The story of a Solar type system starts from an initial molecular clump and ends up into a specific planetary system, with its bag of organic complexity acquired during its evolution. In the first step, the so-called prestellar core phase, the grains become coated with icy mantles, containing simple hydrogenated molecules and perhaps more complex ones. The molecules composing these mantles are crucial for the subsequent chemical development, since they constitute the bricks for more complex organic molecules. In a second step, when the collapse sets in, a central source is formed and heats up the dust around, likely surrounded by a circumstellar disk where the process of planet formation starts. Simultaneously with the collapse, material is ejected outwards causing shocks along the path. Heat and shocks release the content of the icy dust mantles into the gas, triggering a series of reactions that perhaps synthesize more complex molecules in the gas. A plethora of complex molecules are observed in hot corinos and molecular shocks. Probably, these molecules subsequently freeze-out into icy mantles in the denser and coldest zones of the protoplanetary disk and are “passed on” to the forming planets, comets and asteroids. Thus, the questions that astrochemical community needs to answer to build a reliable theory of the dawn of organic chemistry are: Which organic molecules are formed, where, when and how? The discovery of COMs (Complex Organic Molecules) in Solar type hot corinos demonstrated that molecular complexity is not an exclusive prerogative of high mass hot cores and, most important, setting a direct link between organic chemistry in the interstellar medium and in the Solar System. More recently came the discovery that COMs can be also present in prestellar cores, against theoretical expectations, and in outflow shocks close to Solar type forming stars. I will present the results from 2 IRAM Large Programs (ASAI and SOLIS) on the chemical composition of Solar-like protostars and will then present the need for a much higher spatial resolution. This need will be covered by the FAUST ALMA Large Program (http://stars.riken.jp/faust/fausthome.htm), which attacks the issue of the chemical diversity of young Solar-like systems at planet-formation scales (50 au). I will also present how the community is organizing to develop tools, useful for an easy line identification in spectral surveys, as well as their links with radiative transfer modelling (e.g. CASSIS: http://cassis.irap.omp.eu/).

The simple hydrocarbons CCH, CCCH, c-C₃H, H₂CCC, and c-C₃H₂ are common in the interstellar gas and are thought to be important in the production of larger molecules, yet their abundances are poorly understood. Observations of the carbon chain ion CCCH⁺, a key intermediate in the chemistry of these species, have begun to shed some light on their abundances: (i) maps of CCCH⁺ in the Horsehead nebula photodissociation region (PDR) suggest that besides ion-molecule chemistry, the fragmentation of large molecules or very small interstellar grains contributes to the production of small hydrocarbons;Guzmán, V., Pety, J., Goicoechea, J. R., et al. 2015, ApJL, 800, L33nd (ii) there is important but limited evidence that the CCCH⁺ abundance is uniform in diffuse clouds in the Galactic disk, and is remarkably similar to CCCH⁺ abundances inferred in PDRs.Gerin, M., Liszt, H., Neufeld, D., et al. 2019, A&A, 622, A26; and references therein.urthermore, there is clear evidence for a very large molecule-the fullerene ion C₆₀⁺-in the diffuse gas,Maier, J. P. & Campbell, E. K. 2016, Phil. Trans. R. Soc. A, 374, (issue 2076), 1o studies of CCCH⁺ and similar ions in diffuse clouds should allow robust constraints on chemistry over a very large scale in molecular size. Using the 100-m Green Bank Telescope, we recently detected the two lowest rotational transitions of CCCH⁺ along with transitions of several related hydrocarbons in absorption from diffuse clouds toward the luminous H II region W49N. Our observations demonstrate that absorption spectroscopy is a highly sensitive means to detect trace polyatomic species such as CCCH⁺, owing to the large pathlengths through the Spiral Arms and the availability of bright centimeter continuum sources. We will discuss our results toward W49N within the context of elucidating the abundances of small hydrocarbons in diffuse clouds. We will also discuss the prospects of detecting CCCH⁺ toward several other Galactic continuum regions, and detecting larger polyatomic molecules in diffuse clouds through dedicated spectral line surveys.

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Footnotes:

Guzmán, V., Pety, J., Goicoechea, J. R., et al. 2015, ApJL, 800, L33a Gerin, M., Liszt, H., Neufeld, D., et al. 2019, A&A, 622, A26; and references therein.F Maier, J. P. & Campbell, E. K. 2016, Phil. Trans. R. Soc. A, 374, (issue 2076), 1s

While massive star-forming regions are known to exhibit an extremely rich and diverse chemistry, few such sources have been mapped at high spatial resolution. Since the chemical structure of these sources displays substantial spatial variation among species on small scales ( ∼ 10⁴ AU), high spatial resolution observations are needed to constrain chemical evolution models of massive star formation. We will present new ALMA 1.3 mm observations toward massive OB cluster-forming region G10.6-0.4 at a resolution of 0.12^′′ (600 AU). While the kinematics of G10.6 have been extensively studied at centimeter wavelengths, sensitive and high angular resolution observations in the millimeter and submillimeter regime have been lacking. Given the high sensitivity and bandwidth of our ALMA observations, we are able to derive rotational temperature and column density maps toward the central 8^′′ by 8^′′ region of G10.6 for over 10 different species, including traditional warm gas tracers such as CH₃CN, shock tracers HNCO and SiO, and a variety of complex organic molecules. Combined with our simultaneous observations of ionized gas in hydrogen recombination lines, our exquisite spatial resolution allows us to constrain the chemical influences of massive stellar feedback in the form of highly structured and inhomogeneous molecular emission, prominent spatial anti-correlations between molecular and ionized gas, and order-of-magnitude variations in physical gas conditions.

Several studies have demonstrated that the cosmic ray ionization rate is highly variable in the interstellar medium. However, constraints of this rate for several regions including those that contain hot cores are lacking. Hot cores are appealing sources to study given their rich chemical complexity. The chemistry of these cores can be influenced by both their cosmic ray ionization rates and their warm-up timescales, however, understanding the chemical response to these parameters requires further investigation. We study these effects using the astrochemical hot-core modeling code MAGICKAL, in which we construct a grid of 81 models using nine ionization rates and nine warm-up timescales. We also simulate LTE radiative transfer for these models to obtain results that can be directly compared with observations. We compare molecular emission of these models with observations toward NGC 6334 IRS 1, NGC 7538 IRS 1, W3(H₂O), and W33A in an effort to constrain their cosmic ray ionization rates and warm-up timescales. Our best fits to the observations suggest that these sources possess elevated cosmic ray ionization rates compared to the canonical value used in previous modeling studies, and rapid warm-up timescales. We also demonstrate that there exists a strong correlation among the cosmic ray ionization rate and the total hydrogen column density of a source, and a strong correlation among the warm-up timescale and total source mass. Furthermore, these relationships are in good agreement with other theoretical studies.

The photo-dissociation of methanol (CH₃OH) in the interstellar medium is still not a particularly well-understood phenomenon. Since many of the radicals that are formed from this process go on to form the C₂H₄O₂ isomers glycolaldehyde, methyl formate, and acetic acid, measuring the relative abundances of these molecules can give us clues as to the rates at which the radicals are produced. Data on the relative abundances of these molecules also has the potential to constrain formation pathways for the molecules that are necessary for life to emerge. For this analysis we derived molecular abundances of the isomers in two massive cores of NGC 6334I using ALMA spectroscopic data, then examined the literature to find every source for which at least two of the isomers had measured column densities. This resulted in 15 total sources among which we could compare relative abundances of the C₂H₄O₂ isomers.

The reaction of cyano radical with hydrocarbon chains and rings is thought to be important in the formation of complex nitriles, particularly in the formation of polycyclic aromatic hydrocarbons (PAHs). Difficulties in studying these reactions arise from both the plethora of possible product channels, and gaps in our knowledge as to the key species in each pathway. One reaction that has been studied in some detail is cyano radical with phenylacetylene.Bennett et al., Phys. Chem. Chem. Phys. 12, 8737-8749 (2010)ne of the products identified in this reaction is cyanophenylacetylene (3-Phenyl-2-propynenitrile, ), the rotational spectrum of which has not been previously studied. Motivated in part by the recent detection of benzonitrile in the ISM,McGuire et al., Science 359, 202–205 (2018)nd the presence of large cyanopolyyne chains there,Broten et al., ApJL 223, L105-L107 (1978) the pure rotational spectrum of has been investigated in the 8-18 GHz and 75-220 GHz regions. We will present our results (experimental spectrum and rotational constants), and discuss the various methods we used in fitting the data. The new data now allow a search for this species in the ISM.

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Footnotes:

Bennett et al., Phys. Chem. Chem. Phys. 12, 8737-8749 (2010)O McGuire et al., Science 359, 202–205 (2018)a Broten et al., ApJL 223, L105-L107 (1978),

While the rotational spectrum of vinyl cyanide () was first published in 1959 and has been detected in molecular clouds Sgr B2(N) and TMC-1, the cis- and trans-β-cyanovinyl radicals (, CV) not only have not been detected in the interstellar medium (ISM), their rotational spectra have not previously been reported. These radicals have been implicated in the low temperature, gas-phase formation of pyridine, making their study critical to questions of whether pyridine and other N-containing heterocycles can form in cold molecular clouds. Currently there have been no astronomical detections of N-heterocycles anywhere in the ISM. Here we present the theoretical equilibrium geometries calculated at the CCSD(T)/ANO1 level and the rotational spectra of both cis- and trans-β-CV from 5 to 80 GHz. These results will support future spectroscopy in the millimeter-wave region, astronomical searches, and kinetics and dynamics studies of N-heterocycle formation.

We will present an overview of the GOTHAM (GBT Observations of TMC-1: Hunting Aromatic Molecules) and ARKHAM (A Rigorous K-band Hunt for Aromatic Molecules) projects on the 100 m Robert C. Byrd Green Bank Telescope, and a number of first results. These observations, prompted by our earlier detection of benzonitrile (c-C₆H₅CN) in TMC-1, are designed to probe the extent of hidden chemical complexity at the earliest stages of the star formation process. We will discuss the detections of new molecules in TMC-1, comment on the prospects for probing additional aromatic chemistry in this source, and examine the apparently widespread nature of benzonitrile through the early protostellar phase of star formation.

The identification and quantification of molecules in space is based on spectroscopic methods (in particular rotational spectroscopy) and laboratory work is essential to provide the community with the spectral features needed to analyze the cosmological surveys. Many of the molecules which are searched for in space, are complex organic molecules which show a high degree of molecular flexibility. The high number of low energy conformations and the presence of large amplitude motions on shallow potential energy surfaces are peculiar to this kind of systems giving rise to very complex rotational spectra, which represent a challenge for spectroscopic and computational methods. Spectroscopic strategies for the rotational study of flexible organic molecules include the use of the cold and isolated conditions of a free jet expansion and heated sources for the non-volatile systems while the computational methods must deal with complex conformational surfaces and large amplitude motions which can cause tunneling splittings of the rotational transitions. As examples, we will discuss the complex conformational space of 1,2-butandiol and the problem of internal rotation in thioacetamide investigated by rotational spectroscopy in the 60-118 GHz range