Yebes 40m broad band receivers

Highlights	Features	Description
*IRC+10216: Discovery of molecular species*	HC₉N (first time in Space), HC₇N, MgC₃N and MgC₄H	Formation in the external layers of the circumstellar envelope
*TMC-1: Discovery of molecular species*	25 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 experiments	HDCCN, 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

Full spectroscopic characterization in Space
Formation in the outer layers of IRC circumstellar envelope, as occurs for MgNC and other polyatomic metal-cyanides
Press release: Madri+d; Other links: Astromolecule of the Month (MgC₃N); Astromolecule of the Month (MgC₄H);

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 (HC_2n + 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 2_0, 2–1_0, 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

Pages: 1 2