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Study of the physical conditions in active galactic nuclei. Physical conditions in the cores of two nearby radio galaxies
We have carried out a search for compact radio sources in the cores of16 nearby radio galaxies. We detected compact components in four radiogalaxies, and found upper limits for the flux density in compactcomponents in ten radio galaxies. VLBI observations enabled thedetection of a turnover in the spectra of the two nearby radio galaxies3C 111 and 3C 465. Using a method based on an inhomogeneous model for asynchrotron source, we estimate the magnetic-field strength and theenergy densities in the magnetic field and relativistic electrons in thecores of these radio galaxies. Strong inhomogeneity in the distributionof the magnetic fields in the cores of 3C 111 and 3C 465 is implied byour analysis. The magnetic-field strengths in the central regions ofthese galactic nuclei, on scales of 0.1 pc, exceed the meanstrength by four to five orders of magnitude, and lie in the range 102 G< H < 104 G.
| Classifications of the Host Galaxies of Supernovae, Set III
A homogeneous sample comprising host galaxies of 604 recent supernovae,including 212 objects discovered primarily in 2003 and 2004, has beenclassified on the David Dunlap Observatory system. Most SN 1991bg-likeSNe Ia occur in E and E/Sa galaxies, whereas the majority of SN1991T-like SNe Ia occur in intermediate-type galaxies. This differenceis significant at the 99.9% level. As expected, all types of SNe II arerare in early-type galaxies, whereas normal SNe Ia occur in all Hubbletypes. This difference is significant at the 99.99% level. A smallnumber of SNe II in E galaxies might be due to galaxy classificationerrors or to a small young-population component in these mainly oldobjects. No significant difference is found between the distributionsover the Hubble type of SNe Ibc and SNe II. This confirms that both ofthese types of objects have similar (massive) progenitors. The presentdata show that in order to understand the dependence of supernova typeon host-galaxy population, it is more important to obtain accuratemorphological classifications than it is to increase the size of thedata sample.
| Supernova 2004H in IC 708
IAUC 8273 available at Central Bureau for Astronomical Telegrams.
| Supernovae 2004H, 2004I, and 2004J
IAUC 8272 available at Central Bureau for Astronomical Telegrams.
| Simulations of Galaxy Formation in a ΛCDM Universe. III. The Dissipative Formation of an Elliptical Galaxy
We examine the dynamical structure of an elliptical galaxy simulated inthe ΛCDM scenario. The morphology of the galaxy evolvesdramatically over time in response to the mode and timing of massaccretion; smooth deposition of cooled gas leads to the formation ofcentrifugally supported disks, while major mergers disperse stellardisks into spheroids. In the case we consider here, these two modes ofaccretion alternate successively until z~0.6, when the galaxy undergoesone last major (1:3) merger. The event triggers a starburst thatconsumes much of the remaining gas into stars. Little gas cools andaccretes subsequently, and as a result, most stars at z=0 are rather old(75% are older than 9 Gyr) and distributed in a spheroidal componentthat resembles present-day elliptical galaxies. Dynamically, the galaxyis well approximated by an E4 oblate rotator, with rotational supportincreasing steadily from the center outward. The apparent rotationsupport, as measured by Vrot/σ, correlates stronglywith isophotal deviations from perfect ellipses. Boxy isophotes areobtained when the galaxy is seen face-on andVrot/σ<<1. On the other hand, disky isophotes arefound for inclinations that maximize Vrot/σ. Theline-of-sight velocity distribution is nearly Gaussian at all radii,although small but significant deviations are robustly measured. Thesign of the Gauss-Hermite skewness parameter h3 isanticorrelated with the apparent sense of rotation, in agreement withobserved trends. Despite its relatively recent assembly, the simulatedgalaxy has much higher effective surface brightness than normalelliptical galaxies of similar luminosity, in a way reminiscent of theless common type of M32-like ``compact elliptical galaxies.'' This islikely a direct consequence of our star formation and feedbackalgorithm, which allows for efficient transformation of gas into starsin dense, early collapsing progenitors rather than a definitiveprediction for the structure of galaxies assembled in this ΛCDMhalo. Despite this limitation, our simulation suggests that dark matterplays a minor role in the luminous regions of compact ellipticalgalaxies, whose dynamical mass-to-light ratios are thus not dissimilarto those of normal elliptical galaxies. This explains the proximity ofcompact elliptical galaxies to edge-on projections of the fundamentalplane, despite their far greater velocity dispersion at givenluminosity. Overall, our simulation shows that repeated episodes ofdissipational collapse, followed by merger events, lead to stellarspheroids that are only mildly triaxial and of relatively simplekinematic structure. This is in better agreement with observation thanearlier models based on dissipationless mergers of stellar disks and apositive step toward reconciling the observed structure of ellipticalgalaxies with a hierarchical assembly process where mergers play asubstantial role.
| 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
| The origin of wide-angle tailed radio galaxies
To investigate the origins of wide-angle tailed radio sources (WATs), wehave compiled a sample of these systems in Abell clusters for whichX-ray data exist. Contrary to conventional wisdom, the WATs are found tobe significantly displaced from the X-ray centroids of their hostclusters. The bends in the radio jets of WATs are found to be orientedpreferentially such that they point directly away from or toward thecluster centre, with more of the former than the latter. If thismorphology is attributed to ram pressure, then the WATs are on primarilyradial orbits, with more approaching the X-ray centroid than receding.There is also some evidence that the incoming WATs are on averagefurther from the X-ray centroid than the outgoing ones. All of theseobservations strongly support a scenario in which WATs are created incluster mergers.
| Spectrophotometry of Nearby Field Galaxies: The Data
We have obtained integrated and nuclear spectra as well as U, B, Rsurface photometry for a representative sample of 196 nearby galaxies.These galaxies span the entire Hubble sequence in morphological type, aswell as a wide range of luminosities (MB=-14 to -22). Here wepresent the spectrophotometry for these galaxies. The selection of thesample and the U, B, R surface photometry is described in a companionpaper. Our goals for the project include measuring the current starformation rates and metallicities of these galaxies, and elucidatingtheir star formation histories, as a function of luminosity andmorphology. We thereby extend the work of Kennicutt to lower luminositysystems. We anticipate that our study will be useful as a benchmark forstudies of galaxies at high redshift. We describe the observing, datareduction, and calibration techniques and demonstrate that ourspectrophotometry agrees well with that of Kennicutt. The spectra spanthe range 3550-7250 Å at a resolution (FWHM) of ~6 Å andhave an overall relative spectrophotometric accuracy of ~+/-6%. Wepresent a spectrophotometric atlas of integrated and nuclear rest-framespectra as well as tables of equivalent widths and synthetic colors. Theatlas and tables of measurements will be made available electronically.We study the correlations of galaxy properties determined from thespectra and images. Our findings include: (1) galaxies of a givenmorphological class display a wide range of continuum shapes andemission-line strengths if a broad range of luminosities are considered,(2) emission-line strengths tend to increase and continua tend to getbluer as the luminosity decreases, and (3) the scatter on the generalcorrelation between nuclear and integrated Hα emission-linestrengths is large.
| Surface Photometry of Nearby Field Galaxies: The Data
We have obtained integrated spectra and multifilter photometry for arepresentative sample of ~200 nearby galaxies. These galaxies span theentire Hubble sequence in morphological type, as well as a wide range ofluminosities (MB=-14 to -22) and colors (B-R=0.4-1.8). Herewe describe the sample selection criteria and the U, B, R surfacephotometry for these galaxies. The spectrophotometric results will bepresented in a companion paper. Our goals for the project includemeasuring the current star formation rates and metallicity of thesegalaxies, and elucidating their star formation histories, as a functionof luminosity and morphology. We thereby extend the work of Kennicutt tolower luminosity systems. We anticipate that our study will be useful asa benchmark for studies of galaxies at high redshift. We discuss theobserving, data reduction, and calibration techniques and show that ourphotometry agrees well with previous work in those cases in whichearlier data are available. We present an atlas of images, radialsurface brightness profiles, and color profiles as well as tables ofderived parameters. The atlas and tables of measurements will be madeavailable electronically. We study the correlations of galaxy propertiesdetermined from the galaxy images. Our findings include the following:(1) colors determined within the effective radius correlate better withmorphological type than with MB and (2) 50% of thelow-luminosity galaxies are bluest in their centers.
| 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.
| 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.
| The revised GB/GB2 sample of extragalactic radio sources
This paper presents the revised sample of 373 extragalactic radiosources brighter than 0.2 Jy at 1.4 GHz. These sources, selected fromthe finding Green Bank surveys, were mapped at 1465 MHz using the VLA atdifferent configurations. The biases introduced into the original GB andGB2 catalogues by confusion as well as partial resolution by the VLA atA-configuration, are eliminated. In effect, a number of sources havebeen excluded, and a few other are included into the revised sample. Nowthe sample is about 99, 97, and 95 per cent complete for sources withS_{1.4}>= 0.55 ;Jy, 0.25 Jy<= S_{1.4}<0.55 ;Jy, and 0.2 Jy<=S_{1.4}<0.25 ;Jy, respectively. A compilation of the radio, optical,and X-ray data available for the sample sources are presented in Table\ref{tab3}. New 4.9-GHz VLA images of selected sources are included. Anumber of statistics describing radio morphological and spectralcontents of the sample, radio variability, revised source counts,redshift distributions, etc. are given. Table~\protect\ref{tab3
| A 20 Centimeter VLA Survey of Abell Clusters of Galaxies. VII. Detailed Radio Images
We present detailed radio images, and models, obtained with the VeryLarge Array at 20 cm for 199 radio galaxies in Abell clusters ofgalaxies.
| 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.
| The fundamental plane of early-type galaxies: stellar populations and mass-to-light ratio.
We analyse the residuals to the fundamental plane (FP) of ellipticalgalaxies as a function of stellar-population indicators; these are basedon the line-strength parameter Mg_2_ and on UBVRI broad-band colors, andare partly derived from new observations. The effect of the stellarpopulations accounts for approximately half the observed variation ofthe mass-to-light ratio responsible for the FP tilt. The residual tiltcan be explained by the contribution of two additional effects: thedependence of the rotational support, and possibly that of the spatialstructure, on the luminosity. We conclude to a constancy of thedynamical-to-stellar mass ratio. This probably extends to globularclusters as well, but the dominant factor would be here the luminositydependence of the structure rather than that of the stellar population.This result also implies a constancy of the fraction of dark matter overall the scalelength covered by stellar systems. Our compilation ofinternal stellar kinematics of galaxies is appended.
| Briefly noted: Irish astronomy (poem)
Not Available
| A Catalog of Stellar Velocity Dispersions. II. 1994 Update
A catalog of central velocity dispersion measurements is presented,current through 1993 September. The catalog includes 2474 measurementsof 1563 galaxies. A standard set of 86 galaxies is defined, consistingof galaxies with at least three reliable, concordant measurements. It issuggested that future studies observe some of these standard galaxies sothat different studies can be normalized to a consistent system. Allmeasurements are reduced to a normalized system using these standards.
| A 20 CM Survey of Abell Clusters of Galaxies. V. Optical Observations and Surface Photometry
We present results from a program of optical imaging of 265 radiogalaxies in rich clusters. Using isophotal surface photometry, weinvestigate the optical properties such as the morphology, surface-brightness profiles, surface-brightness/size relationships,ellipticities, and the frequency of nonelliptical isophotes. The resultsare compared to a "normal" nonradio-selected sample of ellipticalgalaxies from the same clusters. The goal is to determine if the parentpopulation of FR I radio galaxies can be distinguished optically fromradio-quiet galaxies. The results of the analysis are that clusterellipticals are a very homogeneous class of objects. The opticalproperties are consistent with a one-parameter family, where the opticalluminosity is the fundamental parameter. In all tests considered, radio-loud FR I galaxies cannot be distinguished optically from radio-quietgalaxies selected from the same environment. The local density of nearbycompanions (<20 kpc) and the frequency of morphological peculiaritiesor tidal interactions are not statistically different between theradio-loud and quiet samples. There is some suggestion from comparisonto published samples of non-cluster radio galaxies, that the clusterenvironment is not condusive to long-lived tidal interactions, and thatsuch events may be more important to galaxy evolution in poor groups andlower density environments. Such events appear to have little influenceon the formation of FR I radio galaxies in rich clusters. The resultsare consistent with the idea that all elliptical galaxies may at sometime (or many times) contain powerful (rR I) radio sources.
| A 20 CM VLA Survey of Abell clusters of galaxies. 4: The radio sample and cluster properties
This is the fourth in a series of papers describing an in depth study ofa large statistical sample of radio galaxies in Abell clusters. Thissample forms the basis of a detailed optical and radio study of the hostgalaxy properties, environments, and evolutionary models for radiogalaxies as a class of objects. In this paper, we examine the radiodetection statistics as a function of cluster morphological type, galaxyrichness, and spatial location within the cluster distribution. Theserelationships are also parameterized as a funtion of radio power. Thespatial distributions of the radio sources as a function of distancefrom the cluster center indicate that radio galaxies are preferentiallylocated at small radii from the center of the cluster potential. This isobserved as a factor of 2-3 excess over that predicted by a King-modelsurface-density distribution. The excess is higher in the upper radiopower bin. This result is easily explained, however, from the spatialdistribution of the brightest galaxies and the relationship betweenradio and optical luminosity. The sample is divided into richnessclasses 0, 1, and 2, according to Abell's criterion. and in two radiopower ranges. While simple counting shows that richer clusters have moreradio galaxies in both radio power bins, when the detections are scaledto the number of galaxies surveyed in each cluster, no significantcorrelations are found. This result implies that the number of radiogalaxies detected simply scales with the number of galaxies surveyed.The higher galaxy density (and presumably higher ICM gas density) inricher clusters does not appear to affect the rate of radio sourceformation. The clusters are divided into Rood-Sastry and Bautz-Morganmorphological types. While it would appear that the more regularclusters have higher radio detection rates, when the classes arenormalized to the number of galaxies, the radio detection rates arefound to be identical regardless of cluster morphology. In conclusion,it is the optical properties of the host galaxy which most influenceboth the radio detection rate and the radio source properties. Thecluster properties, galaxy density, and spatial location of the galaxydo not significantly affect the observed radio statistics.
| Properties of nearby clusters of galaxies. II. A 151, A 637, A 646, A 649, A 655, A 1132, A 1314, A 1377, A 1570, A 1589.
We present F band photometry, from digitized 48-inch Palomar plates, of1167 galaxies brighter than m_3_+3 in 10 Abell clusters. For eachgalaxy, absolute coordinates, magnitude, size, ellipticity endorientation are given. For each cluster we provide finding charts andcontour maps of the galaxy surface density.
| A finding list of extragalactic radio jets and statistical results
Extragalactic radio jets are a common phenomenon. Many more jets havebeen found since Bridle and Perley (1984) reviewed the subject. In thispaper, we list 276 radio jets known in December 1989. We investigate theratio of jet emission to core flux as a function of core luminosity andcompare it with the fraction of detections of jets given by Bridle andPerley. We find them to be consistent.
| Surface photometry of radio galaxies. II - Cluster sources
R-band CCD photometric observations are reported for 52 radio galaxiesin clusters for which good radio maps are available. Data obtained withthe No. 1 0.9-m telescope at KPNO (following the procedures described byOwen and Laing, 1989) are presented in tables and graphs and discussedin detail. Optical and radio luminosity are found to be well correlatedin twin-jet, fat-double, narrow-angle-tail, and small-twin-jet sources,all of which are clearly distinguished from the classical doubles as inthe scheme of Fanaroff and Riley (1974). It is also shown that theelliptical parent galaxies of the extended radio sources form aone-parameter family with the optical luminosity as the key parameter.
| The ultraviolet spectra of nearby radio galaxies
New and archival IUE SWP spectra are reported for nine nearby radiogalaxies (V is less than 15 mag), together with optical emissionlikedata for these galaxies as well as a number of candidates with weakerline emission. Both their UV line and continuum properties, as well astheir UV and UV-optical line ratios, are examined. Ly-alpha emission isfound to be common among local radio galaxies, at modest luminosities(typically 10 exp 41-42 erg/s). No apparent relation is found betweenL(Ly-alpha) and radio power for the nearby radio galaxies alone. TheLy-alpha/H-alpha ratio in low power nearby radio galaxies is 2-5 timeslower than the prediction for case B recombination. The destruction ofLy-alpha photons by grains during resonant scattering can explain theobserved deficiency for reasonable metallicities. The nearby radiogalaxies have in general a small C IV/Ly-alpha ratio (less than 0.1).Comparison of the C IV and Ly-alpha strengths with those in luminous AGNsuggests that most of the UV continuum comes from the stellarpopulation, and not from the AGN.
| UGC galaxies stronger than 25 mJy at 4.85 GHz
UGC galaxies in the declination band +5 to +75 deg were identified byposition coincidence with radio sources stronger than 25 mJy on theGreen Bank 4.85 GHz sky maps. Candidate identifications were confirmedor rejected with the aid of published aperture-synthesis maps and new4.86 GHz VLA maps having 15 or 18 arcsec resolution, resulting in asample of 347 nearby radio galaxies plus five new quasar-galaxy pairs.The radio energy sources in UGC galaxies were classified as 'starbursts'or 'monsters' on the basis of their infrared-radio flux ratios, infraredspectral indices, and radio morphologies. The rms scatter in thelogarithmic infrared-radio ratio q is not more than 0.16 for starburstgalaxies selected at 4.85 GHz. Radio spectral indices were obtained fornearly all of the UGC galaxies, and S0 galaxies account for adisproportionate share of the compact flat-spectrum (alpha less than0.5) radio sources. The extended radio jets and lobes produced bymonsters are preferentially, but not exclusively, aligned within about30 deg of the optical minor axes of their host galaxies. The tendencytoward minor-axis ejection appears to be independent of radio-sourcesize and is strongest for elliptical galaxies.
| Infrared properties of nearby radio galaxies
The IRAS data for a sample of nearby radio galaxies (z less than 0.13)are analyzed. Comparison of the infrared, radio, and optical datasuggests that most of the long-wavelength infrared emission comes fromcool interstellar dust for almost all of the galaxies; these galaxiesmay contain large amounts (10 to the 8th - 10 to the 10th solar massesof interstelar matter. About 15 percent of the galaxies show evidencefor a hotter thermal component emitting at the shorter IRAS wavelengths;this could be due to dust in the inner regions of the galaxy heated bythe active galactic nucleus.
| A 20 CM VLA survey of Abell clusters of galaxies. I - Distance class of not greater than 3 clusters
Nearby Abell clusters of distance class of not greater than 3 arestudied based on 20-cm VLA observations, Westerbork Synthesis RadioTelescope results, and Einstein Observatory X-ray data. No significantcorrelation is found between the 20-cm radio power and X-ray luminosity,and no evidence is found that regular-type clusters are statisticallymore likely to be radio loud than irregular-type clusters. A weakcorrelation is noted between X-ray-cooling mass-accretion rates andradio powers for central dominant galaxies in cooling-flow clusters,suggesting that either cooling accretion directly fuels the centralengine and/or cooling flows strongly interact with the radio plasma.
| H I absorption in radio elliptical galaxies - Evidence for infall
A complete sample of 29 radio galaxies with compact cores has beenobserved by the VLA in the H I line to an almost uniform optical-depthsensitivity of about 0.01 at a velocity resolution of 40 km/s. Thesegalaxies were selected using continuum observations of an almostcomplete sample of 49 radio galaxies; 21-cm core flux densities aregiven for these galaxies. H I absorption was detected in four galaxies,NGC 3894, NGC 5363, 3C 236, and 4C 31.06, bringing to eight the numberof radio ellipticals in which H I absorption has been detected. In allcases, absorption is seen redshifted wiht respect to the galaxy'ssystemic velocity, or close to the systemic velocity, or both. Noblueshifted absorption components are seen. These observationsdemonstrate the infall of H I to the inner regions of radio ellipticalgalaxies. The estimated infall rates (a few hundredths of a solar massper year) are more than adequate to fuel the nuclear activity.
| Radio surveys and source counts at 408 MHz and 1420 MHz towards the Abell 1314 cluster of galaxies
Observations of the cluster of Abell 1314 galaxies were performed withthe Penticton synthesis telescope simultaneously at 408 MHz (with asensitivity of about 70 mJy) and at 1420 MHz (with a sensitivity ofabout 4.3 mJy). Detections have been made of 3 cluster sources, 64background radio sources at 1420 MHz, and 169 background sources at 408MHz. No candidate has been identified for very-steep-spectrum relicsources in this cluster of galaxies, nor for very-flat-spectrumblue-background radio galaxies behind the cluster.
| The Extragalactic Zoo II
Not Available
| UBVRI photometry of bright GB/GB2 radio galaxies and quasars
Photoelectric UBVRI observations of 25 radio galaxies brighter than V ofabout 17 mag as well as 14 quasars and other stellar objects brighterthan V of about 18 mag are presented and discussed. It is shown thatbroadband spectra and colors of the observed GB/GB2 galaxies are typicalfor the population of giant ellipticals, though some of the galaxieshave a peculiarity in the ultraviolet band. For the quasar candidates,it is shown how the data distinguish between typical quasars and BLLacertae objects. Two detected BL Lacs have been confirmed with furtheroptical polarimetry, infrared photometry, and optical spectroscopy.
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