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Boxy/peanut `bulges': comparing the structure of galaxies with the underlying families of periodic orbits
The vertical profiles of disc galaxies are built by the material trappedaround stable periodic orbits, which form their `skeletons'. Therefore,knowledge of the stability of the main families of periodic orbits inappropriate 3D models enables one to predict possible morphologies foredge-on disc galaxies. In a pilot survey we compare the orbitalstructures that lead to the appearance of `peanut'- and `X'-likefeatures with the edge-on profiles of three disc galaxies (IC 2531, NGC4013 and UGC 2048). The subtraction from the images of a modelrepresenting the axisymmetric component of the galaxies reveals thecontribution of the non-axisymmetric terms. We find a directcorrespondence between the orbital profiles of 3D bars in models and theobserved main morphological features of the residuals. We also apply asimple unsharp masking technique in order to study the sharpest featuresof the images. Our basic conclusion is that the morphology of the boxy`bulges' of these galaxies can be explained by considering disc materialtrapped around stable 3D periodic orbits. In most models, thesebuilding-block periodic orbits are bifurcated from the planar centralfamily of a non-axisymmetric component, usually a bar, at low-ordervertical resonances. In such a case, the boxy `bulges' are parts of barsseen edge-on. For the three galaxies we study, the families associatedwith the `peanut' or `X'-shape morphology are probably bifurcations atthe vertical 2/1 or 4/1 resonance.
| Two more nearby AGNs among INTEGRAL sources
We report optical spectroscopic identification of two INTEGRAL sources,detected in the INTEGRAL all-sky survey (Krivonos et al. 2006, inpreparation). Optical data were obtained with the Russian-Turkish 1.5-m telescope (RTT-150, Bakirlitepe, TUBITAK National Observatory, Turkey), using the TUG Faint Object Spectrograph and Camera (TFOSC). IGRJ01528-0326 --- The source is associated with the nearby edge-on spiral galaxy MCG-01-05-047.
| Modelling the spectral energy distribution of galaxies. III. Attenuation of stellar light in spiral galaxies
We present new calculations of the attenuation of stellar light fromspiral galaxies using geometries for stars and dust which can reproducethe entire spectral energy distribution from the ultraviolet (UV) to theFar-infrared (FIR)/submillimeter (submm) and can also account for thesurface brightness distribution in both the optical/Near-infrared (NIR)and FIR/submm. The calculations are based on the model of Popescu et al.(\cite{Popescu2000}), which incorporates a dustless stellar bulge, adisk of old stars with associated diffuse dust, a thin disk of youngstars with associated diffuse dust, and a clumpy dust componentassociated with star-forming regions in the thin disk. The attenuations,which incorporate the effects of multiple anisotropic scattering, arederived separately for each stellar component, and presented in the formof easily accessible polynomial fits as a function of inclination, for agrid in optical depth and wavelength. The wavelength range considered isbetween 912 {Å} and 2.2 μm, sampled such that attenuation canbe conveniently calculated both for the standard optical bands and forthe bands covered by GALEX. The attenuation characteristics of theindividual stellar components show marked differences between eachother. A general formula is given for the calculation of compositeattenuation, valid for any combination of the bulge-to-disk ratio andamount of clumpiness. As an example, we show how the optical depthderived from the variation of attenuation with inclination depends onthe bulge-to-disk ratio. Finally, a recipe is given for aself-consistent determination of the optical depth from theHα/Hβ line ratio.Tables \ref{tab4}-\ref{tab6} and Appendix A are only available inelectronic form at http://www.edpsciences.org }
| Extraplanar Emission-Line Gas in Edge-On Spiral Galaxies. I. Deep Emission-Line Imaging
The extraplanar diffuse ionized gas (eDIG) in 17 nearby, edge-on diskgalaxies is studied using deep Taurus Tunable Filter Hα and [N II]λ6583 images and conventional interference filter Hα+[N II]λλ6548, 6583 images that reach flux levels generally below~1×10-17 ergs s-1 cm-2arcsec-2. [N II] λ6583/Hα excitation maps areavailable for 10 of these objects. All but one galaxy in the sampleexhibit eDIG. The contribution of the eDIG to the total Hαluminosity is relatively constant, on the order of 12%+/-4%. TheHα scale height of the eDIG derived from a two-exponential fit tothe vertical emission profile ranges from 0.4 to 17.9 kpc, with anaverage of 4.3 kpc. This average value is noticeably larger than theeDIG scale height measured in our Galaxy and other galaxies. Thisdifference in scale height is probably due in part to the lower fluxlimits of our observations. The ionized mass of the extraplanarcomponent inferred by assuming a constant filling factor of 0.2 and aconstant path length through the disk of 5 kpc ranges from1.4×107 to 2.4×108 Msolar,with an average value of 1.2×108 Msolar.Under these same assumptions, the recombination rate required to keepthe eDIG ionized ranges from 0.44×106 to13×106 s-1 cm-2 of the disk, orabout 10%-325% of the Galactic value. A quantitative analysis of thetopology of the eDIG confirms that several galaxies in the sample have ahighly structured eDIG morphology. The distribution of the eDIG emissionis often correlated with the locations of the H II regions in the disk,supporting the hypothesis that the predominant source of ionization ofthe eDIG is photoionization from OB stars located in the H II regions. Astrong correlation is found between the IR (or far-IR) luminosities perunit disk area (basically a measure of the star formation rate per unitdisk area) and the extraplanar ionized mass, further providing supportfor a strong connection between the disk and eDIG components in thesegalaxies. The excitation maps confirm that the [N II]/Hα ratiosare systematically higher in the eDIG than in the disk. Althoughphotoionization by disk OB stars is generally able to explain theseelevated [N II]/Hα ratios, a secondary source of ionizationappears to be needed when one also takes into account other line ratios;more detail is given in a companion paper (our Paper II).
| An Hα survey aiming at the detection of extraplanar diffuse ionized gas in halos of edge-on spiral galaxies. I. How common are gaseous halos among non-starburst galaxies?
In a series of two papers we present results of a new Hα imagingsurvey, aiming at the detection of extraplanar diffuse ionized gas inhalos of late-type spiral galaxies. We have investigated a sample of 74nearby edge-on spirals, covering the northern and southern hemisphere.In 30 galaxies we detected extraplanar diffuse emission at meandistances of |z| ~ 1-2 kpc. Individual filaments can be traced out to|z|<=6 kpc in a few cases. We find a good correlation between the FIRflux ratio (S60/S100) and the SFR per unit area(LFIR/D225), based on thedetections/non-detections. This is actually valid for starburst, normaland for quiescent galaxies. A minimal SFR per unit area for the lowestS60/S100 values, at which extended emission hasbeen detected, was derived, which amounts to dotEA25thres = (3.2+/-0.5)*E40ergs-1 kpc-2. There are galaxies where extraplanaremission was detected at smaller values ofLFIR/D225, however, only in combinationwith a significantly enhanced dust temperature. The results corroboratethe general view that the gaseous halos are a direct consequence of SFactivity in the underlying galactic disk.Based on observations collected at the European Southern Observatory,Chile (ESO No. 63.N-0070, ESO No. 64.N-0034, ESO No. 65.N.-0002).
| A catalogue and analysis of local galaxy ages and metallicities
We have assembled a catalogue of relative ages, metallicities andabundance ratios for about 150 local galaxies in field, group andcluster environments. The galaxies span morphological types from cD andellipticals, to late-type spirals. Ages and metallicities were estimatedfrom high-quality published spectral line indices using Worthey &Ottaviani (1997) single stellar population evolutionary models. Theidentification of galaxy age as a fourth parameter in the fundamentalplane (Forbes, Ponman & Brown 1998) is confirmed by our largersample of ages. We investigate trends between age and metallicity, andwith other physical parameters of the galaxies, such as ellipticity,luminosity and kinematic anisotropy. We demonstrate the existence of agalaxy age-metallicity relation similar to that seen for local galacticdisc stars, whereby young galaxies have high metallicity, while oldgalaxies span a large range in metallicities. We also investigate theinfluence of environment and morphology on the galaxy age andmetallicity, especially the predictions made by semi-analytichierarchical clustering models (HCM). We confirm that non-clusterellipticals are indeed younger on average than cluster ellipticals aspredicted by the HCM models. However we also find a trend for the moreluminous galaxies to have a higher [Mg/Fe] ratio than the lowerluminosity galaxies, which is opposite to the expectation from HCMmodels.
| Disc scalelengths of non-active and active spiral galaxies
Disc scalelengths rD are determined for a sample of 32non-active and 28 active spiral galaxies from optical CCD images. For 21of the 32 non-active galaxies and 20 of the 28 active galaxies B, V, Rand I data have been obtained, while for the remaining galaxies only Band I images have been taken. For 18 of the 21 non-active galaxies,which are measured in all four passbands, rD decreasessystematically from B to I, whereas such a decrease is found for onlyfour of the 20 active galaxies with BVRI data. For the non-activegalaxies, the ratios rD(B)/rD(I),rD(V)/rD(I) and rD(R)/rD(I)increase systematically with increasing apparent ellipticity ɛof the galaxies. For the active galaxies, no systematic variation of anyof the ratios with increasing ɛ is found. The variation ofrD(B)/rD(I) with ɛ is compared with modelcalculations. For the non-active galaxies, the data are represented bestby a model with a stellar disc that has an intrinsic colour gradient andwith a central optical depth in the B band for face-on view ofτ0B=3. For the active galaxies, the best agreement between data andmodels is found for models with a stellar disc with no intrinsic colourgradient and no dust. The best-fitting model for the non-active galaxiesdoes not reproduce the data of the active galaxies. The main conclusionof this work is that structural differences seem to exist between thediscs of non-active and active galaxies. The non-active galaxies showsignificant colour gradients within their discs, whereas the activegalaxies do not. These gradients are probably caused by a combination ofan intrinsic colour gradient within the stellar disc, and dustextinction. Furthermore, the measurements indicate that the non-activegalaxies show significant dust extinction in the centre, but they areoptically thin in the outer regions. The active galaxies do not seem tohave intrinsic colour gradients within the stellar disc and they areoptically thin throughout the disc.
| Modelling the Dust Content of Spiral Galaxies
We compare optical and near-infrared surface photometry of seven edge-onspiral galaxies with corresponding surface photometry calculated from arealistic model of spiral galaxies which takes into account bothabsorption and scattering by the interstellar dust. For the stars andthe dust in the disc we use exponential distributions in bothdirections, radially and perpendicular to the plane of the disc, whilethe de Vaucouleurs (R^1/4) profile is used for the description of thebulge. The effect of the spiral structure in the galactic discs is alsoexamined and it is found that the simple exponential disc model is ableto describe quite accurately the real galaxy. From this analysis we wereable to obtain some general conclusions, the most significant of whichare: 1) The face-on central optical depth is less than unity in alloptical bands, indicating that typical spiral galaxies like those wehave modelled would be completely transparent if they were to be seenface on. 2) The dust scale height is about half that of the stars, whichmeans that dust is more concentrated near the plane of the disc. 3) Thedust scale length is about 1.4 times larger than that of the stars anddust is more radially extended than the stars. 4) The gas-to-dust massratio calculated, with the dust mass derived from the model, is close tothe value derived for our Galaxy. 5) The derived extinction law matchesthe Galactic extinction law quite well, indicating a universal dustbehaviour.
| Modeling the spectral energy distribution of galaxies. II. Disk opacity and star formation in 5 edge-on spirals
Using tools previously described and applied to the prototype galaxy NGC891, we model the optical to far-infrared spectral energy distributions(SED) of four additional edge-on spiral galaxies, namely NGC 5907, NGC4013, UGC 1082 and UGC 2048. Comparing the model predictions with IRASand, where available, sub-millimeter and millimeter observations, wedetermine the respective roles of the old and young stellar populationsin grain heating. In all cases, the young population dominates, with thecontribution of the old stellar population being at most 40%, aspreviously found for NGC 891. After normalization to the disk area, themassive star-formation rate (SFR) derived using our SED modelingtechnique, which is primarily sensitive to the non-ionizing ultravioletoutput from the young stellar population, lies in the range7*E-4-2*E-2 { M}sunyr-1kpc-2. This is consistent with normalized SFRsderived for face-on galaxies of comparable surface gas densities fromHalpha observations. Though the most active star-forminggalaxy of the five in absolute terms, NGC 891 is not an exceptionalsystem in terms of its surface density in SFR.
| A list of peculiar velocities of RFGC galaxies
A list of radial velocities, HI line widths and peculiar velocities of1327 galaxies from the RFGC catalogue has been compiled using actualobservations and literature data. The list can be used for studying bulkmotions of galaxies, construction of the field of peculiar velocitiesand other tasks.
| Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
| Box- and peanut-shaped bulges. I. Statistics
We present a classification for bulges of a complete sample of ~ 1350edge-on disk galaxies derived from the RC3 (Third Reference Catalogue ofBright Galaxies, de Vaucouleurs et al. \cite{rc3}). A visualclassification of the bulges using the Digitized Sky Survey (DSS) inthree types of b/p bulges or as an elliptical type is presented andsupported by CCD images. NIR observations reveal that dust extinctiondoes almost not influence the shape of bulges. There is no substantialdifference between the shape of bulges in the optical and in the NIR.Our analysis reveals that 45% of all bulges are box- and peanut-shaped(b/p). The frequency of b/p bulges for all morphological types from S0to Sd is > 40%. In particular, this is for the first time that such alarge frequency of b/p bulges is reported for galaxies as late as Sd.The fraction of the observed b/p bulges is large enough to explain theb/p bulges by bars. Partly based on observations collected at ESO/LaSilla (Chile), DSAZ/Calar Alto (Spain), and Lowell Observatory/Flagstaff(AZ/U.S.A.). Tables 6 and 7 are only available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Three-dimensional modelling of edge-on disk galaxies
We present detailed three-dimensional modelling of the stellarluminosity distribution for the disks of 31 relatively nearby (<= 110Mpc) edge-on spiral galaxies. In contrast to most of the standardmethods available in the literature we take into account the fullthree-dimensional information of the disk. We minimize the differencebetween the observed 2D-image and an image of our 3D-disk modelintegrated along the line of sight. Thereby we specify the inclination,the fitting function for the z-distribution of the disk, and the bestvalues for the structural parameters such as scalelength, scaleheight,central surface brightness, and a disk cut-off radius. From a comparisonof two independently developed methods we conclude, that thediscrepancies e.g. for the scaleheights and scalelengths are of theorder of ~10%. These differences are not due to the individual methoditself, but rather to the selected fitting region, which masks the bulgecomponent, the dust lane, or present foreground stars. Other seriouslimitations are small but appreciable intrinsic deviations of real diskscompared to the simple input model. In this paper we describe themethods and present contour plots as well as radial profiles for allgalaxies without previously published surface photometry. Resultingparameters are given for the complete sample. Based on observationscollected at the European Southern Observatory, Chile and LowellObservatory, Flagstaff (AZ), U.S.A.
| The Revised Flat Galaxy Catalogue.
We present a new improved and completed version of the Flat GalaxyCatalogue (FGC) named the Revised Flat Galaxy Catalogue (RFGC)containing 4236 thin edge-on spiral galaxies and covering the whole sky.The Catalogue is intended to study large-scale cosmic streamings as wellas other problems of observational cosmology. The dipole moment ofdistribution of the RFGC galaxies (l = 273 degr; b =+19 degr) lieswithin statistical errors (+/-10 degr) in the direction of the LocalGroup motion towards the Microwave Background Radiation (MBR).
| 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.
| Near-infrared observations of galaxies in Pisces-Perseus. I. vec H-band surface photometry of 174 spiral
We present near-infrared, H-band (1.65 $() μm), surface photometry of174 spiral galaxies in the area of the Pisces-Perseus supercluster. Theimages, acquired with the ARNICA camera mounted on various telescopes,are used to derive radial profiles of surface brightness, ellipticities,and position angles, together with global parameters such as H-bandmagnitudes and diameters Radial profiles in tabular form and images FITSfiles are also available upon request from gmorio@arcetri.astro.it.}.The mean relation between H-band isophotal diameter D_{21.5} and theB-band D25 implies a B-H color of the outer disk bluer than3.5; moreover, D_{21.5}/D25 depends on (global) color andabsolute luminosity. The correlations among the various photometricparameters suggest a ratio between isophotal radius D_{21.5}/2 and diskscale length of ~ m3.5 and a mean disk central brightness ~ meq 17.5H-mag arcsec^{-2}. We confirm the trend of the concentration indexC31$ with absolute luminosity and, to a lesser degree, withmorphological type. We also assess the influence of non-axisymmetricstructures on the radial profiles and on the derived parameters. Basedon observations at the TIRGO, NOT, and VATT telescopes. TIRGO(Gornergrat, CH) is operated by CAISMI-CNR, Arcetri, Firenze. NOT (LaPalma, Canary Islands) is operated by NOTSA, the Nordic ObservatoryScientific Association. VATT (Mt. Graham, Az) is operated by VORG, theVatican Observatory Research Group Table 3 and Fig. 4 are only availablein electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html.
| Are spiral galaxies optically thin or thick?
The opacity of spiral galaxies is examined by modelling the dust andstellar content of individual galaxies. The three dimensional model thatwe use assumes exponential distributions for the dust and the stars inthe disk, while the R(1/4) law is used to describe the bulge. In thismodel, both absorption and scattering by the dust are taken intoaccount. The model is applied to five late-type spiral galaxies (NGC4013, IC 2531, UGC 1082, NGC 5529 and NGC 5907) using their optical (andnear infrared for IC 2531) surface photometry. For these galaxies wehave determined the scalelengths and scaleheights of the stars and thedust in the disk, the bulge characteristics, the inclination angle andthe face-on optical depth. Computation of the dust masses, as well asthe extinction as a function of the wavelength, are also reported.Having analyzed a total of seven galaxies thus far, the five galaxiesmentioned above plus UGC 2048 and NGC 891 presented in (Xilouris et al.1997, 1998), we are able to draw some general conclusions, the mostsignificant of which are: 1) The face-on central optical depth is lessthan one in all optical bands, indicating that typical spiral galaxieslike the ones that we have modelled would be completely transparent ifthey were to be seen face-on. 2) The dust scaleheight is about half thatof the stars, which means that the dust is more concentrated near theplane of the disk. 3) The dust scalelength is about 1.4 times largerthan that of the stars and the dust is more radially extended than thestars. 4) The dust mass is found to be about an order of a magnitudemore than previously measured using the IRAS fluxes, indicating theexistence of a cold dust component. The gas-to-dust mass ratiocalculated is close to the value derived for our Galaxy. 5) The derivedextinction law matches quite well the Galactic extinction law,indicating a universal dust behaviour.
| Optical and NIR modelling of NGC 891
We compare B, V, I, J, K surface photometry of the edge-on spiral galaxyNGC 891 with corresponding surface photometry calculated from arealistic model of spiral galaxies, taking into account both absorptionand scattering by dust. For the stars and the dust in the disk, we useexponential distributions in both directions, radially and perpendicularto the plane of the disk. For the bulge we use the emissivitydistribution given by the Hubble profile. Apart from the exponentialmain stellar disk, it was found necessary to include also a secondstellar disk, describing the young stellar population in this galaxy.This disk has a scaleheight about three times less than that of the maindisk and its emissivity is constant in the radial direction with a cutoff at the visual end of the galaxy. The young stars are detected onlyin the B and V bands, indicating that in these bands they contributesignificantly to the light near the major axis. For this galaxy we havefound a face-on central optical depth of less than one in all bands,indicating that if the galaxy were seen face-on, it would be transparentin the optical and near infrared region of the spectrum. The total dustmass is calculated from the model parameters and the gas to dust ratiois found to be very similar to that of our Galaxy. The ratiosA_λ/A_V of the extinction values are computed for the five bandsand compare quite well with the values given for our Galaxy.
| Spectroscopy of Edge-On Spirals
We present HI line observations of \Ntot edge-on spiral galaxies,extracted from the Flat Galaxy Catalog of Karachentsev \etal (1993).Fluxes, systemic velocities and line widths are given for \Ndet detectedgalaxies, as well as search parameters for \Nnod undetected systems.Widths are corrected for instrumental broadening, smoothing,signal-to-noise and profile shape, and an estimate of the error on thewidth is given. When corrected for turbulent broadening and inclinationangle of the disks, the velocity widths presented here can provide theappropriate line width parameter needed to derive distances via theTully-Fisher relation.
| The distribution of stars and dust in spiral galaxies: the edge-on spiral UGC 2048.
We compare B, V, I surface photometry of the edge-on spiral galaxy UGC2048 with corresponding surface photometry calculated from a realisticmodel of spiral galaxies, taking into account both absorption andscattering by dust. Our goal is to determine the distribution of starsand dust in the galaxy from the observed surface photometry. In themodel that we use we assume that the stars and the dust in the disk aredistributed axisymmetrically and exponentially in both directions, theradial and the perpendicular to the plane of the disk. The deVaucouleurs R^1/4^ law and the modified Hubble profile are used to fitthe central region of the galaxy and a comparison is made between thetwo. For UGC 2048 we have found a face-on central optical depth of lessthan one in all three bands. This means that, if the galaxy were seenface-on, it would be transparent in the optical region of the spectrum,despite the prominent dust lane seen in the edge-on picture. We havealso determined the scalelengths and scaleheights of the stars and thedust in the disk, the bulge characteristics and the inclination angle ofthe galaxy.
| 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.
| Extraplanar emission-line gas in edge-on galaxies
Seven edge-on galaxies were imaged H alpha in order to determine ifextraplanar emission-line gas (as seen in NGC 891) is a common featureof spiral galaxies. Four of the seven are found to have one or twoprominent filamentary extraplanar structures apiece, with typicalfilament H alpha luminosities of 1037-1038 ergss-1 and scales of 1-2 kpc. Unlike NGC 891, none of thegalaxies has an extensive emission-line halo, to within the sensitivityof the observations, approximately 24 mag per square arcsec in H-alpha(equivalent to an emission measure of 19 pc cm-6 -- more than7 times fainter than the diffuse emission of NGC 891.
| Flat galaxy catalogue
A systematic search for disklike edge-on-galaxies with a diameter largerthan a = 40 arcsec and a major-to-minor axis ratio a/b greater than 7was carried out by means of the Palomar Observatory Sky Survey and theESO/SERC survey. As a result, we present a new catalog of flat galaxies(FGC) containing 4455 objects and covering about 56 percent of the wholesky for the first time. The catalogue is assigned to study large-scalecosmic streamings and other problems of observational cosmology.
| General study of group membership. II - Determination of nearby groups
We present a whole sky catalog of nearby groups of galaxies taken fromthe Lyon-Meudon Extragalactic Database. From the 78,000 objects in thedatabase, we extracted a sample of 6392 galaxies, complete up to thelimiting apparent magnitude B0 = 14.0. Moreover, in order to considersolely the galaxies of the local universe, all the selected galaxieshave a known recession velocity smaller than 5500 km/s. Two methods wereused in group construction: a Huchra-Geller (1982) derived percolationmethod and a Tully (1980) derived hierarchical method. Each method gaveus one catalog. These were then compared and synthesized to obtain asingle catalog containing the most reliable groups. There are 485 groupsof a least three members in the final catalog.
| Axial ratios of edge-on spirals
A diameter-limited sample of 888 normal Sa-Sc galaxies was compiled fromthe Uppsala General Catalog. New micrometer measures of the axial ratiosR of the disk components of 262 edge-on spirals in this sample were madeon copies of blue Palomar Sky Survey plates and calibrated againstphotometric standards. The distribution of isophotal axial ratios forthe whole sample was analyzed to give information on the true axialratios R0 of spiral disks. The mean value of logR0 is 0.95 +/- 0.03 and the dispersion about this mean is0.12 +/- 0.04. A similar mean value (0.90) was obtained from avolume-limited sub-sample of 348 spirals. The dispersion in logR0 is partly due to a dependence of R0 onmorphological type, and the mean value of log R0 for eachtype was estimated. Inclinations of 342 edge-on (R is greater than about3) spirals were determined from their isophotal axial ratios and types.No significant dependence of R0 on luminosity at each typewas found.
| Groups of galaxies within 80 Mpc. II - The catalogue of groups and group members
This paper gives a catalog of the groups and associations obtained bymeans of a revised hierarchical algorithm applied to a sample of 4143galaxies with diameters larger than 100 arcsec and redshifts smallerthan 6000 km/s. The 264 groups of galaxies obtained in this way (andwhich contain at least three sample galaxies) are listed, with the looseassociations surrounding them and the individual members of eachaggregate as well; moreover, the location of every entity among 13regions corresponding roughly to superclusters is specified. Finally,1729 galaxies belong to the groups, and 466 to the associations, i.e.,the total fraction of galaxies within the various aggregates amounts to53 percent.
| Groups of galaxies within 80 Mpc. I - Grouping hierarchical method and statistical properties
An all-sky sample of 4143 galaxies comprising all the objects with anapparent diameter D(25) larger than 100 arcsec and with recessionvelocities smaller than 6000 km/s (i.e., closer than 80 Mpc) wasanalyzed using a hierarchical algorithm similar to Tully's (1987)algorithm, in order to classify the galaxies into groups defined asentities having an average luminosity density higher than 8 x 10 exp 9solar luminosity in the B band/Mpc cubed. The hierarchy is built on themass density of the aggregates progressively formed by the method,corrected for the loss of faint galaxies with the distance. In this way,264 groups of at least three members were identified, among which 82have more than five members and are located at distances lower than 40Mpc. It was found that (1) almost all the crossing times are lower thanH0 exp -1, confirming the bound nature of the groups; (2) themedian virial mass to blue luminosity ratio of the groups is 74 solarmass per solar luminosity in the B band; and (3) the M/L ratio increaseswith the group size, indicating the presence of dark matter aroundgalaxies to a distance of 500 kpc.
| KISO survey for ultraviolet-excess galaxies. XIII.
Not Available
| An Effelsberg/VLA radio continuum survey of an optically selected sample of edge-on spiral galaxies
The results of an extensive radio continuum survey at 5 GHz with the 100m Effelsberg telescope and the Very Large Array of a large sample ofedge-on spiral galaxies (181 galaxies) are presented. The aim of thissurvey was to find candidates for more extensive studies on radio halosand on outflow phenomena from the nuclei of these galaxies.
| Periodicities in galaxy redshifts
Using new data for unassociated galaxies with wide H I profiles andvalues of period and solar motion predicted by Tifft and Cocke (1984), aperiodicity has been found which is significant at the conventional 5percent level. Together with Tifft's work on galaxy pairs and smallgroups, this result appears to provide evidence in favor of thehypothesis that measured galaxy redshifts occur in steps of a littlemore than 72 km/s or a simple multiple of this period.
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