Perspective from a Younger Generation -- The Astro-Spectroscopy of Gisbert Winnewisser

Gisbert Winnewisser's astronomical career was practically coextensive with the whole development of molecular radio astronomy. Here I would like to pick out a few of his many contributions, which I, personally, find particularly interesting and put them in the context of newer results.Comment: 14 pages. (Co)authored by members of the MPIfR (Sub)millimeter Astronomy Group. To appear in the Proceedings of the 4th Cologne-Bonn-Zermatt-Symposium "The Dense Interstellar Medium in Galaxies" eds. S. Pfalzner, C. Kramer, C. Straubmeier, & A. Heithausen (Springer: Berlin

New Class II Methanol Masers in W3(OH)

We report interferometric observations of nine class II methanol maser candidate lines toward W3(OH). Narrow maser emission spikes at ν LSR = -43.1 km s -1 are present in three of the lines: 3 1-4 0 A +, 7 2-6 3 A +, and 7 2-6 3 A -. For all three lines the maser position is near the northern edge of the W3(OH) ultracompact H II region (maser emission is also seen near the southern edge in the 3 1-4 0 A + line). For the remaining six lines there is no obvious counterpart to the narrow maser spike at -43.1 km s -1. Additional spatially extended emission is present in all nine lines over the range from -41 to -48 km s -1. By comparing our observed flux densities with an extensive set of model calculations, we infer physical characteristics of the maser region. In these calculations the methanol is excited by infrared radiation from warm dust, and this excited gas amplifies the free-free background emission from the ultracompact H II region. The gas forming the narrow maser spikes appears to have both high kinetic temperature, T kin ≥ 110 K, and high density, n H2 ≈ 10 7 cm -3. Low-temperature solutions are ruled out by the observed line ratios and low-density solutions by the unphysically large path length that would be required. The gas is rich in methanol (2N M = N A + N E ≥ 10 -6N H2), and the methanol column density in the tangential direction for each symmetry species (divided by line width) is N M/ΔV ≈ 10 12 cm -3 s. Somewhat lower values of n H2 and N M/ΔV are also acceptable. The size of the region emitting the maser spike is of order 100 × 1000 AU. In most of the lines the broad emission from -41 to -48 km s -1 can also be attributed to weak maser action, produced in gas with similar physical conditions (high density and temperature). It differs from the narrow spike emission mainly through a beaming factor that can be interpreted as an elongation factor for clumps of maser gas. The combination of narrow and broad emission can arise naturally from an ensemble of clumps of different elongations and orientations. In this unified picture the best fit to the data is provided by n H2 ≈ 2 × 10 6 cm -3 and N M/ΔV ≈ 4 × 10 11 cm -3 s, somewhat lower than the values obtained for just the spike component. The methanol maser clumps may be present in an expanding shell surrounding the H II region, similar to the material producing OH maser emission in this source

Masers and Outflows in the W3(OH)/W3(H2O) Region

No description availabl

Ion–Molecule Reactions as a Possible Synthetic Route for the Formation of Prebiotic Molecules in Space

International audienceThanks to many astrophysical observations, the number of prebiotic molecules observed in space is growing daily. Organic molecules, which can be the first building blocks for appearance of life, were found in both interstellar medium and comets. As an example, several molecules with the peptide bond moiety were reported, like formamide and urea. The glycine detection has a long and controversial history, and it was recently reported on the comet 67P/Churyumov-Gerasimenko. A general question concerns how these molecules could be formed given the extreme conditions of space. Theoretical chemistry, combined in some cases with laboratory experiments, can help in quantifying the physical chemistry conditions which can allow their synthesis. Here, we summarize some studies on the particular case of ion-molecule collisions

Support for global climate reorganization during the "Medieval Climate Anomaly"

Widely distributed proxy records indicate that the Medieval Climate Anomaly (MCA; *900–1350 AD) was characterized by coherent shifts in large-scale Northern Hemisphere atmospheric circulation patterns. Although cooler sea surface temperatures in the central and eastern equatorial Pacific can explain some aspects of medieval circulation changes, they are not sufficient to account for other notable features, including widespread aridity through the Eurasian sub-tropics, stronger winter westerlies across the North Atlantic and Western Europe, and shifts in monsoon rainfall patterns across Africa and South Asia. We present results from a full-physics coupled climate model showing that a slight warming of the tropical Indian and western Pacific Oceans relative to the other tropical ocean basins can induce a broad range of the medieval circulation and climate changes indicated by proxy data, including many of those not explained by a cooler tropical Pacific alone. Important aspects of the results resemble those from previous simulations examining the climatic response to the rapid Indian Ocean warming during the late twentieth century, and to results from climate warming simulations—especially in indicating an expansion of the Northern Hemisphere Hadley circulation. Notably, the pattern of tropical Indo-Pacific sea surface temperature (SST) change responsible for producing the proxy-model similarity in our results agrees well with MCA-LIA SST differences obtained in a recent proxy-based climate field reconstruction. Though much remains unclear, our results indicate that the MCA was characterized by an enhanced zonal Indo-Pacific SST gradient with resulting changes in Northern Hemisphere tropical and extra-tropical circulation patterns and hydroclimate regimes, linkages that may explain the coherent regional climate shifts indicated by proxy records from across the planet. The findings provide new perspectives on the nature and possible causes of the MCA—a remarkable, yet incompletely understood episode of Late Holocene climatic change