Contents
Images
Upload your image
DSS Images Other Images
Related articles
Nuclear Properties of Nearby Spiral Galaxies from Hubble Space Telescope NICMOS Imaging and STIS Spectroscopy
We investigate the central regions of 23 spiral galaxies using SpaceTelescope Imaging Spectrograph (STIS) spectroscopy and archivalNear-Infrared Camera and Multi-Object Spectrometer (NICMOS) imaging. Thesample is taken from our program to determine the masses of centralmassive black holes (MBHs) in 54 nearby spiral galaxies. Stars arelikely to contribute significantly to any dynamical central massconcentration that we find in our MBH program, and this paper is part ofa series to investigate the nuclear properties of these galaxies. We usethe Nuker law to fit surface brightness profiles, derived from theNICMOS images, to look for nuclear star clusters and find possibleextended sources in three of the 23 galaxies studied (13%). The factthat this fraction is lower than that inferred from optical Hubble SpaceTelescope studies is probably due to the greater spatial resolution ofthose studies. Using R-H and J-H colors and equivalent widths ofHα emission (from the STIS spectra), we investigate the nature ofthe stellar population with evolutionary models. Under the assumption ofhot stars ionizing the gas, as opposed to a weak active galactic nucleus(AGN), we find that there are young stellar populations (~10-20 Myr);however, these data do not allow us to determine what percentage of thetotal nuclear stellar population they form. In addition, in an attemptto find any unknown AGN, we use [N II] and [S II] line flux ratios(relative to Hα) and find tentative evidence for weak AGNs in NGC1300 and NGC 4536.Based on observations with the NASA/ESA Hubble Space Telescope obtainedat the Space Telescope Science Institute, which is operated by theAssociation of Universities for Research in Astronomy (AURA), Inc.,under NASA contract NAS 5-26555.
| Nuclear Properties of a Sample of Nearby Spiral Galaxies from Hubble Space Telescope STIS Imaging
We present surface photometry for the central regions of a sample of 48spiral galaxies (mostly unbarred and barred of type Sbc or Sc) observedwith the Space Telescope Imaging Spectrograph on board the Hubble SpaceTelescope. Surface brightness profiles (SBPs) were derived and modeledwith a Nuker law. We also analyzed archival Wide Field Planetary Camera2 images with a larger field of view, which are available for 18galaxies in our sample. We modeled the extracted bulge SBPs with anexponential, an r1/4, or an rn profile. Inagreement with previous studies, we find that bulges of Sbc galaxiesfall into two categories: bulges well described by an exponentialprofile and those well described by an r1/4 profile. Only onegalaxy requires the use of a more general Sérsic profile toproperly describe the bulge. Nuclear photometrically distinct componentsare found in ~55% of the galaxies. For those that we classify as starclusters on the basis of their resolved extent, we find absolutemagnitudes that are brighter on average than those previously identifiedin spiral galaxies. This might be due to a bias in our sample towardstar-forming galaxies, combined with a trend for star-forming galaxiesto host brighter central clusters.Based on observations with the NASA/ESA Hubble Space Telescope, obtainedat the Space Telescope Science Institute, which is operated by theAssociation of Universities for Research in Astronomy, Inc., under NASAcontract NAS 5-26555.
| An Atlas of Hubble Space Telescope Spectra and Images of Nearby Spiral Galaxies
We have observed 54 nearby spiral galaxies with the Space TelescopeImaging Spectrograph (STIS) on the Hubble Space Telescope to obtainoptical long-slit spectra of nuclear gas disks and STIS optical (~Rband) images of the central 5''×5'' of thegalaxies. These spectra are being used to determine the velocity fieldof nuclear disks and hence to detect the presence of central massiveblack holes. Here we present the spectra for the successfulobservations. Dust obscuration can be significant at opticalwavelengths, and so we also combine the STIS images with archivalNear-Infrared Camera and Multi-Object Spectrometer H-band images toproduce color maps to investigate the morphology of gas and dust in thecentral regions. We find a great variety in the different morphologies,from smooth distributions to well-defined nuclear spirals and dustlanes.Based on observations with the NASA/ESA Hubble Space Telescope obtainedat the Space Telescope Science Institute, which is operated by theAssociation of Universities for Research in Astronomy, Inc., under NASAcontract NAS5-26555.
| Modified Newtonian Dynamics as an Alternative to Dark Matter
Modified Newtonian dynamics (MOND) is an empirically motivatedmodification of Newtonian gravity or inertia suggested by Milgrom as analternative to cosmic dark matter. The basic idea is that ataccelerations below ao ~ 10-8 cm/s2 ~cHo/6 the effective gravitational attraction approaches√(gnao), where gn is the usualNewtonian acceleration. This simple algorithm yields flat rotationcurves for spiral galaxies and a mass-rotation velocity relation of theform M ∝ V4 that forms the basis for the observedluminosity-rotation velocity relation-the Tully-Fisher law. We reviewthe phenomenological success of MOND on scales ranging from dwarfspheroidal galaxies to superclusters and demonstrate that the evidencefor dark matter can be equally well interpreted as evidence for MOND. Wediscuss the possible physical basis for an acceleration-basedmodification of Newtonian dynamics as well as the extention of MOND tocosmology and structure formation.
| Bar Galaxies and Their Environments
The prints of the Palomar Sky Survey, luminosity classifications, andradial velocities were used to assign all northern Shapley-Ames galaxiesto either (1) field, (2) group, or (3) cluster environments. Thisinformation for 930 galaxies shows no evidence for a dependence of barfrequency on galaxy environment. This suggests that the formation of abar in a disk galaxy is mainly determined by the properties of theparent galaxy, rather than by the characteristics of its environment.
| Massive Star Formation in Luminous Infrared Galaxies: Giant H II Regions and Their Relation to Super-Star Clusters
We have used Hubble Space Telescope Near-Infrared Camera andMulti-Object Spectrometer broadband (at 1.6 μm) and narrowbandPaα (λrest=1.87 μm) images to identify,respectively, star clusters and H II regions in a sample of eightluminous infrared galaxies (LIRGs). These observations have revealed thepresence of a large population of super-star clusters and bright H IIregions. A significant fraction of the H II regions shows Hαluminosities above that of 30 Doradus, the prototypical giant H IIregion. The excess of extremely luminous H II regions in LIRGs has beenconfirmed by comparison with normal galaxies observed at similar spatialresolutions. Despite the large numbers of identified star clusters and HII regions in LIRGs, we find only a small fraction of coincidences,between 4% and 30% of the total number of detected sources. Usingevolutionary synthesis models we have reproduced the relative fractionsof young H II regions and intermediate and old star clusters observed inArp 299 and the central region NGC 3256 by using a Salpeter initial massfunction and instantaneous star formation. H II regions with no detectednear-infrared cluster counterpart (25%-39% of the detected sources)represent the youngest sites of star formation, with ages up toapproximately 5 Myr and mostly intermediate mass (~=105Msolar) ionizing clusters. For these two galaxies, within thepresent detection threshold we can detect only coincidences (4%-10% ofthe detected sources) between an H II region and a near-infrared starcluster for the most massive star clusters (~=106Msolar) during the first 7 Myr of their evolution. If thereis significant extinction during the first million years, we may notdetect the youngest star-forming regions, and hence the observedfractions of H II regions and coincidences will be lower limits. Theidentified near-infrared super-star clusters with no detectablePaα emission represent the ``old'' population (53%-66% of thedetected sources), with ages between 7 and 20-40 Myr. Older clusterspossibly created in this or previous episodes of star formation arelikely to exist in these systems but cannot be identified with thepresent detection threshold. Our study demonstrates that Paαnarrowband imaging of LIRGs and interacting galaxies identifies theyoungest sites of star formation that could be otherwise missed bynear-infrared broadband continuum surveys. Based on observations withthe NASA/ESA Hubble Space Telescope, obtained from the data archive atthe Space Telescope Science Institute, which is operated by theAssociation of Universities for Research in Astronomy, Inc., under NASAcontract NAS 5-26555.
| The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| Rotation curves and metallicity gradients from HII regions in spiral galaxies
In this paper we study long slit spectra in the region of Hαemission line of a sample of 111 spiral galaxies with recognizable andwell defined spiral morphology and with a well determined environmentalstatus, ranging from isolation to non-disruptive interaction withsatellites or companions. The form and properties of the rotation curvesare considered as a function of the isolation degree, morphological typeand luminosity. The line ratios are used to estimate the metallicity ofall the detected HII regions, thus producing a composite metallicityprofile for different types of spirals. We have found that isolatedgalaxies tend to be of later types and lower luminosity than theinteracting galaxies. The outer parts of the rotation curves of isolatedgalaxies tend to be flatter than in interacting galaxies, but they showsimilar relations between global parameters. The scatter of theTully-Fisher relation defined by isolated galaxies is significantlylower than that of interacting galaxies. The [NII]/Hα ratios, usedas a metallicity indicator, show a clear trend between Z andmorphological type, t, with earlier spirals showing higher ratios; thistrend is tighter when instead of t the gradient of the inner rotationcurve, G, is used; no trend is found with the change in interactionstatus. The Z-gradient of the disks depends on the type, being almostflat for early spirals, and increasing for later types. The[NII]/Hα ratios measured for disk HII regions of interactinggalaxies are higher than for normal/isolated objects, even if all thegalaxy families present similar distributions of Hα EquivalentWidth. Tables 3 and 4 and Figs. 6, 7 and 21 are only available inelectronic form at http://www.edpsciences.org. Table 5 is only availablein electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/389 Based on dataobtained Asiago/Ekar Observatory. Also based on observations made withINT operated on the island of La Palma by ING in the SpanishObservatorio del Roque de Los Muchachos of the Instituto deAstrofísica de Canarias.
| The Ursa Major Cluster of Galaxies. V. H I Rotation Curve Shapes and the Tully-Fisher Relations
This paper investigates the statistical properties of the Tully-Fisher(TF) relations for a volume-limited complete sample of spiral galaxiesin the nearby Ursa Major Cluster. The merits of B, R, I, and K' surfacephotometry and the availability of detailed kinematic information from HI synthesis imaging have been exploited. In addition to the corrected HI global profile widths WiR,I, the available H Irotation curves allow direct measurements of the observed maximumrotational velocities Vmax and the amplitudesVflat of the outer flat parts. The dynamical state of the gasdisks could also be determined in detail from the radio observations.The four luminosity and three kinematic measures allowed theconstruction of 12 correlations for various subsamples. For large galaxysamples, the Mb,iR-logWiR,Icorrelation in conjunction with strict selection criteria is preferredfor distance determinations with a 7% accuracy. Galaxies with rotationcurves that are still rising at the last measured point liesystematically on the low-velocity side of the TF relation. Galaxieswith a partly declining rotation curve(Vmax>Vflat) tend to lie systematically on thehigh-velocity side of the relation when usingWiR,I or Vmax. However, systematicoffsets are eliminated when Vflat is used. Residuals of theMb,iB-log(2Vflat) relation correlateconsistently with global galaxy properties along the Hubble sequencelike morphological type, color, surface brightness, and gas massfraction. These correlations are absent for the near-infraredMb,iK'-log(2Vflat)residuals. The tightest correlation(χ2red=1.1) is found for theMb,iK'-log(2Vflat) relation,which has a slope of -11.3+/-0.5 and a total observed scatter of 0.26mag with a most likely intrinsic scatter of zero. The tightness of thenear-infrared correlation is preserved when converting it into abaryonic TF relation that has a slope of -10.0 in the case(Mgas/LK')=1.6 while a zerointrinsic scatter remains most likely. Based on the tightness of thenear-infrared and baryonic correlations, it is concluded that the TFrelation reflects a fundamental correlation between the mass of the darkmatter halo, measured through its induced maximum rotational velocityVflat, and the total baryonic mass Mbar of agalaxy where Mbar~V4flat. Althoughthe actual distribution of the baryonic matter inside halos of similarmass can vary significantly, it does not affect this relation.
| Statistical Properties of Circumnuclear H II Regions in Nearby Galaxies
We analyze the statistical properties of the circumnuclear H II regionsof a sample of 52 nearby galaxies (v<1000 km s-1) fromarchival HST/NICMOS H-band and Paα (1.87 μm) observations atunprecedented spatial resolutions of between 1 and 30 pc. We catalog HII regions from the continuum-subtracted Paα images and find H IIregions in the central regions of most galaxies, and more than a hundredin each of eight galaxies. In contrast to disk H II regions, thephysical properties (luminosity and size) of individual circumnuclear HII regions do not vary strongly with the morphological type of the hostgalaxy, nor does the number of circumnuclear H II regions per unit area.The Hα luminosity within the central kiloparsec, as derived from HII region emission, is significantly enhanced in early-type (S0/a-Sb)galaxies. We find evidence that bars increase the circumnuclear starformation, presumably by funneling gas from the disk toward the nucleus.Barred galaxies exhibit enhanced luminosities of the brightest H IIregion, the central kiloparsec Hα luminosities (an effect mostlydue to the early-type galaxies in our sample), and the star formationrates per unit stellar mass (which could also be understood as theintegral equivalent widths of Paα) over the central kiloparsecwith respect to nonbarred galaxies. We fit the luminosity functions(LFs) and diameter distributions of the circumnuclear H II regions ineight galaxies where we can catalog enough H II regions to do so in ameaningful way. We use power laws and find that the fitted slopes of theH II region LF are exactly in the previously found ranges and evenconfirm a trend with steeper slopes in galaxies of earlier morphologicaltype. This implies that the physical processes giving rise to enhancedstar formation in the circumnuclear regions of galaxies must be similarto those in disks. Based on observations with the NASA/ESA Hubble SpaceTelescope, obtained from the data archive at the Space Telescope ScienceInstitute, which is operated by the Association of Universities forResearch in Astronomy, Inc., under NASA contract NAS 5-26555.
| The Ursa Major cluster of galaxies. IV. HI synthesis observations
In this data paper we present the results of an extensive 21 cm-linesynthesis imaging survey of 43 spiral galaxies in the nearby Ursa Majorcluster using the Westerbork Synthesis Radio Telescope. Detailedkinematic information in the form of position-velocity diagrams androtation curves is presented in an atlas together with HI channel maps,21 cm continuum maps, global HI profiles, radial HI surface densityprofiles, integrated HI column density maps, and HI velocity fields. Therelation between the corrected global HI linewidth and the rotationalvelocities Vmax and Vflat as derived from therotation curves is investigated. Inclination angles obtained from theoptical axis ratios are compared to those derived from the inclined HIdisks and the HI velocity fields. The galaxies were not selected on thebasis of their HI content but solely on the basis of their clustermembership and inclination which should be suitable for a kinematicanalysis. The observed galaxies provide a well-defined, volume limitedand equidistant sample, useful to investigate in detail the statisticalproperties of the Tully-Fisher relation and the dark matter halos aroundthem.
| 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.
| The Correlation between Galaxy H I Line Widths and K'Luminosities
The relationship between galaxy luminosities and rotation rates isstudied with total luminosities in the K' band. Extinction problems areessentially eliminated at this band centered at 2.1 μm. A templateluminosity-line width relation is derived based on 65 galaxies drawnfrom two magnitude-limited cluster samples. The zero point is determinedusing four galaxies with accurately known distances. The calibration isapplied to give the distance to the Pisces Cluster (59 Mpc) at aredshift in the cosmic microwave background frame of 4771 kms-1. The resultant value of the Hubble constant is 81 kms-1Mpc-1. The largest sources of uncertainty arethe small number of zero-point calibrators at this time at K' and thepresent application to only one cluster.
| Distances to Galaxies from the Correlation between Luminosities and Line Widths. III. Cluster Template and Global Measurement of H0
The correlation between the luminosities and rotation velocities ofgalaxies can be used to estimate distances to late-type galaxies. It isan appropriate moment to reevaluate this method given the great deal ofnew information available. The major improvements described hereinclude: (1) the template relations can now be defined by large,complete samples, (2) the samples are drawn from a wide range ofenvironments, (3) the relations are defined by photometric informationat the B, R, I, and K' bands, (4) the multiband information clarifiesproblems associated with internal reddening, (5) the template zeropoints are defined by 24 galaxies with accurately known distances, and(6) the relations are applied to 12 clusters scattered across the skyand out to velocities of 8000 km s-1. The biggest change fromearlier calibrations are associated with point 5. Roughly a 15% increasein the distance scale has come about with the fivefold increase in thenumber of zero-point calibrators. The overall increase in the distancescale from the luminosity-line width methodology is about 10% afterconsideration of all factors. Modulo an assumed distance to the LargeMagellanic Cloud of 50 kpc and no metallicity corrections to the Cepheidcalibration, the resulting value of the Hubble constant isH0=77+/-8 km s-1 Mpc-1, where the erroris the 95% probable statistical error. Cumulative systematic errorsinternal to this analysis should not exceed 10%. Uncertainties in thedistance scale ladder external to this analysis are estimated at ~10%.If the Cepheid calibration is shifted from the LMC to NGC 4258 with adistance established by observations of circumnuclear masers, thenH0 is larger by 12%.
| 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 NICMOS Snapshot Survey of Nearby Galaxies
We present ``snapshot'' observations with the Near-Infrared Camera andMulti-Object Spectrometer (NICMOS) on board the Hubble Space Telescope(HST) of 94 nearby galaxies from the Revised Shapley Ames Catalog.Images with 0.2" resolution were obtained in two filters, a broadbandcontinuum filter (F160W, roughly equivalent to the H band) and anarrowband filter centered on the Paα line (F187N or F190N,depending on the galaxy redshift) with the 51^''x51^'' field of view ofthe NICMOS camera 3. A first-order continuum subtraction is performed,and the resulting line maps and integrated Paα line fluxes arepresented. A statistical analysis indicates that the average Paαsurface brightness in the central regions is highest in early-type(Sa-Sb) spirals.
| Internal extinction, population incompleteness bias and the faint-end of the B-band Tully-Fisher relation
We analyse the distribution of three different samples of spiralgalaxies of the Local Universe in the B-band luminosity-maximumrotational velocity (L_B-VMax) plane, i.e. the B-magnitudeTully-Fisher (TF) relation. The first sample comprises 25+31 late-type(from Sa to Im-BCD) galaxies, selected from, respectively, the Virgo andthe Ursa Major clusters. In addition, a sample of 20 group extremelate-type (ELT) spiral (from Sd to Sm) galaxies and a sample of 13 dwarflate-type galaxies are selected. First, we analyse the influence ofthree different corrections for internal extinction (IE) on both theslope and the zero-point of the relation. These recipes reflect eitheri) the morphological type dependence of the IE or ii) the assumption ofa ``sandwich-model'' for the distribution of the dust and the stellarcomponents within the disk or iii) the existence of the metallicity-massrelation. As a first result we find that the latter recipe of IEcorrection systematically makes Sa-Sc galaxies brighter than laterspirals. Since the former galaxies mainly populate the region of thebright, fast rotators, the slope of the corresponding TF relationbecomes much steeper than in the other two cases. Under the hypothesisthat the ELT spiral galaxies in clusters and in groups share the sameLF, we show that the claimed skew of the group ELT spiral galaxies withrespect to the extrapolated TF relation of more luminous systems (i.e.the local TF calibrators) is due both to the population incompletenessbias affecting such a template and to the type segregation. Finally, weconfirm that the distribution of dwarf galaxies with comparablerotational and random velocities in the L_B-VMax plane isconsistent with the relation of more luminous systems, while therotationally supported dwarf galaxies are underluminous with respect tothe ELT galaxies of the same VMax. However, the latterresults may suffer from the heterogeneous methods of measurement ofdwarf galaxy distances that were adopted.
| Rotation Curves of Ursa Major Galaxies in the Context of Modified Newtonian Dynamics
This is the third in a series of papers in which spiral galaxy rotationcurves are considered in the context of Milgrom's modified dynamics(MOND). The present sample of 30 objects is drawn from a complete sampleof galaxies in the Ursa Major cluster, with photometric data from Tullyet al. and 21 cm line data from Verheijen. The galaxies are roughly allat the same distance (15 to 16 Mpc). The radio observations are madewith the Westerbork Synthesis Array, which means that the linearresolution of all rotation curves is comparable. The greatest advantageof this sample is the existence of K'-band surface photometry for allgalaxies; the near-infrared emission, being relatively free of theeffects of dust absorption and less sensitive to recent star formation,is a more precise tracer of the mean radial distribution of the dominantstellar population. The predicted rotation curves are calculated fromthe K'-band surface photometry and the observed distribution of neutralhydrogen using the simple MOND prescription, in which the one adjustableparameter is the mass of the stellar disk or the implied mass-to-lightratio. The predicted rotation curves generally agree with the observedcurves, and the mean M/L in the near-infrared is about 0.9 with a smalldispersion. The fitted M/L in the B-band correlates with B-V color inthe sense predicted by population synthesis models. Including earlierwork, about 80 galaxy rotation curves are now well reproduced from theobserved distribution of detectable matter using the MOND formula tocalculate the gravitational acceleration; this lends considerableobservational support to Milgrom's unconventional hypothesis.
| Groups of galaxies. III. Some empirical characteristics.
Not Available
| Bulge-Disk Decomposition of 659 Spiral and Lenticular Galaxy Brightness Profiles
We present one of the largest homogeneous sets of spiral and lenticulargalaxy brightness profile decompositions completed to date. The 659galaxies in our sample have been fitted with a de Vaucouleurs law forthe bulge component and an inner-truncated exponential for the diskcomponent. Of the 659 galaxies in the sample, 620 were successfullyfitted with the chosen fitting functions. The fits are generally welldefined, with more than 90% having rms deviations from the observedprofile of less than 0.35 mag. We find no correlations of fittingquality, as measured by these rms residuals, with either morphologicaltype or inclination. Similarly, the estimated errors of the fittedcoefficients show no significant trends with type or inclination. Thesedecompositions form a useful basis for the study of the lightdistributions of spiral and lenticular galaxies. The object base issufficiently large that well-defined samples of galaxies can be selectedfrom it.
| The Ursa Major Cluster of Galaxies.I.Cluster Definition and Photometric Data
The Ursa Major Cluster has received remarkably little attention,although it is as near as the Virgo Cluster and contains a comparablenumber of H I-rich galaxies. In this paper, criteria for groupmembership are discussed and data are presented for 79 galaxiesidentified with the group. Of these, all 79 have been imaged at B,R,Ibands with CCDs, 70 have been imaged at K' with a HgCdTe array detector,and 70 have been detected in the HI 21 cm line. A complete sample of 62galaxies brighter than M_B_ = - 16.5 is identified. Images and gradientsin surface brightness and color are presented at a common linear scale.As has been seen previously, the galaxies with the reddest global colorsare reddest at the centers and get bluer at large radii. However,curiously, among the galaxies with the bluest global colors there aresystems with very blue cores that get redder at large radii.
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| The orientation of spin vectors of galaxies in the Ursa Major filament
Spin vectors of 60 galaxies in the 'Ursa Major filament' are obtainedfrom CCD images and spectroscopic determinations of the directions ofrotation. These data are used to remove the fourfold degeneracyintroduced by the projected images of galaxies, making possible thecomplete reconstruction of the galaxy spin vectors. Several possibleorganizations of spin vectors are investigated by means of statisticalanalyses of the three-dimensional spin vector maps. The results indicatethat there exists no significant alignment of galaxy spin vectors withrespect to the supergalactic plane, the supergalactic axis, or thecylindrical axis of the filament itself. No tendency for linearalignment of spin vectors toward any specific direction was detected. Wealso obtain a statistically negative result for azimuthal, radial, andcircular-helical orientation of spin vectors.
| A Preliminary Classification Scheme for the Central Regions of Late-Type Galaxies
The large-scale prints in The Carnegie Atlas of Galaxies have been usedto formulate a classification scheme for the central regions oflate-type galaxies. Systems that exhibit small bright central bulges ordisks (type CB) are found to be of earlier Hubble type and of higherluminosity than galaxies that do not contain nuclei (type NN). Galaxiescontaining nuclear bars, or exhibiting central regions that are resolvedinto individual stars and knots, and galaxies with semistellar nuclei,are seen to have characteristics that are intermediate between those oftypes CB and NN. The presence or absence of a nucleus appears to be auseful criterion for distinguishing between spiral galaxies andmagellanic irregulars.
| Arm structure in normal spiral galaxies, 1: Multivariate data for 492 galaxies
Multivariate data have been collected as part of an effort to develop anew classification system for spiral galaxies, one which is notnecessarily based on subjective morphological properties. A sample of492 moderately bright northern Sa and Sc spirals was chosen for futurestatistical analysis. New observations were made at 20 and 21 cm; thelatter data are described in detail here. Infrared Astronomy Satellite(IRAS) fluxes were obtained from archival data. Finally, new estimatesof arm pattern radomness and of local environmental harshness werecompiled for most sample objects.
| A revised catalog of CfA1 galaxy groups in the Virgo/Great Attractor flow field
A new identification of groups and clusters in the CfA1 Catalog ofHuchra et al. is presented, using a percolation algorithm to identifydensity enhancements. It is shown that in the resulting catalog,contamination by interlopers is significantly reduced. The Schechterluminosity function is redetermined, including the Malmquist bias.
| The Infrared Tully-Fisher Relation in the Ursa Major Cluster
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993ApJ...418..626P&db_key=AST
| 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.
| 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.
| The dustiness, luminosity, and metallicity of galaxies
B-band CCD images have been obtained of 230 galaxies in and near theVirgo and Ursa Major clusters. A coarse classification of these imagesshows that the 'dustiness' of late-type galaxies correlates stronglywith their luminosity. Luminous spirals are seen to be much dustier thanlate-type systems of lower luminosity. The reason for this correlationis probably that luminous galaxies are more metal-rich than fainterobjects. Systems with Fe/H less than about -1.0 are observed to beessentially dust-free.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
Catalogs and designations:
|
