We have obtained ALMA data of Sagittarius (Sgr for short) B2(N) between 84.0 and 114.4 GHz in its Early Science Cycles 0 and 1. We have focused our analyses on the northern, secondary hot molecular core Sgr B2(N2) because of the smaller line widths. The survey led to the first detection of a branched alkyl compound, iso-propyl cyanide, i-C₃H₇CN, in spaceA. Belloche et al., Science 345 (2014) 1584.esides the  ∼ 2.5 times more abundant straight chain isomer n-propyl cyanide, a molecule which we had detected in our IRAM 30 m survey.A. Belloche et al., A&A 499 (2009) 215.e suspected to be able to detect n-propyl cyanide in vibrationally excited states in our ALMA data. We have recorded laboratory rotational spectra of this molecule in three large frequency regions and identified several excited vibrational states. The analyses of these spectra have focused on the 36 to 70 GHz and 89 to 127 GHz regions and on the four lowest excited vibrational states of both the lower lying gauche- and the slightly higher lying anti-conformer for which rotational constants had been published.E. Hirota, J. Chem. Phys. 37 (1962) 2918.e will present results of our laboratory spectroscopic investigations and will report on the detection of these states toward Sgr B2(N2).

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Footnotes:

A. Belloche et al., Science 345 (2014) 1584.b A. Belloche et al., A&A 499 (2009) 215.W E. Hirota, J. Chem. Phys. 37 (1962) 2918.W

A new interstellar molecule, CH₃NCO (methyl isocyanate), has been detected for the first time using the 12 m telescope of the Arizona Radio Observatory (ARO). CH₃NCO was identified in spectra covering 68 - 116 GHz in the 3 mm segment of a broadband survey of Sgr B2(N). This study was based on previous laboratory work by Koput (1986) and new Fourier transform millimeter-wave (FTmmW) measurements performed at Arizona in the 60 - 88 GHz range. Spectroscopic constants were determined for CH₃NCO in a combined fit, and were used to predict other transitions at 3 mm. Thirty very favorable rotational lines (K_a = 0 and K_a = 1 only; E_u < 60 K) originating in five consecutive transitions of CH₃NCO in both the A and E internal rotation states were found to be present in the Sgr B2(N) survey from 68 - 105 GHz. Emission was observed at all of the predicted frequencies, with 17 lines appearing as distinct, uncontaminated spectral features, clearly showing the classic a-type, asymmetric top pattern. The CH₃NCO spectra also appear to exhibit two velocity components near V_LSR ≈ 62 and 73 km s⁻¹, both with ∆V_1/2 ≈ 10 km s⁻¹, typical of most molecules in Sgr B2(N). The fractional abundances were determined to be f = 7.6 x 10⁻¹² and 5.0 x 10⁻¹² for the 62 and 73 km s⁻¹ components, relative to H₂, respectively. CH₃NCO was recently detected in volatized material from comet 67P/Churyumov-Gerasimenko by Rosetta's Philae lander.

Following the first interstellar detection of CH₃NCO in Sgr B2(N) by Halfen et al. (2015), a survey of this species and its likely precursor HNCO has been conducted towards several dense molecular clouds. Three transitions of CH₃NCO in its K_a = 0 ladder for both A and E internal rotation states were searched for at 3 mm, using the new ARO ALMA Prototype 12 m telescope. In addition, two transitions of HNCO in its K_a = 0 and 2 ladders were observed near 88 and 110 GHz. Emission from CH₃NCO was detected towards Orion-KL, G34.3, W51M, Sgr B2(2N), and DR-21(OH) with intensities of T_A^* ≈ 10-40 mK. HNCO was also found in each source observed. The ratio of HNCO/CH₃NCO estimated from these data is around 25 - 45, consistent with that derived from Sgr B2(N). These results suggest that HNCO is most likely the chemical precursor to CH₃NCO.

Ethanimine (CH3CHNH) , including both the E- and Z- isomers, were detected towards the star-forming region Sgr B2(N) using the GBT PRIMOS data (Loomis et al 2013), and were recently imaged by the ACTA (Corby et al. 2015). These aldimines can serve as precursors of biological molecules such as amino acids thus are considered prebiotic molecules in interstellar medium. In this study, we present chemical simulations of ethanimine with various physical conditions. From models for Sgr B2(N) and environs, calculated ethanimine abundances show reasonable agreement with observed values, while the translucent cloud models yield much lower abundances. These results agree with locations suggested by observations that ethanimine isomers were detected in the foreground of the shells of the hot core.

A confusion-limited spectral line survey of the Galactic center molecular cloud Sgr B2(N) at 3, 2, and 1 mm (68 - 116, 130 - 172, and 210 - 280 GHz) using the Kitt Peak 12 m and the Submillimeter Telescope (SMT) of the Arizona Radio Observatory was recently completed. About 15,000 spectral lines were observed in the survey range. The data have been analyzed using two techniques. First, the rotational temperature diagram methods was used for each individual species. Second, an LTE code was used to model and ultimately fit the data to a set of parameters for each species, using a least squares approach. Seventy-four molecules are identified in the data, along with 81 isotopologue species. In addition, 26 excited vibrational states of the identified molecules were detected, as well as H and He recombination lines. Source and Galactic absorption lines are seen in several abundant species, as well as multiple maser lines of methanol and possibly SO₂.

Life on Earth relies on chiral molecules, that is, species not superimposable on their mirror images. This manifests itself as a reliance on a single molecular handedness, or homochirality that is characteristic of life and perhaps most readily apparent in the large enhancement in biological activity of particular amino acid and sugar enantiomers. Yet, the ancestral origin of biological homochirality remains a mystery. The non-racemic ratios in some organics isolated from primitive meteorites hint at a primordial chiral seed but even these samples have experienced substantial processing during planetary assembly, obscuring their complete histories. To determine the underlying origin of any enantiomeric excess, it is critical to understand the molecular gas from which these molecules originated. Here, we present the first extra-solar, astronomical detection of a chiral molecule, propylene oxide (CH₃CHCH₂O), in absorption toward the Galactic Center. With the detection of propylene oxide, we at last have a target for broad-ranging searches for the possible cosmic origin of the homochirality of life.

The atomic to molecular transitions occurring in diffuse interstellar gas surrounding molecular clouds are affected by the local physical conditions (density and temperature) and the radiation field penetrating the material. The material is closely connected to CO-dark gas, which is not associated with emission from H I at 21 cm or from CO at 2.6 mm. Using optical observations of CH, CH⁺ and CN absorption from McDonald Observatory and the European Southern Observatory in conjunction with UV observations of CO and H₂ absorption from FUSE, we explore the changing environment between diffuse and dense gas, emphasizing trends in column density, excitation temperature, gas density, and velocity structure. This presentation will focus on the completed analysis involving H₂ and on the preliminary results of CO for our sample.

A low-resolution 2.0-2.5 μm survey of  ∼ 500 very red point-like objects in the Central Molecular Zone (CMZ) of our Galaxy, initiated in 2008, has revealed many new bright objects with featureless spectra that are suitable for high resolution absorption spectroscopy of H₃⁺ and CO.Geballe, T. R., Oka, T., Lambridges, E., Yeh, S. C. C., Schlegelmilch, B., Goto, M., Westrick, C. W., WI07 at the 70th ISMS, Urbana, IL, USA,2015e now have altogether 48 objects mostly close to the Galactic plane located from 142 pc to the west of Sgr A* to 120 pc east allowing us to probe dense and diffuse gas by H₃⁺ and dense gas by CO. Our observations demonstrate that the warm ( ∼ 250 K) and diffuse ( ≤ 100 cm⁻³) gas with a large column length ( ≥ 30 pc) initially observed toward the brightest star in the CMZ, GCS3-2 of the Quintuplet Cluster,Oka, T., Geballe, T. R., Goto, M., Usuda, T., McCall, B. J. 2005, ApJ, 632, 882xists throughout the CMZ with the surface filling factor of  ∼  100% dominating the region. The column densities of CO in the CMZ are found to be much less than those in the three foreground spiral arms except in the directions of Sgr B and Sgr E complexes and indicate that the volume filling factor of dense clouds of 10% previously estimated is a gross overestimate for the front half of the CMZ. Nevertheless the predominance of the newly found diffuse molecular gas makes the term "Central Molecular Zone" even more appropriate. The ultra-hot X-rays emitting plasma which some thought to dominate the region must be non existent except near the stars and SNRs. Recently the H₂ fraction f(H₂) in diffuse gas of the CMZ has been reported to be  ∼ 0.6Le Petit, F., Ruaud, M., Bron, E., Godard, B., Roueff, E., Languignon, D., Le Bourlot, J. 2016, A&A, 585, A105 If we use this value, the cosmic ray H₂ ionization rate ζ of a few times 10⁻¹⁵ s⁻¹ reported earlier^b on the assumption of f(H₂)=1 needs to be increased by a factor of  ∼ 3 since the value is approximately inversely proportional to f(H₂)². Geballe, T. R., Oka, T., Lambridges, E., Yeh, S. C. C., Schlegelmilch, B., Goto, M., Westrick, C. W., WI07 at the 70th ISMS, Urbana, IL, USA,2015W Oka, T., Geballe, T. R., Goto, M., Usuda, T., McCall, B. J. 2005, ApJ, 632, 882e Le Petit, F., Ruaud, M., Bron, E., Godard, B., Roueff, E., Languignon, D., Le Bourlot, J. 2016, A&A, 585, A105.

We observed the three ¹³C isotopic species of HC₃N with the high signal-to-noise ratios in L1527 using Green Bank 100 m telescope and Nobeyama 45 m telescope to explore the production scheme of HC₃N, where L1527 is the low-mass star forming region in the phase of a warm carbon chain chemistry region.Sakai, N., Sakai, T., Hirota, T., & Yamamoto, S. 2008, ApJ, 672, 371he spectral lines of the J = 5-4, 9-8, 10-9, and 12-11 transitions in the 44–109 GHz region were used to measure isotopic ratios. The abundance of HCCCN was determined from the line intensities of the two weak hyperfine components of the J = 5–4 transition. The isotopic ratios were precisely determined to be 1.00 : 1.01 : 1.35 : 86.4 for [H¹³CCCN] : [HC¹³CCN] : [HCC¹³CN] : [HCCCN]. It was found that the abundance of H¹³CCCN is equal to that of HC¹³CCN, and it was implied that HC₃N is mainly formed by the reaction schemes via C₂H₂ and C₂H₂⁺ in L1527. This would suggest a universality of dicarbide chemistry producing HC₃N irrespective of evolutional phases from a starless dark cloudTakano, S., Masuda, A., Hirahara, Y., et al. 1998, A&A, 329, 1156o a warm carbon chain chemistry region.

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Footnotes:

Sakai, N., Sakai, T., Hirota, T., & Yamamoto, S. 2008, ApJ, 672, 371T Takano, S., Masuda, A., Hirahara, Y., et al. 1998, A&A, 329, 1156t

L1157, a molecular dark cloud with an embedded Class 0 protostar possessing a bipolar outflow, is an excellent source for studying shock chemistry, including grain-surface chemistry prior to shocks, and post-shock, gas-phase processing. Prior to shock events an estimated  ∼ 2000 and 4000 years ago, temperatures were too low for most complex organic molecules to undergo thermal desorption. Thus, the shocks should have liberated these molecules from the ice grain-surfaces en masse. Here, we present high spatial resolution ( ∼ 3") maps of CH₃OH, HNCO, HCN, and HCO⁺ in the southern portion of the outflow containing B1 and B2, as observed with CARMA. The HNCO maps are the first interferometric observations of this species in L1157. The maps show distinct differences in the chemistry within the various shocked regions in L1157B. This is further supported through constraints of the molecular abundances using the non-LTE code RADEX. We find the east/west chemical differentiation in C2 may be explained by the contrast of the shock's interaction with either cold, pristine material or warm, previously-shocked gas, as seen in enhanced HCN abundances. In addition, the enhancement of HNCO abundance toward the the older shock, B2, suggests the importance of high-temperature O-chemistry in shocked regions.

Shocks have been found to be ubiquitous throughout the interstellar medium and in star forming regions. How these phenomena affect the chemistry, especially the interplay between gas-phase and grain-surface processes, in these regions has yet to be fully understood. In the prototypical shocked-outflow of L1157, we can study the effects that recent shocks ( ∼ 10³-10⁴ years ago) can have on previously cold, quiescent gas, where many of the complex molecules are thought to be locked within grains. Toward a single shock event, C2, a significant chemical differentiation is observed between the previously shocked gas along the eastern wall and the newly shocked gas along the western wall. In addition, substantial enhancement of HNCO towards the younger shock, C1, may imply high-temperature O-chemistry is important soon after the passage of a shock. Here, we utilize the gas-grain chemical network model NAUTILUS in order to investigate the prominence of these effects.

We present the N₂H⁺ (J = 1 → 0) map of the Serpens Main and Serpens South molecular cloud obtained as part of the CARMA Large Area Star Formation Survey (CLASSy). The observations cover 150 arcmin² and 250 arcmin², respectively, and fully sample structures from 3000 AU to 3 pc with a velocity resolution of 0.16 km s⁻¹. They can be used to constrain the origin and evolution of molecular cloud filaments. The spatial distribution of the N₂H⁺ emission is characterized by long filaments that resemble those observed in the dust continuum emission by Herschel. However, the gas filaments are typically narrower such that, in some cases, two or three quasi-parallel N₂H⁺ filaments comprise a single observed dust continuum filament. Our results suggest that single filaments seen in Serpens South by Herschel may in fact be comprised of multiple narrower filaments. Some molecular filaments show velocity gradients along their major axis, and two are characterized by a steep velocity gradient in the direction perpendicular to the filament axis. The observed velocity gradient along one of these filaments was previously postulated as evidence for mass infall toward the central cluster, but these kind of gradients can be interpreted as projection of large-scale turbulence. Finally we compare the morphologies of these N₂H⁺ filaments with those detected in HCO⁺ and HCN. In Serpens South we find that the N₂H⁺ and dust maps are well correlated, whereas HCO⁺ and HCN do not have regularly have N₂H⁺ counterparts. We postulate that this difference is due to large-scale shocks creating the HCO⁺ and HCN emission.

A comprehensive analysis of a broadband 1.2 THz wide spectral survey of the Orion Kleinmann-Low nebula (Orion KL) from the Herschel Space Telescope has shown that nitrogen bearing complex organics trace systematically hotter gas than O-bearing organics toward this source. The origin of this O/N dichotomy remains a mystery. If complex molecules originate from grain surfaces, N-bearing species may be more difficult to remove from grain surfaces than O-bearing organics. Theoretical studies, however, have shown that hot (T=300 K) gas phase chemistry can produce high abundances of N-bearing organics while suppressing the formation of O-bearing complex molecules. In order to distinguish these distinct formation pathways we have obtained extremely high angular resolution observations of methyl cyanide (CH₃CN) using the Atacama Large Millimeter/Submillimeter Array (ALMA) toward Orion KL. By simultaneously imaging ¹³CH₃CN and CH₂DCN we map the temperature structure and D/H ratio of CH₃CN. We will present the initial results of these observations and discuss their implications for the formation of N-bearing organics in the interstellar medium.

Individual spectral lines in astrophysical data are ordinarily assigned by comparison with line frequency and intensities predicted by catalogs. Here we seek to fit the spectra of specific sources within Orion KL that are first selected by ALMA’s angular resolution and then by Doppler velocity class. For each molecule in this study, astrophysical reference lines are selected. Subsequent analyses of individual velocity components provide the astrophysical column density and temperature for these velocity regimes. These column densities and temperatures are then combined with results from the complete experimental spectra obtained from our laboratory spectra to model the molecule’s contribution to the entire astrophysical spectrum [1]. Effects due to optical thickness and spectral overlap are included in the analyses. Examples for ethyl cyanide in the hot core and methanol in the compact ridge will be presented. [1] J. P. McMillan, S. M. Fortman, C. F. Neese, and F. C. De Lucia, ”The Complete, Temperature Resolved Experi- mental Spectrum of Methanol (CH3OH) between 214.6 and 265.4 GHz,” Astrophys. J., vol. 795, pp. 56(1-9), 2014.