Joanna F. Corby

DETECTION OF E-CYANOMETHANIMINE TOWARD SAGITTARIUS B2(N) IN THE GREEN BANK TELESCOPE PRIMOS SURVEY

The detection of E-cyanomethanimine (E-HNCHCN) toward Sagittarius B2(N) is made by comparing the publicly available Green Bank Telescope (GBT) PRIMOS survey spectra to laboratory rotational spectra from a reaction product screening experiment. The experiment uses broadband molecular rotational spectroscopy to monitor the reaction products produced in an electric discharge source using a gas mixture of NH3 and CH3CN. Several transition frequency coincidences between the reaction product screening spectra and previously unassigned interstellar rotational transitions in the PRIMOS survey have been assigned to E-cyanomethanimine. A total of eight molecular rotational transitions of this molecule between 9 and 50?GHz are observed with the GBT. E-cyanomethanimine, often called the HCN dimer, is an important molecule in prebiotic chemistry because it is a chemical intermediate in proposed synthetic routes of adenine, one of the two purine nucleobases found in DNA and RNA. New analyses of the rotational spectra of both E-cyanomethanimine and Z-cyanomethanimine that incorporate previous millimeter-wave measurements are also reported.

An ATCA survey of Sagittarius B2 at 7 mm: Chemical complexity meets broad-band interferometry

We present a 30 - 50 GHz survey of Sagittarius B2(N) conducted with the Australia Telescope Compact Array (ATCA) with 5 - 10 arcsec resolution. This work releases the survey data and demonstrates the utility of scripts that perform automated spectral line fitting on broadband line data. We describe the line-fitting procedure, evaluate the performance of the method, and provide access to all data and scripts. The scripts are used to characterize the spectra at the positions of three HII regions, each with recombination line emission and molecular line absorption. Towards the most line-dense of the three regions characterised in this work, we detect ~500 spectral line components of which ~90 per cent are confidently assigned to H and He recombination lines and to 53 molecular species and their isotopologues. The data reveal extremely subthermally excited molecular gas absorbing against the continuum background at two primary velocity components. Based on the line radiation over the full spectra, the molecular abundances and line excitation in the absorbing components appear to vary substantially towards the different positions, possibly indicating that the two gas clouds are located proximate to the star forming cores instead of within the envelope of Sgr B2. Furthermore, the spatial distributions of species including CS, OCS, SiO, and HNCO indicate that the absorbing gas components likely have high UV-flux. Finally, the data contain line-of-sight absorption by

CSO and Carma Observations of L1157. I. A Deep Search for Hydroxylamine (NH_2OH)

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Interstellar Carbodiimide (HNCNH): A New Astronomical Detection from the GBT PRIMOS Survey via Maser Emission Features

15 molecules observed in translucent gas in the Galactic Center, bar, and intervening spiral arm clouds, revealing the complex chemistry and clumpy structure of this gas. Formamide (NH

CHEMICAL SIMULATIONS OF PREBIOTIC MOLECULES: INTERSTELLAR ETHANIMINE ISOMERS

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Modelling study of interstellar ethanimine isomers

CHO) is detected for the first time in a translucent cloud.

Carma observations of L1157: chemical complexity in the shocked outflow

A deep search for the potential glycine precursor hydroxylamine (NH_2OH) using the Caltech Submillimeter Observatory (CSO) at λ = 1.3 mm and the Combined Array for Research in Millimeter-wave Astronomy at λ = 3 mm is presented toward the molecular outflow L1157, targeting the B1 and B2 shocked regions. We report non-detections of NH_2OH in both sources. We perform a non-LTE analysis of CH_3OH observed in our CSO spectra to derive the kinetic temperatures and densities in the shocked regions. Using these parameters, we derive upper limit column densities of NH_2OH of ≤1.4 × 10^(13) cm^(−2) and ≤1.5 × 10^(13) cm^(−2) toward the B1 and B2 shocks, respectively, and upper limit relative abundances of N_(NH_2OH)/N_H_2 ≤ 1.4 x 10^(-8) and ≤1.5 × 10^(−8), respectively.

Chemical differentiation in Sagittarius B2(N): first high resolution results

In this work, we identify carbodiimide (HNCNH), which is an isomer of the well-known interstellar species cyanamide (NH2CN), in weak maser emission, using data from the Green Bank Telescope PRIMOS survey toward Sgr B2(N). All spectral lines observed are in emission and have energy levels in excess of 170 K, indicating that the molecule likely resides in relatively hot gas that characterizes the denser regions of this star-forming region. The anticipated abundance of this molecule from ice mantle experiments is ∼10% of the abundance of NH2CN, which in Sgr B2(N) corresponds to ∼2 × 10 13 cm −2 . Such an abundance results in transition intensities well below the detection limit of any current astronomical facility and, as such, HNCNH could only be detected by those transitions which are amplified by masing.

The Detection of Interstellar Ethanimine (CH3CHNH) from Observations Taken during the GBT PRIMOS Survey

The E- and Z-isomers of ethanimine (CH3CHNH) were recently detected toward the star-forming region Sagittarius (Sgr) B2(N) using the Green Bank Telescope PRIMOS cm-wave spectral data, and imaged by the Australia Telescope Compact Array. Ethanimine is not reported in the hot cores of Sgr B2, but only in gas that absorbs at +64 and +82 km s−1 in the foreground of continuum emission generated by H ii regions. The ethanimine isomers can serve as precursors of the amino acid alanine and may play important roles in forming biological molecules in the interstellar medium. Here we present a study of the chemistry of ethanimine using a gas-grain simulation based on rate equations, with both isothermal and warm-up conditions. In addition, the density, kinetic temperature, and cosmic ray ionization rate have been varied. For a variety of physical conditions in the warm-up models for Sgr B2(N) and environs, the simulations show reasonable agreement with observationally obtained abundances. Isothermal models of translucent clouds along the same line of sight yield much lower abundances, so that ethanimine would be much more difficult to detect in these sources despite the fact that other complex molecules have been detected there.

Non-detection of HC11N towards TMC-1: constraining the chemistry of large carbon-chain molecules

DONGHUI QUAN, Department of Chemistry, Eastern Kentucky University, Richmond, KY, USA; ERIC HERBST, Department of Chemistry, The University of Virginia, Charlottesville, VA, USA; JOANNA F. CORBY, Department of Astronomy, The University of Virginia, Charlottesville, VA, USA; ALLISON DURR, Department of Chemistry NSB, Eastern Kentucky University, Richmond, Kentucky, United States; GEORGE HASSEL, Department of Physics and Astronomy, Siena College, Loudonville, NY, USA.