Yebes 40m broad band receivers

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

Space and laboratory observation of the deuterated cyanomethyl radical HDCCN (C. Cabezas et al., A&A, 02/2021)

  • HDCCN (forest of lines) – New detection in TMC-1, laboratory production and full spectroscopically characterization
  • Deuteration is driven by deuteron transfer from the H2D+ molecular ion
  • Further constraints on molecular formation pathways and identification of U-lines in molecular surveys

Detection of two C4H3N isomers towards the cold dark cloud TMC-1

A study of C4H3N isomers in TMC-1: line by line detection of HCCCH2CN (N. Marcelino et al., A&A, 02/2021)

  • HCCCH2CN (22 lines) – New detection and confirmation
  • CH2CCHCN (16 lines) – New detection and confirmation
  • The derived abundances suggest a common origin in the formation of the C4H3N isomers: reaction of the CN radical with unsaturated hydrocarbons methyl acetylene and allene

First time detection in Space and laboratory production and characterization of the acetyl cation, CH3CO+

Discovery of the acetyl cation, CH3CO+, in space and in the laboratory (J. Cernicharo et al., A&A, 02/2021)

  • CH3CO+ (8 lines) – First time detection in Space (TMC-1 and other cold dark clouds), laboratory production and characterization of the protonated form of ketene (H2CCO)
  • The derived high abundance of the protonated form of ketene is due to the high proton affinity of the neutral species
  • Further constraints on formation/destruction rates and/or chemical formation routes to CH3CO+
  • The reaction of ketene with H3+ is the most favourable for protonation, from the thermodynamical point of view

Space and laboratory discovery of HC3S+ (J. Cernicharo et al., A&A, 02/2021)

  • HC3S+ (4 lines) – First time detection in Space (TMC-1), laboratory production and characterization of the protonated form of C3S
  • The spectroscopic parameters obtained for HC3S+ from ab initio calculations agree very well with that obtained from observations and in the laboratory
  • Constraint in chemical formation routes: The derived C3S/HC3S+ ratio is well reproduced by a gas-phase chemical model in which HC3S+ is mostly formed through protonation of C3S and the reactions S+ + C3H2 and S + C3H3+

Tentative detection of HC5NH+ in TMC-1 (N. Marcelino et al., A&A, 11/2020)

  • HC5NH+ (7 lines in Q band) – First time detection in Space
  • Existence of additional formation routes at stake: Our pseudo time-dependent gas-phase chemical models of cold dark clouds underestimate the abundance of protonated molecules

Discovery of HC3O+ in space: The chemistry of O-bearing species in TMC-1 (J. Cernicharo et al., A&A, 10/2020)

  • HC3O+ (4 lines) – First time detection in Space and laboratory characterization of the protonated form of C3O
  • The high abundance of the protonated form of C3O, (HC3O+) is due to the high proton affinity of the neutral species
  • Reactions between hydrocarbon ions and atomic oxygen probably participate in the growth of these long O-bearing carbon chains (e.g. c-H2C3O and HCCCHO)
  • Existence of additional formation routes at stake: Our pseudo time-dependent gas-phase chemical models of cold dark clouds underestimate the abundance of protonated molecules

Discovery of HC4NC in TMC-1: A study of the isomers of HC3N, HC5N and HC7N (J. Cernicharo et al., A&A, 10/2020)

  • HC4NC (5 lines, Q band) – First time detection in Space
  • Cold molecular clouds favor the formation of metastable isomers due to their low temperatures.
  • In the ejecta of AGB stars, where the temperature is higher, the presence of high-energy isomers is less favorable because chemical reactions, including isomerization, are expected to favor the most stable isomer. The same pattern is expected for isotopic fractionation

Lines of C3N− observed towards TMC-1 in the 31.0−50.3 GHz frequency range

Interstellar nitrile anions: Detection of C3N_ and C5N_ in TMC-1 (J. Cernicharo et al., A&A, 09/2020)

  • C3N_ (2 lines) – First time detection in the Interstellar Medium
  • C5N_ (6 lines) – First time detection in the Interstellar Medium
  • Derivation of new rotational constants for C5N_
  • Our work definitively excludes metal-bearing species, or vibrationally excited states of other known species, as carriers for the series of lines assigned to C5N_
  • The derived abundance ratios between neutral radicals CnN and their anions are very similar in interstellar and circumstellar environments
  • Further constraints in the formation of CnN− anions through radiative electron attachment to CnN radicals, for which calculated rate constants differ by orders of magnitude

What twirls around this star?

Image credits: Izan Leao (Universidade Federal do Rio Grande do Norte, Brazil).
Image credits: Izan Leao (Universidade Federal do Rio Grande do Norte, Brazil).

A Rotating Spiral Structure Around IRC+10216

Our cosmos is full of star dust, the ashes of stars that died and ejected their matter to the interstellar medium, filling it with dust and gas. When solar like stars consume the hydrogen in their cores, we say that their “main sequence” stage is finished and they begin their final phase. Because IRC+10216 is the high mass-loss star closest to us, it is the best studied evolved star and it seems to keep a secret: it is not alone.

As solar like stars evolve into the Asymptotic Giant Brach (AGB) phase, they eject large amounts of material into the interstellar medium, forming a circumstellar envelope around these objects. Thanks to the Atacama Large Millimeter /submillimeter Array (ALMA) we can now study the innermost regions of the circumstellar envelopes of those evolved stars with unprecedented precision and sensitivity.

IRC +10216 is the best studied evolved carbon-rich star. Located at an estimated distance of 424 light years, this AGB star is the high mass-loss star closest to us. This proximity has allowed the detection of a large number of molecules in its circumstellar envelope. These detections have in turn provided a deep and fruitful study of the chemical processes occurring in the ejected material of this star. The importance of these regions is fundamental since it covers the zone where the dust is formed and accelerated, and the dust grains trigger many chemical reactions.

But, after many studies from different research groups, one question remained unanswered: why was the gas shells irregularly distributed around the central star? In fact, the ejecta around it go from roughly spherical at the large scale, to relatively complex in the innermost regions.

There was a theory to explain the shape of the envelope of this evolved star.

Spiral structure, a companion star?

Understanding the structure of the circumstellar envelope and the molecular gas around this star is fundamental to reveal the chemical processes therein. For example, a clumpy structure may allow the UV radiation coming from the interstellar medium to reach the inner regions of the molecular gas and trigger chemical reactions.

Also the kinematics of these ejecta allows us to study the ejection process from the inner zones and to infer the mechanism involved: the data suggests that the matter released by the ejecta is slowly expanding and rotating.

As gas shells ejected by the evolved star are expected to be spherical, the irregular distribution around it, forming a spiral front, can be explained by the presence of a companion star.

Salts as tracers to confirm the companion star

Astrochemistry uses the data obtained by the different instruments to unveil the role of the different molecules in the chemical processes that take place in the Universe.

For instance, the emission from molecules such as CO and SiS has been found to show the spiral structure of IRC +10216 while that from radicals such as CN or C3H show that the abundance of these molecules is enhanced relatively far from the star. The shape of this distribution fits with the theory of a companion star.

In this work, the metal-bearing molecules were expected to probe the innermost regions of the circumstellar envelope around IRC +10216. The first author, Guillermo Quintana- Lacaci, says “Certain characteristics of the molecules affect to their emission, for instance Sodium Chloride (NaCl) and Potassium Chloride (KCl) provide much better contrast (dynamic range) to see weak structures in regions where other molecules as (Al)-bearing molecules can’t. In particular, NaCl confirms the presence of a face-on spiral extending to the innermost regions of IRC +10216 as well as it shows that this spiral structure is rotating.”

More observations with high angular and spectral resolution would allow the researchers to better constrain the characteristics of the structures detected here, but with this work, the presence of a star orbiting IRC+10216 becomes the explanation that fits the most with the rotating spiral structure seen around it.

 

More information:

The results of this work were published in the paper “HINTS OF A ROTATING SPIRAL STRUCTURE IN THE INNERMOST REGIONS AROUND IRC+10216”, by G. Quintana-Lacaci (Group of Molecular Astrophysics, ICMM, CSIC, Spain); J. Cernicharo (Group of Molecular Astrophysics, ICMM, CSIC, Spain); M. Agúndez (Group of Molecular Astrophysics, ICMM, CSIC, Spain); L. Velilla Prieto (Group of Molecular Astrophysics, ICMM, CSIC; Centro de Astrobiología, INTA-CSIC, Spain); A. Castro-Carrizo (Institut de Radioastronomie Millimétrique, France); N. Marcelino (INAF, Istituto di Radioastronomia, Italy); C. Cabezas (Grupo de Espectroscopía Molecular (GEM), Unidad asociada CSIC, Universidad de Valladolid (UVA), Spain); I. Peña (GEM, Unidad asociada CSIC, UVA, Spain); J. L. Alonso (GEM, Unidad asociada CSIC, UVA, Spain); J. Zúñiga (Dpto. de Química-Física, Faculdad de Química de la Universidad de Murcia, Spain); A. Requena (Dpto. de Química-Física, Faculdad de Química de la Universidad de Murcia, Spain); A. Bastida (Dpto. de Química-Física, Faculdad de Química de la Universidad de Murcia, Spain); Y. Kalugina (LOMC-UMR 6294, CNRS-Université du Havre, France; Department of Optics and Spectroscopy, Tomsk State University, Russia); F. Lique (LOMC-UMR 6294, CNRS-Université du Havre, France); and M. Guélin (Institut de Radioastronomie Millimétrique; LERMA, Observatoire de Paris, PSL Research University, CNRS, France).

High-Resolution Submillimeter Spectroscopy of the Interstellar Medium and Star Forming Regions — From Herschel to ALMA and Beyond (Zakopane, Poland, May 12 – 16, 2015)

copyright © : Subaru Telescope, National Astronomical Observatory of Japan (NAOJ)
copyright © : Subaru Telescope, National Astronomical Observatory of Japan (NAOJ)

Two NANOCOSMOS members, Prof. José Cernicharo and Dr. Javier R. Goicoechea gave two invited talks at this workshop in Poland. José Cernicharo showed the NANOCOSMOS latests results from the ALMA observations of the archetypical AGB carbon-star IRC+10216. The NANOCOSMOS team has published 4 articles (see publications) on these results (including IRAM observations) and new exciting results are expected for the coming months. Javier R. Goicoechea talked about the velocity-resolved [CII] emission and [CII]/FIR mapping along Orion. The [CII] 158μm fine structure line is arising in gas irradiated by UV-photons from the Trapezium cluster and contributes significantly to the cooling of the cold neutral medium. These observations in combination with Far-Infrared photometric images of the dust emission and maps of the H41α hydrogen recombination and CO provide an unprecedented close view (0,16 light-years in resolution) of the Orion Cloud surrounding the Trapezium. Stay tuned¡

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 →