A systematic search for disklike edge-on galaxies with a diameter larger than a=40 arcsec and major-to-minor axis ratio a/b>7 has been carried out by means of Palomar Observatory Sky Survey and ESO/SERC survey. As a result, we present new catalog of a flat galaxies (FGC) containing 4455 objects and covering about 56% of the whole sky for the first time. The catalog is assigned to study large-scale cosmic streamings and another problems of observational cosmology. Due to a better quality of the photographic emulsions used for the southern sky survey, the galaxies measured on ESO/SERC films extend to a surface magnitude slightly fainter than the same galaxies measured on POSS prints. So we present the catalog data separately for northern sky (DEC from -17.5 to +90 degrees) - FLAT GALAXY CATALOG , FGC, N = 2573 and for southern sky (DEC from -90 to -17.5 degrees) - SOUTHERN EXTENSION OF FLAT GALAXY CATALOG, FGCE, N = 1882. There are about 200 galaxies in a common region which were found and measured independently on POSS prints and ESO/SERC films. They were included in FGC, not in FGCE. The mean ratio <a(ESO)/a(POSS)> for them is equal to 1.26+/-0.4. This value is near to the result obtained by Lauberts (1982). Making some statistics it is easy to exclude FGCE galaxies with a <50arcsec to have the same depth of the sample. The Appendix to Flat Galaxy Catalog - Addendum - contains the data of 291 galaxies. They were selected in preliminary survey but rejected after more precise diameter measurements because of violation the a/b >= 7 criterion. In every case, these galaxies can be used in different observational programs.
We examine relations between shape, richness, and velocity dispersion for a sample of 350 clusters of galaxies of all morphologies, including those with visible substructure. For our sample the apparent shape of clusters is correlated with velocity dispersion and Abell (1958ApJS....3..211A) richness in the sense that poor, low dispersion clusters are flatter in the mean than their richer, higher dispersion counterparts. These characteristics are also exhibited by the X-ray emitting gas. There are virtually no highly flattened clusters having high richness or high velocity dispersions in the sample. We find that the variation of richness and velocity dispersion with apparent shape is too steep to be assigned to projection effects, and conclude rich, high dispersion clusters are intrinsically more nearly spherical than poorer clusters and that two-body relaxation is probably not an effective anisotropy damping mechanism in Abell clusters.
The results of observations of a complete sample of flat-spectrum radio sources with spectral indices {alpha}>-0.5 are presented. The sample was selected from the Zelenchuk Survey at 3.9GHz (See Cat. <VIII/49>) and contains all sources with declinations 4-6 degrees, galactic latitudes |b|>10 degrees, and 3.9-GHz fluxes >200mJy. Spectra at 0.97-21.7 GHz were obtained for all 69 sample sources. The spectra were classified and a correlation between variability amplitude and spectrum shape was found.
The paper reports the results of ten-year centimeter-wavelength observations with the RATAN-600 radio telescope of a complete sample of 83 flat-spectrum sources from the GB6 catalog of the MGB Survey (Cat. VIII/40), with S_4.85_>200mJy at declinations 10{deg}-12{deg}30'. Starting in 2000, the observations were conducted simultaneously at six frequencies in the range 0.97-21.7GHz. Seventy-six sources (including 54 quasars) have been identified with optical objects, which have redshifts in the range z=0.331-3.601.
The radio sources listed below were selected from the Jodrell-VLA Astrometric Survey and the Cosmic-Lens All-Sky Survey (part 1) and constitute a (non-complete) parent sample for the selection of flat-spectrum symmetric object candidates (the ones which show structure, when their VLA-A 8.4GHz data are analysed). The parent sample contains northern hemisphere objects with 8.4GHz flux densities greater than 100mJy, galactic latitudes greater than 10 degrees and 1.40-to-4.85GHz spectral indices (when known; if not, the source is kept in the sample) smaller than 0.50 (flat). The most relevant properties of the parent sample are listed in the Table.
The all sky survey run by the Galaxy Evolution Explorer (GALEX AIS) mapped about 85 % of the Galaxy at ultraviolet (UV) wavelengths and detected the diffuse UV background produced by the scattering of the radiation from OBA stars by interstellar dust grains. Against this background, diffuse weak structures are detected as well as the UV counterparts to nebulae and molecular clouds. To make full profit of the survey, unsupervised and semi-supervised procedures need to be implemented. The main objective of this work is to implement and analyze the results of the method developed by us for the blind detection of ISM features in the GALEX AIS. Most ISM features are detected at very low signal levels (dark filaments, globules) against the already faint UV background. We have defined an index the UV background fluctuations index (or UBF index) to identify areas of the sky where these fluctuations are detected. The algorithm is applied to the images obtained in the FUV (1344-1786{AA}) band since this is less polluted by stellar sources, facilitating the automated detection. The UBF index is shown to be sensitive to the main star forming regions within the Gould's Belt, as well as to some prominent loops like Loop I or the Eridanus and Monogem areas. The catalogue with the UBF index values is made available on-line to the community.
Ammonia is a major reservoir of nitrogen atoms in cometary materials. However, detections of ammonia in comets are rare, with several achieved at radio wavelengths. A few more detections were obtained through near-infrared observations (around the 3um wavelength region), but moderate relative velocity shifts are required to separate emission lines of cometary ammonia from telluric absorption lines in the 3um wavelength region. On the other hand, the amidogen radical (NH_2_, a photodissociation product of ammonia in the coma) also shows rovibrational emission lines in the 3um wavelength region. Thus, gas production rates for ammonia can be determined from the rovibrational emission lines of ammonia (directly) and amidogen radical (indirectly) simultaneously in the near-infrared. In this article, we present new fluorescence excitation models for cometary ammonia and amidogen radical in the near-infrared, and we apply these models to the near-infrared high-dispersion spectra of comet C/2004 Q2 (Machholz) to determine the mixing ratio of ammonia to water in the comet. Based on direct detection of NH_3_ lines, the mixing ratio of NH_3_/H_2_O is 0.46%+/-0.03% in C/2004 Q2 (Machholz), in agreement with other results. The mixing ratio of ammonia determined from the NH_2_ observations (0.31%-0.79%) is consistent but has relatively larger error, owing to uncertainty in the photodissociation rates of ammonia. At the present level of accuracy, we confirm that NH_3_ could be the sole parent of NH_2_ in this comet.
The basic physical processes responsible for X-ray emission from thin plasmas are considered. Collisional ionization or photoionization of inner shells of neutral atoms and ions leads to the creation of a vacancy in one of the inner shells of the ion or atom, which is filled by a cascade of radiative (fluorescent) and nonradiative (Auger) transitions. The net result is the ejection of several electrons and photons, leaving the atom in a multiply ionized state. In this paper, the distribution of the number of emitted photons and electrons after the creation of a hole in an inner shell of an atom or ion is calculated for all ions from H to Zn. The method consists of two stages: the calculation of transition rates for a given electron configuration, and calculation of probabilities of the several cascade sequences using these transition rates.