Contents
Images
Upload your image
DSS Images Other Images
Related articles
An Extended FUSE Survey of Diffuse O VI Emission in the Interstellar Medium
We present a survey of diffuse O VI emission in the interstellar medium(ISM) obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE).Spanning 5.5 yr of FUSE observations, from launch through 2004 December,our data set consists of 2925 exposures along 183 sight lines, includingall of those with previously published O VI detections. The data wereprocessed using an implementation of CalFUSE version 3.1 modified tooptimize the signal-to-noise ratio and velocity scale of spectra from anaperture-filling source. Of our 183 sight lines, 73 show O VIλ1032 emission, 29 at >3 σ significance. Six of the 3σ features have velocities |vLSR|>120 kms-1, while the others have |vLSR|<=50 kms-1. Measured intensities range from 1800 to 9100 LU (lineunit; 1 photon cm-2 s-1 sr-1), with amedian of 3300 LU. Combining our results with published O VI absorptiondata, we find that an O VI-bearing interface in the local ISM yields anelectron density ne=0.2-0.3 cm-3 and a path lengthof 0.1 pc, while O VI-emitting regions associated with high-velocityclouds in the Galactic halo have densities an order of magnitude lowerand path lengths 2 orders of magnitude longer. Although the O VIintensities along these sight lines are similar, the emission isproduced by gas with very different properties.Based on observations made with the NASA-CNES-CSA Far UltravioletSpectroscopic Explorer. FUSE is operated for NASA by Johns HopkinsUniversity under NASA contract NAS5-32985.
| The spectral energy distributions of the revised 200-mJy sample
We address the question of why low-luminosity radio sources withsimilar flat radio spectra show a range of optical activity. Theinvestigation is based on the spectral energy distributions (SEDs) ofobjects from the 200-mJy sample. We gathered new data from the VLA at 43GHz, from SCUBA in the JCMT at 2000, 1350 and 850 μm, and from theISOPHOT instrument on ISO at 170, 90, 60 and 25 μm. There isconsiderable diversity amongst the SEDs of the objects: there areobjects with steep broad-band spectra between centimetre and millimetrebands (14 per cent of the sample); there are those with flat broad-bandspectra over most of the spectral range (48 per cent of the sample); andthere are those which show pronounced submillimetre/infrared excesses(27 per cent of the sample). Some objects of the first group havetwo-sided radio morphology, indicating that their parsec-scale emissionis not dominated by beamed jet emission. Amongst the objects that havesmooth broad-band spectra from the radio to the infrared, there arepassive elliptical galaxies as well as the expected BL Lacertae objects.The most pronounced submillimetre/infrared excesses are shown by thebroad-emission-line objects.
| VLBA polarization observations of BL Lac objects and passive elliptical galaxies
We present Very Long Baseline Array (VLBA) 5-GHz polarimetricobservations of 23 BL Lacertae (BL Lac) objects and radio galaxiesselected from the 200-mJy sample. BL Lac objects have core polarizationvalues lower than those found in previous samples. The magnetic fieldgeometry in the jets is not unique: both parallel and perpendiculargeometries are observed, even in the same sources. The parsec-scalemorphology of radio galaxies is clearly divided in two classes:one-sided core-jet sources, which show polarized emission in the coreand/or jet, and two-sided symmetric objects which are not polarized. Wediscuss and compare the parsec-scale polarization properties of theradio cores and jets for the BL Lac objects and the radio galaxies inrelation to their parsec-scale morphology and high-frequency integratedspectral index.
| The nuclear region of low luminosity flat radio spectrum sources. II. Emission-line spectra
We report on the spectroscopic study of 19 low luminosity Flat RadioSpectrum (LL FRS) sources selected from Marchã's et al.(\cite{March96}) 200 mJy sample. In the optical, these objects aremainly dominated by the host galaxy starlight. After correcting the datafor this effect, we obtain a new set of spectra clearly displaying weakemission lines; such features carry valuable information concerning theexcitation mechanisms at work in the nuclear regions of LL FRS sources.We have used a special routine to model the spectra and assess theintensities and velocities of the emission lines; we have analyzed theresults in terms of diagnostic diagrams. Our analysis shows that 79% ofthe studied objects harbour a Low Ionization Nuclear Emission-lineRegion (or LINER) whose contribution was swamped by the host galaxystarlight. The remaining objects display a higher ionization spectrum,more typical of Seyferts; due to the poor quality of the spectra, it wasnot possible to identify any possible large Balmer components. The factthat we observe a LINER-type spectrum in LL FRS sources supports theidea that some of these objects could be undergoing an ADAF phase; inaddition, such a low ionization emission-line spectrum is in agreementwith the black hole mass values and sub-Eddington accretion ratespublished for some FRS sources.Based on observations collected at the Multiple Mirror Telescope on Mt.Hopkins.Full Fig. 1 is only available in electronic form athttp://www.edpsciences.org
| The nuclear region of low luminosity flat radio spectrum sources. I. Stellar content
In this work we have examined the spectroscopic properties of a sampleof 19 optically bright, low luminosity Flat Radio Spectrum (LL FRS)sources. Our study focuses on the properties of their host galaxies,namely the nuclear stellar populations and dust content. In the optical- spectral region covered by our data - the objects in the sample aremainly dominated by the host galaxy starlight, which strongly dilutesthe non-thermal continuum as well as possible emission-line featuresrelated to the active nucleus. We have computed the nuclear stellarpopulations contributing to the spectra of the objects in our sample.The stellar population synthesis has been performed by using a veryreliable mathematical method, which yields a Global PrincipalGeometrical solution. Our results show that, for most of the objects inthe sample, the populations are composed of old stars of solarmetallicity, or lower; the populations are mainly composed of late-typestars, i.e. G, K and M spectral types, the young component coming thusfrom supergiant stars; the dust content is weak. Both the stellarpopulations and the dust content are in agreement with what is usuallyobserved in ``normal'' elliptical galaxies. Similar stellar content hasequally been found in the nuclear regions of galaxies hosting a LowIonization Nuclear Emission Line Region, or LINER.The present work is important in illustrating the different applicationsof stellar population synthesis in the study of low luminosity radiosources. In fact, the synthesis allows us not only to obtain valuableinformation about the stellar populations and dust content of the hostgalaxies, therefore providing material for further studies on theconnection between host galaxy and active nucleus, but also to revealthe so-far unstudied optical emission-line features present in thespectrum of our objects.Based on observations collected at the Multiple Mirror Telescope on Mt.Hopkins.Tables 2, 3 and full Fig. 1 are only available in electronic form athttp://www.edpsciences.org
| The Redshift Distribution of Flat-Spectrum Radio Sources
The redshift distribution of flat-spectrum radio sources with 5 GHz fluxdensities S5>~5 mJy is a key component in using currentradio lens surveys to probe the cosmological model. We have constructedthe first flat-spectrum radio sample in the flux density range 3-20 mJy.Our new sample has 33 sources; we have determined the redshifts of 14 ofthese (42% complete). The low mean redshift, ~=0.75, of ourfaintest sample needs to be confirmed by further observations to improvethe sample completeness. We also increased the redshift completeness ofseveral surveys of brighter flat-spectrum sources. While the meanredshift ~=1.1 of flat-spectrum samples fainter than 1 Jy isnearly constant, the fraction of the sources identifiable as quasarssteadily drops from ~80% to ~10% as the flux density of the sourcesdecreases.
| Redshift-Distance Survey of Early-Type Galaxies: Spectroscopic Data
We present central velocity dispersions and Mg2 line indicesfor an all-sky sample of ~1178 elliptical and S0 galaxies, of which 984had no previous measures. This sample contains the largest set ofhomogeneous spectroscopic data for a uniform sample of ellipticalgalaxies in the nearby universe. These galaxies were observed as part ofthe ENEAR project, designed to study the peculiar motions and internalproperties of the local early-type galaxies. Using 523 repeatedobservations of 317 galaxies obtained during different runs, the dataare brought to a common zero point. These multiple observations, takenduring the many runs and different instrumental setups employed for thisproject, are used to derive statistical corrections to the data and arefound to be relatively small, typically <~5% of the velocitydispersion and 0.01 mag in the Mg2 line strength. Typicalerrors are about 8% in velocity dispersion and 0.01 mag inMg2, in good agreement with values published elsewhere.
| Automated optical identification of a large complete northern hemisphere sample of flat-spectrum radio sources with [formmu1]S6 cm>200 mJy
This paper describes the automated optical APM identification of radiosources from the Jodrell Bank-VLA Astrometric Survey (JVAS), as used forthe search for distant radio-loud quasars. Since JVAS was not intendedto be complete, a new complete sample, JVAS++, has been constructed withselection criteria similar to those of JVAS (S5GHz>200mJy,α1.4-5GHz>-0.5), and with the use of the moreaccurate GB6 and NVSS surveys. Comparison between this sample and JVASindicates that the completeness and reliability of the JVAS survey are~90 and ~70 per cent respectively. The complete sample has been used toinvestigate possible relations between optical and radio properties offlat-spectrum radio sources. From the 915 sources in the sample, 756have an optical APM identification on a red (e) and/or blue (o) plate,resulting in an identification fraction of 83 per cent with acompleteness and reliability of 98 and 99 per cent respectively. About20 per cent are optically identified with extended APM objects on thered plates, e.g., galaxies. However, the distinction between galaxiesand quasars can not be made properly near the magnitude limit of thePOSS-I plates. The identification fraction appears to decrease from>90 per cent for sources with a 5-GHz flux density of >1Jy, to<80 per cent for sources at 0.2Jy. The identification fraction, inparticular that for unresolved quasars, is found to be lower for sourceswith steeper radio spectra. In agreement with previous studies, we findthat the quasars at low radio flux density levels also tend to havefainter optical magnitudes, although there is a large spread. Inaddition, objects with a steep radio-to-optical spectral index are foundto be mainly highly polarized quasars, supporting the idea that in theseobjects the polarized synchrotron component is more prominent. It isshown that the large spread in radio-to-optical spectral index ispossibly caused by source-to-source variations in the Doppler boostingof the synchrotron component.
| Intermediate BL Lac objects
The 200-mJy sample, defined by Marchã et al., contains about 60nearby, northern, flat-spectrum radio sources. In particular, the samplehas proved effective at finding nearby radio-selected BL Lac objectswith radio luminosities comparable to those of X-ray-selected objects,and low-luminosity flat-spectrum weak emission-line radio galaxies(WLRGs). The 200-mJy sample contains 23 BL Lac objects (including 6 BLLac candidates) and 19 WLRGs. We will refer to these subsamples as the200-mJy BL Lac sample and the 200-mJy WLRG sample, respectively. We havestarted a systematic analysis of the morphological pc-scale propertiesof the 200-mJy radio sources using VLBI observations. This paperpresents VLBI observations at 5 and 1.6GHz of 14 BL Lac objects andWLRGs selected from the 200-mJy sample. The pc-scale morphology of theseobjects is briefly discussed. We derive the radio beaming parameters ofthe 200-mJy BL Lac objects and WLRGs and compare them with those ofother BL Lac samples and with a sample of FR I radio galaxies. Theoverall broad-band radio, optical and X-ray properties of the 200-mJy BLLac sample are discussed and compared with those of other BL Lacsamples, radio- and X-ray-selected. We find that the 200-mJy BL Lacobjects fill the gap between HBL and LBL objects in the colour-colourplot, and have intermediate αXOX as expected in thespectral energy distribution unification scenario. Finally, we brieflydiscuss the role of the WLRGs.
| Flat radio-spectrum galaxies and BL Lacs. I. Core properties
This paper concerns the relationship of BL Lacs and flat-spectrum weakemission-line galaxies. We compare the weak emission-line galaxies andthe BL Lacs in a sample of 57 flat-spectrum objects (March{ãet al. 1996), using high-frequency radio and non-thermal optical fluxdensities, spectral indices and polarization properties. We considerwhether objects which are not `traditional' BL Lacs - due to theirlarger emission line strengths, and larger Ca II spectral breaks - aresimply starlight diluted BL Lacs. Their broad-band spectral propertiesare consistent with this interpretation, but their radio polarizationmay indicate more subtle effects. Comparison of the weak emission-linegalaxies and the BL Lacs shows that, on average, the former have steeperspectra between 8 and 43 GHz, and are less polarized at 8.4 GHz. This isconsistent with many of the weak-lined objects being at larger angles tothe line of sight than the BL Lacs. In addition to this population, weindicate a number of the weak emission-line galaxies which may be`hidden BL Lacs': relativistically boosted objects very close to theline of sight with an apparently weak AGN.
| 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 ROSAT Brightest Cluster Sample - I. The compilation of the sample and the cluster log N-log S distribution
We present a 90 per cent flux-complete sample of the 201 X-ray-brightestclusters of galaxies in the northern hemisphere (delta>=0 deg), athigh Galactic latitudes (|b|>=20 deg), with measured redshiftsz<=0.3 and fluxes higher than 4.4x10^-12 erg cm^-2 s^-1 in the0.1-2.4 keV band. The sample, called the ROSAT Brightest Cluster Sample(BCS), is selected from ROSAT All-Sky Survey data and is the largestX-ray-selected cluster sample compiled to date. In addition to Abellclusters, which form the bulk of the sample, the BCS also contains theX-ray-brightest Zwicky clusters and other clusters selected from theirX-ray properties alone. Effort has been made to ensure the highestpossible completeness of the sample and the smallest possiblecontamination by non-cluster X-ray sources. X-ray fluxes are computedusing an algorithm tailored for the detection and characterization ofX-ray emission from galaxy clusters. These fluxes are accurate to betterthan 15 per cent (mean 1sigma error). We find the cumulative logN-logSdistribution of clusters to follow a power law kappa S^alpha withalpha=1.31^+0.06_-0.03 (errors are the 10th and 90th percentiles) downto fluxes of 2x10^-12 erg cm^-2 s^-1, i.e. considerably below the BCSflux limit. Although our best-fitting slope disagrees formally with thecanonical value of -1.5 for a Euclidean distribution, the BCS logN-logSdistribution is consistent with a non-evolving cluster population ifcosmological effects are taken into account. Our sample will allow us toexamine large-scale structure in the northern hemisphere, determine thespatial cluster-cluster correlation function, investigate correlationsbetween the X-ray and optical properties of the clusters, establish theX-ray luminosity function for galaxy clusters, and discuss theimplications of the results for cluster evolution.
| Limits on Cosmological Models from Radio-selected Gravitational Lenses
We are conducting a redshift survey of 177 flat-spectrum radio sourcesin three samples covering the 5 GHz flux ranges 50-100, 100-200, and200-250 mJy. So far, we have measured 124 redshifts with completenessesof 80%, 68%, and 58% for the bright, intermediate, and faint fluxranges. Using the newly determined redshift distribution, we can derivecosmological limits from the statistics of the six gravitational lensesin the Jodrell Bank-VLA Astrometric Survey sample of 2500 flat-spectrumradio sources brighter than 200 mJy at 5 GHz. For flat cosmologicalmodels with a cosmological constant, the limit using only radio data isOmega 0 > 0.27 at 2 sigma (0.47 < Omega 0 < 1.38 at 1 sigma ).The limits are statistically consistent with those for lensed quasars,and the combined radio + optical sample requires Omega 0 > 0.38 at 2sigma (0.64 < Omega 0 < 1.66 at 1 sigma ) for our mostconservative redshift completeness model, assuming that there are noquasar lenses produced by spiral galaxies. Our best-fit model improvesby approximately 1 sigma if extinction in the early-type galaxies makesthe lensed quasars fainter by Delta m = 0.58 +/- 0.45 mag, but we stillfind a limit of Omega 0 > 0.26 at 2 sigma in flat cosmologies. Theincreasing fraction of radio galaxies as compared to quasars at fainterradio fluxes (rising from ~10% at 1 Jy to ~50% at 0.1 Jy) explains whylensed optical emission is common for radio lenses and partly explainsthe red color of radio-selected lenses.
| 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.
| Bright galaxies from WENSS. I. The minisurvey
A search for bright galaxies associated with radio sources from theWENSS minisurvey has been carried out. A galaxy counterpart was foundfor 402 of almost 10,000 radio sources. Of these a radio and opticallycomplete sample, with a flux density limit at 325 MHz of 30 mJy and alimiting red magnitude of 16, can be constructed, which contains 119galaxies. This paper is the first step of a more general study, in whichwe aim to derive a bright galaxy sample from the entire WENSS survey(which is now available in the public domain) and thus to constructpractically definitive local radio luminosity functions of ellipticaland spiral galaxies. We briefly describe the WENSS minisurvey, and thesteps that are needed for the optical identification of its radiosources. Due to the large numbers of sources involved (over 200,000)completely automated procedures are obviously needed and we discussthese in some detail. It is shown that with modern utilities projects asdescribed here have become quite feasible. Some results (e.g. apreliminary determination of the local radio luminosity function) arepresented. Table 1 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
| The peculiar motions of early-type galaxies in two distant regions. III - The photometric data
We present R-band CCD photometry for 776 galaxies observed in the EFARproject. The photometry is compared with photoelectric data, showingthat a common zero-point good to better than 1 per cent and a precisionof 0.03 mag per zero-point have been achieved. We give the circularlyaveraged surface brightness profiles and the photometric parameters ofthe 762 program galaxies, D(n) diameters, half-luminosity radii, totalmagnitudes, and average effective surface brightnesses. More than 80percent of the profiles have a global S/N ratio larger than 300. Theextrapolation needed to derive total magnitudes is less than 10 percentfor 80 percent of the fits. More than 80 percent of the galaxies havemean effective surface brightness larger than the observed skybrightness. In 90 percent of the profiles the estimate of thecontamination of the sky by the galaxy light is less than 1 percent. Wederive total magnitudes and half-luminosity radii to better than 0.15mag and 25 percent, respectively, for 90 percent of our sample. Incontrast, external comparisons show that data in the literature can bestrongly affected by systematic errors due to large extrapolations,small radial range, sky subtraction errors, seeing effects, and the useof a simple R exp 1/4 fit. The resulting errors can easily amount tomore than 0.5 mag in the total magnitudes and 50 percent in thehalf-luminosity radii.
| Optical spectroscopy and polarization of a new sample of optically bright flat radio spectrum sources
A new sample of bright flat radio spectrum sources selected at 8.4 GHzand consisting of objects brighter than V=17 is discussed. The samplewas selected with three purposes in mind: (i) to find low-luminosity BLLacertae (BL Lac) objects with radio luminosities comparable to those ofBL Lacs selected at X-ray frequencies; (ii) to investigate thedifferences between BL Lacs and other flat radio spectrum sources; and(iii) to define a sample of nearby radio-loud objects, the host galaxiesof which are easy to study. Using information on four observationalparameters, radio polarization, optical percentage polarization, breakcontrast and equivalent width of the strongest emission line, we comparethe properties of BL Lacs with those of other types of active galacticnuclei (AGN) found in the sample We find that most of the objects haveweak emission lines although some sources with Seyfert-type spectra werealso found. With only a few exceptions, the two types of sources appearwell separated in their observational properties. Among the objectsstudied we report 10 new BL Lacs and BL Lac candidates, and we define a`complete' sample of bright flat radio spectrum sources that consists ofthose objects with redshift <=0.1.
| The Peculiar Motions of Early-Type Galaxies in Two Distant Regions. I. Cluster and Galaxy Selection
The EFAR project is a study of 736 candidate elliptical galaxies in 84clusters lying in two regions, toward Hercules-Corona Borealis andPerseus-Pisces-Cetus, at distances cz ~ 6000-15,000 km s^-1^. In thispaper (the first of a series), we present an introduction to the EFARproject and describe in detail the selection of the clusters andgalaxies in our sample. Fundamental data for the galaxies and clustersare given, including accurate new positions for each galaxy andredshifts for each cluster. The galaxy selection functions aredetermined by using diameters measured from Schmidt sky survey imagesfor 2185 galaxies in the cluster fields. Future papers in this serieswill present the spectroscopic and photometric observations of thissample, investigate the properties of the fundamental plane forelliptical galaxies, and determine the large- scale peculiar velocityfields in these two regions of the universe.
| 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.
| Groups of Galaxies in the ROSAT North Ecliptic Pole Survey
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...449..422H&db_key=AST
| A Complete Sample of Sources in the North Ecliptic CAP Selected at 38-MHZ - Part Two - CCD Observations and Their Implications
We present 55 CCD images and six spectra of a complete sample of 57 8Cradio sources selected at 38 MHz in the North Ecliptic Cap. All buteight sources appear to be optically identified to a limiting magnitudeof R ~ 23.5. Using spectroscopic redshifts where available and redshiftestimates from the R magnitudes of the identifications otherwise,together with data on a bright comparison sample, we investigate thedependence of radio spectral index and physical size on redshift andradio luminosity. We find evidence that spectral index is more stronglycorrelated with redshift than with radio luminosity, and that there is aweak anticorrelation of size with redshift. The number density evolutionseen within and between the samples is discussed, as are the relativefractions of quasars and cluster halo sources in the two samples. Wealso comment on the use of radio spectral indices in the search fordistant radio galaxies.
| Photoelectric and CCD photometry of E and S0 galaxies
We present BR photoelectric photometry for 352 E and S0 galaxies thatare part of a large survey of the properties and peculiar motions ofgalaxies in distant clusters. Repeat measurements show our internalerrors to be 2-3 percent in B and R and 1-2 percent in B-R. Comparisonsof BR and BVR reductions for 10 galaxies also observed in V show smallsystematic errors due to differences between the spectral energydistributions of stars and galaxies. External comparisons with B-Vcolors in the literature confirm that these colors are good to 1percent. We also describe R-band CCD observations for 95 of the galaxiesand place these on a BR photometric system for photoelectric and CCDphotomerry, with a common zero-point good to better than 1 percent. Wefind the rms precision of both our photoelectric and CCD R magnitudes tobe 2-3 percent for galaxies as faint as R = 15.
| Interferometer phase calibration sources. I - The region 35-75 deg
A catalog of 800 compact radio sources in the declination range 35-75deg is presented whose positions have been measured to an rms accuracyof about 12 milliarcsec with the VLA. They are primarily intended foruse as phase reference sources for the Jodrell Bank Merlin but they willalso be suitable phase calibrators for the VLA and the VLBI networks.
| 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.
| Radio identifications of UGC galaxies - Starbursts and monsters
New and previously published observational data on galaxies withdeclination less than +82 deg from the Uppsala General Catalog (Nilson,1973) are compiled in extensive tables and characterized in detail.Optical positions are confirmed by measurement of Palomar Sky Survey Oprints, and radio identifications for 176 galaxies are made on the basisof 1.4-GHz Green Bank sky maps or 1.49-GHz observations obtained withthe C configuration of the VLA in November-December 1986; contour mapsbased on the latter observations are provided. Radio-selected andIR-selected galaxy populations are found to be similar (and distinctfrom optically selected populations), and three radio/IR criteria aredeveloped to distinguish galaxies powered by starbursts from those withsupermassive black holes or other 'monster' energy sources.
| Masses of quasars
Quasar masses are investigated assuming that accretion on to massiveblack holes is the ultimate source of energy produced by quasars. Lowerlimit for the total energy emitted and the mass accumulated in blackholes in one cubic Gpc is calculated using various data on quasar countsand bolometric luminosities. The energy produced is at least 8.5 x 10 tothe 66th erg/cubic Gpc. This result is independent of the cosmologicalmodel. Assuming that quasars reside in nuclei of giant galaxies it isshown that minimum masses of dead quasars are of the order of 100million solar masses, close to the observational threshold forground-based telescopes.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
Catalogs and designations:
|
