Category: NANOCOSMOS

High-resolution Infrared Observations

HighlightsFeaturesDescription
Discovery of molecular species in IRC+10216Diacetylene (C4H2)Major emission arises at 50 AU or less from the star in the dust formation zone. Constraints on chemical models
Distribution of molecular emission in IRC+10216Ethylene (C2H4)Part of the emission arises in the inner dust formation zone contrary to previous findings. Constraints on chemical models
Detection of molecular emission in R LeoCO2 Infrared fluorescence More systematic study of the CO2 emission in O-rich stars to understand how CO2 forms
Major NANOCOSMOS highlights in “High spectral resolution IR observations” (see dedicated descriptions below)

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.

Our IR observations have led to the discovery of diacetylene (C4H2) in the envelope of IRC+10216 with the major emission arising in the dust formation zone at less than 50 AU from the center of the star. Ethylene (C2H4) shows emission from the inner dust formation zone in IRC+10216 contrary to previous findings. These studies pose further constraints on current chemical models.

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, 07/2021)

  • 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
  • More info on diacetylene: Astromolecule of the Month

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 ethylene 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 ethylene 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 in cold molecular clouds 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.

These achievements are based on groundbreaking innovative setups at CSIC and CNRS, e.g. Stardust, AROMA, PIRENEA 2 and cold plasma reactors, that foster the study of complex 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, the interstellar medium (ISM) 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 in CSEs. 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)
  • First detection of a pure PAH (indene) in the TMC-1 cold dark molecular cloud. This is totally an unexpected discovery and suggests an in-situ bottom-up formation process in these environments from smaller molecules in the gas-phase (Yebes 40m radio telescope + new mm receivers).
  • 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).

Yebes 40m broad band receivers

HighlightsFeaturesDescription
IRC+10216: Discovery of molecular speciesHC9N (first time in Space), HC7N, MgC3N and MgC4HFormation in the external layers of the circumstellar envelope
TMC-1: Discovery of molecular species25 molecules, including 1 PAH (indene), 2 hydrocarbon cycles, 3 protonated forms and 2 nitrile anions (15 of them, first time in Space)See dedicated descriptions below
Complementary laboratory experimentsHDCCN, CH3CO+, HC3S+ and HC3O+Laboratory production and full spectroscopical characterization
Table: Major NANOCOSMOS highlights with the “Yebes 40m broad band receivers” (see dedicated descriptions below)

NANOCOSMOS successfully designed and constructed two new millimeter broad band receivers for the Q frequency band (31.5 − 50 GHz) and the W band (72 − 90.5 GHz) for the Yebes 40m radio telescope. One of our main achievements is the instantaneous frequency coverage in order to observe many molecular transitions with single tunings in single-dish mode.

Our Yebes observations have led to the discovery of multiple molecular species. These were made in 2019 (Q2, Q4), and 2020 (Q1) and were complemented with the IRAM 30m radio telescope in Granada (W band).

  • Objects: IRC+10216 as the archetypal AGB carbon rich star and the cold dark Taurus Molecular Cloud -1 or TMC-1.
  • Methodology: observations, laboratory characterization, ab-initio quantum calculations, rotational diagrams, gas-phase chemical models and radiative transfer calculations.

Summary of results with the NANOCOSMOS mm broad band receivers at Yebes 40m radio telescope:

Detection of vibrationally excited HC7N and HC9N in IRC+10216 (J. R. Pardo et al., A&A, 08/2020)

  • HC9N (26 doublets, vib. exc.) – First time detection and characterization in Space
  • HC7N (17 doublets, vib. exc.) – New detection
  • Emission arising from the external layers of the circumstellar envelope
  • Possibe effects on intensity line variations with the stellar phase
  • These vibrationally excited states must be taken into account for precise abundance determinations of long carbon chains
MgCCCN (top) and MgCCCCH (bottom) optimized structures

Discovery of two new magnesium-bearing species in IRC+10216: MgC3N and MgC4H (J. Cernicharo et al., A&A, 10/2019)

  • MgC3N (16 doublets) – New detection
  • MgC4H (6 doublets) – New detection
  • MgCCH (2 doublets) – Confirmation

TMC-1, the starless core sulfur factory: Discovery of NCS, HCCS, H2CCS, H2CCCS, and C4S and detection of C5S (J. Cernicharo et al., A&A, 04/2021)

  • Sulfur-bearing species NCS, HCCS, H2CCS, H2CCCS, and C4S – First time discovery in Space (TMC-1)
  • C5S – First time detection in a cold dark cloud (TMC-1)
  • State-of-the-art gas-phase chemical networks fail to reproduce the observed column densities. Thus, important reactions involving S and S+(neutral-neutral, neutral-ion) and those on dust grain surfaces are missing and much laboratory and theoretical work need be performed in order to understand the chemistry of sulfur
  • The analysis of C4S and C5S shows that S-bearing carbon chains do not follow the smooth decrease in abundance observed in cold dark molecular clouds and circumstellar envelopes for other carbon chains such as cyanopolyynes (HC2n + 1N; a factor 3–5 between members of this molecular species)

Discovery of the propargyl radical (CH2CCH) in TMC-1: One of the most abundant radicals ever found and a key species for cyclization to benzene in cold dark clouds (M. Agúndez et al., A&A, 03/2021)

  • Propargyl radical (CH2CCH) 6 strongest hyperfine components of the 20, 2–10, 1 rotational transition – First time discovery in interstellarr Space (TMC-1)
  • Similar abundance as methyl acetylene. Thus, it is one of the most abundant radicals detected in TMC-1. Moreover, it is probably the most abundant organic radical with a certain chemical complexity ever found in a cold dark cloud
  • The observed high abundance, points out that CH2CCH probably plays a key role in the synthesis of large organic molecules and, in particular, the cyclization towards the first aromatic ring (benzene). This also happens in combustion processes where the CH2CCH radical has a key role in the synthesis of benzene and polycyclic aromatic hydrocarbons (PAHs).

Discovery of allenyl acetylene, H2CCCHCCH, in TMC-1. A study of the isomers of C5H4 (J. Cernicharo et al., A&A, 03/2021)

  • Allenyl Acetylene (H2CCCHCCH) 19 rotational transitions – First time detection in Space (TMC-1)
  • We find that allenyl acetylene and methyl diacetylene are the two most stable C5H4 isomers and both have similar observed abundances in TMC-1
  • State-of-the-art chemical models understimate the observed abundances by an order of magnitude. We need to assess the main formation routes in the chemical models, mainly the reactions of the CCH radical with methyl acetylene (CH3CCH) and allene (H2CCCH2)

Discovery of CH2CHCCH and detection of HCCN, HC4N, CH3CH2CN, and, tentatively, CH3CH2CCH in TMC-1 (J. Cernicharo et al., A&A, 03/2021)

  • Vynil Acetylene (CH2CHCCH) – First time detection in Space (TMC-1)
  • HCCN, HC4N, and CH3CH2CN – First time detection in a cold dark cloud (TMC-1)
  • Ethylene could be a likely precursor of CH2CHCCH and CH2CHCN through reactions with CCH and CN, respectively
  • The reaction between CN and vinyl acetylene is a viable route to the C5H3N isomers recently found in TMC-1 at very low temperatures
  • Our observations show that the cyano methylene radical HCCN and the linear cyano ethynyl-methylene radical HC4N have similar abundances unlike predictions from current chemical models
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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 32 more in the interstellar medium until April 2021. These findings include the detection for the first time in Space of three new pure hydrocarbon cycles: c-C3HCCH (ethynyl cyclopropenylidene), c-C5H6 (cyclopentadiene), and the polycyclic aromatic hydrocarbon (PAH) c-C9H8 (indene). These hydrocarbons could be one of the keystones to elucidate bottom-up mechanisms in the formation of the first aromatic ring in cold molecular clouds, from which large PAHs may grow.

Our discoveries amount 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:

  • Yebes 40 m radio telescope new broad band receivers and complementary observations with the IRAM 30 m radio telescope. Multiple discoveries of molecular species in IRC+10216 and TMC-1. Further contraints on chemical models.
  • High-resolution observations of the inner dust formation zone in IRC+10216 with the ALMA radio interferometer. Our analysis is ongoing.
  • ALMA and IRAM 30m observations of the circumstellar envelopes of AGB stars, cold dark clouds and prestellar cores. These observations include two IRAM molecular surveys of 40 AGB stars. Several discoveries of molecular species in IRC+10216 and in other objects.
  • High spectral resolution Infrared observations of R Leo with the airborne Stratospheric Observatory for Infrared Astronomy (SOFIA), IRC+10216 with the NASA Infrared Telescope Facility (IRTF) and Y CVn with both observatories.

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: Red labels (Yebes 40m); Black (IRAM/ALMA); Green (IRTF/TEXES). 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
c-C3HCCH
c-C5H6
c-C9H8 (PAH)
Table: Red labels (Yebes 40m); Black (IRAM/ALMA). See the internal menu pages for more information on these molecular species. Left image: Taurus Molecular Cloud – credit 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.