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...

/pdf/luminous-infrared-galaxies-zoi3y3hutv.pdf

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

THE discovery of microwave background radiation by Penzias and Wilson1 is one of the most interesting events in observational astronomy in recent years. On the basis of the first observations at a single wavelength, the radiation was interpreted2 as being of the black-body type, and it was concluded that this was the remnant of the primordial radiation of a big-bang universe. Later results by different observers have strengthened this interpretation. Indeed it is now claimed3,4 that the black-body curve applies for a wavelength range of 1 : 90, and corresponds to a temperature T = 2.68° K. The observers5 go as far as to state that the exact black-body intensity curve fits the observations better than the “grey-body” approximation at long wavelengths—namely

Interpretation of Cosmic Microwave Background

The infrared spectrum of Comet Hale-Bopp over the wavelength range 7.5 to 45 micrometers, obtained when it was at a heliocentric distance of 2.9 AU, is shown to be consistent with a model dominated by a mixed microbial culture including diatoms with an approximately 10% mass contribution from crystalline olivine. Crystalline olivine by itself is unable to account for the data.

Infrared Radiation From Comet Hale-Bopp

/pdf/organic-dust-in-comet-halley-dn7pjf9zyh.pdf

Organic dust in comet Halley

RADIO observations of the 21 cm line of neutral hydrogen have indicated that the mean kinetic temperature of interstellar clouds is ∼100 K. Temperatures close to this value would seem to be valid for a large fraction, ∼75 per cent, of the mass of interstellar material within clouds.

Small Dust Grains and the Heating of HI Clouds

Canonical models for bolides in the atmosphere predict that fragile bolides break up at much higher altitudes than those actually observed. Here, we investigate the hypothesis that such fragile bolides may survive to low altitudes by a protective outgassing sheath of volatile ices and organics that shields the meteoroid from direct atmospheric heating.

/pdf/on-the-dynamics-of-volatile-meteorites-4328721vb2.pdf

N. C. Wickramasinghe

Papers

Interpretation of Cosmic Microwave Background

Infrared Radiation From Comet Hale-Bopp

Organic dust in comet Halley

Small Dust Grains and the Heating of HI Clouds

On the dynamics of volatile meteorites