Examinando por Autor "Schilke, P."

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Acceso Abierto
Chemical complexity in high-mass star formation An observational and modeling case study of the AFGL 2591 VLA 3 hot core
(EDP Sciences, 2019-11-08) Gieser, C.; Semenov, D.; Beuther, H.; Ahmadi, A.; Mottram, J. C.; Henning, T.; Beltrán, M. T.; Maud, L. T.; Bosco, F.; Leurini, S.; Peters, T.; Klaassen, P. D.; Kuiper, R.; Feng, S.; Urquhart, J. S.; Moscadelli, L.; Csengeri, T.; Lumsden, S.; Winters, J. M.; Suri, S.; Zhang, Q.; Pudritz, R.; Palau, A.; Menten, K. M.; Galván Madrid, R.; Wyrowski, F.; Schilke, P.; Sánchez Monge, A.; Linz, H.; Johnston, K. G.; Jiménez Serra, I.; Longmore, S.; Möller, T.; Deutsche Forschungsgemeinschaft (DFG); Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); European Research Council (ERC); Kuiper, R. [0000-0003-2309-8963]; Sánchez Monge, A. [0000-0002-3078-9482]; Galván Madrid, R. [0000-0003-1480-4643]; Leurini, S. [0000-0003-1014-3390]; Ahmadi, A. [0000-0003-4037-5248]; Semenov, D. [0000-0002-3913-7114]; Gieser, C. [0000-0002-8120-1765]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Aims. In order to understand the observed molecular diversity in high-mass star-forming regions, we have to determine the underlying physical and chemical structure of those regions at high angular resolution and over a range of evolutionary stages. Methods. We present a detailed observational and modeling study of the hot core VLA 3 in the high-mass star-forming region AFGL 2591, which is a target region of the NOrthern Extended Millimeter Array (NOEMA) large program CORE. Using NOEMA observations at 1.37 mm with an angular resolution of ~0″. 42 (1400 au at 3.33 kpc), we derived the physical and chemical structure of the source. We modeled the observed molecular abundances with the chemical evolution code MUSCLE (MUlti Stage ChemicaL codE). Results. With the kinetic temperature tracers CH3CN and H2CO we observe a temperature distribution with a power-law index of q = 0.41 ± 0.08. Using the visibilities of the continuum emission we derive a density structure with a power-law index of p = 1.7 ± 0.1. The hot core spectra reveal high molecular abundances and a rich diversity in complex molecules. The majority of the molecules have an asymmetric spatial distribution around the forming protostar(s), which indicates a complex physical structure on scales <1400 au. Using MUSCLE, we are able to explain the observed molecular abundance of 10 out of 14 modeled species at an estimated hot core chemical age of ~21 100 yr. In contrast to the observational analysis, our chemical modeling predicts a lower density power-law index of p < 1.4. Reasons for this discrepancy are discussed. Conclusions. Combining high spatial resolution observations with detailed chemical modeling allows us to derive a concise picture of the physical and chemical structure of the famous AFGL 2591 hot core. The next steps are to conduct a similar analysis for the whole CORE sample, and then use this analysis to constrain the chemical diversity in high-mass star formation to a much greater depth.
Acceso Abierto
Fragmentation in the massive G31.41+0.31 protocluster
(EDP Sciences, 2021-04-20) Beltrán, M. T.; Rivilla, V. M.; Cesaroni, R.; Maud, L. T.; Galli, D.; Moscadelli, L.; Lorenzani, A.; Ahmadi, A.; Beuther, H.; Csengeri, T.; Etoka, S.; Goddi, C.; Klaassen, P. D.; Kuiper, R.; Kumar, M. S. N.; Peters, T.; Sánchez Monge, Á.; Schilke, P.; Van der Tak, F.; Vig, S.; Zinnecker, H.; Comunidad de Madrid; Deutsche Forschungsgemeinschaft (DFG); European Research Council (ERC); Fundacao para a Ciencia e a Tecnologia (FCT)
Context. ALMA observations at 1.4 mm and ~0.′′2 (~750 au) angular resolution of the Main core in the high-mass star-forming region G31.41+0.31 have revealed a puzzling scenario. On the one hand, the continuum emission looks very homogeneous and the core appears to undergo solid-body rotation, suggesting a monolithic core stabilized by the magnetic field; on the other hand, rotation and infall speed up toward the core center, where two massive embedded free-free continuum sources have been detected, pointing to an unstable core having undergone fragmentation. Aims. To establish whether the Main core is indeed monolithic or if its homogeneous appearance is due to a combination of large dust opacity and low angular resolution, we carried out millimeter observations at higher angular resolution and different wavelengths. Methods. We carried out ALMA observations at 1.4 mm and 3.5 mm that achieved angular resolutions of ~0.′′1 (~375 au) and ~0.′′075 (~280 au), respectively. VLA observations at 7 mm and 1.3 cm at even higher angular resolution, ~0.′′05 (~190 au) and ~0.′′07 (~260 au), respectively, were also carried out to better study the nature of the free-free continuum sources detected in the core. Results. The millimeter continuum emission of the Main core has been clearly resolved into at least four sources, A, B, C, and D, within 1″, indicating that the core is not monolithic. The deconvolved radii of the dust emission of the sources, estimated at 3.5 mm, are ~400–500 au; their masses range from ~15 to ~26 M⊙; and their number densities are several 109 cm−3. Sources A and B, located closer to the center of the core and separated by ~750 au, are clearly associated with two free-free continuum sources, likely thermal radio jets, and are brightest in the core. The spectral energy distribution of these two sources and their masses and sizes are similar and suggest a common origin. Source C has not been detected at centimeter wavelengths, while source D has been clearly detected at 1.3 cm. Source D is likely the driving source of an E–W SiO outflow previously detected in the region, which suggests that the free-free emission might be coming from a radio jet. Conclusions. The observations have confirmed that the Main core in G31 is collapsing, that it has undergone fragmentation, and that its homogeneous appearance previously observed at short wavelengths is a consequence of both high dust opacity and insufficient angular resolution. The low level of fragmentation together with the fact that the core is moderately magnetically supercritical, suggests that G31 could have undergone a phase of magnetically regulated evolution characterized by a reduced fragmentation efficiency, eventually leading to the formation of a small number of relatively massive dense cores.
Acceso Abierto
The GUAPOS project: G31.41+0.31 Unbiased ALMA sPectral Observational Survey I. Isomers of C2H4O2
(EDP Sciences, 2020-12-02) Mininni, C.; Beltrán, M. T.; Rivilla, V. M.; Sánchez Monge, A.; Fontani, F.; Möller, T.; Cesaroni, R.; Schilke, P.; Viti, S.; Jiménez Serra, I.; Colzi, L.; Lorenzani, A.; Testi, L.; Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR); Agencia Estatal de Investigación (AEI); European Research Council (ERC); Mininni, C. [0000-0002-2974-4703]; Beltrán Sorolla, M. T. [0000-0003-3315-5626]; Rivilla, V. M. [0000-0002-2887-5859]; Sánchez Monge, A. [0000-0002-3078-9482]; Fontani, F. [0000-0003-0348-3418]; Möller, T. [0000-0002-9277-8025]; Cesaroni, R. [0000-0002-2430-5103]; Schilke, P. [0000-0003-2141-5689]; Viti, S. [0000-0001-8504-8844]; Jiménez Serra, I. [0000-0003-4493-8714]; Colzi, L. [0000-0001-8064-6394]; Lorenzani, A. [0000-0002-4685-3434]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. One of the goals of astrochemistry is to understand the degree of chemical complexity that can be reached in star-forming regions, along with the identification of precursors of the building blocks of life in the interstellar medium. To answer such questions, unbiased spectral surveys with large bandwidth and high spectral resolution are needed, in particular, to resolve line blending in chemically rich sources and identify each molecule (especially for complex organic molecules). These kinds of observations have already been successfully carried out, primarily towards the Galactic Center, a region that shows peculiar environmental conditions. Aims. We present an unbiased spectral survey of one of the most chemically rich hot molecular cores located outside the Galactic Center, in the high-mass star-forming region G31.41+0.31. The aim of this 3mm spectral survey is to identify and characterize the physical parameters of the gas emission in different molecular species, focusing on complex organic molecules. In this first paper, we present the survey and discuss the detection and relative abundances of the three isomers of C2H4O2: methyl formate, glycolaldehyde, and acetic acid. Methods. Observations were carried out with the ALMA interferometer, covering all of band 3 from 84 to 116 GHz (~32 GHz bandwidth) with an angular resolution of 1.2′′ × 1.2′′ (~ 4400 au × 4400 au) and a spectral resolution of ~0.488 MHz (~1.3−1.7 km s−1). The transitions of the three molecules have been analyzed with the software XCLASS to determine the physical parameters of the emitted gas. Results. All three isomers were detected with abundances of (2 ± 0.6) × 10−7, (4.3−8) × 10−8, and (5.0 ± 1.4) × 10−9 for methyl formate, acetic acid, and glycolaldehyde, respectively. Methyl formate and acetic acid abundances are the highest detected up to now, if compared to sources in the literature. The size of the emission varies among the three isomers with acetic acid showing the most compact emission while methyl formate exhibits the most extended emission. Different chemical pathways, involving both grain-surface chemistry and cold or hot gas-phase reactions, have been proposed for the formation of these molecules, but the small number of detections, especially of acetic acid and glycolaldehyde, have made it very difficult to confirm or discard the predictions of the models. The comparison with chemical models in literature suggests the necessity of grain-surface routes for the formation of methyl formate in G31, while for glycolaldehyde both scenarios could be feasible. The proposed grain-surface reaction for acetic acid is not capable of reproducing the observed abundance in this work, while the gas-phase scenario should be further tested, given the large uncertainties involved.