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Amino acids are essential for the synthesis of protein. Amino acids contain both amine (R–NH2) and carboxylic acid (R–COOH) functional groups, which help to understand the possible formation mechanism of life in the universe. Among the 20 types of amino acids, glycine (NH2CH2COOH) is known as the simplest non-essential amino acid. In the last 40 years, all surveys of NH2CH2COOH in the interstellar medium, especially in the star-formation regions, have failed at the millimetre and sub-millimetre wavelengths. We aimed to identify the possible precursors of NH2CH2COOH, because it is highly challenging to identify NH2CH2COOH in the interstellar medium. Many laboratory experiments have suggested that methylenimine (CH2NH) plays a key role as a possible precursor of NH2CH2COOH in the star-formation regions via the Strecker synthesis reaction. After spectral analysis using the local thermodynamic equilibrium (LTE) model, we successfully identified the rotational emission lines of CH2NH towards the hot molecular core G10.47+0.03 using the Atacama Compact Array (ACA). The estimated column density of CH2NH towards G10.47+0.03 is (3.40 ± 0.2) × 1015 cm−2 with a rotational temperature of 218.70 ± 20 K, which is estimated from the rotational diagram. The fractional abundance of CH2NH with respect to H2 towards G10.47+0.03 is 2.61 × 10−8. We found that the derived abundance of CH2NH agree fairly well with the existing two-phase warm-up chemical modelling abundance value of CH2NH. We discuss the possible formation pathways of CH2NH within the context of hot molecular cores, and we find that CH2NH is likely mainly formed via neutral–neutral gas-phase reactions of CH3 and NH radicals towards G10.47+0.03.
Amino acids are essential for the synthesis of protein. Amino acids contain both amine (R–NH2) and carboxylic acid (R–COOH) functional groups, which help to understand the possible formation mechanism of life in the universe. Among the 20 types of amino acids, glycine (NH2CH2COOH) is known as the simplest non-essential amino acid. In the last 40 years, all surveys of NH2CH2COOH in the interstellar medium, especially in the star-formation regions, have failed at the millimetre and sub-millimetre wavelengths. We aimed to identify the possible precursors of NH2CH2COOH, because it is highly challenging to identify NH2CH2COOH in the interstellar medium. Many laboratory experiments have suggested that methylenimine (CH2NH) plays a key role as a possible precursor of NH2CH2COOH in the star-formation regions via the Strecker synthesis reaction. After spectral analysis using the local thermodynamic equilibrium (LTE) model, we successfully identified the rotational emission lines of CH2NH towards the hot molecular core G10.47+0.03 using the Atacama Compact Array (ACA). The estimated column density of CH2NH towards G10.47+0.03 is (3.40 ± 0.2) × 1015 cm−2 with a rotational temperature of 218.70 ± 20 K, which is estimated from the rotational diagram. The fractional abundance of CH2NH with respect to H2 towards G10.47+0.03 is 2.61 × 10−8. We found that the derived abundance of CH2NH agree fairly well with the existing two-phase warm-up chemical modelling abundance value of CH2NH. We discuss the possible formation pathways of CH2NH within the context of hot molecular cores, and we find that CH2NH is likely mainly formed via neutral–neutral gas-phase reactions of CH3 and NH radicals towards G10.47+0.03.
In the star formation regions, the complex organic molecules that contain peptide bonds (–NH–C(=O)–) play a major role in the metabolic process because –NH–C(=O)– is connected to amino acids (R-CHNH2–COOH). Over the past few decades, many complex organic molecules containing peptide-like bonds have been detected in hot molecular cores, hot corinos, and cold molecular clouds, however, their prebiotic chemistry is poorly understood. We present the first detection of the rotational emission lines of formamide (NH2CHO) and isocyanic acid (HNCO), which contain peptide-like bonds towards the chemically rich hot molecular core G358.93–0.03 MM1, using high-resolution and high-sensitivity Atacama Large Millimeter/submillimeter Array (ALMA) bands 6 and 7. We estimate that the column densities of NH2CHO and HNCO towards G358.93–0.03 MM1 are (2.80±0.29)×10^{15} cm^{−2} and (1.80±0.42)×10^{16} cm^{−2} with excitation temperatures of 165±21 K and 170±32 K, respectively. The fractional abundances of NH2CHO and HNCO towards G358.93–0.03 MM1 are (9.03±1.44)×10^{−10} and (5.80±2.09)×10^{−9}. We compare the estimated abundances of NH2CHO and HNCO with the existing three-phase warm-up chemical model abundance values and notice that the observed and modelled abundances are very close. We conclude that NH2CHO is produced by the reaction of NH2 and H2CO in the gas phase towards G358.93–0.03 MM1. Likewise, HNCO is produced on the surface of grains by the reaction of NH and CO towards G358.93–0.03 MM1. We also found that NH2CHO and HNCO are chemically linked towards G358.93–0.03 MM1.
The identification of complex prebiotic molecules using millimeter and submillimeter telescopes allows us to understand how the basic building blocks of life are formed in the universe. In the interstellar medium (ISM), ethylene glycol ((CH2OH)2) is the simplest sugar alcohol molecule, and it is the reduced alcohol of the simplest sugar-like molecule, glycolaldehyde (CH2OHCHO). We present the first detection of the rotational emission lines of aGg′ conformer of ethylene glycol ((CH2OH)2) towards the hot molecular core G358.93–0.03 MM1 using the Atacama Large Millimeter/Submillimeter Array (ALMA). The estimated column density of aGg′-(CH2OH)2 towards the G358.93–0.03 MM1 is (4.5±0.1) × 1016 cm−2 with an excitation temperature of 155±35 K. The abundance of aGg′-(CH2OH)2 with respect to H2 is (1.4±0.5) × 10−8. Similarly, the abundances of aGg′-(CH2OH)2 with respect to CH2OHCHO and CH3OH are 3.1±0.5 and (6.1±0.3) × 10−3. We compare the estimated abundance of aGg′-(CH2OH)2 with the existing three-phase warm-up chemical model abundance of (CH2OH)2, and we notice the observed abundance and modelled abundance are nearly similar. We discuss the possible formation pathways of aGg′-(CH2OH)2 towards the hot molecular cores, and we find that aGg′-(CH2OH)2 is probably created via the recombination of two CH2OH radicals on the grain surface of G358.93–0.03 MM1.
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