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|The optical jet in 3C 31 on 15 arcsec scales|
Evidence has been found for optical emission from the northern radio jetof 3C 31, the radio source associated with NGC 383. The jet emerges fromthe dust disc and ring of emission at a radius of 5 arcsec, and within10.4 arcsec is measured to have a B-band flux of 2.1 μJy and anR-band flux of 2.3 μJy. The radio-to-optical spectral index of thisregion is 0.78. A second connected region, 11.8 arcsec along the jet inposition angle 340°, found to have similar optical colours andradio-to-optical spectral index may also be jet emission. We combine ournew data with recent radio and X-ray results to conclude that theemission of the jet is synchrotron from the radio to the X-ray.
|A Chandra observation of the X-ray environment and jet of 3C 31|
We have used a deep Chandra observation of the central regions of thetwin-jet Fanaroff-Riley class I (FRI) radio galaxy 3C 31 to resolve thethermal X-ray emission in the central few kpc of the host galaxy, NGC383, where the jets are thought to be decelerating rapidly. This allowsus to make high-precision measurements of the density, temperature andpressure distributions in this region, and to show that the X-rayemitting gas in the centre of the galaxy has a cooling time of only5×107yr. In a companion paper, these measurements areused to place constraints on models of the jet dynamics. A previouslyunknown one-sided X-ray jet in 3C 31, extending up to 8arcsec from thenucleus, is detected and resolved. Its structure and steep X-rayspectrum are similar to those of X-ray jets known in other FRI sources,and we attribute the radiation to synchrotron emission from ahigh-energy population of electrons. In situ particle acceleration isrequired in the region of the jet where bulk deceleration is takingplace. We also present X-ray spectra and luminosities of the galaxies inthe Arp 331 chain of which NGC 383 is a member. The spectrum and spatialproperties of the nearby bright X-ray source 1E 0104+3153 are used toargue that the soft X-ray emission is mostly due to a foreground groupof galaxies rather than to the background broad absorption-line quasar.
|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.
|Redshift-Distance Survey of Early-Type Galaxies. I. The ENEARc Cluster Sample|
This paper presents data on the ENEARc subsample of the larger ENEARsurvey of nearby early-type galaxies. The ENEARc galaxies belong toclusters and were specifically chosen to be used for the construction ofa Dn-σ template. The ENEARc sample includes newmeasurements of spectroscopic and photometric parameters (redshift,velocity dispersion, line index Mg2, and the angular diameterdn), as well as data from the literature. New spectroscopicdata are given for 229 cluster early-type galaxies, and new photometryis presented for 348 objects. Repeat and overlap observations withexternal data sets are used to construct a final merged catalogconsisting of 640 early-type galaxies in 28 clusters. Objectivecriteria, based on catalogs of groups of galaxies derived from completeredshift surveys of the nearby universe, are used to assign galaxies toclusters. In a companion paper, these data are used to construct thetemplate Dn-σ distance relation for early-typegalaxies, which has been used to estimate galaxy distances and derivepeculiar velocities for the ENEAR all-sky sample. Based on observationsat Complejo Astronomico El Leoncito, operated under agreement betweenthe Consejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; Cerro Tololo Inter-American Observatory,National Optical Astronomical Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation; the EuropeanSouthern Observatory (ESO), partially under the ESO-ON agreement; theFred Lawrence Whipple Observatory; the Observatório do Pico dosDias, operated by the Laboratório Nacional de Astrofísicaand the MDM Observatory at Kitt Peak.
|Streaming motions of galaxy clusters within 12 000 km s-1 - III. A standardized catalogue of Fundamental Plane data|
We report the construction of a new, standardized all-sky catalogue ofFundamental Plane (FP) data from early-type galaxies in clusters, forpeculiar velocity applications. This catalogue is based on a compilationof spectroscopic and photometric data consisting of data reported inprevious papers of this series, plus data from published sources. Wecompare velocity dispersion and Mg2 line-strength data from27 sources, and determine the corrections that bring all data sets on toa standardized system. For the velocity dispersions, the corrections aretypically at the level of ~0.015dex, corresponding to 5 per cent in theFP-estimated distance. The uncertainties in these corrections, however,are considerably smaller: the new data obtained by our group are closelymatched on to the standard system, with systematic uncertainties at thelevel of ~0.005dex in velocity dispersion (<2 per cent in distance).In this respect our catalogue significantly improves upon previouslypublished FP data sets. For the Mg2 line-strength index,corrections are typically at the level of 0.01mag, but the uncertaintiesin these corrections are only ~0.002mag. A similar procedure is employedto compare photometric data from nine different sources, correcting forthe average colours of early-type galaxies. We focus on the combinationof parameters appearing in the FP,XFP=logRe-0.32<μ>e, whereRe and <μ>e are the effective radius andeffective surface brightness, respectively. For the data sets consideredhere we show that no further corrections are required to XFP,given the typical systematic zero-point uncertainties per data source(0.003-0.006dex, or 0.7-1.4 per cent in distance). Finally, we useredshift data to assign galaxies to clusters in an objective way. Wepresent a master catalogue of FP data for 699 galaxies in 56 clusters,the largest high-quality data set of its kind. These data will be usedin future papers to determine the distances and peculiar velocities ofthese clusters, and thus probe the peculiar velocity field within12000kms-1.
|X-ray luminosities of galaxies in groups|
We have derived the X-ray luminosities of a sample of galaxies ingroups, making careful allowance for contaminating intragroup emission.The LX:LB and LX:LFIRrelations of spiral galaxies in groups appear to be indistinguishablefrom those in other environments, however the elliptical galaxies fallinto two distinct classes. The first class is central-dominant groupgalaxies, which are very X-ray luminous and may be the focus of groupcooling flows. All other early-type galaxies in groups belong to thesecond class, which populates an almost constant band ofLX/LB over the range9.8
|Spectral energy distributions of FR I nuclei and the FR I/BL Lac unifying model|
We consider archival ROSAT and Hubble Space Telescope (HST) observationsof five FR I radio galaxies and isolate their nuclear emission from thatof the host galaxy. This enables us to determine the spectral energydistributions (SEDs) of their nuclei spanning the region from the radioto the X-ray band. They cannot be described as single power laws, butrequire the presence of an emission peak located between the infrared(IR) and soft X-ray band. We found consistency between the SED peakposition and the values of the broad-band spectral indices of radiogalaxies compared with those of BL Lacs, once the effects of beaming areproperly taken into account. FR I SEDs are thus qualitatively similar tothose of BL Lacs, supporting the identification of FR I sources as theirmisoriented counterparts. No dependence of the shape of the SED on theFR I orientation is found.
|The Dust-Radio Connection in 3CR Radio Galaxies|
We investigate dust in the nuclear regions of radio galaxies on thebasis of 120 images of 3CR radio galaxies in the redshift range0
|Stellar population of ellipticals in different environments: near-infrared spectroscopic observations|
Near-infrared spectra of 50 elliptical galaxies in the Pisces, Abell2199 and 2634 clusters, and in the general field, have been obtained.The strength of the CO (2.3-mu m) absorption feature in these galaxiesis used to explore the presence of an intermediate-age population (e.g.asymptotic giant branch stars) in ellipticals in different environments.We find that the strongest evidence for such a population comes fromellipticals in groups of a few members, which we interpret as the resultof recent minor merging of these galaxies with later-type galaxies.Field galaxies from very isolated environments, on the other hand, showno evidence for young or intermediate-age stars as revealed by Hβand CO absorptions, and appear to form a very uniform, old populationwith very little scatter in metallicity and star formation history.
|Young and Old Galaxies at High Redshift|
We review the results from recent deep HST imaging on faint galaxies.Artificial Neural Networks (ANNs) were used to classify faint galaxiesbased on surface brightness and light profiles. We use available UV +ground-based U-band images of nearby galaxies to address the effectsfrom the uncertain redshifted UV-morphology on the classifications,resulting in `restframe ANN' classifiers. These distinguish quiteconsistently between E/S0's, Sabc's, and Sd/Irr for B <~ 27 mag. AFourier-based method is used to quantify higher order morphologicalfeatures and asymmetries in faint galaxies. We review the faint bluegalaxy population as classified with these restframe ANN's. The medianscale-length at B ~ 27 mag is r_hl~= 0''.25- 0''.3 (~ 1-2 kpc at z ~=1-2). Early and late-type galaxies are fairly well separated in BVIcolor-magnitude diagrams for B<~ 27 mag, with E/S0's being thereddest and Sd/Irr's generally blue. We discuss the B-band galaxy countsas a function of type for 18.5 <~ B <~ 28 mag. We briefly reviewdeep medium-band imaging with HST/WFPC2 in the filter F410M (Lyαat z ~= 2.4) which yielded 18 faint, compact objects surrounding theradio galaxy 53W002 at z ~= 2.39, as well as another 30 in random HSTparallel fields, plus ground-based images over a larger area. DeepHST/PC images of 53W002 at ~ 0''.06 FWHM resolution in BVI + redshiftedLyα suggest that both reflected AGN continuum-light shiningthrough a cone and jet-induced star-formation play a role in its`alignment effect'. We discuss the formation and evolution of 53W002 inthe context of its many surrounding sub-galactic sized objects. Wediscuss the nature of a μJy radio source that remained essentiallyunidentified in HDF flanking fields. The object was identified in deepHST/NICMOS J- and H-band images, and a single emission line at 6595Å was detected, most likely Lyα at z=4.42. This faint (H=23.9 mag), compact (r_e ~= 0''.2), red (I-K = 2.0 mag) object is mostlikely a dusty, star-forming young galaxy with an embedded activenucleus. Finally, HST/NICMOS images are presented of some of the oldestknown red galaxies at z ~= 1.5. Both galaxies are dominated by ar^1/4-profile with 5 kpc scale-length, and are amongst the oldest knownrelaxed systems at that epoch.
|X-ray study of the NGC 383 group of galaxies and the source 1E 0104+3153|
We present results from an analysis of the X-ray properties of the NGC383 galaxy group based on ROSAT PSPC and HRI data. X-ray emission can betraced out to ~ 1 h50(-1) Mpc, the estimated virial radius ofthe system. We determine a total mass of 6 10(13) h50(-1)Msun for the group inside this radius with a gas massfraction of 21%. The intragroup gas temperature of 1.5 keV is bothconsistent with the galaxy velocity dispersion and the X-ray luminosity- temperature relation of groups and clusters suggesting that the groupis fairly relaxed. This is also indicated by the almost sphericallysymmetric appearance of the group's X-ray halo. The X-ray properties ofthe radio galaxy NGC 383 (3C 31) which is located near the center of thegroup are discussed. Its spectrum is best described by a two-componentmodel, consisting of emission from a low-temperature Raymond-Smithplasma, and a hard tail. The emission from NGC 383 is not resolved bythe ROSAT HRI. The possible interaction of the radio jets of 3C 31 withthe IGM is studied. A spatial, spectral and temporal analysis of theEinstein source 1E0104+3153 located within the field of view isperformed, one goal being the identification of the optical counterpart(with both, a high-redshift BAL quasar and a nearby elliptical galaxy,member of a small group, located within the Einstein X-ray errorcircle). We find evidence that the IGM of the small group contributessignificantly to the X-ray emission of 1E0104, which can be described bya Raymond-Smith model of kT =~ 2 keV and a soft X-ray luminosity of L_x=~ 3 10(43) erg/s.
|The Universality of the Fundamental Plane of E and S0 Galaxies: Spectroscopic Data|
We present central velocity dispersion measurements for 325 early-typegalaxies in eight clusters and groups of galaxies, including newobservations for 212 galaxies. The clusters and groups are the A262,A1367, Coma (A1656), A2634, Cancer, and Pegasus Clusters and the NGC 383and NGC 507 Groups. The new measurements were derived frommedium-dispersion spectra that cover 600 Å centered on the Mg I btriplet at lambda ~ 5175 Å. Velocity dispersions were measuredusing the Tonry & Davis cross-correlation method, with a typicalaccuracy of 6%. A detailed comparison with other data sources is made.
|The Universality of the Fundamental Plane of E and S0 Galaxies: Sample Definition and I-Band Photometric Data|
As part of a project to compare the fundamental plane and Tully-Fisherdistance scales, we present here I-band CCD photometry for 636early-type galaxies in eight clusters and groups of galaxies. These arethe A262, A1367, Coma (A1656), A2634, Cancer and Pegasus Clusters, andthe NGC 383 and NGC 507 Groups. Sample selection, cluster properties,and cluster membership assignment criteria are discussed. We presentphotometric parameters that are used in the fundamental plane relation,the effective radius r_e, and the effective surface brightness mu_e, asderived from a r^1/4 fit to the observed radial photometric profile ofeach galaxy. A comparison with similar data found in the literature forthe Coma Cluster shows that large systematic uncertainties can beintroduced in the measurement of r_e and mu_e by the particular methodused to derive those parameters. However, the particular combination ofthese two parameters that enters in the fundamental plane relation is aquantity that can be measured with high accuracy.
|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 220.127.116.11. 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.
|Galaxy clusters in the Perseus-Pisces region. I - Spectroscopic and photometric data for early-type galaxies|
We present new spectroscopic and photometric data for 137 early-typegalaxies in nine clusters and for a set of nearby standard galaxies. Ourspectroscopic data comprise radial velocities, central velocitydispersions, and magnesium line strength indices. We demonstrate thatour new velocity dispersion data can be brought into consistency withthe standard system, to an uncertainty of percent 0.01 dex. From R-bandCCD photometry, we derive the effective diameter, the mean surfacebrightness within the effective diameter, and an R-band diameterequivalent to the Dn parameter of Dressler et al. Internal comparisonsindicate an average error of 0.005 in each measurement of log Dn. Thephotometric data can be brought on to a system consistent with externaldata at the level of 0.5 per cent in distance.
|VLBI Observations of a Complete Sample of Radio Galaxies. VII. Study of the FR I Sources 3C 31, 4C 35.03, and 3C 264|
We present results from global VLBI and VLA observations of threeFanaroff-Riley type I radio galaxies, 3C 31, 4C 35.03, and 3C 264, at afrequency of 5 GHz. In all three cases, we observe asymmetricparsec-scale structures consisting of a compact core and a single jetpointing in the direction of the more prominent kiloparsec jet. Weinterpret such alignment as evidence for the relativistic nature of FR Iradio jets at parsec scales. Comparing the VLBI and VLA images of thesesources, we find a progressive deceleration of the plasma flow fromparsec to kiloparsec scales. We consider another five FR I radiogalaxies studied previously by us and find that, in a set of eight FR Iobjects, the estimated jet bulk velocities and orientation angles withrespect to the observer are consistent with the requirements of theunification model for low-power radio sources.
|Optical Rotation Curves and Linewidths for Tully-Fisher Applications|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.2402C&db_key=AST
|Hot coronae in nearby radio galaxies.|
We present Rosat X-ray observations (with PSPC and HRI instruments) of asample of radio galaxies belonging to the B2 catalog (3C31, 0206+35,1113+29 and 1553+24). The source 3C31 (B2 0104+32) belongs to the groupArp 331 which shows emission from a diffuse hot intra-group gas and fromthe brightest members of the group. We discuss both the morphologicaland spectral features of this extended region deriving, in the frameworkof an isothermal beta model, the core radius, the central density, themass of the emitting material and gravitational mass, obtainingindications on the presence of dark matter. A comparison of X-ray andradio data shows that the thermal pressure of the external gas exceedsthe minimum pressure of the radio components, apart from the regionclose to the nucleus where the jet is over-pressured. The X-ray emissionfrom the single members of the group and from the other galaxies of thesample are consistent with a thermal spectrum originating from hothalos, which is a common feature in early type galaxies. We discuss themain morphological and physical properties of these coronae.Furthermore, using also the data of previous works, we confirm thestrong correlation between the X-ray and optical luminosities of allthese galaxies.
|Stellar population of elliptical galaxies in different environments: spectroscopic CO observations|
Near-infrared spectra of a sample of 21 elliptical galaxies in thePisces and Abell 2634 clusters and the general field have been obtained.The strengths of CO (2.3 μm) absorption features in these galaxiesare used to explore the presence of an intermediate-age population(e.g., asymptotic giant branch stars) in ellipticals in differentenvironments. The CO absorption features in the spectra of fieldellipticals are found to be stronger than those in clusters, withaverage indices of 0.247+/-0.018 and 0.218+/-0.018 respectively. The twodistributions are different at the 95 per cent confidence level.Differences in metallicities and absolute magnitudes among the field andcluster ellipticals cannot explain these observations. This isinterpreted as evidence for an intermediate-age stellar population inthe field galaxies, indicative of a more extended or recent epoch ofstar formation. The effect of CO indices on the scatter in the opticalD_n-sigma and L-sigma relations of ellipticals is explored, and thereare indications of a smaller intrinsic scatter in these relations forisolated galaxies compared to those in richer environments.
|Redshift and Optical Properties for S Statistically Complete Sample of Poor Galaxy Clusters|
From the poor cluster catalog of White et al. (1996), we define a sampleof 71 optically-selected poor galaxy clusters. The surface-densityenhancement we require for our clusters falls between that of the looseassociations of Turner & Gott [AJ, 91,204(1976)] and the Hicksoncompact groups [Hickson, ApJ, 255, 382(1982)]. We review the selectionbiases and determine the statistical completeness of the sample. Forthis sample, we report new velocity measurements made with the ARC 3.5-mDual-Imaging spectrograph and the 2.3-m Steward Observatory MX fiberspectrograph. Combining our own measurements with those from theliterature, we examine the velocity distributions, velocity dispersions,and ID velocity substructure for our poor cluster sample, and compareour results to other poor cluster samples. We find that approximatelyhalf of the sample may have significant ID velocity substructure. Theoptical morphology, large-scale environment, and velocity field of manyof these clusters are indicative of young, dynamically evolving systems.In future papers, we will use this sample to derive the poor clusterx-ray luminosity function and gas mass function, and will examine theoptical/x-ray properties of the clusters in more detail.
|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.
|Determination of the relative spectrophotometric gradients of galaxies. IV|
Relative spectrophotometric gradients of continua are determined for 195galaxies. The spectra have been obtained with the 70-cm meniscustelescope of the Abastumani Astrophysical Observatory using a 2-degpreobjective prism (the reverse linear dispersion was 1200 A/mm inH-gamma). The gradient values were reduced to the AO spectral class andcorrected for light absorption in the Galaxy.
|Double galaxy investigations. I - Observations|
Redshift information from 240 A/mm spectrograms is presented for 370double arcsec galaxy systems from the Karachentsev (1972) catalog,including all pairs in that catalog with separation less than 80 arcsec.An extensive error discussion utilizing internal and external (21 cm)comparisons provides calibration of systematic error and determines theuncertainty for a typical high weight optical redshift to be plus orminus 65 km/sec. Internal differential redshifts within single spectrausing common lines achieve accuracies of 18-30 km/sec, depending uponseparation, and are available for about 200 pairs. Extensive informationon emission and other properties is also provided.
|The anomalous luminosity function of galaxies in compact groups|
Determination of the luminosity function of galaxies in compact groupsis presented. It is different from the luminosity functions of galaxiesin rich clusters, normal small groups, and the field in a way such thatthe number of galaxies per unit magnitude decreases with decreasingbrightness at the faint end. The deficiency of low-luminosity galaxiesin the compact groups cannot be ascribed easily to statisticalfluctuations, selection effects, or other systematic biases; possibleexplanations for the anomaly are discussed.
|Redshifts of galaxies in the cluster Abell 262, and in the region of the Pisces group /centred on NGC 383/|
Redshifts are presented for galaxies in the Abell 262 cluster and forgalaxies within approximately 2 deg on the sky of the Pisces group,otherwise known as the chain of galaxies centered on NGC 383. Meanredshifts and corrected velocity dipersions are determined for bothgroupings, the distribution of bright galaxies in Abell 262 is shown toexhibit a flattened structure, and the problem of distinguishing clustermembers from nonmembers is examined. Velocity distributions are comparedfor the Virgo, Abell 1367, Abell 262, Abell 194, and Centaurus clusters.A model of cluster formation involving the collapse of an expandinginitial bound perturbation is considered, and virial-mass determinationis discussed.
|Radio Sources and Elliptical Galaxies|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969ApJ...157..481R&db_key=AST
|Atlas of Peculiar Galaxies|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966ApJS...14....1A&db_key=AST
|A Group of Galaxies Centered on NGC 383|
|Recent investigations of groups and clusters of galaxies.|
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