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

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 of the singly deuterated isotopolog of H2CCN
  • 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