Prestellar cores, such as L183 (= L134N), are the first phase of the star formation process and the nursery of chemical complexity. Despite the lack of embedded sources, whose energy input to the cloud can complicate the analysis by permitting a wider range of gas-phase reactions to occur, and can cause the release of molecules formed on grain surface back into the gas phase, cold dark clouds exhibit a complex molecular inventory and distribution.
Here we present single-pointing observations of L183 performed with the IRAM 30m telescope at 3mm wavelength. The focus of the present study is to compare the chemical abundances of the detected molecular species with those found previously in L1544, a very similar astronomical environment, to study similarities and differences between these two prestellar cores. Also, our results will be put in comparison with an astrochemical model recently developed, providing a valuable test for its validity in the context of pre-stellar cores.

The millimeter/sub-mm spectrum of the CrP radical in its X⁴Σ⁻ ground electronic state has been recorded using direct absorption techniques in the frequency range of 340-540 GHz. This study is the first pure rotational measurement of a metal-phosphide species. CrP was synthesized in an AC discharge by the reaction of gas-phase chromium, generated from Cr(CO)₆, with phosphorus vapor, in argon carrier gas. Twelve rotational transitions were measured, each consisting of four fine structure components. The data were analyzed using a Hund’s case b Hamiltonian; rotational, spin-spin, and spin-rotation constants were determined, improving on previous optical work. Comparison with our previous study of CrN indicates differences between metal-nitrogen and metal-phosphorus bonds.

The source of molecular complexity in the interstellar medium is strongly dependent on the build up of carbon-chain molecules. As such, it is crucial to develop a robust chemical inventory of the largest of these carbon-chain species and, in turn, constrain their formation mechanisms. The cold core TMC-1 has long been a source of new molecular detections, particularly for unsaturated carbon-rich molecules. Through deep observations with the Green Bank Telescope of TMC-1, we report 8 new isotopologues of HC₅N and HC₇N and an entirely new molecular family (HC₅O, HC₇O). These new detections provide crucial insights to the formation of PAHs and the underlying carbon-chain chemistry of dark clouds. In addition, we will also discuss preliminary results from the next stage of GBT chemical surveys toward TMC-1.

In 2012, McGuire et al. identified carbodiimide (HNCNH), an isomer of the well-known interstellar species cyanamide (NH2CN) which was first detected in 1975 at millimeter wavelengths by Turner et al. The detection of HNCNH was done using the Robert C. Byrd Green Bank Telescope as part of the PRIMOS survey toward Sgr B2(N). Given the excitation of the detected transitions, it was concluded that NHCNH was a weak astronomical maser and the only way HNCNH could be detected was by those transitions which are amplified by masing. Many other species detected at centimeter wavelengths also have transitions amplified by masing which include, but is not limited to, cyanoacetylene (HC₃N), methyl formate (CH₃OCHO), methanol (CH₃OH) and more recently, formamide (NH₂CHO) and possibly methylamine (CH₃NH₂). The outstanding question remains as to whether the transitions are being enhanced by radiative or collisional processes. To try to ascertain the answer to this question, several low frequency transitions ( ∼ 4 GHz) were observed with the Karl G. Jansky Very Large Array to determine the overall spatial distribution with respect to the background continuum sources and other sources of molecular emission. This talk will present the results of these observations and discuss the possible time variability of some of these low frequency, large molecule astronomical masers.

Organic molecules have been detected mainly in dense clouds. As diffuse clouds are a previous phase of dense clouds in evolutionary history of interstellar clouds, detection of organic molecules in diffuse clouds can reveal a longer history of organic molecules. Despite of its importance, emission lines from molecules in diffuse clouds are difficult to detect because of inactive excitation by collisions and active cooling by radiations. However, for CH₃CN, a rotation around a molecular axis cannot be cooled by radiations. Thus, this molecule can be detected by absorption having a relatively strong line from J = K rotational levels, because these levels are well populated. In our previous work, this rotational behavior was formulated as "Hot Axis Effect" [1]. In this work, to detect this molecule in diffuse clouds that are more diffuse than the known diffuse clouds carrying organic molecules [2], we have been searched for absorption lines of the J_K = 4₃–3₃ transition of CH₃CN at 73 GHz toward the galactic center SgrB2(M) by using Nobeyama 45 m telescope. As a result, this transition was detected in the diffuse cloud of SgrB2 envelop. The column density was derived to be 2 × 10¹⁴ cm⁻². Therefore, we detected an organic molecule in the diffuse cloud that are more diffuse than the known diffuse cloud carrying CH₃CN [2] because this molecule detected shows the low excitation temperature of  ∼  3 K and the high kinetic temperature of  ∼  70 K. [1] Araki et al. Astronomical Journal, 148, 87 (2014) [2] Muller et al., A&A, 535, 103 (2011)

Carbonaceous chondrite class meteorites exhibit isotopic enrichments in deuterium, ¹³C, ¹⁵N, and possibly ³³S, implying interstellar origins. To study possible sulfur enrichments, we have been conducting observations of SO in molecular clouds to determine abundance ratios between ³²S, ³⁴S, and ³³S. The N=2-1 3mm transitions of SO have been measured towards W51M, DR21, G34.3, W3(OH), and NGC7538 using the ARO 12m telescope. The sulfur isotope ratios are currently being calculated and will be compared to meteoritic samples (Bose et al. 2017). The results presented will help to determine the connection between molecular cloud and meteoritic materials.

The Orion Nebula is the closest massive star forming region, which allows us to study its physical conditions at high spatial resolution. We used the far infrared integral-field spectrometer, FIFI-LS, on-board the airborne observatory SOFIA to study the Orion Nebula’s atomic and molecular gas. We obtained large maps of fine structure and CO lines that span the nebula from the BN/KL-object to the bar. These maps allow us to study the conditions of the photon-dominated region and the interface to the molecular cloud. A five-hundred-year-old violent explosion in the Orion Nebula has been stirring up the BN/KL region via wide-angled molecular outflows. We present maps of several high-J CO observations, allowing analysis of the heated molecular gas.

We explore the transition from diffuse to dense molecular gas by combining a variety of tracers for density and composition. Observations and chemical modeling of CH, CH⁺, and CN absorption at visible wavelengths from McDonald Observatory and the European Southern Observatory are combined with ultraviolet observations of CO and H₂ absorption from the Far Ultraviolet Spectroscopic Explorer and the Hubble Space Telescope, as well as emission data from the GOT C+ survey with the Herschel Space Telescope. The selected tracers from visible, ultraviolet, and radio wavelengths allow the characterization of neutral diffuse gas, including CO-dark gas. Sight lines, such as those toward h and χ Persei or those toward Chamaeleon provide a opportunity to examine the transition from atomic to molecular gas and help to describe the nature of the gas.

We present 1.3 mm ALMA dust polarization observations of three T Tauri stars: DG Tauri, DL Tauri, and LkCA 15. All three sources show some degree of polarization at a resolution of  0.5". DL Tauri shows a polarization morphology that is consistent with polarization produced by dust scattering. DG Tauri and LkCa 15 have polarization morphologies that may be produced by dust grain alignment with the disk's radiation field and/or magnetic field. Dust grains can serve as a site for chemical reactions in protostellar disks. Observations of dust polarization can constrain the distribution and properties of dust within the disk, which would provide insight into the chemical evolution of protostellar disks.

The remarkable Red Rectangle nebula is well known for its emission bands (RRBs), excited by the central binary star HD 44179.Schmidt, G. D., & Witt, A. N. 1991, ApJ, 383:698he proximity in wavelength between the strong λ5800 RRB and the long known and intense Diffuse Interstellar Band λ5797 DIB has led to speculation that these two bands originate from identical molecules. This speculation, however, has been challenged on the grounds that the peak wavelength of λ5800 RRB fails to converge to 5797 Å when observed at large angular offsets from HD 44179. Consequently, λ5800 RRB has been interpreted as being caused by various PAHs.Sharp, R. G., Reilly, N. J., Kable, S. H., & Schmidt, T. W. 2006, ApJ, 639:194e investigate the possibility that λ5800 RRB and λ5797 DIB originate from the same molecule. We speculate that absorption in the foreground gas causes the peak wavelength discrepancy, and that the red-shifting of the λ5800 RRB peaks is a combined effect of the extended tail toward the red (ETR)Oka, T., Welty, D. E., Johnson, S., York, D. G., Dahlstrom, J., & Hobbs, L. M. 2013, ApJ, 773:42esulting from the high radiative temperature near HD 44179 and the foreground gas absorption. We use the temperatures and luminosities of the binary star reported by Witt et al.Witt, A. N., Vijh, U. P., Hobbs, L. M., Aufdenberg, J. P., Thorburn, J. A., & York, D. G. 2009, 693:1946or calculating the emission. However, radio to far infrared radiation emanating directly from the stars is far too weak to produce ETR, and we rely on stellar heating of the environment. We find that radiative temperatures on the order of 1000 K are sufficient to explain the largest tail and red-shifted peak at the smallest angular offset. We believe the molecules causing λ5797 DIBHuang, J. & Oka, T. 2015, Mol. Phys. 113, 15nd λ5800 RRB are identical.

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Schmidt, G. D., & Witt, A. N. 1991, ApJ, 383:698T Sharp, R. G., Reilly, N. J., Kable, S. H., & Schmidt, T. W. 2006, ApJ, 639:194W Oka, T., Welty, D. E., Johnson, S., York, D. G., Dahlstrom, J., & Hobbs, L. M. 2013, ApJ, 773:42r Witt, A. N., Vijh, U. P., Hobbs, L. M., Aufdenberg, J. P., Thorburn, J. A., & York, D. G. 2009, 693:1946f Huang, J. & Oka, T. 2015, Mol. Phys. 113, 15a

Velocity-resolved spectra of infrared lines of H₃⁺ at 3.7 μm and CO at 2.3 μm have been obtained toward  ∼ 40 stars in the Central Molecular Zone (CMZ), a region of radius  ∼ 150 pc centered on the Galactic center. Although the coverage of the region is limited by the available number of suitable stars for absorption spectroscopy, the rich Doppler profiles of the H₃⁺ lines in warm (T ∼ 250 K) and diffuse (n ≤ 100 cm⁻³) cloudsOka, T., Geballe, T.R., Goto, M., Usuda, M., McCall, B.J., Indriolo, N. to be submitted (2018)ave allowed us to draw a longitude-velocity (l-v) plot to reach the following conclusions. (1) Based on the blue-shifted profiles of H₃⁺ absorption lines, which are dominantly in the velocity range from - 200 km s⁻¹ to 10  km s⁻¹, the warm diffuse gas is moving outward from the center. (2) Although limited in uniformity of longitudinal coverage, the observed (l-v) plot for H₃⁺ suggests that the outer surface of the expanding gas forms a ring of radius of  ∼ 140 pc and has a velocity of expansion of  ∼ 140 km s⁻¹. This finding revives the idea of the expanding molecule ring proposed by Kaifu et al.(1972)Kaifu, N., Kato, T. Iguchi, T., 1972, Nature, 238, 105nd Scoville (1972)Scoville, N.Z. 1972, ApJ, 175, L127hich contrasts with a more recent interpretation of the overall gas kinematics as due to a barred gravitational potential (Binney et al. 1991).Binney, J., Gerhard, O.E., Stark, A.A., Bally J., Uchida, K.I. 1991, Mon. Not. R. astr. Soc. 252, 2103) The results revive the idea of an explosion or overall expulsion of gas from the center within the last few million years. Unlike the original proposals that the EMR is also rotating, the H₃⁺ l-v plot indicates purely expanding gas.

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Oka, T., Geballe, T.R., Goto, M., Usuda, M., McCall, B.J., Indriolo, N. to be submitted (2018)h Kaifu, N., Kato, T. Iguchi, T., 1972, Nature, 238, 105a Scoville, N.Z. 1972, ApJ, 175, L127w Binney, J., Gerhard, O.E., Stark, A.A., Bally J., Uchida, K.I. 1991, Mon. Not. R. astr. Soc. 252, 210(