Persona: Rivilla, Victor M.
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Centro de Astrobiologia
El Centro de Astrobiología (CAB) es un centro mixto de investigación en astrobiología, dependiente tanto del Instituto Nacional de Técnica Aeroespacial (INTA) como del Consejo Superior de Investigaciones Científicas (CSIC).
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Rivilla
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Victor M.
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Publicación Acceso Abierto The ionized heart of a molecular disk ALMA observations of the hyper-compact HII region G24.78+0.08 A1(EDP Sciences, 2021-06-21) Moscadelli, L.; Cesaroni, R.; Beltrán, M. T.; Rivilla, Victor M.Context. Hyper-compact (HC) or ultra-compact H II regions are the first manifestations of the radiation feedback from a newly born massive star. Therefore, their study is fundamental to understanding the process of massive (≥8 M⊙) star formation. Aims. We employed Atacama Large Millimeter/submillimeter Array (ALMA) 1.4 mm Cycle 6 observations to investigate at high angular resolution (≈0.′′050, corresponding to 330 au) the HC H II region inside molecular core A1 of the high-mass star-forming cluster G24.78+0.08. Methods. We used the H30α emission and different molecular lines of CH3CN and 13CH3CN to study the kinematics of the ionized and molecular gas, respectively. Results. At the center of the HC H II region, at radii ≲500 au, we observe two mutually perpendicular velocity gradients, which are directed along the axes at PA = 39° and PA = 133°, respectively. The velocity gradient directed along the axis at PA = 39° has an amplitude of 22 km s−1 mpc−1, which is much larger than the other’s, 3 km s−1 mpc−1. We interpret these velocity gradients as rotation around, and expansion along, the axis at PA = 39°. We propose a scenario where the H30α line traces the ionized heart of a disk-jet system that drives the formation of the massive star (≈20 M⊙) responsible for the HC H II region. Such a scenario is also supported by the position-velocity plots of the CH3CN and 13CH3CN lines along the axis at PA = 133°, which are consistent with Keplerian rotation around a 20 M⊙ star. Conclusions. Toward the HC H II region in G24.78+0.08, the coexistence of mass infall (at radii of ~5000 au), an outer molecular disk (from ≲4000 au to ≳500 au), and an inner ionized disk (≲500 au) indicates that the massive ionizing star is still actively accreting from its parental molecular core. To our knowledge, this is the first example of a molecular disk around a high-mass forming star that, while becoming internally ionized after the onset of the H II region, continues to accrete mass onto the ionizing star.Publicación Acceso Abierto The Origin of the E/Z Isomer Ratio of Imines in the Interstellar Medium(IOP Science Publishing, 2021-04-29) García de la Concepción, J.; Jimenez-Serra, Izaskun; Corchado, J. C.; Rivilla, Victor M.; Martín Pintado, J.; Agencia Estatal de Investigación (AEI); Comunidad de Madrid; Junta de Andalucía; García de la Concepción, j. [0000-0001-6484-9546]; Jiménez Serra, I. [0000-0003-4493-8714]; Corchado, J. C. [0000-0002-8463-3168]; Rivilla, V. M. [0000-0002-2887-5859]; Martín Pintado, J. [0000-0003-4561-3508]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737Recent astronomical observations of both isomers E and Z of imines such as cyanomethanimine, ethanimine, and 2-propyn-1-imine have revealed that the abundances in the interstellar medium (ISM) of these isomers differ by factors of ~3–10. Several theories have been proposed to explain the observed behavior, but none of them successfully explains the [E]/[Z] ratios. In this work we present a detailed study of the kinetics of the one-step E-Z isomerization reactions of cyanomethanimine, ethanimine, and 2-propyn-1-imine under interstellar conditions (in the 10–400 K temperature range). This reaction was previously thought to be nonviable in the ISM due to its associated high-energy barrier (about 13,000 K). In this Letter, we show that considering the multidimensional small curvature tunneling approximation, the tunneling effect enables the isomerization even at low temperatures. This is due to the fact that the representative tunneling energy lies in the vibrational ground state of the least stable isomer up to approximately 150 K, making the reaction constants of the isomerization from the least stable to the most stable isomer basically constant. The predicted [E]/[Z] ratios are almost the same as those reported from the astronomical observations for all imines observed. This study demonstrates that the [E]/[Z] ratio of imines in the ISM strongly depends on their relative stability.Publicación Acceso Abierto Thiols in the Interstellar Medium: First Detection of HC(O)SH and Confirmation of C2H5SH(IOP Science Publishing, 2021-04-30) Rodríguez Almeida, L. F.; Jimenez-Serra, Izaskun; Rivilla, Victor M.; Martín Pintado, J.; Zeng, S.; Tercero, B.; De Vicente, P.; Colzi, L.; Rico Villas, F.; Martín, S.; Requena Torres, Miguel Angel; Comunidad de Madrid; Agencia Estatal de Investigación (AEI); European Research Council (ERC); European Commission (EC); Rodríguez Almeida, L. F. [0000-0002-9785-703X]; Jiménez Serra, I. [0000-0003-4493-8714]; Rivilla, V. M. [0000-0002-2887-5859]; Martín Pintado, J. [0000-0003-4561-3508]; Tercero, B. [0000-0002-4782-5259]; Martín, S. [0000-0001-9281-2919]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737The chemical compounds carrying the thiol group (-SH) have been considered essential in recent prebiotic studies regarding the polymerization of amino acids. We have searched for this kind of compound toward the Galactic Center quiescent cloud G+0.693–0.027. We report the first detection in the interstellar space of the trans-isomer of monothioformic acid (t-HC(O)SH) with an abundance of ~1 × 10−10. Additionally, we provide a solid confirmation of the gauche isomer of ethyl mercaptan (g-C2H5SH) with an abundance of ~3 × 10−10, and we also detect methyl mercaptan (CH3SH) with an abundance of ~5 × 10−9. Abundance ratios were calculated for the three SH-bearing species and their OH analogs, revealing similar trends between alcohols and thiols with increasing complexity. Possible chemical routes for the interstellar synthesis of t-HC(O)SH, CH3SH, and C2H5SH are discussed, as well as the relevance of these compounds in the synthesis of prebiotic proteins in the primitive Earth.Publicación Acceso Abierto Cloud–cloud collision as drivers of the chemical complexity in Galactic Centre molecular clouds.(Oxford Academics: Blackwell Publishing, 2020-07-29) Zeng, S.; Zhang, Q.; Jiménez Serra, I.; Tercero, B.; Lu, X.; Martín Pintado, J.; De Vicente, P.; Rivilla, Victor M.; Li, S.; European Research Council (ERC); Agencia Estatal de Investigación (AEI); European Commission (EC); Japan Society for the Promotion of Science (KAKENHI); De Vicente, P. [0000-0002-5902-5005]; Rivilla, V. M. [0000-0002-2887-5859]; Li, S. [0000-0003-1275-5251]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737G+0.693-0.03 is a quiescent molecular cloud located within the Sagittarius B2 (Sgr B2) star-forming complex. Recent spectral surveys have shown that it represents one of the most prolific repositories of complex organic species in the Galaxy. The origin of such chemical complexity, along with the small-scale physical structure and properties of G+0.693-0.03, remains a mystery. In this paper, we report the study of multiple molecules with interferometric observations in combination with single-dish data in G+0.693-0.03. Despite the lack of detection of continuum source, we find small-scale (0.2 pc) structures within this cloud. The analysis of the molecular emission of typical shock tracers such as SiO, HNCO, and CH3OH unveiled two molecular components, peaking at velocities of 57 and 75 km s(-1). They are found to be interconnected in both space and velocity. The position-velocity diagrams show features that match with the observational signatures of a cloud-cloud collision. Additionally, we detect three series of class I methanol masers known to appear in shocked gas, supporting the cloud-cloud collision scenario. From the maser emission we provide constraints on the gas kinetic temperatures (similar to 30-150 K) and H-2 densities (10(4)-10(5) cm(-2)). These properties are similar to those found for the starburst galaxy NGC 253 also using class I methanol masers, suggested to be associated with a cloud-cloud collision. We conclude that shocks driven by the possible cloud-cloud collision is likely the most important mechanism responsible for the high level of chemical complexity observed in G+0.693-0.03.Publicación Acceso Abierto On the Effects of UV Photons/X-Rays on the Chemistry of the Sgr B2 Cloud(The Institute of Physics (IOP), 2020-05-26) Armijos Abendaño, J.; Martín Pintado, J.; López, Ericson; Llerena, M.; Harada, N.; Requena Torres, Miguel Angel; Martín, S.; Rivilla, Victor M.; Riquelme, D.; Aldas, F.; Comisión Nacional de Investigación Científica y Tecnológica (CONICYT); European Research Council (ERC); Armijos Abendaño, J. [0000-0003-3341-6144]; Llerena, M. [0000-0003-1354-4296]; Martín, S. [0000-0001-9281-2919]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737The lines of HOC+, HCO, and CO+ are considered good tracers of photon-dominated regions (PDRs) and X-ray-dominated regions. We study these tracers toward regions of the Sgr B2 cloud selected to be affected by different heating mechanisms. We find the lowest values of the column density ratios of HCO+ versus HOC+, HCO, and CO+ in dense H ii gas, where UV photons dominate the heating and chemistry of the gas. The HOC+, HCO, and CO+ abundances and the above ratios are compared with those of chemical modeling, finding that high-temperature chemistry, a cosmic-ray ionization rate of 10(-16) s(-1), and timescales >10(5.0) yr explain well the HOC+ abundances in quiescent Sgr B2 regions, while shocks are also needed to explain the highest HCO abundances derived for these regions. The CO+ is mainly formed in PDRs, since the highest CO+ abundances of similar to(6-10) x 10(-10) are found in H ii regions with electron densities >540 cm(-3) and CO+ emission is undetected in quiescent gas. Among the ratios, the HCO+/HCO ratio is sensitive to the electron density, as it shows different values in dense and diffuse H ii regions. We compare SiO J = 2-1 emission maps of Sgr B2 with X-ray maps from 2004 and 2012. One known spot shown on the 2012 X-ray map is likely associated with molecular gas at velocities of 15-25 km s(-1). We also derive the X-ray ionization rate of similar to 10(-19) s(-1) for Sgr B2 regions pervaded by X-rays in 2004, which is quite low to affect the chemistry of the molecular gas.Publicación Acceso Abierto Prebiotic Precursors of the Primordial RNA World in Space: Detection of NH2OH(The Institute of Physics (IOP), 2020-08-19) Rivilla, Victor M.; Martín Pintado, J.; Jimenez-Serra, Izaskun; Martín, S.; Rodríguez Almeida, L. F.; Requena Torres, Miguel Angel; Rico Villas, F.; Zeng, S.; Briones, C.; European Research Council (ERC); Agencia Estatal de Investigación (AEI); Comunidad de Madrid; Briones, C. [0000-0003-2213-8353]; Martín Ruiz, S. [0000-0001-9281-2919]; Rico Villas, F. [0000-0002-5351-3497]; Rivilla, V. M. [0000-0002-2887-5859]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737One of the proposed scenarios for the origin of life is the primordial RNA world, which considers that RNA molecules were likely responsible for the storage of genetic information and the catalysis of biochemical reactions in primitive cells, before the advent of proteins and DNA. In the last decade, experiments in the field of prebiotic chemistry have shown that RNA nucleotides can be synthesized from relatively simple molecular precursors, most of which have been found in space. An important exception is hydroxylamine, NH2OH, which, despite several observational attempts, it has not been detected in space yet. Here we present the first detection of NH2OH in the interstellar medium toward the quiescent molecular cloud G+0.693-0.027 located in the Galactic Center. We have targeted the three groups of transitions from the J = 2−1, 3−2, and 4−3 rotational lines, detecting five transitions that are unblended or only slightly blended. The derived molecular abundance of NH2OH is (2.1 ± 0.9) × 10−10. From the comparison of the derived abundance of NH2OH and chemically related species, with those predicted by chemical models and measured in laboratory experiments, we favor the formation of NH2OH in the interstellar medium via hydrogenation of NO on dust grain surfaces, with possibly a contribution of ice-mantle NH3 oxidation processes. Further laboratory studies and quantum chemical calculations are needed to completely rule out the formation of NH2OH in the gas phase.Publicación Acceso Abierto Synthesis and Spectroscopic Characterization of Interstellar Candidate Ethynyl Thiocyanate: HCCSCN(IOP Publishing, 2024-11-14) Alonso, Elena R.; Insausti, Aran; Kolesniková, Lucie; León, Iker; McGuire, Brett A.; Shingledecker, Christopher N.; Agúndez, Marcelino; Cernicharo, José; Rivilla, Victor M.; Cabezas, Carlos; Jimenez-Serra, Izaskun; Martín-Pintado, Jesús; Guillemin, Jean Claude; National Science Foundation (NSF); Junta de Castilla y León; European Commission (EC); El Consejo Superior de Investigaciones Científicas (CSIC); Centre National de la Recherche Scientifique (CNRS); Ministerio de Ciencia e Innovación (MICINN)This work aims to spectroscopically characterize and provide for the first time direct experimental frequencies of the ground vibrational state and two excited states of the simplest alkynyl thiocyanate (HCCSCN) for astrophysical use. Both microwave (8-16 GHz) and millimeter-wave regions (50-120 GHz) of the spectrum have been measured and analyzed in terms of Watson’s semirigid rotor Hamiltonian. A total of 314 transitions were assigned to the ground state of HCCSCN, and a first set of spectroscopic constants have been accurately determined. Spectral features of the molecule were then searched for in Sgr B2(N), NGC 6334I, G+0.693−0.027, and TMC-1 molecular clouds. Upper limits to the column density are provided.Publicación Acceso Abierto Vibrationally excited HC3N emission in NGC 1068: tracing the recent star formation in the starburst ring(Oxford Academics: Oxford University Press, 2021-01-25) Rico Villas, F.; Martín Pintado, J.; González Alfonso, E.; Rivilla, Victor M.; Martín, S.; García Burillo, S.; Jimenez-Serra, Izaskun; Sánchez García, M.; Agencia Estatal de Investigación (AEI); European Research Council (ERC); Rivilla, V. M. [0000-0002-2887-5859]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737Using the ALMA data, we have studied the HC3N and continuum emission in the starburst pseudo-ring (SB pseudo-ring) and the circumnuclear disc (CND) of the SB/active galactic nucleus (AGN) composite galaxy NGC 1068. We have detected emission from vibrationally excited HC3N (HC3N*) only towards one star-forming region of the SB pseudo-ring. Remarkably, HC3N* was not detected towards the CND despite its large HC3N v = 0 column density. From local thermodynamic equilibrium (LTE) and non-LTE modelling of HC3N*, we obtained a dust temperature (Tdust) of ∼250 K and a density (nH2) of 6×105 cm−3 for this star-forming region. The estimated infrared (IR) luminosity of 5.8 × 108 L⊙ is typical of proto-superstar clusters (proto-SSCs) observed in the SB galaxy NGC 253. We use the continuum emissions at 147 and 350 GHz, along with CO and Pa α, to estimate the ages of other 14 SSCs in the SB pseudo-ring. We find the SSCs to be associated with the region connecting the nuclear bar with the SB pseudo-ring, supporting the inflow scenario. For the CND, our analysis yields Tdust ≤ 100 K and nH2∼(3−6)×105 cm−3. The very different dust temperatures found for the CND and the proto-SSC indicate that, while the dust in the proto-SSC is being efficiently heated from the inside by the radiation from massive protostars, the CND is being heated externally by the AGN, which in the IR optically thin case can only heat the dust to 56 K. We discuss the implications of the non-detection of HC3N* near the luminous AGN in NGC 1068 on the interpretation of the HC3N* emission observed in the SB/AGN composite galaxies NGC 4418 and Arp 220.Publicación Acceso Abierto Magnetic field morphology and evolution in the Central Molecular Zone and its effect on gas dynamics(EDP Sciences, 2024-11-22) Tress, Robin; Sormani, Mattia Carlo; Girichidis, P.; Glover, Simon; Klessen, Ralf Stephan; Smith, Rowan; Sobacchi, E.; Armillotta, Lucia; Barnes, A. T.; Battersby, C.; Bogue, Kamran R. J.; Brucy, Noé; Colzi, Laura; Federrath, C.; García, Pablo; Ginsburg, A.; Göller, Junia Aletta Beatrix; Hatchfield, H. P.; Henkel, C.; Hennebelle, P.; Henshaw, J. D.; Hirschmann, M.; Hu, Y.; Kauffmann, J.; Kruijssen, J. M. D.; Lazarian, A.; Lipman, Dani R.; Longmore, S. N.; Morris, Mark; Nogueras Lara, Francisco; Petkova, Maya A.; Pillai, Thushara; Rivilla, Victor M.; Sanchez-Monge, Alvaro; Soler, Juan Diego; Whitworth, David; Zhang, Qizhou; European Research Council (ERC); Royal Society; National Science Foundation (NSF); Consejo Superior de Investigaciones Científicas (CSIC); European Commission (EC); Deutsche Forschungsgemeinschaft (DFG); Ministerio de Ciencia e Innovación (MICINN); Agencia Estatal de Investigación (AEI); Chinese Academy of Science (CAS); Consejo Nacional de Ciencia y Tecnología (CONACyT); Unidad de Excelencia Científica María de Maeztu INSTITUTO DE CIENCIAS DEL ESPACIO, CEX2020-001058-MThe interstellar medium in the Milky Way’s Central Molecular Zone (CMZ) is known to be strongly magnetised, but its large-scale morphology and impact on the gas dynamics are not well understood. We explore the impact and properties of magnetic fields in the CMZ using three-dimensional non-self gravitating magnetohydrodynamical simulations of gas flow in an external Milky Way barred potential. We find that: (1) The magnetic field is conveniently decomposed into a regular time-averaged component and an irregular turbulent component. The regular component aligns well with the velocity vectors of the gas everywhere, including within the bar lanes. (2) The field geometry transitions from parallel to the Galactic plane near ɀ = 0 to poloidal away from the plane. (3) The magneto-rotational instability (MRI) causes an in-plane inflow of matter from the CMZ gas ring towards the central few parsecs of 0.01−0.1 M⊙ yr−1 that is absent in the unmagnetised simulations. However, the magnetic fields have no significant effect on the larger-scale bar-driven inflow that brings the gas from the Galactic disc into the CMZ. (4) A combination of bar inflow and MRI-driven turbulence can sustain a turbulent vertical velocity dispersion of σɀ = 5 km s−1 on scales of 20 pc in the CMZ ring. The MRI alone sustains a velocity dispersion of σɀ ≃ 3 km s−1. Both these numbers are lower than the observed velocity dispersion of gas in the CMZ, suggesting that other processes such as stellar feedback are necessary to explain the observations. (5) Dynamo action driven by differential rotation and the MRI amplifies the magnetic fields in the CMZ ring until they saturate at a value that scales with the average local density as B ≃ 102 (n/103 cm−3)0.33 µG. Finally, we discuss the implications of our results within the observational context in the CMZ.Publicación 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, Victor M.; Sánchez Monge, Álvaro; 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-2017-0737Context. 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.
