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Supernovae 2006du, 2006dv, 2006dw
IAUC 8733 available at Central Bureau for Astronomical Telegrams.
| Chandra and XMM-Newton Observations of a Sample of Low-Redshift FR I and FR II Radio Galaxy Nuclei
We present spectral results from Chandra and XMM-Newton observations ofa sample of 22 low-redshift (z<0.1) radio galaxies and considerwhether the core emission originates from the base of a relativisticjet, or an accretion flow, or contains contributions from both. We findcorrelations between the unabsorbed X-ray, radio, and optical fluxes andluminosities of FR I-type radio-galaxy cores, implying a common originin the form of a jet. On the other hand, we find that the X-ray spectraof FR II-type radio galaxy cores are dominated by absorbed emission,with NH>~1023 atoms cm-2, which islikely to originate in an accretion flow. We discuss several models thatmay account for the different nuclear properties of FR I- and FR II-typecores and also demonstrate that both heavily obscured, accretion-relatedand unobscured, jet-related components may be present in all radiogalaxy nuclei. Any absorbed, accretion-related components in FR I-typegalaxies have low radiative efficiencies.
| Implications for unified schemes from the quasar fraction and emission-line luminosities in radio-selected samples
We use a principal components analysis of radio-selected (3CRR, 6CE and7CRS) active galactic nuclei (AGN) data sets to define two parametersrelated to low-frequency (151-MHz) radio luminosity L151 and[OIII] luminosity L[OIII]: a parameter α encoding theL151-L[OIII] correlation and a parameter βencoding scatter about this correlation. We describe methods forconstructing generalized luminosity functions (GLFs) based on α,β, redshift and schemes for unifying quasars and radio galaxies.These GLFs can be used to generate radio luminosity functions (RLFs)which improve on those of Willott et al. (2001a), mostly because theyincorporate scatter and are therefore much smoother.Luminosity-dependent unified schemes (e.g. a receding-torus scheme) havebeen invoked to explain the low quasar-to-radio galaxy fraction at lowα and the differences in emission-line luminosities of radioquasars and radio galaxies. With the constraints of the 3CRR, 6CE and7CRS data sets and radio source counts, our GLF approach was used todetermine whether a receding-torus-like scheme is required if there aretwo populations of radio sources: one at low α, consisting of`starved AGN' the other at high α, consisting of `Eddington-tunedAGN'. Because of the overlap between these two populations and theeffects of the β parameter, schemes with or without a recedingtorus can produce a low quasar fraction at low α and differencesin [OIII] luminosity between radio galaxies and quasars. The recedingtorus may be a physical process important in one or more populations ofradio sources, but this is not yet proved either by the quasar fractionor the emission-line properties of radio-selected samples.
| K-band Properties of Galaxy Clusters and Groups: Brightest Cluster Galaxies and Intracluster Light
We investigate the near-infrared K-band properties of the brightestcluster galaxies (BCGs) in a sample of 93 X-ray galaxy clusters andgroups, using data from the Two Micron All Sky Survey. Our clustersample spans a factor of 70 in mass, making it sensitive to any clustermass-related trends. We derive the cumulative radial distribution forthe BCGs in the ensemble and find that 70% of the BCGs are centered inthe cluster to within 5% of the virial radius r200; thisquantifies earlier findings that BCG position coincides with the clustercenter as defined by the X-ray emission peak. We study the correlationsbetween the luminosity of the BCGs (Lb) and the mass and theluminosity of the host clusters, finding that BCGs in more massiveclusters are more luminous than their counterparts in less massivesystems and that the BCGs become less important in the overall clusterlight (L200) as cluster mass increases. By examining a largesample of optically selected groups, we find that these correlationshold for galactic systems less massive than our clusters(<3×1013 Msolar). From the differencesbetween luminosity functions in high- and low-mass clusters, we arguethat BCGs grow in luminosity mainly by merging with other luminousgalaxies as the host clusters grow hierarchically; the decreasing BCGluminosity fraction (Lb/L200) with cluster massindicates that the rate of luminosity growth in BCGs is slow compared tothe rate at which clusters acquire galaxy light from the field or othermerging clusters. Utilizing the observed correlation between the clusterluminosity and mass and a merger tree model for cluster formation, weestimate that the amount of intracluster light (ICL) increases withcluster mass; our calculations suggest that in 1015Msolar clusters more than 50% of total stellar mass is inICL, making the role of ICL very important in the evolution andthermodynamic history of clusters. The cluster baryon fractionaccounting for the ICL is in good agreement with the value derived fromcosmic microwave background observations. The inclusion of ICL reducesthe discrepancy between the observed cluster cold baryon fraction andthat found in hydrodynamical simulations. Based on the observed ironabundance in the intracluster medium, we find that the ICL predicted byour model, together with the observed galaxy light, match the ironmass-to-light ratio expected from simple stellar population models,provided that the Salpeter initial mass function is adopted. The ICLalso makes it easier to produce the ``iron excess'' found in the centralregions of cool-core clusters.
| Decametric survey of discrete sources in the Northern sky. XIIIb. Spectra of discrete sources in the declination zone from +300 to +400
New data obtained in the course of the decametric survey of the Northernsky with the UTR-2 radiotelescope in the declination zone from+300 to +400 were used together with data fromhigh-frequency radio surveys to construct spectra for 62 radio sourcesin the frequency range from 12.6 to 50000 MHz. Spectra plots andparameters for these radio sources are given together with statisticalanalysis.
| Unifying B2 radio galaxies with BL Lacertae objects
In an earlier paper we presented nuclear X-ray flux densities, measuredwith ROSAT, for the B2 bright sample of nearby low-luminosity radiogalaxies. In this paper we construct a nuclear X-ray luminosity functionfor the B2 radio galaxies, and discuss the consequences of our resultsfor models in which such radio galaxies are the parent population of BLLacertae (BL Lac) objects. Based on our observations of the B2 sample,we use Monte Carlo techniques to simulate samples of beamed radiogalaxies, and use the selection criteria of existing samples of BL Lacobjects to compare our simulated results to what is observed. We findthat previous analytical results are not applicable since the BL Lacsamples are selected on beamed flux density. A simple model in which BLLacs are the moderately beamed (γ~ 3) counterparts of radiogalaxies, with some random dispersion (~0.4 decades) in the intrinsicradio-X-ray relationship, can reproduce many of the features of theradio-selected and X-ray-selected BL Lac samples, including their radioand X-ray luminosity functions and the distributions of theirradio-to-X-ray spectral indices. In contrast, models in which the X-rayand radio emission have systematically different beaming parameterscannot reproduce important features of the radio-galaxy and BL Lacpopulations, and recently proposed models in which the radio-to-X-rayspectral index is a function of source luminosity cannot in themselvesaccount for the differences in the slopes of the radio- andX-ray-selected BL Lac luminosity functions. The redshift distributionand number counts of the X-ray-selected Einstein Medium SensitivitySurvey (EMSS) sample are well reproduced by our best models, supportinga picture in which these objects are beamed Fanaroff-Riley type I radiogalaxies with intrinsic luminosities similar to those of the B2 sample.However, we cannot match the redshift distribution of the radio-selected1-Jy sample, and it is likely that a population of Fanaroff-Riley typeII radio galaxies is responsible for the high-redshift objects in thissample, in agreement with previously reported results on the sample'sradio and optical emission-line properties.
| Supernova 2003ia in NGC 6109
IAUC 8204 available at Central Bureau for Astronomical Telegrams.
| Supernovae 2003hz, 2003ia, 2003ib, 2003ic, 2003id
IAUC 8201 available at Central Bureau for Astronomical Telegrams.
| An X-Ray Atlas of Groups of Galaxies
A search was conducted for a hot intragroup medium in 109 low-redshiftgalaxy groups observed with the ROSAT PSPC. Evidence for diffuse,extended X-ray emission is found in at least 61 groups. Approximatelyone-third of these detections have not been previously reported in theliterature. Most of the groups are detected out to less than half of thevirial radius with ROSAT. Although some spiral-rich groups do contain anintragroup medium, diffuse emission is restricted to groups that containat least one early-type galaxy.
| High-energy sources before INTEGRAL. INTEGRAL reference catalog
We describe the INTEGRAL reference catalog which classifies previouslyknown bright X-ray and gamma-ray sources before the launch of INTEGRAL.These sources are, or have been at least once, brighter than ~ 1 mCrababove 3 keV, and are expected to be detected by INTEGRAL. This catalogis being used in the INTEGRAL Quick Look Analysis to discover newsources or significantly variable sources. We compiled several publishedX-ray and gamma-ray catalogs, and surveyed recent publications for newsources. Consequently, there are 1122 sources in our INTEGRAL referencecatalog. In addition to the source positions, we show an approximatespectral model and expected flux for each source, based on which wederive expected INTEGRAL counting rates. Assuming the default instrumentperformances and at least ~ 105 s exposure time for anypart of the sky, we expect that INTEGRAL will detect at least ~ 700sources below 10 keV and ~ 400 sources above 20 keV over the missionlife.The Catalog is available in electronic form at the CDS via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?/A+A/411/L59
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| Mass Profile of the Infall Region of the Abell 2199 Supercluster
Using a redshift survey of 1323 galaxies (1092 new or remeasured) in aregion of 95 deg2 centered on the nearby galaxy cluster Abell2199, we analyze the supercluster containing A2199, A2197, and an X-raygroup. The caustic technique accurately reproduces the true massprofiles of simulated simple superclusters (i.e., superclusters forwhich the virial mass of one cluster is 2-10 times the virial mass ofall other clusters in the supercluster). We calculate the masses of thetwo main components of A2197 (A2197W and A2197E) by using archival X-rayobservations and demonstrate that the A2199 supercluster is simple (themass of A2199 is 5 and 12 times larger than A2197W and A2197E,respectively) and thus that the caustic technique should yield anaccurate mass profile. The masses of A2199, A2197W, and A2197E withinr500 (the radius within which the enclosed density is 500times the critical density) are 22.0, 3.8, and 1.7 times 1013h-1 Msolar, respectively. The mass profile isuncertain by ~30% within 3 h-1 Mpc and by a factor of 2within 8 h-1 Mpc and is one of only a few for a superclusteron such large scale. Independent X-ray mass estimates agree with ourresults at all radii where they overlap. The mass profile stronglydisagrees with an isothermal sphere profile but agrees with profilessuggested by simulations. We discuss the interplay of the superclusterdynamics and the dynamics of the bound subclusters. The agreementbetween the infall mass profile and other techniques shows that thecaustic technique is surprisingly robust for simple superclusters.
| Redshifts for a Sample of Radio-selected Poor Clusters
Multifiber optical spectroscopy has been performed on galaxies in thevicinity of strong, nearby radio galaxies. These radio galaxies wereselected from the 3CR and B2 catalogs based on their exclusion from theAbell catalog, which is puzzling given the hypothesis that an externalmedium is required to confine the radio plasma of such galaxies.Velocities derived from the spectra were used to confirm the existenceof groups and poor clusters in the fields of most of the radio galaxies.We find that all radio galaxies with classical Fanaroff-Riley type Imorphologies prove to reside in clusters, whereas the other radiogalaxies often appear to be recent galaxy-galaxy mergers in regions oflow galaxy density. These findings confirm the earlier result that theexistence of extended X-ray emission combined with a statistical excessof neighboring galaxies can be used to identify poor clusters associatedwith radio galaxies.
| The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| A new list of extra-galactic radio jets
A catalogue of extra-galactic jets is very useful both in observationaland theoretical studies of active galaxies. With the use of new powerfulradio instruments, the detailed structures of very compact or weak radiosources are investigated observationally and many new radio jets aredetected. In this paper, we give a list of 661 radio sources withdetected radio jets known to us prior to the end of December 2000. Allreferences are collected for the observations of jets in radio, IR,optical, UV and X-ray wave-bands. Table 1 and references to Table 1 areonly available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/381/757
| New Evidence for the Unified Scheme of BL Lacertae Objects and FR I Radio Galaxies
In this paper, we collect radio and X-ray observations for mostFanaroff-Riley I (FR I) radio galaxies in the Zirbel-Baum radio galaxysample and investigate the distribution of the radio-to-X-ray effectivespectral index, αrx, to test the unified scheme of BLLac objects and FR I radio galaxies. It is found that the range ofαrx for FR I radio galaxies is almost the same as thatfor BL Lac objects, that the distribution of αrxprobably peaks at the same position as BL Lac objects, and that thedistribution of αrx for FR I galaxies is similar tothat for BL Lac objects. These suggest that there exist two subclassesof FR I radio galaxies: one is HBL-like, and the other is LBL-like,corresponding to high-energy-peaked (HBL) and low-energy-peaked (LBL) BLLac objects, respectively. This result is consistent with previous VLAobservations and supports the unified scheme of BL Lac objects and FR Iradio galaxies.
| Radio, optical and X-ray nuclei in nearby 3CRR radio galaxies
HST observations have shown that low-redshift 3CR radio galaxies oftenexhibit a point-like optical component positionally coincident with theGHz-frequency radio core. In this paper we discuss the correlationbetween the luminosities of the radio, optical and X-ray cores in theseobjects, and argue that all three components have a common origin at thebase of the relativistic jets. In unified models, FR I radio galaxiesshould appear as dimmed, redshifted versions of BL Lac objects. We showthat such models are consistent with the spectral energy distributionsof the radio galaxies only if the nuclear X-ray emission in radiogalaxies is inverse Compton in origin.
| Surface photometry of radio loud elliptical galaxies from the B2 sample
V-band CCD imaging is presented for 72 galaxies from the B2 radio sample(Colla et al. \cite{colla}; Fanti et al. \cite{fanti78}), with redshiftsup to 0.2 and radio powersP408=1023-1026.5 W Hz-1.According to the morphology on the optical images 57 galaxies areclassified as ellipticals, 6 as spirals and 7 as irregular. Surfacephotometry of the sample of ellipticals was obtained fitting ellipses tothe light distribution. The light profile of these galaxies generallyfollows a de Vaucouleurs law, although in three cases the profiles showlarge excesses relative to the r1/4 law at large radii. Thefitted mu_e and r_e parameters for the de Vaucouleurs galaxies are givenin the paper. Three of the ellipticals show a bright nucleus. One ofthem is a known broad line radio galaxy (B2 1833+32) and the remainingtwo are Markarian galaxies, classified in the literature as BL Lacobjects (B2 1101+38 and B2 1652+39). The radial profiles forellipticity, position angle, and B_4 term of the Fourier analysis arepresented in the paper, and the morphological peculiarities of theellipticals are described, including the presence of shells, tails,nuclear dust, isophote twisting, off-centering, and boxiness or disknessof the isophotes. Only one of the galaxies in this work is included inthe subsample of B2 radio galaxies with well-defined jets (Parma et al.\cite{parma87}). In this sense the present sample complements the sampleof 24 radio galaxies with well-defined radio jets in Parma et al. forwhich a similar study was presented in González-Serrano et al.(\cite{gserrano93}). The irregular galaxy B2 0916+33 appears to bemisclassified, and we suggest that the right identification of the radiosource is a nearby point like object with V=18.45 mag. The spiral galaxyassociated with B2 1441+26 is also misclassified. A point-like opticalobject with V=18.88 mag, located at ~ 36 arcsec from the originalidentification and coincident with the radio core is the most probablecounterpart. Table 4 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html Complete Figure 1 and Figure 2are only available at http://www.edpsciences.org
| Radio-loud active galaxies in the northern ROSAT All-Sky Survey. IV. Properties of sources stronger than 100 mJy at 5 GHz
We present multi-frequency radio data for 741 extragalactic sources witha 5 GHz integrated flux density of > 100 mJy. These sources have beenselected from a cross-correlation of an early ROSAT All-Sky Surveysource list with a list of compact radio sources of the 5 GHz Green Banknorthern sky survey (RGB sample). The majority of sources werequasi-simultaneously observed with the Effelsberg 100-m telescope at 11cm, 6 cm, and 2.8 cm. We have determined the spectrum, size and linearpolarization properties of these sources. We compare the radio data withROSAT measurements and optical data. We find that the X-ray selectedradio sources, when compared with unbiased radio source samples, are onaverage slightly more compact, show a higher fractional polarization, ahigher absolute rotation measure (RM), and have flatter spectra.Absolute RMs are larger for steep spectrum than for flat spectrumsources and for extended than for compact sources. The average redshiftincreases with the radio flux density, which indicates that the X-rayselected radio sources have a larger fraction of beamed radio emission.All source characteristics of the sample are in accordance with presentunification schemes for AGN, where X-ray selected sources are preferablelooked at face on. Tables~1 and 2 are only available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/Abstract.html
| Optical and CO Radio Observations of Poor Cluster Zwicky 1615.8+3505
The cluster Zwicky 1615.8+3505 is considered to be a dynamically youngpoor cluster. To investigate the morphology and star-formation activityof galaxies under the environment of a dynamically young poor cluster,we have performed V, R, and I surface photometry, optical low-resolutionspectroscopy, and 12CO (J=1-0) line observations for membergalaxies. Our data show that more than 90% of the observed galaxies showregular morphologies and no star-formation activities, indicating thatthe environment does not affect these galaxy properties. Among sixteengalaxies observed, only NGC 6104 shows a significant star-formationactivity, and shows a distorted morphology, indicating a tidalinteraction. This galaxy contains double knots, and only one knotpossesses Seyfert activity, though the sizes and luminosities aresimilar to each other; we also discuss this feature. Based onobservations made at Okayama Astrophysical Observatory (OAO), KisoObservatory (KISO), and Nobeyama Radio Observatory (NRO). KISO isoperated by Institute of Astronomy, School of Science, The University ofTokyo. OAO and NRO are branches of the National AstronomicalObservatory, an inter-university research institute operated by theMinistry of Education, Science, Sports and Culture.
| X-ray observations of low-power radio galaxies from the B2 catalogue
We present an analysis of X-ray data, taken with ROSAT, for awell-defined sample of low-power radio galaxies from the Bologna B2catalogue. Where possible, the HRI has been used in order to takeadvantage of the high spatial resolution provided by this instrument. Avariety of models are fitted to radial profiles in order to separate theresolved and unresolved X-ray emission from the galaxies. We demonstratea strong, approximately linear, correlation between the luminosities ofthe unresolved X-ray components and the 5-GHz luminosities of the radiocores in this sample. This suggests a physical relationship between thesoft X-ray emission of radio galaxies and the jet-generated radio coreemission. We infer a nuclear jet-related origin for at least some of theX-ray emission.
| ROSAT X-ray observations of 3CRR radio sources
Over half the 3CRR sample of radio galaxies and quasars has beenobserved in X-rays with ROSAT pointed observations, and we presentresults from these observations, discussing many of the sources indetail. The improved spatial resolution of ROSAT over earlier missionsallows a better separation of the nuclear and extended components of theX-ray emission. We investigate the relationship between nuclear X-rayand core radio luminosity, and show that our results support a model inwhich every radio galaxy and quasar has a beamed nuclear soft X-raycomponent directly related to the radio core. We report evidence forrich cluster environments around several powerful quasars. These X-rayenvironments are comparable to those of high-redshift radio galaxies.
| The peculiar motions of early-type galaxies in two distant regions - II. The spectroscopic data
We present the spectroscopic data for the galaxies studied in the EFARproject, which is designed to measure the properties and peculiarmotions of early-type galaxies in two distant regions. We have obtained1319 spectra of 714 early-type galaxies over 33 observing runs on 10different telescopes. We describe the observations and data reductionsused to measure redshifts, velocity dispersions and the Mgb and Mg_2Lick linestrength indices. Detailed simulations and intercomparison ofthe large number of repeat observations lead to reliable error estimatesfor all quantities. The measurements from different observing runs arecalibrated to a common zero-point or scale before being combined,yielding a total of 706 redshifts, 676 velocity dispersions, 676 Mgblinestrengths and 582 Mg_2 linestrengths. The median estimated errors inthe combined measurements are Delta cz=20 km s^-1, Delta sigma sigma=9.1 per cent, Delta Mgb Mgb=7.2 per cent and Delta Mg_2=0.015 mag.Comparison of our measurements with published data sets shows nosystematic errors in the redshifts or velocity dispersions, and onlysmall zero-point corrections to bring our linestrengths on to thestandard Lick system. We have assigned galaxies to physical clusters byexamining the line-of-sight velocity distributions based on EFAR andZCAT redshifts, together with the projected distributions on the sky. Wederive mean redshifts and velocity dispersions for these clusters, whichwill be used in estimating distances and peculiar velocities and to testfor trends in the galaxy population with cluster mass. The spectroscopicparameters presented here for 706 galaxies combine high-quality data,uniform reduction and measurement procedures, and detailed erroranalysis. They form the largest single set of velocity dispersions andlinestrengths for early-type galaxies published to date.
| 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.
| The Dynamics of Poor Systems of Galaxies
We assemble and observe a sample of poor galaxy systems that is suitablefor testing N-body simulations of hierarchical clustering and otherdynamical halo models. We (1) determine the parameters of the densityprofile rho(r) and the velocity dispersion profile sigma_p(R), (2)separate emission-line galaxies from absorption-line galaxies, examiningthe model parameters and as a function of spectroscopic type, and (3)for the best-behaved subsample, constrain the velocity anisotropyparameter, beta, which determines the shapes of the galaxy orbits. Oursample consists of 20 systems, 12 of which have extended X-ray emissionin the ROSAT All-Sky Survey. We measure the 877 optical spectra ofgalaxies brighter than m_R~15.4 within 1.5 h^-1 Mpc of the systemcenters (we take H_0=100 h km s^-1 Mpc^-1). Thus, we sample the systemmembership to a radius typically three times larger than other recentoptical group surveys. The average system population is 30 galaxies, andthe average line-of-sight velocity dispersion is ~300 km s^-1. TheNavarro, Frenk, & White universal profile and the Hernquist modelboth provide good descriptions of the spatial data. In most cases anisothermal sphere is ruled out. Systems with declining sigma_p(R) arewell-matched by theoretical profiles in which the star-forming galaxieshave predominantly radial orbits (beta>0) many of these galaxies areprobably falling in for the first time. There is significant evidencefor spatial segregation of the spectroscopic classes regardless ofsigma_p(R).
| An X-Ray and Optical Investigation of the Environments around Nearby Radio Galaxies
Investigations of the cluster environment of radio sources have notshown a correlation between radio power and degree of clustering.However, it has been demonstrated that extended X-ray luminosity andgalaxy clustering do exhibit a positive correlation. This studyinvestigates a complete sample of 25 nearby (z<=0.06) radio galaxiesthat are not cataloged members of Abell clusters. The environment ofthese radio galaxies is studied in both the X-ray and the optical bymeans of the ROSAT All-Sky Survey (RASS), ROSAT pointed observations,and the Palomar optical Digitized Sky Survey (DSS). X-ray luminositiesand extents are determined from the RASS, and the DSS is used toquantify the degree of clustering via the spatial two-point correlationcoefficient, Bgg. Of the 25 sources, 20 are >=3 σdetections in the X-ray and 11 possessed Bgg's significantlyin excess of that expected for an isolated galaxy. Adding the criterionthat the X-ray emission be resolved, 10 of the radio galaxies do appearto reside in poor clusters with extended X-ray emission suggestive ofthe presence of an intracluster medium. Eight of these galaxies alsopossess high spatial correlation coefficients. Taken together, thesedata suggest that the radio galaxies reside in a low-richness extensionof the Abell clusters. The unresolved X-ray emission from the othergalaxies is most likely associated with active galactic nucleusphenomena. Furthermore, although the sample size is small, it appearsthat the environments of FR I and FR II sources differ. FR I's tend tobe more frequently associated with extended X-ray emission (10 of 18),whereas FR II's are typically point sources or nondetections in theX-ray (none of the seven sources exhibit extended X-ray emission).
| Radiative ages in a representative sample of low luminosity radio galaxies
Two frequency observations, mainly at 1.4 and 5 GHz from the VLA, havebeen used to study spectral variations along the lobes of some nearbylow luminosity radio galaxies that constitute a representative sampleselected from the B2 catalogue. The variations of the spectral indexhave been interpreted as being due to synchrotron and inverse Comptonlosses and characteristic spectral ages are deduced for the relativisticelectrons. The radiative ages are in the range of several 10(7) years.These ages correlate well with the source sizes. They also appear to beconsistent with dynamical ages determined from ram-pressure arguments,if we make reasonable assumptions about the ambient gas density andallow for very moderate deviations from the equipartition conditions.There appears to be a significant difference between the radiative agesof sources in our sample and those of more powerful 3CR radio sources.We briefly discuss the possibility of re-acceleration processes andindicate some objects where these may occur.
| A catalogue of Mg_2 indices of galaxies and globular clusters
We present a catalogue of published absorption-line Mg_2 indices ofgalaxies and globular clusters. The catalogue is maintained up-to-datein the HYPERCAT database. The measurements are listed together with thereferences to the articles where the data were published. A codeddescription of the observations is provided. The catalogue gathers 3541measurements for 1491 objects (galaxies or globular clusters) from 55datasets. Compiled raw data for 1060 galaxies are zero-point correctedand transformed to a homogeneous system. Tables 1, 3, and 4 areavailable in electronic form only at the CDS, Strasbourg, via anonymousftp 130.79.128.5. Table 2 is available both in text and electronic form.
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
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