Contenidos
Imágenes
Subir su imagen
DSS Images Other Images
Artículos relacionados
Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| A quantitative model of the FIR/radio correlation for normal late-type galaxies.
This paper investigates the physical reasons for the existence, thetightness and the near universality of the FIR/radio correlation forlate-type field galaxies whose emission is not dominated by an activenucleus. We develop theoretical models for the radio and far-infrared(FIR) emission of such normal galaxies and study the influence of theirmain parameters on the ratio of the two emissions. In addition, data areused from a sample of 114 late-type galaxies which allow an estimate ofthe mean energy densities of the radiation field and the magnetic field,the latter crudely calculated from the synchrotron luminosity using theminimum energy condition, and of the dust opacity. These data reveal,for the first time, a reasonably good, linear correlation between theenergy density of the radiation field and the energy density of themagnetic field. Interestingly this implies that the two most importantenergy loss rates for electrons, synchrotron and Inverse Compton losses,are proportional to each other. As a consequence the radio synchrotronemission is proportional to the total flux of radiative energy loss fromthe nonthermal Cosmic Ray electrons of a given energy. Furthermore wefind that on average the galaxies are marginally optically thick for thenon-ionizing UV light. Including their extended magnetic halos, galaxiesare also found to be on average marginally optically thick regarding theradiative energy losses of the radio synchrotron emitting, non-thermalCosmic Ray electrons. Exceptions may be galaxies with a very low(compared to our Galaxy) present star formation rate. Combining thesesemi-empirical results with the theoretical emission models we showfirst of all that in the optically thick case the linear correlationbetween the energy densities of the radiation field and the magneticfield is a necessary condition for the existence of the observedFIR/radio correlation. Secondly we show that the individual dispersionof the FIR to radio continuum ratio caused by uncertainties of anysingle one of the parameters considered is significantly less than theempirical dispersion of the FIR/radio correlation. The radio and the FIRemission are mainly determined by their sources, i.e. massive Supernovaprecursor stars, because galaxies act in a reasonable approximation ascalorimeters for the stellar UV radiation and for the energy flux of theCosmic Ray electrons produced in their disks. This constitutes a verygeneral theoretical explanation for the FIR/radio correlation. Inprinciple one can now go a significant step further and use thisobserved correlation plus the theory and the parameters of one galaxy asa normalization to deduce in turn the mean magnetic field strength ofother normal galaxies simply from their total mean radiation energydensity.
| Large-Scale Structures in the Zone of Avoidance: The Galactic Anticenter Region
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...449..527L&db_key=AST
| The far-infrared properties of the CfA galaxy sample. I - The catalog
IRAS flux densities are presented for all galaxies in the Center forAstrophysics magnitude-limited sample (mB not greater than 14.5)detected in the IRAS Faint Source Survey (FSS), a total of 1544galaxies. The detection rate in the FSS is slightly larger than in thePSC for the long-wavelength 60- and 100-micron bands, but improves by afactor of about 3 or more for the short wavelength 12- and 25-micronbands. This optically selected sample consists of galaxies which are, onaverage, much less IR-active than galaxies in IR-selected samples. Itpossesses accurate and complete redshift, morphological, and magnitudeinformation, along with observations at other wavelengths.
| KISO survey for ultraviolet-excess galaxies. XIII.
Not Available
| Objective prism survey of emission-line galaxies. IV
The results of an objective prism survey of emission-line galaxies usingthe Beijing Observatory 60-cm Schmidt are given. The survey includes 100emission-line objects, of which 96 are emission-line galaxies, 3 areplanetary nebulae and 1 is an emission-line star. Of the emission-linegalaxies, 69-72 percent are of types s or sd; 27-28 percent are of typesd and ds. In addition to 4 known Seyfert galaxies, there are at least 5probable Seyferts. Twenty-three of the objects are IRAS sourcescharacterized by strong emission phenomena.
| Star burst activity in high surface brightness galaxies
High surface brightness galaxies are also galaxies with highstar-forming activity. About a half of them omit, on the average, twiceas much energy in the IR than in the blue. The rates of star formationare 10-30 times higher than those in normal galaxies. On average 100-300solar masses gas are converted into stars every year and 10-30 aremassive stars.
| Low-dispersion spectra of emission-line galaxies
Spectroscopic observations of 57 emission-line objects (including 51galaxies) are reported, continuing the survey described by Liu et al.(1985). The data were obtained in 80-min exposures on hypersensitizedIIIa-J plates using 5.3-deg and 2-deg objective prisms on the Schmidttelescope at Beijing Astronomical Observatory; the limiting B magnitudewas 18 mag. The data are presented in tables and briefly characterized.
| New galaxies with high surface brightness in the Nilson system
Using Arkelian's criteria (1974, 1975), data for 47 new High SurfaceBrightness Galaxies (HSBG) in the system of the Uppsala GeneralCatalogue of Galaxies are presented. Of the 193 Arkelian galaxies listedin the catalog, 46 were also found to be HSBGs in the Nilson system(1973). The present list contains 19 Zwicky (1971) compact galaxies (40percent), two of which are listed as HSBGs by Nilson.
| A 21 CM survey of the Pisces-Perseus supercluster. I - The declination zone +27.5 to +33.5 degrees
Neutral-hydrogen 21 cm line data for a sample of galaxies in the regionbounded by 22 h less than R.A. less than 04h, + 27 deg 30 arcmin Dec.less than + 33 deg 30 arcmin are presented as the first installment of asurvey of galaxies in the region of the Pisces-Perseus supercluster. Ofthe 415 galaxies observed in this strip with the Arecibo 305 mtelescope, 342 have been detached in the 21 cm line; another ten haveuseful upper limits to their H I content. The sample includes mostspiral, irregular, and dwarf galaxies larger than 1 arcmin; in selectedareas, spirals to a limiting magnitude of + 15.7 have been observed. Thevelocity distribution of the 511 galaxies with known redshift in thiszone deviates markedly from that expected for a similar sample ofrandomly placed objects. The region contains significant clustering inall three dimensions.
| A survey of galaxy redshifts. IV - The data
The complete list of the best available radial velocities for the 2401galaxies in the merged Zwicky-Nilson catalog brighter than 14.5mz and with b (II) above +40 deg or below -30 deg ispresented. Almost 60 percent of the redshifts are from the CfA surveyand are accurate to typically 35 km/s.
|
Enviar un nuevo artículo
Enlaces relacionados
- - No se han encontrado enlaces -
En viar un nuevo enlace
Miembro de los siguientes grupos:
|
Datos observacionales y astrométricos
Catálogos y designaciones:
|
