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).

    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.

    NANOCOSMOS at the recent ALMA / Herschel Archival Workshop (Garching, Germany)

    alma_herschel_low_resFour NANOCOSMOS researchers gave their presentations at the ALMA/Herschel Archival Workshop held in Garching (Germany) at the ESO headquarters in April 15 -17, 2015. José Cernicharo (NANOCOSMOS Corresponding P.I.) talked about the synergies between the ALMA high resolution observations in the innermost zones of star-forming regions, AGB, post-AGBs stars and extragalactic objects and those of Herschel´s archive submillimeter and far-IR observations. Our postdoctoral researchers, Marcelino Agúndez, Guillermo Quintana-Lacaci and Belén Tercero talked about the following topics: Continue reading →

    Gas cell for Laboratory Astrophysics (GACELA)

    The Gas Cell for Laboratory Astrophysics (GACELA) consists of a stainless-steel chamber 1 meter long and a diameter of 60 cm. It is equipped with two teflon windows that allows the study of gases through rotational spectroscopy inside the chamber.

    Hence, the team coupled the new NANOCOSMOS millimeter broad band receivers into the setup. These receivers are twins of those built for the Yebes 40 meter radio telescope. A series of vacuum chamber ports allow the injection of gas and liquids to perform plasma generation, ultraviolet photochemistry and optical spectroscopy. GACELA was built at the Segainvex Laboratories located at the Universidad Autónoma de Madrid.

    Outstanding publications on our experimetal setup:

    1) Broad-band high-resolution rotational spectroscopy for laboratory astrophysics  (J. Cernicharo, J. D. Gallego, J. A. López-Pérez, and 32 co-authors). Astronomy & Astrophysics, 2019 June; 626, A34. Published online 2019, June 7.

    2) Using radio astronomical receivers for molecular spectroscopic characterization in astrochemical laboratory simulations: A proof of concept (I. Tanarro, B. Alemán, P. de Vicente, and 26 co-authors). Astronomy & Astrophysics, 2018 Jan; 609: A15. Published online 2017 Dec 22.

    GACELA addresses an innovative potential to perform novel experiments on plasma physics, photochemistry and ices. We also address the spectroscopical characterization of a gas injected in the cell. Thus, we performed a first set of experiments in February 2018 with the detection of CH3CN in a few seconds with a very high signal-to-noise ratio (S/N). The whole system was further improved and we have made multiple runs in the full-experimental phase from May 2018.

    Check our posts on the GACELA setup

    AROMA set-up

    AROMA (Astrochemistry Research of Organics with Molecular Analyzer) is a new analytical experimental set-up developed at IRAP/LCAR (Toulouse, France). The main purpose of AROMA is the study and identification, with micro-scale resolution, of the molecular content of cosmic dust analogues, including stardust analogues produced in the Stardust machine and meteoritic samples. AROMA combines laser desorption/ionization (LDI) techniques with a linear ion trap coupled to an orthogonal time of flight mass spectrometer (LQIT-oTOF).

    Outstanding publications on our innovative setup

    Molecular content of nascent soot: Family characterization using two-step laser desorption laser ionization mass spectrometry (H. Sabbah, M. Commodo, F. Picca, G. de Falco, P. Minutolo, A. D´Anna and C. Joblin). Proceedings of the Combustion Institute, Volume 38, Issue 1, 2021, Pages 1241-1248.

    Impact of Metals on (Star)Dust Chemistry: A Laboratory Astrophysics Approach (R. Bérard, K. Makasheva, K. Demyk, A. Simon, D. Nuñez-Reyes, F. Mastrorocco, H. Sabbah and C. Joblin). Frontiers in Astronomy and Space Sciences, 2021 March 21. IRAP Press Release: Role des metaux dans la chimie des poussieres detoiles

    Characterization of large carbonaceous molecules in cosmic dust analogues and meteorites (H. Sabbah, M. Carlos and C. Joblin). Proceedings of the International Astronomical Union, 2019 Apr; 15(Suppl 350): 103–106.

    Identification of PAH Isomeric Structure in Cosmic Dust Analogues: the AROMA setup (H. Sabbah, A. Bonnamy, D. Papanastasiou, J. Cernicharo, J.-A. Martín-Gago, and C. Joblin). Astrophysical Journal, 2017 Jul 1; 843(1): 34.

    Check our posts on the AROMA set-up