serra, I.; Lu, X.; Liu, T.; Wang, K.; Zhang, Y.; Zahorecz, S.; Li, G.; Liu, H. B.; Yuan, J.; National Natural Science Foundation of China (NSFC); Max-Planck-Gesellschaft (MPG); European Research Council (ERC); Chinese Academy of Sciences (CAS); Agencia Estatal de Investigación (AEI); Japan Society for the Promotion of Science (JSPS); Feng, S. [0000-0002-4707-8409]; Li, D. [0000-0003-3010-7661]; Caselli, P. [0000-0003-1481-7911]; Du, F. [0000-0002-7489-0179]; Lin, Y. [0000-0001-9299-5479; Sipilä, O. [0000-0002-9148-1625]; Beuther, H. [0000-0002-1700-090X]; Sanhueza, P. [0000-0002-7125-7685]; Tatematsu, K. [0000-0002-8149-8546]; Liu, S. Y. [0000-0003-4603-7119]; Zhang, Q. [0000-0003-2384-6589]; Wang, Y. [0000-0003-2226-4384]; Hogge, T. [0000-0002-7211-7078]; Jiménez Serra, I. [0000-0003-4493-8714]; Lu, X. [0000-0003-2619-9305]; Liu, T. [0000-0002-5286-2564]; Wang, K. [0000-0002-7237-3856]; Zhang, Z. Y. [0000-0002-7299-2876]; Zahorecz, S. [0000-0001-6149-1278]; Li, G. [0000-0003-3144-1952]; Liu, H. B. [0000-0003-2300-2626]; Yuan, J. [0000-0001-8060-3538]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The physical and chemical properties of cold and dense molecular clouds are key to understanding how stars form. Using the IRAM 30 m and NRO 45 m telescopes, we carried out a Multiwavelength line-Imaging survey of the 70 μm-dArk and bright clOuds (MIAO). At a linear resolution of 0.1–0.5 pc, this work presents a detailed study of parsec-scale CO depletion and HCO+ deuterium (D-) fractionation toward four sources (G11.38+0.81, G15.22–0.43, G14.49–0.13, and G34.74–0.12) included in our full sample. In each source with T < 20 K and nH ~ 104–105 cm−3, we compared pairs of neighboring 70 μm bright and dark clumps and found that (1) the H2 column density and dust temperature of each source show strong spatial anticorrelation; (2) the spatial distribution of CO isotopologue lines and dense gas tracers, such as 1–0 lines of H13CO+ and DCO+, are anticorrelated; (3) the abundance ratio between C18O and DCO+ shows a strong correlation with the source temperature; (4) both the C18O depletion factor and D-fraction of HCO+ show a robust decrease from younger clumps to more evolved clumps by a factor of more than 3; and (5) preliminary chemical modeling indicates that chemical ages of our sources are ~8 × 104 yr, which is comparable to their free-fall timescales and smaller than their contraction timescales, indicating that our sources are likely dynamically and chemically young.
Restringido
The Complex Organic Molecular Content in the L1498 Starless Core
(IOP Science Publishing, 2021-08-13) Jiménez Serra, I.; Vasyunin, A. I.; Spezzano, S.; Caselli, P.; Cosentino, G.; Viti, S.; Agencia Estatal de Investigación (AEI); Ministry of Education and Science of the Russian Federation (Minobrnauka); Consejo Superior de Investigaciones Científicas (CSIC); Jiménez Serra, I. [0000-0003-4493-8714]; Vasyunin, A. I. [0000-0003-1684-3355]; Caselli, P. [0000-0003-1481-7911]; Cosentino, G. [0000-0001-5551-9502]; Viti, S. [0000-0001-8504-8844]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Observations carried out toward starless and prestellar cores have revealed that complex organic molecules are prevalent in these objects, but it is unclear what chemical processes are involved in their formation. Recently, it has been shown that complex organics are preferentially produced at an intermediate-density shell within the L1544 prestellar core at radial distances of ∼4000 au with respect to the core center. However, the spatial distribution of complex organics has only been inferred toward this core, and it remains unknown whether these species present a similar behavior in other cores. We report high-sensitivity observations carried out toward two positions in the L1498 starless core, the dust peak and a position located at a distance of ∼11,000 au from the center of the core where the emission of CH3OH peaks. Similarly to L1544, our observations reveal that small O-bearing molecules and N-bearing species are enhanced by factors of ∼4–14 toward the outer shell of L1498. However, unlike L1544, large O-bearing organics such as CH3CHO, CH3OCH3, or CH3OCHO are not detected within our sensitivity limits. For N-bearing organics, these species are more abundant toward the outer shell of the L1498 starless core than toward the one in L1544. We propose that the differences observed between O-bearing and N-bearing species in L1498 and L1544 are due to the different physical structure of these cores, which in turn is a consequence of their evolutionary stage, with L1498 being younger than L1544.