High-resolution Infrared Observations

High spectral resolution infrared observations of circumstellar envelopes – CSEs – in AGB stars are essential to study important molecular species with no permanent dipole moment (e.g. H2, O2, CO2, SiH4, C2H4). This lack makes them undetectable in the millimeter range due to the absence of rotational transitions. Hence, the best possible observation of these molecules is through its vibration–rotation lines in the mid infrared range.

These observations are vital to study the amount of ejected matter in the pulsation phase and determine the chemical interactions between the ejected molecules in the CSEs. These studies help improve the underlying assumptions of currently available chemical models.

Therefore, we observed the carbon-rich star IRC+10216 with the Texas Echelon-cross-Echelle Spectrograph (TEXES) on the 3 m Infrared Telescope Facility (IRTF). We carried out observations of the oxygen rich star R Leo with the Stratospheric Observatory for Infrared Astronomy (SOFIA) with the high spectral resolution Echelon-cross-Echelle Spectrograph (EXES). Finally, we used both SOFIA/EXES and IRTF/TEXES to observe the carbon rich semi-regular star Y CVn.

Summary of oustanding results with the NANOCOSMOS high-resolution infrared observations of CSEs in AGB stars

Multi-frequency high spectral resolution observations of HCN toward the circumstellar envelope of Y CVn (J. P. Fonfría et al., A&A, submitted)

  • Analysis and Identification of 130 lines of HCN and H13CN with either P-Cygni profiles or pure absorption profiles
  • Dust grains could be mostly made of silicon carbide SiC in the inner layers of the CSE (~ 3.5 stellar radii) and of amorphous carbon in the outer envelope (up to 200 stellar radii)
  • The observed mid-IR lines are broader than expected due to possible high velocity matter ejections or photospheric movements related to stellar pulsation or convection.
  • HCN rotational and vibrational temperatures are out of local thermodynamics equilibrium so collisions do not play any role in the gas thermalization


Detection of infrared fluorescence of carbon dioxide in R Leonis with SOFIA/EXES (J. P. Fonfría et al., A&A, 11/2020)

  • CO2 (≃240 emission lines in the range 12.8−14.3 μm) New detection in R Leo
  • The observed CO2 lines can be grouped into three different populations, (warm, hot, and very hot), with approximate temperatures of 550, 1150, and 1600 K
  • The CO2 emitting regions at 1600, 1150, and 550 K are located at 2.2, 3.5, and 10 stellar radii from the center of R Leo
  • We need a systematic study of the CO2 emission in O-rich stars to understand how this molecule forms and the possible dependence of the column density on the mass-loss rate


Carbon Chemistry in IRC+10216: Infrared Detection of Diacetylene (J. P. Fonfría et al., ApJ, 01/2018)

  • C4H2 (24 absorption features in the range 8.0 to 8.1 μm) First detection in IRC+10216
  • The major emission of C4H2 arises in the dust formation zone at radii lower than 20 stellar radii (50 Astronomical Units) from the center of IRC+10216
  • Our photochemical models underestimate the observed C4H2 abundance. This finding could imply that the molecules in the envelope are photodissociated in shells closer to the star than is commonly assumed


The Abundance of C2H4 in the Circumstellar Envelope of IRC+10216 (J. P. Fonfría et al., ApJ, 01/2017)

  • C2H4 (80 ro-vibrational features in absorption) Part of the emission arises in the inner dust formation zone contrary to previous findings
  • Part of the emission of acetylene arises in the dust formation zone at radii between 14 and 28 stellar radii from the center of IRC+10216, with no evidence of C2H4 closer to the star. Previous findings supposed all C2H4 arises in the far outer envelopes.
  • Our photochemical models underestimate the observed C2H4 terminal abundance by a factor of 4. We estimate that a fraction of the acetylene gas-phase could condense onto the dust grains around 20 stellar radii. this fact could affect the chemistry evolution of the envelope

New theoretical grounds in Astrochemistry

For the first time, NANOCOSMOS has attempted to reproduce the complex molecular chemistry and stardust formation in circumstellar envelopes (CSEs) of asymptotic giant branch (AGB) stars and interstellar environments under accurate and realistic laboratory conditions. These conditions differ from previous studies and techniques to produce stardust analogs, mostly based on laser ablation and pyrolysis, flames, and other far related conditions from those in the CSEs of AGB stars.

Hence, we have used our innovative setups at CSIC and CNRS, e.g. Stardust, AROMA, PIRENEA 2 and cold plasma reactors, to study the processes that lead to carbon dust formation including polycyclic aromatic hydrocarbons (PAHs) and fullerenes. We have studied the chemistry of atomic silicon and the formation of silicate dust grains. We have also investigated the aromatic content of two different meteorites, Murchison and Almahata Sitta.

In summary, our synergetic results provide significant and surprising breakthroughs in our current understanding of the chemical processes at play in CSEs and meteoritic samples. These new and open theoretical grounds have also important implications in current chemical models. These NANOCOSMOS breakthroughs are the following:

  • Aliphatic nature of carbonaceous cosmic dust analogs. Our realistic laboratory conditions do not lead to the efficient formation of aromatic molecules (PAHs and fullerenes) in the gas phase, contrary to all previous studies (Stardust, AROMA).
  • Efficient mechanism for the formation of silane and disilane in the gas phase from Si, H, and H2 in the innermost regions of the CSEs around AGB stars (Stardust).
  • Further evidence for the role of metal (iron) seeds to increase not only the formation of metal clusters but also catalyzed hydrocarbon growth in the CSEs of AGB stars (Cold plasma reactors, AROMA, PIRENEA 2 and ESPOIRS).

  • First firm detection of fullerenes in meteorites (Almahata Sitta) and co-existence of carbon clusters along with PAHs in this meteorite (AROMA).

    Discovery of Molecular Species in Space

    NANOCOSMOS has performed a systematic work to identify “unknown” gas-phase species in circumstellar envelopes and interstellar molecular clouds. These species are the carriers of the so-called U-lines or unidentified features. Currently, the team has found more than 1,000 U-lines formed in the photosphere surroundings of the AGB carbon star IRC+10216. We are progressing in the identification of these carriers to complete a spectral catalogue and merge this catalogue into the MADEX radiative transfer code.

    Definitely, NANOCOSMOS is characterizing different dust formation places in Space through the observations of molecular lines. So far, the team has already discovered 10 new molecular species in the inner regions of the envelope of IRC+10216 and 29 more in the interstellar medium until the end of March 2021. This amounts to approximately a 20% of known molecules in Space.

    The team has made a joint effort on the following objects. IRC+10216 is the archetypal AGB carbon rich star, given its proximity ~ 130 pc, and unpaired molecular richness with more than 80 molecular species prior to NANOCOSMOS. R Leo is one of the closest AGB oxygen rich stars, at a distance of ~ 80 pc. Multi-wavelength molecular observations of this star show no detection of CO2 despite predictions from chemical models. Y CVn is a carbon rich semi-regular star at ~ 310 pc from the Earth. Its circumnuclear envelope has not been explored in detail mostly due to the lack of sensitive observations. Finally, the Taurus Molecular Cloud -1 or TMC-1, is a cold dark molecular cloud. It presents an interesting carbon-rich chemistry that leads to the formation of long neutral carbon-chain radicals and their anions, as well as cyanopolyynes, and protonated species of abundant large carbon chains.

    This menu splits our stunning discoveries into the following entries:

    The team is currently submitting new exciting results from the NANOCOSMOS legacy molecular survey of evolved stars with the Yebes 40m radio telescope. Also, we are interpreting new challenging results from ALMA high resolution observations of IRC+10216 that will boost our previous observations of this source. The best for NANOCOSMOS is yet to come!

    IRC+10216: new molecules inventory

    3-atoms4-atoms5-atoms6-atoms7 or more
    Si2CPH3MgC3NSiH3CNSiH3CH3
    CaNCMgCCHC4H2
    NCCPMgC4H
    Table: See the internal menu pages for more ongoing information on these molecular species. Left: figure thanks to Dr. J. P. Fonfría.


    Interstellar Medium: new molecules inventory

    2-atoms3-atoms4-atoms5-atoms6-atoms7 or more
    NS+NCOHCCO HC3O+ CH2CCHHC4NC
    HCSCNCNHDCCNH2CCCSHCCCH2CN
    HSCHCCNH2CCSHC4NCH2CCHCN
    NCSHCCSC4SC5S CH2CHCCH
    C3N_HC3S+CH3CO+HC5NH+
    H2NCO+C5N_H2CCCHCCH
    CH3CH2CN
    Table: See the internal menu pages for more information on these molecular species. Left image: Taurus Molecular Cloudcredit ESO.

    OUTSTANDING RESULTS

    NANOCOSMOS has successfully achieved significative breakthroughs to address the fundamental problem of cosmic dust formation. We have designed and implemented innovative experimental set-ups and analytical tools well beyond the state-of-the-art. Next we describe the design, construction, implementation and commissioning of these innovations in the dedicated links:

    NANOCOSMOS is providing new exciting experimental results in different research fields and challenging theoretical grounds. This menu is devoted to the description and analysis of Outstanding Results and potential new challenges.

    Carbon grains around evolved stars

    The Nanocosmos team published in October 21, 2019, at Nature Astronomy (available free at Europe PubMed Central), the results of a set of laboratory experiments showing that gas-phase chemistry, under conditions similar to those of a red giant star environment, can produce very efficiently small amorphous carbon grains and carbon chains similar to those found in oil.

    Stardust, an ultra-high vacuum machine built in the ERC Nanocosmos project (a Synergy project funded by the European Research Council), was specifically conceived to simulate, with a high level of control, the complex conditions of stardust formation and processing in the environment of evolved stars. In addition, the AROMA setup was built to analyse the molecular content of the samples synthesized by Stardust.

    In the words of José Ángel Martín-Gago (Institute of Materials Science of Madrid, ICMM-CSIC, Spain), responsible for the Stardust instrument, “Mimicking the conditions of the envelope of an evolved star, laboratory experiments allow scientists to follow, step by step, the formation process of dust grains, from atoms to simple molecules and their growth to more complex clusters of molecules.”

    For José Cernicharo (Institute of Fundamental Physics, IFF-CSIC, Spain), lead co-investigator of the project together with Martín-Gago and Christine Joblin (Institut de Recherche en Astrophysique et Planétologie, IRAP-CNRS, France), “That process is important because those grains of dust, which emerge from the final stages of the evolution of medium-sized stars like our Sun will provide the fundamental pieces needed for the birth of the planets and the main ingredients for the onset of life once injected into the interstellar medium.”

    This is why it is essential to develop experiments combining laboratory astrophysics, surface science and astronomical observations to unveil the chemical routes that operate in the inner layers of the envelope of evolved stars.

    The results obtained show the formation of amorphous carbon nanograins and aliphatic carbon clusters with traces of aromatic species and no fullerenes. This shows that the latter species cannot form effectively by gas-phase condensation at these temperatures in the zone of the evolved star where the dust is formed, a region that extends up to a few stellar radii.

    Chemical complexity

    Carbon dust analogues were produced in Stardust and analysed with several characterization techniques including Scanning Tunneling Microscopy and mass spectrometry with the AROMA setup. To produce them only gas carbon atoms and molecular hydrogen were used in a ratio close to that in the atmospheres of AGB stars.

    The results showed two types of products: amorphous carbonaceous nanograins – the most abundant, considered to be the main component of carbonaceous star dust – and aliphatic carbon groups. But almost no aromatic molecules were found in the analysis.

    According to Joblin, “Polycyclic aromatic hydrocarbons (PAHs) are widespread in massive star-forming regions and in carbon-rich protoplanetary and planetary nebulae. Large carbonaceous molecules like buckminsterfullerene C60 have also been detected in some of these environments. But it seems that they need different conditions to be formed”.

    One possible pathway could be through thermal processing of aliphatic material on the surface of dust, which could take place as a result of the significant rise in the temperature of nanograins that occurs in highly UV-irradiated environments. Those results give us new insights into the chemistry of carbonaceous stardust seed formation and foster new observations in order to constrain the physical and chemical conditions in the inner shells of the envelops of evolved stars.

    About the ERC

    The European Research Council, set up by the European Union in 2007, is the premier European funding organisation for excellent frontier research. Every year it selects and funds the very best, creative researchers of any nationality and age to run projects based in Europe. The ERC has three grant schemes for individual principal investigators – Starting Grants, Consolidator Grants, and Advanced Grants – and Synergy Grants for small groups of excellent researchers.

    To date, the ERC has funded more than 9,000 top researchers at various stages of their careers, and over 50,000 postdoctoral fellows, PhD students and other staff working in their research teams. The ERC strives to attract top researchers from anywhere in the world to come to Europe.

    The ERC is led by an independent governing body, the Scientific Council. The ERC current President is Professor Jean-Pierre Bourguignon. The ERC has an annual budget of €2 billion for the year 2019. The overall ERC budget from 2014 to 2020 is more than €13 billion, as part of the Horizon 2020 programme, for which European Commissioner for Research, Innovation and Science Carlos Moedas is currently responsible.

    Elegant and fast: the GACELA is running

    The Gas Cell chamber

    On June 7, 2019, a first paper on the GACELA (GAs CEll for Laboratory Astrophysics) experimental set-up is out at the “Astronomy & Astrophysics” journal (A&A, volume 626, A34, 2019).

    More than 3 years have elapsed since the first designs were envisaged for this set-up. Finally, at the end of 2017, the chamber (see figure above) was delivered and successfully tested against leaks. On the other hand, the GACELA broad-band radio receivers (Q and W bands, 31.5–50 and 72–116.5 GHz, respectively) were successfully commissioned in the second semester of 2017 and interfaced with the GACELA set-up in February 2018. Several experimental runs were performed, showing high quality signal-to-noise ratio spectra of molecular species (CH3CN, CH3OH, CH4/N2, CH4/N2/CH3CN, etc).

    As stated by the authors, GACELA has achieved an important milestone. It is the first time that we can observe the thermal emission of molecules with an instantaneous band width of 20 GHz in Q band and 3 × 20 GHz in W band for Laboratory Astrophysics. These rotational spectroscopy measurements are complemented by mass spectrometry and optical spectroscopy.

    In summary, NANOCOSMOS has developed an elegant and fast-responding set-up, the GACELA, to provide high-resolution and high-sensitivity spectra of molecular species produced in cold plasmas or UV experiments.

    More information:

    This research was presented in the paper “Broad-band high-resolution rotational spectroscopy for laboratory astrophysics“, published in Astronomy and Astrophysics 626, A34 (29pp), 2019 June 7. The authors are: José Cernicharo (Instituto de Física Fundamental, IFF-CSIC), Juan D. Gallego (Centro de Desarrollos Tecnológicos, Observatorio de Yebes, IGN), José A. López-Pérez (CDT, OY, IGN), Félix Tercero (CDT, OY, IGN), Isabel Tanarro (Instituto de Estructura de la Materia, IEM-CSIC), Francisco Beltrán (CDT, OY, IGN), Pablo de Vicente (CDT, OY, IGN), Koen Lauwaet (Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC & IMDEA Nanociencia), Belén Alemán (ICMM-CSIC & IMDEA Materiales), Elena Moreno (IFF-CSIC), Víctor J. Herrero (IEM-CSIC), José L. Doménech (IEM-CSIC), Sandra I. Ramírez (Centro de Investigaciones Químicas, UAEM, Mexico), Celina Bermúdez (IFF-CSIC), Ramón J. Peláez (IEM-CSIC), María Patino-Esteban (CDT, OY, IGN), Isaac López-Fernández (CDT, OY, IGN), Sonia García-Álvaro (CDT, OY, IGN), Pablo García-Carreño (CDT, OY, IGN), Carlos Cabezas (IFF-CSIC), Inmaculada Malo (CDT, OY, IGN), Ricardo Amils (CDT, OY, IGN), Jesús Sobrado (Centro de Astrobiología, INTA-CSIC), Carmen Díez-González (CDT, OY, IGN), José M. Hernández (IFF-CSIC/CDT, OY, IGN), Belén Tercero (CDT, OY, IGN), Gonzalo Santoro (ICMM-CSIC), Lidia Martínez (ICMM-CSIC), Marcelo Castellanos (IFF-CSIC), Beatriz Vaquero-Jiménez (CDT, OY, IGN), Juan R. Pardo (IFF-CSIC), Laura Barbas (CDT, OY, IGN), José A. López-Fernández (CDT, OY, IGN), Beatriz Aja (Universidad de Cantabria), Arnulf Leuther (Fraunhofer Institut fur Angewandte Festkorperphysik, Germany), José A. Martín-Gago (ICMM-CSIC).

    The GACELA experimental set-up is located at the Centro de Desarrollos Tecnológicos, Observatorio de Yebes, thanks to a bilateral agreement between CSIC and IGN for the development of the NANOCOSMOS project.

    Astrochemistry Insights in Science Magazine, by Christine Joblin and José Cernicharo

    Cone Nebula (NGC 2264) Credits: NASA, H. Ford (JHU), G. Illingworth (UCSC/LO), M.Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA.

    Detecting the building blocks of aromatics” is the title of this “Insight” written by Christine Joblin and José Cernicharo (both NANOCOSMOS PIs together with J.A. Martín Gago) and talking about the history and importance of the work published by Brett A. McGuire et al. (“Detection of the aromatic molecule benzonitrile (c-C6H5CN) in the interstellar medium“) in the “Science Magazine” (12/01/2018).

    This is the summary of the article from C. Joblin and J. Cernicharo:

    “Interstellar clouds are sites of active organic chemistry. Many small, gasphase molecules are found in the dark parts of the clouds that are protected from ultraviolet (UV) photons, but these molecules photodissociate in the external layers of the cloud that are exposed to stellar radiation (see the photo). These irradiated regions are populated by large polycyclic aromatic hydrocarbons (PAHs) with characteristic infrared (IR) emission features. These large aromatics are expected to form from benzene (C6H6), which is, however, difficult to detect because it does not have a permanent dipole moment and can only be detected via its IR absorption transitions against a strong background source (2). On page 202 of this issue, McGuire et al. (3) report the detection of benzonitrile (c-C6H5CN) with radio telescopes. Benzonitrile likely forms in the reaction of CN with benzene; from its observation, it is therefore possible to estimate the abundance of benzene itself”.

     

    NANOCOSMOS at the Guillermo Haro School on Molecular Astrophysics (Puebla, Mexico)

    Prof. José Cernicharo has been awarded with the Guillermo Haro Visiting Professorship 2016 at the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE, posterGH16Puebla, Mexico). Following this award, INAOE has organized the Guillermo Haro School on Molecular Astrophysics (October 11 – 21, 2016). Several NANOCOSMOS scientists (Asunción Fuente from CNIG-IGN, Nuria Marcelino, José Pablo Fonfría and Luis Velilla from ICMM-CSIC) will give lectures on the following topics:

    • Molecular Astrophysics, Spectroscopy, Chemistry in the ISM (José Cernicharo)
    • Physical and chemical processes in the ISM, Protoplanetary disks (Asunción Fuente)
    • Observational methods and interpretation (Nuria Marcelino)
    • Molecular excitation and radiative transfer, Circumstellar medium (José Pablo Fonfría)
    • Chemistry in the circumstellar medium, atmospheric  effects and calibration (Luis Velilla)

    José Cernicharo will give a public talk in Puebla downtown on Thursday 13: “Moléculas en el espacio: Astroquímica”.

    NANOCOSMOS on top: Press releases from Nature´s “Compression and ablation of the photo-irradiated molecular cloud the Orion Bar”

    The paper “Compression and ablation of the photo-irradiated molecular cloud the Orion Bar” (Goicoechea et al. 2016) recently published in Nature, has put Astrochemistry and NANOCOSMOS in the leading edge forefront of many research institutIons, newspapers and mass media. A few examples can be found below:

    ESO Picture of the week

    CSIC

    L´Observatoire de Paris

    Institut de Radioastronomie Millimétrique (IRAM)

    Institut de Recherche en Astrophysique et Planétologie (IRAP)

    ALMA news

    El Mundo newspaper

    ABC newspaper

    La Vanguardia newspaper

    El diario newspaper

     

    ECLA 2016 – webpage open

    Ecla2016-1125x510

    The second announcement of the European Conference on Laboratory Astrophysics – “Gas on the Rocks” – ECLA 2016 has been issued today.  This conference will be held at the CSIC headquarters (Madrid, Spain) in November 21 – 25, 2016. The webpage is open with all the relevant information.

    www.ecla2016.com

    More than 30 invited researchers will address new insights on the following science topics:

    • Comets, asteroids, meteorites and the primitive Solar System nebula: formation and evolution
    • Protoplanetary disks and planet formation
    • Planet, Moon, and exoplanet surfaces and atmospheres
    • The signatures of the evolving interstellar medium
    • Dense Clouds: the gas-ice interface and molecular complexity
    • Chemical fingerprints of star formation
    • The late stages of star evolution: dust formation
    • Supernovae and shocks: high-energy processing of matter