ALMA will open up new avenues of exploration encompassing the wide range of star formation in our galaxy and peering into the central heart of planet-forming circumstellar disks. As we seek to explore the origins of stars and planets molecular emission will be at the front and center of many studies probing gas physics and chemistry. In this talk I will discus some of the areas where we can expect significant advances due to the increased sensitivity and superb spatial resolution of ALMA. In star-forming cores, a rich chemistry is revealed that may be the simpler molecular precursors to more complex organics, such as amino acids, seen within primitive rocks in our own solar system. ALMA will provide new information regarding the relative spatial distribution within a given source for a host of organics, sampling tens to hundreds of transitions of a variety of molecules, including presumably new ones. In this area there is a rich synergy with existing ground and space-based data, including Herschel/Spitzer. Here the increased sampling of sources to be enabled by ALMA should bring greater clarity toward the key products of interstellar chemistry and further constrain processes. On smaller Solar System scales, for over a decade most observations of planet-forming disks focused on the dust thermal continuum emission as a probe of the gas content and structure. ALMA will enable reliable and direct studies of gas to explore the evolving physics of planet-formation, the gas dissipation timescales (i.e. the upper limit to the timescale for giant planet birth), and also the chemistry. It is this chemistry that sets the composition of gas giants and also influences the ultimate composition of water and organic materials that are delivered to terrestrial worlds. Here I will show how we can use molecular emission to determine the gas thermal structure of a disk system and the total gas content - key astrophysical quantities. This will also enable more constrained chemical studies that will seek to determine whether the chemistry of planetary birth is universal and similar to our own.

ArH⁺ is isoelectronic with HCl. The J = 1 − 0 and 2 − 1 transitions of ³⁶ArH⁺ near 617.5 and 1234.6 GHz, respectively, have been identified very recently as emission lines in spectra obtained with Herschel toward the Crab Nebula supernova remnant.¹ On Earth, ⁴⁰Ar is by far the most abundant isotope, being almost exclusively formed by the radioactive decay of ⁴⁰K. However, ³⁶Ar is the dominant isotope in the Universe. In the course of unbiased line surveys of the massive and very luminous Galactic Center star-forming regions Sagittarius B2(M) and (N) with the high-resolution instrument HIFI on board of Herschel, we detected the J = 1 − 0 transition of ³⁶ArH⁺ as a moderately strong absorption line initially associated with an unidentified carrier.² In both cases, the absorption feature is unique in its appearance at all velocity components associated with diffuse foreground molecular clouds, together with its conspicuous absence at velocities related to the denser sources themselves. Model calculations are able to reproduce the derived ArH⁺ column densities and suggest that argonium resides in the largely atomic, diffuse interstellar medium with a molecular fraction of no more than  ∼ 10⁻⁴. The ³⁸ArH⁺ isotopolog was also detected. Subsequent observations toward the continuum sources W51, W49, W31C, and G34.3+0.1 resulted in unequivocal detections of ³⁶ArH⁺ absorption. Hence, argonium is a good probe of the transition zone between atomic and molecular gas, in particular in combination with OH⁺ and H₂O⁺, whose abundances peak at a molecular fraction of  ∼ 0.1. Moreover, argonium is a good indicator of an enhanced cosmic ray ionization rate. Therefore, it may be prominent toward, e.g., active galactic nuclei (AGNs) in addition to supernova remnants.
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¹M. J. Barlow et al., Science 342 (2013) 1343. ²H. S. P. Müller et al., Proceedings of the IAU Symposium 297, 2013, "The Diffuse Interstellar Bands", Eds. J. Cami & N. Cox.

The protonated Ar ion ³⁶ArH⁺ has recently been identified in space,¹ in the Crab Nebula, from Herschel spectra. Its R(0) and R(1) transitions lie at 617.5 and 1234.6 GHz, respectively, where atmospheric transmission is rather poor, even for a site as good as that of ALMA. As an alternative, especially after the end of the Herschel mission, rovibrational transitions of ArH⁺ could be observed in absorption against bright background sources such as the galactic center, or other objects. We report on accurate laboratory wavenumber measurements of 19 lines of the v=1−0 band of ³⁶ArH⁺ and ³⁸ArH⁺, using a hollow cathode discharge cell, a difference frequency laser spectrometer and Ar with natural isotopic composition. Of those lines, only eight had been reported before and with much less accuracy.² The data have also been used in a Dunham-type global fit of all published laboratory data (IR and sub-mm) of all isotopologues.³
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¹Barlow et al., Science, 342, 1343 (2013) ²R.R. Filgueira and C.E. Blom, J. Mol. Spectrosc., 127, 279 (1988) ³M. Cueto et al, Astrophys. J. Lett, 783, L5 (2014)

This presentation will provide an overview of the ALMA Science Verification observations taken toward the Orion KL region - the most massive star forming region to the Solar System at a distance of  ∼ 450 pc - in a 30 GHz total bandwidth spectral survey in ALMA Band 6 from 214 - 246 GHz frequency range (lower 2/3 of the total frequency coverage available in ALMA Band 6). In total, over 70000 spectral channels were observed over the 30 GHz of bandwidth. To make a fully cleaned image of these  ∼ 70000 channels would require (at the very least) several thousand unique clean boxes for the molecular emission. This is because the molecular emission is not uniformly distributed but rather concentrated toward several distinct regions and these regions all contain distinct chemistry which lead to unique molecular emission features toward each site. A rough approximation of the spectrum taken toward the Orion "hot core" pointing position gives  ∼ 20 lines per 200 MHz of bandwidth above a signal-to-noise ratio of 5 (the noise level in the maps is  ∼ 50 mJy/beam) for a total of  ∼ 4000 spectral features. To date these data have resulted in 9 referred publications since 2012. In just over an hour, ALMA has collected more interferometric data toward the Orion KL region at 1mm wavelengths than all other arrays

We report the detection in IRC+10216 of lines of HNC J = 3-2 pertaining to nine excited vibrational states with energies up to  ∼ 5300 K. The spectrum, observed with ALMA, also shows a surprising large number of narrow, unidentified lines that arise in the vicinity of the star. The HNC data are interpreted through a 1D-spherical non-local radiative transfer model, coupled to a chemical model that includes chemistry at thermochemical equilibrium for the innermost regions and reaction kinetics for the external envelope. Although unresolved by the current early ALMA data, the radius inferred for the emitting region is  ∼ 0.06 (i.e., 3 stellar radii), similar to the size of the dusty clumps reported by IR studies of the innermost region (r < 0.3). The derived abundance of HNC relative to H₂ is 10⁻⁸ < X(HNC) < 10⁻⁶, and drops quickly where the gas density decreases and the gas chemistry is dominated by reaction kinetics. Merging HNC data with that of molecular species present throughout the inner envelope, such as vibrationally excited HCN, SiS, CS, or SiO, should allow us to characterize the physical and chemical conditions in the dust formation zone. The interpretation of ALMA observations of C-rich evolved stars will require spectroscopic studies of highly excited states of HCN and HNC including accurate determination of l-doubling frequencies for all combination vibrational levels involving the bending mode. Several l-doubling transitions for which laboratory data allow the determination of their frequencies have been identified in the spectrum of IRC+10216.

Determination of elemental isotopic ratios is valuable for understanding the chemical evolution of interstellar material. Until now the ¹²C/¹³C ratio has predominantly been measured in simple species such as CO, CN and H₂CO and, becomes larger with increasing distance from the Galactic Center. We have investigated the carbon isotopic ratio for methyl formate HCOOCH₃, and its isotopologues H¹³COOCH₃ and HCOO¹³CH₃ addressing the issue whether the ¹²C/¹³C ratio is the same for both simple and large molecules. Using ALMA science verification observations of Orion-KL and the spectroscopic characterization of the complex H¹³COOCH₃ and HCOO¹³CH₃ species that we have performed, we have 1) confirmed the detection of the ¹³C-methyl formate species in Orion-KL and, 2) image for the first time their spatial distribution. I will present some of these results. In particular, our analysis shows that the ¹²C/¹³C isotope ratio in methyl formate toward the Compact Ridge and Hot Core-SW components that are associated with Orion-KL are, for both the ¹³C-methyl formate isotopologues, commensurate with the well-known ¹²C/¹³C ratio of the simple species CO. Our findings suggest that grain surface chemistry very likely prevails in the formation of methyl formate main and ¹³C isotopologues.

Recent observations of the Orion-KL region^1,2,3 have shown that the chemical distribution in the region is much more complex than originally thought. There are not just one nitrogen rich core and one diffuse oxygen rich region. But rather, at higher resolution, each of these regions breaks up into smaller more compact components associated with individual heating/energy sources. Additionally, one molecular species, acetone [(CH₃)₂CO], has a distinctly different distribution from any other large molecular species. These results cannot be explained by current chemical models. In order to expand our understanding of the chemistry in complex regions like Orion-KL, we have observed four additional high mass star forming regions: W3, G34.3+0.2, W75N, and W51 e1/e2 at several spatial resolutions (1" - 5"). The results of these multi-resolution observations (with an emphasis on G34.3), a comparison to the results from Orion-KL, and their implications for astrochemical models, will be presented.

I will present recent study of molecular line observations of the Galactic center. On a scale of 2pc from Sgr A*, I show signatures of protostellar outflows within 2pc of Sgr A* based on SiO (5-4), SiO (2-1) line data taken with ALMA, SMA and CARMA. On a larger scale, I discuss the origin of widespread SiO and methanol emission detected from Galactic center molecular clouds. A time-dependent chemical model in which cosmic rays drive the gas chemistry is discussed in order to account for high abundance of SiO and methanol and the high molecular gas temperature.

Many infrared dark clouds (IRDCs) in our Galaxy have filamentary structures, and some of them present converging filaments to a central hub, known as hub-filament systems (HFSs). These filaments could play a crucial role in feeding gas to the star forming regions at the hub. We analyzed NH₃ (J,K)=(1,1) and (2,2) spectral lines data obtained with the Very Large Array (VLA) towards five filamentary IRDCs, and derived the gas temperature based on the line ratios. Furthermore, with the Submillimeter Array (SMA) in the compact and sub-compact configurations, we obtained dust emission and spectra lines at 1.3 mm towards these sources. We found filamentary structures in both dust continuum and spectral line emission, with a characteristic width of 0.1 pc and length of 1 pc. The dust emission is consistent with the infrared extinction features, indicating the existence of dense and cold gas, while massive dust cores are usually associated with the hubs. Complex organic molecules including CH₃OH are found towards the dust cores. In particular, optically-thin intermediate density gas tracers, such as C¹⁸O, reveal a possible trend of gas infall along filaments towards hubs. This is consistent with the scenario that dense gas is accreted onto dense cores through filaments and form high-mass star clusters.

The spectroscopy of molecular clouds probes their structure and kinematics from large to small spatial scales and covering a range of environments are of fundamental importance to understanding how clouds evolve to form stars. CARMA has the unique ability to survey the gas participating in star formation in nearby clouds on scales from parsecs to  ∼ 1,000 AU. We will present the results from the CARMA Large Area Star-formation Survey (CLASSy) Key Project. CLASSy has mapped 3 fields in Perseus (NGC 1333, Barnard 1, and L1451) and 2 fields in Serpens (Serpens Main and Serpens South) totaling 700 square-arcminutes in HCN, HCO⁺, and N₂H⁺ J=1-0 emission lines (dense gas tracers) to: 1) test the predictions of turbulence-driven star formation, 2) test if magnetic fields are dynamically important in turbulent clouds, 3) clarify the relationship between dense cores, their surrounding cloud, and the local YSOs, and 4) study core evolution. The data products from CLASSy will be available to the community.

Molecular gas temperatures in the Galactic Center have been shown to much higher than the gas temperatures of molecular clouds in the disk. These Galactic Center clouds also show large line widths characteristic of turbulence. However, the origin of this heating and turbulence is not well known. In order to investigate this question we analyzed two Galctic Center molecular clouds that showed these characteristic: the G0.10-0.08 cloud and the M0.25+0.01 cloud. We observed these clouds using the VLA at K (25 GHz) and Ka (36 GHz) bands, both of which contain multiple molecular transitions including NH₃, CH₃OH and HC₃N. Using multiple transitions of NH₃, we determined that the rotational gas temperature in the clouds was  ∼ 90-100 K. We also discovered multiple 36 GHz CH₃OH class I masers in both the G0.10-0.08 and M0.25+0.01 clouds,  ∼ 50 and  ∼ 80 respectively. Since these masers trace shocked gas, this indicates that some of this heating and turbulence is caused by these strong shocks. We also present images of the HC₃N line which is a high density tracer and shows dense cores at the center of both clouds.

Hydrides are key ingredients of interstellar chemistry since they are the initial products of chemical networks that lead to the formation of more complex molecules. The fundamental rotational transitions of light hydrides fall into the submillimeter wavelength range and are therefore difficult to observe from the ground. Here we report on new observation of hydrides using the Atacama Pathfinder Experiment telescope (APEX) at the excellent Chajnantor site at 5100m altitude and the Stratospheric Observatory for Infrared Astronomy (SOFIA). Detections of SH,SH⁺, H₂O, OH, OH⁺, NH₂, NH₃ in diffuse clouds and the envelopes of star forming regions will be discussed.

Zeeman observations are essential since they provide the only direct measurement of magnetic field strengths in molecular clouds. Earlier single-dish CN Zeeman N=1-0 measurements of field strengths toward high-mass star formation regions such as W3OH and DR21OH were with 23 arcsec resolution; needed now are higher angular resolution Zeeman maps of magnetic field strengths. Our CARMA Zeeman-effect commissioning observations reported here were carried out for the N=2-1 CN transitions with ~3 arcsec resolution toward W3OH and DR21OH. These are the first interferometric CN Zeeman observations of dense molecular cores. Results will be presented with discussion of the astrophysical implications and the implications for future ALMA observations.

Numerical PDR codes are commonly limited to a pure gas-phase chemistry, with the exception of the Formation of H2. For most species this is reasonably well assumption given the usual physical conditions in photondominated regions. However, for some species, such as H2O, O2, or CH3OH, the pure gas-phase computation is insufficient. We present a recent update of the chemistry included in the Cologne PDR code KOSMA-τ, where we included a network of grain surface reactions into our chemical computation scheme.