Upload your image
DSS Images Other Images
Submit a new article
|Magnetic Energy of the Intergalactic Medium from Galactic Black Holes|
We present a quantitative analysis of two radio source samples havingopposite extremes of ambient gas density that leads to important newconclusions about the magnetic energy in the intergalactic medium (IGM).We analyze here (1) a new, large sample of well-imaged ``giant''extragalactic radio sources that are found in rarefied IGM environmentsand (2) at the other extreme, radio galaxies situated in the densestknown IGM environments, within 150 kpc of rich cluster cores. We findthat sources in the former sample contain magnetic energiesEB~1060-1061 ergs and could be viewedas important ``calorimeters'' of the minimum energy a black hole (BH)accretion disk system injects into the IGM. In contrast to the radiationenergy released by BH accretion, most of the magnetic energy is``trapped'' initially in a volume, up to ~1073cm3, around the host galaxy. But since these large,megaparsec-scale radio lobes are still overpressured after the activegalactic nucleus phase (AGN), their subsequent expansion and diffusionwill magnetize a large fraction of the entire IGM. This suggests thatthe energy stored in intergalactic magnetic fields will have a major, asyet underestimated effect on the evolution of subsequently forminggalaxies. Comparison with the second, cluster core-embedded sample showsthat the minimum magnetic energy EB can be a stronglyvariable fraction of the inferred accretion energy Eacc, andthat it depends on the ambient IGM environment. Cluster embedded AGNsinject significant energy as PdV work on the thermal ICM gas, and theirmagnetic energy, even ignoring the contribution from stellar andstarburst outflows, is sufficient to account for that recently foundbeyond the inner cores of galaxy clusters. We discuss the various energyloss processes as these magnetized CR clouds (lobes) undergo theirenormous expansion into the IGM. We conclude that the aggregate IGMmagnetic energy derived purely from galactic black holes since the firstepoch of significant galaxy BH formation is sufficiently large that itwill have an important influence on the process of both galaxy andvisible structure formation on scales up to ~1 Mpc.
|An image database. II. Catalogue between δ=-30deg and δ=70deg.|
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
|A 20 centimeter VLA survey of Abell clusters of galaxies. III - Images and optical identifications|
Radio contour maps, models, and optical identifications for 250 radiogalaxies in Abell clusters of galaxies are presented. Consideration isgiven to the effect of environment on radio galaxies, the evolution ofradio galaxies in rich clusters, and the importance of beaming in acomplete sample of radio galaxies.
|Tailed radio sources as probes of the intergalactic medium pressure|
The study analyzes a sample of tailed radio galaxies in Abell clustersin order to estimate their internal pressure under the assumption thattheir tails are in static equilibrium with the thermal pressure of theambient X-ray emitting gas. When projection effects are not taken intoaccount, the external pressure Pth is a factor from 5 to 100larger than the minimum internal nonthermal pressure, Peq,evaluated under equipartition conditions with a volume filling factorand a ratio between relativistic protons and electrons both equal toone. A statistical method is developed to take the projection effectsinto account. The internal pressure is set equal to s x Peq,with s as a free parameter, and the distance of each galaxy from thecluster center is determined by imposing s x Peq -Pth, where Pth is inferred from the availableX-ray data. Acceptable values of s fall in the range 5-10. Theimplications of this result are briefly discussed.
|Detection of excess rotation measure due to intracluster magnetic fields in clusters of galaxies|
The Faraday rotation measures of a sample of extragalactic radio sourcesprojected within a third of an Abell radius of a galaxy cluster werecompared with those of sources located further from cluster centers. Theresult strongly indicates that the distribution of the residual rotationmeasure (RRM) in the former population is broadened, at a confidencelevel exceeding 99 percent. The broadening is detectable out to1/h50 Mpc. The best present estimate of the excess Faradayrotation measure varies from 100 + or - 36 rad/sq m in the central sixthof an Abell radius to 36 + or - 15 rad/sq m further out. The combinationof these results with electron densities determined from X-ray data forsome of the clusters suggests that magnetic field strengths in clustergas are of order 1 microgauss.
|Molonglo Radio Sources in the Directions of Southern Abell Clusters|
We present lists of the radio sources from the 408-MHz MolongloReference Catalogue which have projected separations less than 500kpc(0.33 R_Abell_) from rich southern clusters of galaxies in the newAbell, Corwin & Olowin catalogue. There are 107 such sources in thedirections of 94 clusters for the new southern catalogue, of which weestimate about 27 sources are chance alignments, not associated with thecluster concerned. We also list 89 sources similarly 'coincident' withclusters in the supplementary southern catalogue, and 99 for the revisednorthern catalogue (to the northern declination limit of the MolongloReference Catalogue, +18.5^deg^). We find a stronger concentration ofthe radio sources to the cluster centre than in previous work. Weattribute this to the effects of dominant galaxies at the clustercentres, as revealed by better positional accuracy than for previouslarge-scale radio surveys of clusters.
|Emission-line galaxies in the Virgo region|
Spectroscopic observations, obtained at 490-690 nm using a grismspectrograph with a 1.4-arcsec-wide slit and a CCD detector (dispersion4 A/pixel at scale 0.68 arcsec/pixel) on the 88-inch University ofHawaii telescope on March 22-24, 1983, are reported for fiveemission-line galaxies identified in a search for quasars on UK SchmidtTelescope plates of the Virgo region (He et al., 1984). The data arepresented in tables, spectra, and line-ratio plots and characterized.The systems are found to have M(V) from -19 to -14, strong narrow linesof large equivalent width, and no evidence of power-law excitation orbroad line components, and are classified as compact metal-poorextragalactic H II regions or blue compact dwarf galaxies. Three of thegalaxies (EG4, HII2, and OEG1) are shown to be members of the Virgocluster.
|WSRT radio observations at 1.4 GHz of 22 Abell clusters of distance class 5|
A survey of 63 Abell clusters was carried out at 1.4 GHz with theWesterbork Synthesis Radio Telescope. Radio data and opticalidentifications on 22 Abell clusters of distance class 5 are presented.Finding charts are given for all radio galaxies as well as contour mapsfor interesting radio structures.
Submit a new link
Member of following groups:
Observation and Astrometry data
Catalogs and designations: