To date, 204 individual molecular species, comprised of 16 different elements, have been detected in the interstellar and circumstellar medium by astronomical observations. These molecules range in size from two atoms to seventy, and have been detected across the electromagnetic spectrum from cm-wavelengths to the ultraviolet. This census presents a summary of the first detection of each molecular species, including the observational facility, wavelength range, transitions, and enabling laboratory spectroscopic work, as well as listing tentative and disputed detections. Tables of molecules detected in interstellar ices, external galaxies, protoplanetary disks, and exoplanetary atmospheres are provided. A number of visual representations of this aggregate data are presented and briefly discussed in context.

https://iopscience.iop.org/article/10.3847/1538-4365/aae5d2/pdf

2018 Census of Interstellar, Circumstellar, Extragalactic, Protoplanetary Disk, and Exoplanetary Molecules

The chemical mechanisms that lead to the formation and destruction of molecules in the interstellar gas are reviewed. Grain surface catalysis is discussed briefly. Detailed attention is given to gas-phase chemical processes and to the modifications they produce in the molecular compositions of interstellar clouds following the initial molecular formation. The effects of chemical fractionation processes on the abundances of molecules containing different isotopes are explored. The review was completed in March 1976.

http://iopscience.iop.org/article/10.1088/0034-4885/39/6/002/pdf

Molecule formation in the interstellar gas

We present the first unbiased molecular line survey toward an extragalactic source, namely the nuclear region of the starburst galaxy NGC 253. The scan covers the frequency band from 129.1 to 175.2 GHz, i.e., most of the 2 mm atmospheric window. We identify 111 spectral features as transitions from 25 different molecular species. Eight of which (three tentatively) are detected for the first time in the extragalactic interstellar medium. Among these newly detected species, we detected the rare isotopomers 34SO and HC18O+. Tentative detections of two deuterated species, DNC and N2D+, are reported for the first time from a target beyond the Magellanic Clouds. In addition, three hydrogen recombination lines are identified, while no organic molecules larger than methanol are detected. Column densities and rotation temperatures are calculated for all the species, including an upper limit to the ethanol abundance. A comparison of the chemical composition of the nuclear environment of NGC 253 with those of selected nearby galaxies demonstrates the chemical resemblance of IC 342 and NGC 4945 to that of NGC 253. On the other hand, the chemistries characterizing NGC 253 and M82 are clearly different. We also present a comparison of the chemical composition of NGC 253 with those observed in Galactic prototypical sources. The chemistry of NGC 253 shows a striking similarity with the chemistry observed toward the Galactic center molecular clouds, which are thought to be dominated by low-velocity shocks. This resemblance strongly suggests that the heating in the nuclear environment of NGC 253 is dominated by the same mechanism as that in the central region of the Milky Way.

/pdf/a-2-millimeter-spectral-line-survey-of-the-starburst-galaxy-1jam97935u.pdf

A 2 millimeter spectral line survey of the starburst galaxy NGC 253

The expected characteristics of the solar wind, extrapolated from the vicinity of the earth are described. Several models are examined for the interaction of the solar wind with the interstellar plasma and magnetic field. Various aspects of the penetration of neutral interstellar gas into the solar wind are considered. The dynamic effects of the neutral gas on the solar wind are described. Problems associated with the interaction of cosmic rays with the solar wind are discussed.

/pdf/the-interaction-of-the-solar-wind-with-the-interstellar-avvs0yy19i.pdf

The interaction of the solar wind with the interstellar medium

An attempt to account quantitatively for the pulse width, polarization and spectrum of the pulses.

Possible mechanism for the pulsar radio emission.

FURTHER to our observations of OH in the edge-on spiral galaxies NGC253 and NGC4945 (ref. 1), we now report the detection of H2CO absorption in both galaxies—the first evidence of this molecule in external galaxies.

Physical Sciences: Detection of formaldehyde in external galaxies

WE have previously found1 intensity ratios of the four microwave lines of OH in disagreement with the theoretical and laboratory ratios2 of 1 : 5 : 9 : 1 for the lines at 1,612, 1,665, 1,667 and 1,720 Mc/s. For the strong OH absorption of the radio source Sagittarius A it appeared that the ratios might be attributed to high opacity3. We now report a more detailed series of measurements which shows that high opacity alone cannot account for the observations and that disturbed populations of the levels have to be invoked.

Anomalous Intensity Ratios of the Interstellar Lines of OH in Absorption and Emission

Distribution and Motions of OH Near the Galactic Centre

THE main features of the local magnetic field have been reasonably well established from determinations of the Faraday rotation of the polarized radiation from extra-galactic radio sources1–5. Previously, however, the projected density of observed sources on the sky has been too low to show fine structure in the field distribution. Between November 1963 and October 1966, with the Parkes 210-ft. telescope, determinations were made of the polarization of about 500 sources and we now have evidence for irregularities in the magnetic field in two directions of our Galaxy.

Evidence for an Association between Magnetic Field and Gas Outflow from a Spiral Arm

RYDBECK, Ellder and Irvine1 have recently detected the 9-cm lines of the 2П1/2, J = 1/2Λ doublet of interstellar CH. The F = 1 → 1 transition at 3,335.475 MHz was observed in emission in a wide range of galactic sources ranging from dark clouds to the spiral arms in front of Cassiopea A. The two satellite transitions F = 0 → 1 (at 3,263.788 MHz) and F 1 → 0 (at 3,349.185 MHz) were also observed in emission in several sources.

F. F. Gardner

Papers

Physical Sciences: Detection of formaldehyde in external galaxies

Anomalous Intensity Ratios of the Interstellar Lines of OH in Absorption and Emission

Distribution and Motions of OH Near the Galactic Centre

Evidence for an Association between Magnetic Field and Gas Outflow from a Spiral Arm

Absorption and emission by interstellar CH at 9 cm