We present a very large extension of the Galactic plane CO survey of Dame et al. to the entire northern sky ( δ > −17°). The extension was carried out with the same telescope as was used for the plane survey, the CfA 1.2 m, and perfectly meshes with its irregular boundaries in latitude. A total of 382,202 CO(1–0) spectra uniformly sample the high-latitude sky with a true-angle spacing of 0.°25 or better. The final reduced and folded spectra have a uniform sensitivity of 0.18 K in 0.65 km s −1 channels and provide a velocity coverage of ±47.1 km s −1 . We describe the observational techniques and the data reduction and provide various summary maps of the spatial and velocity distributions of CO emission over the northern sky, and a catalog of the molecular clouds we found there. We also describe the CO spectral line data cubes that we have made available online.

During their late pulsating phase, AGB stars expel most of their mass in the form of massive dusty envelopes, an event that largely controls the composition of interstellar matter. The envelopes, however, are distant and opaque to visible and NIR radiation: their structure remains poorly known and the mass-loss process poorly understood. Millimeter-wave interferometry, which combines the advantages of longer wavelength, high angular resolution and very high spectral resolution is the optimal investigative tool for this purpose. Mm waves pass through dust with almost no attenuation. Their spectrum is rich in molecular lines and hosts the fundamental lines of the ubiquitous CO molecule, allowing a tomographic reconstruction of the envelope structure. The circumstellar envelope IRC +10 216 and its central star, the C-rich TP-AGB star closest to the Sun, are the best objects for such an investigation. Two years ago, we reported the first detailed study of the CO(2-1) line emission in that envelope, made with the IRAM 30-m telescope. It revealed a series of dense gas shells, expanding at a uniform radial velocity. The limited resolution of the telescope (HPBW 11″) did not allow us to resolve the shell structure. We now report much higher angular resolution observations of CO(2-1), CO(1-0), CN(2-1) and C4H(24-23) made with the SMA, PdB and ALMA interferometers (with synthesized half-power beamwidths of 3″, 1″ and 0.3″, respectively). Although the envelope appears much more intricate at high resolution than with an 11″ beam, its prevailing structure remains a pattern of thin, nearly concentric shells. The average separation between the brightest CO shells is 16″ in the outer envelope, where it appears remarkably constant. Closer to the star (< 40″), the shell pattern is denser and less regular, showing intermediary arcs. Outside the small (r < 0.3″) dust formation zone, the gas appears to expand radially at a constant velocity, 14.5 km s-1, with small turbulent motions. Based on that property, we have reconstructed the 3-D structure of the outer envelope and have derived the gas temperature and density radial profiles in the inner (r < 25″) envelope. The shell-intershell density contrast is found to be typically 3. The over-dense shells have spherical or slightly oblate shapes and typically extend over a few steradians, implying isotropic mass loss. The regular spacing of shells in the outer envelope supports the model of a binary star system with a period of 700 years and a near face-on elliptical orbit. The companion fly-by triggers enhanced episodes of mass loss near periastron. The densification of the shell pattern observed in the central part of the envelope suggests a more complex scenario for the last few thousand years.

We report detection of protonated isocyanic acid in two isomeric forms, H2NCO+ and HNCOH+, by highresolution spectroscopy. The two ions were first observed at centimeter wavelengths by Fourier Transform (FT) microwave spectroscopy, in a discharge through HNCO heavily diluted in hydrogen in the throat of a supersonic nozzle. Spectroscopic constants derived from the two lowest rotational transitions of both isomers agree very well with those derived from theoretical structures computed at the coupled cluster level of theory. In the same molecular beam, the fundamental rotational transition of NCO- was observed with well-resolved nitrogen quadrupole hyperfine structure. Detection of NCO- and H2NCO+ in our beam was subsequently confirmed by observation of several millimeter-wave transitions in a low pressure discharge through cyanogen and water, The spectroscopic constants of NCO- obtained earlier by infrared laser spectroscopy are in good agreement with the highly accurate constants derived here. Owing to the high abundance of HNCO in many galactic molecular sources, both ions are excellent candidates for astronomical detection in the radio band.

The rotational spectra of the normal and seven isotopic species of cyclopropenylidene c-C3H2 have been measured at high spectral resolution by Fourier transform microwave spectroscopy of a supersonic molecular beam between 10 and 43 GHz. Deuterium quadrupole coupling and carbon-13 spin-rotation hyperfine constants were determined in addition to the rotational constants. Quartic and sextic centrifugal distortion constants derived from 28 lines between 150 and 316 GHz of the doubly deuterated species c-C3D2 allow the rotational spectrum to be calculated to 0.5 km s−1 or better in equivalent radial velocity up to 500 GHz. Spectroscopic constants determined from four centimeter-wave and 19 millimeter-wave lines of the normal species c-C3H2, including 15 with sharp Lamb-dips, allow prediction of the most important astronomical transitions (i.e., those with ΔJ = 1 and Ka ⩽ 3) to 0.05 km s−1 or better at 500 GHz. The doubly deuterated species is a good candidate for detection in cold dark clouds, because deuterium fractionation is high in c-C3H2 and lines of C3HD are fairly intense in these sources. An accurate empirical equilibrium structure of c-C3H2, derived from the experimental rotational constants of normal and isotopic c-C3H2, corrected for zero-point vibrational effects, is compared with previously reported structures.

The pure rotational spectrum of HPS, as well as its (34)S and D isotopologues, has been recorded at microwave, millimeter, and submillimeter wavelengths, the first observation of this molecule in the gas phase. The data were obtained using a combination of millimeter direct absorption, Fourier transform microwave (FTMW), and microwave-microwave double-resonance techniques, which cover the total frequency range from 15 to 419 GHz. Quantum chemical calculations at the B3LYP and CCSD(T) levels were also performed to aid in spectral identification. HPS was created in the direct absorption experiment from a mixture of elemental phosphorus, H(2)S, and Ar carrier gas; DPS was produced by adding D(2). In the FTMW study, these species were generated in a pulsed discharge nozzle from PH(3) and H(2)S or D(2)S, diluted in neon. The spectra recorded for HPS and its isotopologues exhibit clear asymmetric top patterns indicating bent structures; phosphorus hyperfine splittings were also observed in HPS, but not DPS. Analysis of the data yielded rotation, centrifugal distortion, and phosphorus nuclear spin-rotation parameters for the individual species. The r(m) ((1)) structure for HPS, calculated from the rotational constants, is r(H-P) = 1.438(1) Å, r(P-S) = 1.9320(1) Å, and θ(H-P-S) = 101.85(9)°. Empirically correcting for zero-point vibrational effects yields the geometry r(e)(H-P) = 1.4321(2) Å, r(e)(P-S) = 1.9287(1) Å, and θ(e)(H-P-S) = 101.78(1)°, in close agreement with the r(m) ((1)) structure. A small inertial defect was found for HPS indicating a relatively rigid molecule. Based on these data, the bonding in this species is best represented as H-P=S, similar to the first-row analog HNO, as well as HNS and HPO. Therefore, substitution of phosphorus and sulfur for nitrogen and oxygen does not result in a dramatic structural change.

The pure rotational spectrum of HPS, as well as its 34S and D isotopologues, has been recorded at microwave, millimeter, and submillimeter wavelengths, the first observation of this molecule in the gas phase. The data were obtained using a combination of millimeter direct absorption, Fourier transform microwave (FTMW), and microwave–microwave double-resonance techniques, which cover the total frequency range from 15 to 419 GHz. Quantum chemical calculations at the B3LYP and CCSD(T) levels were also performed to aid in spectral identification. HPS was created in the direct absorption experiment from a mixture of elemental phosphorus, H2S, and Ar carrier gas; DPS was produced by adding D2. In the FTMW study, these species were generated in a pulsed discharge nozzle from PH3 and H2S or D2S, diluted in neon. The spectra recorded for HPS and its isotopologues exhibit clear asymmetric top patterns indicating bent structures; phosphorus hyperfine splittings were also observed in HPS, but not DPS. Analysis of the data yielded rotation, centrifugal distortion, and phosphorus nuclear spin-rotation parameters for the individual species. The rm(1) structure for HPS, calculated from the rotational constants, is r(H–P) = 1.438(1) Å, r(P–S) = 1.9320(1) Å, and θ(H–P–S) = 101.85(9)°. Empirically correcting for zero-point vibrational effects yields the geometry re(H–P) = 1.4321(2) Å, re(P–S) = 1.9287(1) Å, and θe(H–P–S) = 101.78(1)°, in close agreement with the rm(1) structure. A small inertial defect was found for HPS indicating a relatively rigid molecule. Based on these data, the bonding in this species is best represented as H–P=S, similar to the first-row analog HNO, as well as HNS and HPO. Therefore, substitution of phosphorus and sulfur for nitrogen and oxygen does not result in a dramatic structural change.

Aims. We report on the millimeter-wave rotational spectrum of protonated sulfur dioxide, HOSO+.Methods. Ten rotational transitions between 186 and 347 GHz have been measured to high accuracy in a negative glow discharge.Results. The present measurements improve the accuracy of the previously reported centimeter-wave spectrum by two orders of magnitude, allowing a frequency calculation of the principal transitions to about 4 km s(-1) in equivalent radial velocity near 650 GHz, or one linewidth in hot cores and corinos.Conclusions. Owing to the high abundance of sulfur-bearing molecules in many galactic molecular sources, the HOSO+ ion is an excellent candidate for detection, especially in hot cores and corinos in which SO2 and several positive ions are prominent.

The rotational spectra of (SiC2)-Si-29 and (SiC2)-Si-30, two silicon isotopic species of the abundant astronomical ring (SiC2)-Si-28, have been characterized in the millimeter band between 140 and 360 GHz in a low pressure discharge through SiH4, C2H2, and Ar. Precise rotational and centrifugal distortion constants have been derived for both species by fitting a standard asymmetric top Hamiltonian to 38 a-type transitions of (SiC2)-Si-29 and 35 of (SiC2)-Si-30; the data sets include transitions up to K-a = 8 and at least J = 16. With these new measurements in hand, the most intense radio transitions of both species either have been measured or can now be predicted to better than 1 km s(-1) in equivalent radial velocity up to 500 GHz, more than adequate accuracy for spectral line identifications in circumstellar shells of evolved carbon stars such as IRC+10216 where SiC2 is conspicuous. More than 10 new lines of (SiC2)-Si-29 and (SiC2)-Si-30 have been identified between 295 and 354 GHz in the interferometric spectral line survey of IRC+10216 with the Submillimeter Array.

The rotational spectra of two small silicon sulfides, silanethione H(2)SiS and the disilicon sulfide ring Si(2)S, have been detected in the centimeter band by Fourier transform microwave spectroscopy of a molecular beam; lines of H(2)SiS were also observed in the millimeter band up to 377 GHz in a glow discharge. Precise rotational and centrifugal distortionconstants have been determined for the normal and a number of the more abundant rare isotopic species of both closed-shell molecules. Theoretical equilibrium (r(e)) structures of H(2)SiS and Si(2)S were derived from coupled-cluster calculations that included triple and quadruple excitations, core correlation, and extrapolation to the basis-set limit. The r(e) structures agree to within 5×10(-4) Å and 0.1(∘) with empirical equilibrium (r(e)(emp)) structures derived from the experimental rotational constants, combined with theoretical vibrational and electronic corrections. Both H(2)SiS and Si(2)S are good candidates for radioastronomical detection in the circumstellar shells of evolved carbon-rich stars such as IRC+10216, because they are fairly polar and are similar in composition to the abundant astronomical molecule SiS.

We have identified a spiral arm lying beyond the Outer Arm in the first Galactic quadrant similar to 15 kpc from the Galactic center. After tracing the arm in existing 21 cm surveys, we searched for molecular gas using the CfA 1.2 m telescope and detected CO at 10 of 220 positions. The detections are distributed along the arm from l = 13 degrees, v = -21 km s(-1) to l = 55 degrees, v = -84 km s(-1) and coincide with most of the main Hi concentrations. One of the detections was fully mapped to reveal a large molecular cloud with a radius of 47 pc and a molecular mass of similar to 50,000 M-circle dot. At a mean distance of 21 kpc, the molecular gas in this arm is the most distant yet detected in the Milky Way. The new arm appears to be the continuation of the Scutum-Centaurus Arm in the outer Galaxy, as a symmetric counterpart of the nearby Perseus Arm.