This talk will review recent highlights from early shared risk observations of the rotational emission lines from small molecules in the protoplanetary disks around young Sun-like stars. Particular emphasis will be placed on the synergy of the ALMA observations of the outer disk with high resolution spectroscopy from the ground and space (Herschel, Spitzer) at infrared through THz wavelenghts, and on observational constraints that can be placed on the location of key condensation fronts such as the (water) snow line.

We have conducted the first comprehensive mm-wave molecular emission line survey of the circumstellar disk orbiting the nearby, pre-main sequence (T Tauri) star LkCa 15 (D = 140 pc). The outer disk is chemically rich, with numerous previous detections of molecular emission lines revealing a significant gas mass. The disk around this young ( ∼ 3-5 Myr), actively accreting solar analog likely hosts a young protoplanet (LkCa 15b) within its central cavity. Hence, LkCa 15 is an excellent target for an unbiased radio spectroscopic survey intended to produce a full census of the detectable molecular species within an evolved, protoplanetary disk. Our survey of LkCa 15 was conducted with the Institute de Radioastronomie Millimétrique (IRAM) 30 meter telescope over the 1.1-1.4 mm wavelength range. The survey includes detections of the three most abundant CO isotopologues (¹²CO, ¹³CO, and C¹⁸O) which facilitate estimates of the spatially integrated CO emission line optical depths, and complete coverage of the hyperfine line complexes of CN and C₂H that provide diagnostics of excitation and opacity for these species. This work demonstrates the value of comprehensive single-dish line surveys in guiding future high resolution interferometric imaging by ALMA of protoplanetary disks orbiting T Tauri stars.

T Tauri stars are low mass young stars that may serve as analogs to the early solar system. Observations of organic molecules in the protoplanetary disks surrounding T Tauri stars are important for characterizing the chemical and physical processes that lead to planet formation. We used NIRSPEC on Keck 2 to perform a high resolution (λ/∆λ  ∼  25,000) L-band survey of T Tauri star GV Tau N, a nearly edge-on young star in the L1524 molecular cloud. The nearly edge-on orientation is rare but necessary to sample the disk in absorption, rather than the more common emission line measurements. GV Tau N is one of only two sources for which HCN and C₂H₂ have been reported in absorption (Gibb et al. 2007; Doppmann et al. 2008). More recently, we reported the first detection of methane, CH₄ (Gibb & Horne 2013). The rotational temperatures are relatively high, implying that HCN, C₂H₂, CH₄, and water originate in the warm molecular layer of the inner protoplanetary disk. Differences in rotational temperature for different molecules suggest that the absorbing column for each molecule samples a different radial distribution.

Doppmann, G. W., Najita, K. R., & Carr, J. S. 2008, ApJ, 685, 298
Gibb, E. L., Van Brunt, K. A., Brittain, S. D., & Rettig, T. W. 2007, ApJ, 660, 1572
Gibb, E. L., Horne, D. 2013, ApJ, 776, L28

E.L.G. was supported by NSF Astronomy grant AST-0908230 and NASA Exobiology grant NNX07AK38G.

To understand our own solar origins, we must investigate the composition of the protoplanetary disk from which the solar system formed. To infer this, we study analogs to the early solar system called T Tauri stars. These objects are low-mass, pre-main sequence stars surrounded by circumstellar disks of material from which planets are believed to form. We present high-resolution (λ/∆λ ∼ 25,000), near-infrared spectroscopic data from the T Tauri star AA Tau using NIRSPEC at the Keck II telescope, located on Mauna Kea, HI, taken in 2009 and 2010. AA Tau has a close to edge-on geometry, with an inclination of 70^° ± 10^° (Donati et al. 2010). Objects must have a nearly edge-on inclination for the disk to be sampled via absorption line spectroscopy. We observed strong absorption lines of both water and OH to which a spectroscopic model was fit in order for us to determine column density and rotational temperature. These near-infrared observations complement the work being done with ALMA, allowing us to probe the inner most disk regions and the chemistry contained within while ALMA primarily samples and is most sensitive to the outer disk.

Molecular lines are used to trace the structure of the interstellar medium and the physical conditions of the gas in different environments, from protoplanetary disks to high-z galaxies. To fully benefit from the diagnostic power of molecular lines, the formation and destruction paths of the molecules, including the interplay between gas-phase and grain surface chemistry, must be quantitatively understood. Well-defined sets of observations of simple template sources are key to benchmark the theoretical models. In this context the PDR of the Horsehead mane is a particularly interesting case because it has a simple geometry (almost 1D, viewed edge-on) and the density profile across the PDR is well constrained. In this talk, I will summarize our recent results on the ISM physics and chemistry in the Horsehead, from a complete and unbiased line survey at 1, 2 and 3mm performed with the IRAM-30m telescope, where approximately 30 species (plus their isotopologues) are detected with up to 7 atoms. I will show the importance of the interplay between the solid and gas phase chemistry in the formation of (complex) organic molecules, like H₂CO, CH₃OH, and CH₃CN, which reveal that photo-desorption of ices is an efficient mechanism to release molecules into the gas phase. The case of CH₃CN is especially surprising, as it is 40 times more abundant in the warm (T_kin ∼ 60 K) UV-illuminated edge of the nebula, than in the shielded and colder (T_kin ∼ 20 K) inner layers. I will show that complex molecules, such as HCOOH, CH₂CO, CH₃CHO, and CH₃CCH are easily detected in the PDR. I will also discuss new diagnostics of the UV-illuminated gas, like CF⁺ (for which we recently resolved its hyperfine structure for the first time), which is observable from the ground, and we propose it can be used as a proxy of C⁺. I will finish by reporting the first detection of a new molecule, recently confirmed to be the small hydrocarbon C₃H⁺, which shows that photo-erosion of PAHs is needed to explain the enhanced abundance of other small hydrocarbons, like C₃H and C₃H₂.

Molecular clouds are the sites where new stars form. Spectroscopic observations of different molecular species in these clouds can provide invaluable information regarding the dynamical evolution of star forming sites: first, they provide direct dynamical information (velocities as a function of density); second, they reveal the abundance of various molecules, which in turn depends on the chemodynamical evolutionary stage and history of the observed region. However, the connection between theoretical models of cloud dynamics and astronomical molecular spectroscopy is far from straight forward. The chemistry and dynamics of the clouds are interlinked, and various parameters such as the cloud temperature and its initial elemental abundances affect theoretical predictions, resulting in large model degeneracies: radically different dynamical models can often result in similar molecular abundances. In this talk, I will discuss first results from a massive effort undertaken to overcome this problem. By coupling non-equilibrium chemistry with a large array of different dynamical models of molecular cloud evolution, we are looking for these molecular line observables that are least affected by varying parameters and model degeneracies, and can be used to drastically constrain the possible dynamical histories of observed star-forming regions. To this end, we have studied a variety of dynamical models describing the evolution of pre- stellar molecular cloud cores (the initial phase of star formation) that cover the entire spectrum of proposed mechanisms, including pure hydrodynamical collapse and magnetically mediated collapse at various levels of importance of the magnetic field in the cloud dynamics. These models have been coupled to a network of chemical reactions that follow the relative abundances for  ∼ 100 molecular species, by solving the non- equilibrium chemical reactions for the first time simultaneously with the dynamical equations. I will present highlights from the results of this work, including newly proposed observables with maximal potential for discrimination between different models of cloud evolution and star formation. These results are especially timely as ALMA is able to measure many of these quantities and contribute to the resolution of long-standing questions in star formation, such as the timescale of pre-stellar core evolution, and the relative importance of magnetic field and turbulence in their dynamics.

A hyperfine line fitting program is presented, which decomposes an observed rotational transition into its individual hyperfine components. The fit is optimized by the use of the Levenberg-Marquardt algorithm (for non-linear fitting) or Caruana’s algorithm (linearization of the Gaussian function). From the optimal fit, various parameters from the decomposed components are derived such as the linewidth dispersion, peak brightness temperature and peak position in velocity units. The closeness in frequency units of two neighbouring hyperfine components within a rotational transition spectrum allows the derivation of a more credible estimate of the optical depth for the observed source of emission. Effective smoothing of the data subsequent to the fitting procedure greatly reduces the perceived error in the determination of various physical conditions of the observed region. The technique has been employed in observations of massive hot molecular cores (HMCs), considered to be the birthplace of high mass stars. In particular, observations of the cyanopolyynes HC₃N and HC₅N, each of which include a quadrupole hyperfine structure, as well as methyl cyanide, CH₃CN, have been analysed with this technique and modelled with a radiative transfer code incorporating non-LTE conditions, in order to derive abundances and column densities for a total of 10 HMCs and 5 massive cores. Using these derived parameters for each core, we have been able to test the time-dependent chemical models presented for these species by Chapman et al. (2009) and thus verify the suitability of their usefulness as "chemical clocks" by which to constrain the ages of the observed objects. In addition to this work, a detailed study of the magnetic hyperfine structure of a selection of inversion transitions of NH₃ is presented. As part of the continuing preparatory work for Herschel, SOFIA and, in particular, ALMA - improved rest frequencies for this commonly used kinetic temperature detecting species in star-forming cores will be forthcoming.

We present a study of outflows driven by  ∼ 30 protostars using CARMA 1.3 mm observations ( ∼ 2.5^′′ resolution) of CO (J = 2 → 1) and SiO (J = 5 → 4). The sample is taken from the CARMA protostellar polarization survey. The polarization measurements revealed that the magnetic fields are either randomly oriented or preferentially oriented perpendicular to the molecular outflow axis. To probe the properties of the outflow itself, we calculate the mass, momentum, and kinetic energy of each outflow. To examine outflow evolution, we measure the opening angles of each outflow and examine how these vary with age determined from the bolometric temperature. When the protostellar targets are multiple systems, we attempt to disentangle the outflows originating from each component in order to study the system in detail. Observations of molecules such as CO and SiO are key to detecting outflows and determining their properties, which in turn helps constrain the details of the underlying physics driving outflows and how the outflows relate to their driving protostars.

As protostars form through the gravitational infall of material from their parent molecular cloud, they power energetic bipolar outflows that interact with the surrounding medium. Protostellar outflows are important to the chemical evolution of star forming regions, as the shocks produced by the interaction of the high-velocity protostellar wind and the ambient cloud can heat the surrounding medium and trigger chemical and physical processes that would otherwise not take place in a quiescent molecular cloud. Protostellar outflows, are therefore a great laboratory to study shock physics and shock-induced chemistry. I will present results from millimeter-wave observations of a small sample of outflow shocks. The spectra show clear evidence of the existence of complex organic molecules (e.g., methyl formate, ethanol, acetaldehyde) and high abundance of certain simple molecules (e.g., HCO⁺, HCN, H₂O) in outflows. Results indicate that, most likely, the complex species formed on the surface of grains and were then ejected from the grain mantles by the shock. Spectral surveys of shocked regions using ALMA could therefore be used to probe the composition of dust in molecular clouds. Our results demonstrate that outflows modify the chemical composition of the surrounding gaseous environment and that this needs to be considered when using certain species to study active star forming regions.

We present spectral line surveys of 32 galactic sources using the Caltech Submillimeter Observatory (CSO) and the HIFI instrument on the Herschel Space Observatory. This study covers the 220 - 265 GHz frequency range using the CSO, as well as higher frequencies, 645 - 676 GHz and 1.14 THz - 1.19 THz using the HIFI instrument. Deconvolution of the double sideband spectra was performed using the CLASS program and the Herschel/HIFI pipeline. Analysis of the data sets was performed using Global Optimization and Broadband Analysis Software for Interstellar Chemistry (GOBASIC), a new software program developed by our group for the evaluation and study of large astronomical spectroscopic data sets. Initial analysis has focused on 12 complex organic molecules that can be used to trace grain-surface and gas-phase chemical processing in the interstellar medium. GOBASIC was used to determine molecular column densities and rotational temperatures. This information is being used to study correlations between molecular abundances within a given source, and source-to-source correlations for a given molecule, with the ultimate goal of determining which molecules can be used as clocks of the star-formation process. The spectra and the results of this initial analysis will be presented.

The knowledge of molecular gas distribution is necessary to understand star formation in galaxies¹. The molecular gas content of galaxies must be inferred using indirect tracers since H₂ which forms a major component of molecular gas in galaxies is not observable under typical conditions of interstellar medium². Physical processes causing enhancement and reduction of these tracers can cause misleading estimates of the molecular gas content in galaxies. We have devised a new method to measure molecular gas mass using quadrupole rotational lines of H₂ found in the mid infrared spectra of various types of galaxies. We apply our model to derive the amount of molecular gas even in low metallicity galaxies where indirect tracers are unable to estimate the dark molecular gas mass³.
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¹Bigiel, F., Leroy, A., Walter, F., et al. 2008, The Astronomical Journal, 136, 2846 (2008) ²Solomon, P. M., Rivolo, A. R., Barett, J., and Yahil, A. The Astrophysical Journal, 319, 730 (1987) ³Wolfire, M. G., Hollenbach, D., and McKee, C. F. The Astrophysical Journal, 716, 1191 (2010)

While the vast majority of stars in our galaxy will go through the Planetary Nebula (PN) stage near the end of their lives, these objects are not very well understood both physically and chemically. It has long been thought that nebular age is a major factor in determining the chemical content of PNe, but our recent studies have shown this is not likely the case. Millimeter-wave observations of planetary nebulae using the telescopes of the Arizona Radio Observatory have shown that the molecular content of these PNe appears to vary with the C to O ratio of the progenitor star. For example, SO, SO₂, and SiO, molecules that are typically seen in oxygen-righ AGB stars and supergiants, were all detected in the oxygen-rich M2-48. Previous studies of the young, carbon-rich object NGC 7027 show the presence of multiple carbon containing molecules like HC₃N, CCH, and C₃H₂. For NGC 6537, where C/O is close to 1, SO and CCH were identified, indicating an S-type progenitor star. The molecular content of PNe that are carbon-rich, oxygen-rich, and have a C/O ratio close to unity will be compared. The chemical relationship with respect to age will be discussed, as well as implications that the molecular content of the remnant circumstellar shell and its C/O ratio is the main contributing factor behind chemical variation in PNe.

A complete set of molecular abundances have been established for the Oxygen-rich circumstellar envelope (CSE) surrounding the supergiant star VY Canis Majoris (VY CMa). These data were obtained from The Arizona Radio Observatory (ARO) 1-mm spectral line survey of this object using the ARO Sub-millimeter Telescope (SMT), as well as complimentary transitions taken with the ARO 12-meter. The non-LTE radiative transfer code ESCAPADE has been used to obtain the molecular abundances and distributions in VY CMa, including modeling of the various asymmetric outflow geometries in this source. For example, SO and SO₂ were determined to arise from five distinct outflows, four of which are asymmetric with respect to the central star. Abundances of these two sulfur-bearing molecules range from 3 x 10⁻⁸ - 2.5 x 10⁻⁷ for the various outflows. Similar results will be presented for molecules like CS, SiS, HCN, and SiO, as well as more exotic species like NS, PO, AlO, and AlOH. The molecular abundances between the various outflows will be compared and implications for supergiant chemistry will be discussed.

We have performed a systematic analysis of excited-state (up to J=5) H₂ Lyman-Werner absorption lines using archival spectra in the FUSE Magellanic Clouds Legacy Project. The H₂ column densities at different ground state J-levels and the Doppler broadening parameter b are determined for both Magellanic and Galactic components along each line of sight. Combining the results with previously measured total gas column densities of HI and H₂, we derive the H₂ excitation temperature, volume density, and local UV field strength for the absorbing gas. The physical and chemical properties of the absorbers are compared with Galactic samples, and also used to test predictions from multiple-phase ISM equilibrium models. Finally, we compare the absorbing gas from the Magellanic Clouds with its larger-scale ISM environment as revealed in previous surveys of gas and dust emission, extending our results from the UV data measured along moderately reddened sight lines to more dense gas detected in emission.

In this presentation several consequences of the plasma state with spatial structures will be discussed. The basic thought is that a concentration of neutral hydrogen gas in combination with weak magnetic fields will cause elongated plasmas with higher density, which will expand along the field lines. As a consequence the plasma is more concentrated in filamentary structures, the charge density is higher and electron temperature can be higher as well. Clusters will be more charged, which will influence the transport of radicals and charge. The electron density life time may not be limited by dissociative recombination. A comparison is made of the effects of such a stratified medium as compared to a homogeneous plasma for dark clouds conditions. The effect of a structured medium could be that more radicals (as H) are formed and more molecules are formed. Also finite fields and currents may have influence on plasma kinetics.