Evolution and ecology of influenza A viruses.

Cosmochemistry of the rare earth elements: meteorite studies.

▪ Abstract At luminosities above 1011 , infrared galaxies become the dominant population of extragalactic objects in the local Universe (z ≲ 0.3), being more numerous than optically selected starburst and Seyfert galaxies and quasi-stellar objects at comparable bolometric luminosity. The trigger for the intense infrared emission appears to be the strong interaction/merger of molecular gas-rich spirals, and the bulk of the infrared luminosity for all but the most luminous objects is due to dust heating from an intense starburst within giant molecular clouds. At the highest luminosities (Lir > 1012 ), nearly all objects appear to be advanced mergers powered by a mixture of circumnuclear starburst and active galactic nucleus energy sources, both of which are fueled by an enormous concentration of molecular gas that has been funneled into the merger nucleus. These ultraluminous infrared galaxies may represent an important stage in the formation of quasi-stellar objects and powerful radio galaxies. They may al...

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Luminous infrared galaxies

We construct size distributions for carbonaceous and silicate grain populations in different regions of the Milky Way, LMC, and SMC. The size distributions include sufficient very small carbonaceous grains (including polycyclic aromatic hydrocarbon molecules) to account for the observed infrared and microwave emission from the diffuse interstellar medium. Our distributions reproduce the observed extinction of starlight, which varies depending on the interstellar environment through which the light travels. As shown by Cardelli, Clayton, and Mathis in 1989, these variations can be roughly parameterized by the ratio of visual extinction to reddening, RV. We adopt a fairly simple functional form for the size distribution, characterized by several parameters. We tabulate these parameters for various combinations of values for RV and bC, the C abundance in very small grains. We also find size distributions for the line of sight to HD 210121 and for sight lines in the LMC and SMC. For several size distributions, we evaluate the albedo and scattering asymmetry parameter and present model extinction curves extending beyond the Lyman limit.

https://iopscience.iop.org/article/10.1086/318651/pdf

Dust Grain-Size Distributions and Extinction in the Milky Way, Large Magellanic Cloud, and Small Magellanic Cloud

▪ Abstract This review surveys the observed properties of interstellar dust grains: the wavelength-dependent extinction of starlight, including absorption features, from UV to infrared; optical lum...

https://www.ifa.hawaii.edu/users/reipurth/reviews/draine.pdf

Interstellar dust grains

A broad emission band over the wavelength range ∼ 6000–7500 A in submicron dust in the galaxy and in M82 can be explained by fluorescence phenomena in low-temperature chloroplasts and bacterial pigments. Alternative explanations do not appear to be promising.

Biofluorescence and the Extended Red Emission in Astrophysical Sources

We compute the detailed optical properties over the waveband 0.8 μm−1≲λ≲10 μm−1 for the bacterial grain model which we have discussed earlier. A model comprised of three biologically derived components, modified under interstellar conditions, is shown to be in close correspondence with the observed properties of interstellar dust. Data on interstellar extinction and polarization may be accounted for by this model.

On the optical properties of bacterial grains, I

Microorganisms sealed in KBr discs have an absorption spectrum over the 2.5–15 μm waveband that shows thermal stability as they are heated in an inert atmosphere to temperatures of about400 °C. Microfossils tightly sealed within cavities in rocks could be endowed with similar properties of thermal stability. The observed absorption of interstellar material along the line of sight from the solar system to the galactic centre is remarkably similar to the spectrum of dry micro-organisms over the 3.15–3.7 μm waveband.

Infrared Spectroscopy of Micro-Organisms near 3.4 μm in Relation to Geology and Astronomy

The development of infrared emission from Supernova 1987A is modelled on the basis of a mixture of millimetre long iron whiskers of radius 0.01 µm, and spherical iron grains of the same radius. The total mass of iron grains involved is less than 10−5M⊙.

Evidence for iron whiskers in SN1987A

Interstellar polarization with graphite grains covered with dirty ice mantles matched with entire range of observed interstellar extinction

N. C. Wickramasinghe

Papers

Biofluorescence and the Extended Red Emission in Astrophysical Sources

On the optical properties of bacterial grains, I

Infrared Spectroscopy of Micro-Organisms near 3.4 μm in Relation to Geology and Astronomy

Evidence for iron whiskers in SN1987A

Unified Model for Interstellar Extinction and Polarization