Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

Observation of new spontaneous fission activities from elements 100 to 105

Several new Spontaneous Fission (SF) activities have been found. No definite identification could be made for any of the new SF activities; however, half-lives and possible assignments to element-104 isotopes consistent with several cross bombardments include /sup 257/Rf(3.8 s, 14% SF), /sup 258/Rf(13 ms), /sup 259/Rf(approx. 3 s, 8% SF), /sup 260/Rf(approx. 20 ms), and /sup 262/Rf(approx. 50 ms). The 80-ms SF activity claimed by the Dubna group for the discovery of element 104 (/sup 260/104) was not observed. A difficulty exists in the interpretation that /sup 260/Rf is a approx. 20-ms SF activity: in order to be correct, for example, the SF activities with half-lives between 14 and 24 ms produced in the reactions 109- to 119-MeV /sup 18/O + /sup 248/Cm, 88- to 100-MeV /sup 15/N + /sup 249/Bk, and 96-MeV /sup 18/O + /sup 249/Cf must be other nuclides due to their large production cross sections, or the cross sections for production of /sup 260/Rf must be enhanced by unknown mechanisms. Based on calculated total production cross sections a possible approx. 1% electron-capture branch in /sup 258/Lr(4.5 s) to the SF emitter /sup 258/No(1.2 ms) and an upper limit of 0.05% for SF branching in /sup 254/No(55 s) were determined. Other measured half-lives from unknown nuclides produced in respective reactions include approx. 1.6 s (/sup 18/O + /sup 248/CM), indications of a approx. 47-s SF activity (75-MeV /sup 12/C + /sup 249/Cf), and two or more SF activities with 3 s less than or equal to T/sub 1/2/ less than or equal to 60 s (/sup 18/O + /sup 249/Bk). The most exciting conclusion of this work is that if the tentative assignments to even-even element 104 isotopes are correct, there would be a sudden change in the SF half-life systematics at element 104 which has been predicted theoretically and attributed to the disappearance of the second hump of the double-humped fission barrier

Alignment of high Rydberg states in hydrogen

We have measured the light yields and polarizations of the light emitted from several Balmer transitions in atomic hydrogen following beam foil excitation of protons at energies of 50 to 150 keV. The polarizations have been measured as a function of distance downbeam from the exciter foil for several transitions. The measurements indicate a very strong initial alignment which is then perturbed by surface fields out to several mm from the surface. 8 references, 7 figures

Fast ion atomic spectroscopy

We have set up two collinear fast beam/laser excitation systems, one at the Argonne Dynamitron Accelerator (0.5 to 5.0 MeV beam energy) and another at a small electrostatic accelerator (20 to 130 keV). Our objective is to study fine structure, hyperfine structure and QED effects in ions of a few electrons. Initial projects underway include studies of multi-excited transitions in Li/sup -/ and Li/sup 0/, and transitions to high Rydberg states in H/sup 0/ and He/sup 0/. We have simultaneously excited a sodium jet with a laser at the resonance wavelength (D/sub 1/ or D/sub 2/ lines) and a 1-MeV He/sup +/ beam to produce excitation to autoionizing Na and Na/sup +/ states. The Auger electron spectra are compared to spectra obtained without laser excitation, and indicate strong variations in final state populations. 17 references

Simultaneous particulates, NO sub x , SO sub x removal from flue gas by all solid-state electrochemical technology

The process control SO{sub x}, NO{sub x}, and particulate emission from coal combustion flue gases. It is based on a solid-state, electrochemical reactor which converts NO{sub x} and SO{sub 2} to nitrogen, sulfur, and oxygen. Sulfur is condensed downstream at a lower temperature. Particulates are removed with a filter or electrostatic precipitator. The process utilizes no other material input (flue gas is the only fluid), has no moving parts, and produces no sludge(s). The reactor consists of an electrochemical cell where the electrolyte is a solid oxygen ion conducting ceramic such as stabilized ceria or zirconia and the electrodes are electronically conductive material(s). Porous metal such as silver or gold were used as electrodes in the experimental work. Acceptable reduction rates and electric power requirements for sulfur dioxide and nitrogen oxide removal were obtained in up to 1% oxygen with ruthenium and strontium ruthenate electrocatalysts. Electrocatalytic improvements are needed for higher oxygen concentrations, with the NO reduction rates and efficiencies being most sensitive to oxygen concentration. The best electrocatalysts were ruthenium and the perovskite strontium ruthenate. 37 refs., 23 figs., 26 tabs