Contents
Images
Upload your image
DSS Images Other Images
Related articles
Study of the Structure of the Coma Cluster Based on a Hierarchical Force Clustering Method
Six subclusters in the Coma cluster have been selected on the basis of ahierarchical clustering method that takes the gravitational interactionamong galaxies into account. Of these, 3 central subclusters around thegalaxies NGC 4889, NGC 4874, and NGC 4839 have been singled out. We haveused the objective statistical criterion applied by Vennik and Anosovain studies of close groups of galaxies to evaluate each member includedin a subcluster with a high probability. Galaxies with a significantdeficit of hydrogen HI, including objects from the Bravo-Alfaro list,have been identified with members of the subclusters, with the greatestnumber of them in the subclusters around NGC 4874 and NGC 4839. Aquantitative estimate of the hydrogen deficit using the HI index in theRCG3 catalog reveals a statistically significant excess value for thosegalaxies that are members of the subclusters compared to galaxies with ahydrogen deficit in the overall Coma cluster field. A substantial numberof the spiral galaxies with a hydrogen deficit in the subclusters turnedout to be radio galaxies as well.
| Tidally Triggered Star Formation in Close Pairs of Galaxies. II. Constraints on Burst Strengths and Ages
Galaxy-galaxy interactions rearrange the baryons in galaxies and triggersubstantial star formation; the aggregate effects of these interactionson the evolutionary histories of galaxies in the universe are poorlyunderstood. We combine B- and R-band photometry and optical spectroscopyto estimate the strengths and timescales of bursts of triggered starformation in the centers of 190 galaxies in pairs and compact groups.Based on an analysis of the measured colors and EW(Hα), wecharacterize the preexisting and triggered populations separately. Thebest-fitting burst scenarios assume stronger reddening corrections forline emission than for the continuum and continuous star formationlasting for >~100 Myr. The most realistic scenarios require aninitial mass function that is deficient in the highest mass stars. Thecolor of the preexisting stellar population is the most significantsource of uncertainty. Triggered star formation contributessubstantially (probably >~50%) to the R-band flux in the centralregions of several galaxies; tidal tails do not necessarily accompanythis star formation. Many of the galaxies in our sample have bluercenters than outskirts, suggesting that pre- or nonmerger interactionsmay lead to evolution along the Hubble sequence. These objects wouldappear blue and compact at higher redshifts; the older, redder outskirtsof the disks would be difficult to detect. Our data indicate thatgalaxies with larger separations on the sky contain weaker, and probablyolder, bursts of star formation on average. However, confirmation ofthese trends requires further constraints on the colors of the olderstellar populations and on the reddening for individual galaxies.
| The Tully-Fisher Relation in Coma and Virgo Cluster S0 Galaxies
We use the Tully-Fisher relation (TFR) to compare the behavior of S0 andlate-type spiral galaxies. We determine circular velocities based onstellar kinematics derived from stellar absorption line spectroscopy for10 S0's in the Coma Cluster and eight S0's in the Virgo Cluster. Wecombine these results with similar measurements of 13 Coma S0 galaxiesobtained previously. We find that there is only a small offset,ΔmH~0.2, in the H-band luminosity at a given circularvelocity, vc~200 km s-1, between S0 and late-typespirals. This result implies a similar total H-band mass-to-light ratio(within an effective radius) among disk galaxies of different Hubbletypes. As the older stellar population in S0's is dimmer, this suggestsa somewhat larger fraction of stellar mass in these S0's than inlate-type spirals. We also find that the relation between (I- andH-band) luminosity and vc for the S0 galaxies is at bestpoorly defined and has a scatter of ~1 mag, significantly larger thanthe TFR for late-type spirals, where the observed I- and H-band scatteris σ~0.3-0.5 mag. This substantial scatter confirms the originalfindings of Dressler & Sandage and is similar to that found in astudy by Neistein and coworkers of 18 nearby S0 galaxies in the fieldwhere σI~0.7 mag, but differs from the small scatterfound by Mathieu and coworkers, σI~0.3 mag, for sixnearby S0's. Our results suggest that differing formation histories canlead to S0's with diverse properties and that S0's are more likely to bethe outcomes of minor mergers or some ``preprocessing'' in groups ofgalaxies falling into clusters, rather than simply late-type spiralsthat have been stripped of their gas but are kinematically preserved. Wesuggest that it is likely that many mechanisms, such as slow encounters,tidal interactions, and gas stripping, may have occurred in thelifetimes of the galaxies and produced the heterogeneous class of S0'sthat are observed today.
| 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.
| The far-ultraviolet emission of early-type galaxies
We have assembled a UV-flux selected sample of 82 early-type galaxiesand collected additional information at other wavelengths. These dataconfirm a large spread of the UV-V color in the range 2 to 5. The spreadin UV-V is accompanied by a spread in B-V that is mainly attributed tothe range of morphological types and luminosities. A large fraction ofthe objects have red colors, UV-V = 4 +/- 0.4, corresponding to a weakUV-upturn as observed with IUE. If the current interpretation for the UVemission from early-type galaxies is applicable to our sample, the PAGB(Post-Asymptotic Giant Branch) tracks are the most common evolution pathfor the low-mass stars responsible for the UV emission. A small numberof very blue (UV-V < 1.4) objects have been found that can bereasonably interpreted as harbouring some low level of star formation.In contrast to a previous sample based on IUE observations, nocorrelation is found between the UV-V color and the Mg2spectral line index; possible explanations are reviewed. The potentialof a more extended UV survey like GALEX is briefly presented.
| V- and R-band Galaxy Luminosity Functions and Low Surface Brightness Galaxies in the Century Survey
We use 64 deg2 of deep V and R CCD images to measure thelocal V- and R-band luminosity functions of galaxies. TheV0<16.7 and R0<16.2 redshift samples contain1255 and 1251 galaxies and are 98.1% and 98.2% complete, respectively.We apply k-corrections before the magnitude selection so that thecompleteness is to the same depth for all spectral types. The V and Rfaint-end slopes are surprisingly identical: α=-1.07+/-0.09.Representative Schechter function parameters for H0=100 are:M*R=-20.88+/-0.09,φ*R=0.016+/-0.003 Mpc-3 andM*V=-20.23+/-0.09,φ*V=0.020+/-0.003 Mpc-3. The V andR local luminosity densities,jR=(1.9+/-0.6)×108 Lsolar andjV=(2.2+/-0.7)×108 Lsolar, are inessential agreement with the recent 2 Degree Field Galaxy RedshiftSurvey and Sloan Digital Sky Survey determinations. All low surfacebrightness (LSB) galaxies fall in the large-scale structure delineatedby high surface brightness galaxies. The properties and surface numberdensity of our LSB galaxies are consistent with the LSB galaxy catalogof O'Neil, Bothun & Cornell, suggesting that our samples arecomplete for LSB galaxies to the magnitude limits. We measure colors,surface brightnesses, and luminosities for our samples, and find strongcorrelations among these galaxy properties. The color-surface brightnessrelation is(V-R)0=(-0.11+/-0.05)μR,0+(2.6+/-0.9).
| A Comparison of Coma Cluster S0 Galaxies with the Tully-Fisher Relation for Late-Type Spirals
We present I-band photometry for 13 S0 galaxies in the Coma Cluster andestimate their circular velocities based on stellar kinematics derivedfrom stellar absorption-line spectroscopy. We find that there is at mosta small offset, ΔmI<= 0.2, in the I-band luminosityat a given circular velocity, vc~200 km s-1,between late-type spirals and the S0 galaxies studied here. This resultimplies a similar total I-band mass-to-light ratio (within an effectiveradius) among disk galaxies of rather different Hubble types. As theolder stellar population in S0's is dimmer, this suggests a somewhatlarger fraction of stellar mass in these S0's than in late-type spirals.We also find that the relation between I-band luminosity andvc for the S0 galaxies is at best poorly defined and has ascatter of σI~ 0.5 mag, significantly larger than theTully-Fisher relation (TFR) for late-type spirals in clusters, where theobserved I-band scatter is σI<~ 0.3 mag. Thissubstantial scatter is only somewhat less than that found by Neistein etal. in a recent study of 18 nearby S0 galaxies in the field(σI~ 0.7 mag), implying that no tight TFR holds forfield S0 galaxies. These results suggest that differing formationhistories can lead to S0's with diverse properties. Our analysis of S0'sin the Coma Cluster differs from previous analyses in two importantrespects: the data are independent of distance estimate errors, and theycontain S0's formed in a more homogeneous environment.
| 1.65 μm (H-band) surface photometry of galaxies. III. observations of 558 galaxies with the TIRGO 1.5 m telescope
We present near-infrared H-band (1.65 μm ) surface photometry of 558galaxies in the Coma Supercluster and in the Virgo cluster. This dataset, obtained with the Arcetri NICMOS3 camera ARNICA mounted on theGornergrat Infrared Telescope, is aimed at complementing, withobservations of mostly early-type objects, our NIR survey of spiralgalaxies in these regions, presented in previous papers of this series.Magnitudes at the optical radius, total magnitudes, isophotal radii andlight concentration indices are derived. We confirm the existence of apositive correlation between the near-infrared concentration index andthe galaxy H-band luminosity Based on observations taken at TIRGO(Gornergrat, Switzerland). TIRGO is operated by CAISMI-CNR, Arcetri,Firenze, Italy. Tables 1 and 2 are only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 1.65 μm (H-band) surface photometry of galaxies. V. Profile decomposition of 1157 galaxies
We present near-infrared H-band (1.65 μm) surface brightness profiledecomposition for 1157 galaxies in five nearby clusters of galaxies:Coma, A1367, Virgo, A262 and Cancer, and in the bridge between Coma andA1367 in the ``Great Wall". The optically selected (mpg≤16.0) sample is representative of all Hubble types, from E to Irr+BCD,except dE and of significantly different environments, spanning fromisolated regions to rich clusters of galaxies. We model the surfacebrightness profiles with a de Vaucouleurs r1/4 law (dV), withan exponential disk law (E), or with a combination of the two (B+D).From the fitted quantities we derive the H band effective surfacebrightness (μe) and radius (re) of each component, theasymptotic magnitude HT and the light concentration indexC31. We find that: i) Less than 50% of the Ellipticalgalaxies have pure dV profiles. The majority of E to Sb galaxies is bestrepresented by a B+D profile. All Scd to BCD galaxies have pureexponential profiles. ii) The type of decomposition is a strong functionof the total H band luminosity (mass), independent of the Hubbleclassification: the fraction of pure exponential decompositionsdecreases with increasing luminosity, that of B+D increases withluminosity. Pure dV profiles are absent in the low luminosity rangeLH<1010 L\odot and become dominantabove 1011 L\odot . Based on observations taken atTIRGO, Gornergrat, Switzerland (operated by CAISMI-CNR, Arcetri,Firenze, Italy) and at the Calar Alto Observatory (operated by theMax-Planck-Institut für Astronomie (Heidelberg) jointly with theSpanish National Commission for Astronomy). Table 2 and Figs. 2, 3, 4are available in their entirety only 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
| On the local radio luminosity function of galaxies. II. Environmental dependences among late-type galaxies
Using new extensive radio continuum surveys at 1.4 GHz (FIRST and NVSS),we derive the distribution of the radio/optical and radio/NIR luminosity(RLF) of late-type (Sa-Irr) galaxies (m_p<15.7) in 5 nearby clustersof galaxies: A262, Cancer, A1367, Coma and Virgo. With the aim ofdiscussing possible environmental dependences of the radio properties,we compare these results with those obtained for relatively isolatedobjects in the Coma supercluster. We find that the RLF of Cancer, A262and Virgo are consistent with that of isolated galaxies. Conversely weconfirm earlier claims that galaxies in A1367 and Coma have their radioemissivity enhanced by a factor ~ 5 with respect to isolated objects. Wediscuss this result in the framework of the dynamical pressure sufferedby galaxies in motion through the intra-cluster gas (ram-pressure). Wefind that the radio excess is statistically larger for galaxies in fasttransit motion. This is coherent with the idea that enhanced radiocontinuum activity is associated with magnetic field compression. TheX-ray luminosities and temperatures of Coma and A1367 imply that thesetwo clusters have significantly larger intracluster gas density than theremaining three studied ones, providing a clue for explaining the higherradio continuum luminosities of their galaxies. Multiple systems in theComa supercluster bridge (with projected separations smaller than 300kpc) have radio luminosities significantly larger than isolatedgalaxies. 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 distribution of the rotation axes of the disk galaxies in the Coma cluster: statistical samples.
Not Available
| 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.
| Automated surface photometry for the Coma Cluster galaxies: The catalog
A homogeneous photometry catalog is presented for 450 galaxies withB25.5 less than or equal to 16 mag located in the 9.8 deg x9.8 deg region centered on the Coma Cluster. The catalog is based onphotographic photometry using an automated surface photometry softwarefor data reduction applied to B-band Schmidt plates. The catalogprovides accurate positions, isophotal and total magnitudes, major andminor axes, and a few other photometric parameters including rudimentarymorphology (early of late type).
| Ultraviolet observations of galaxies in nearby clusters. III. Star-forming galaxies in the Coma cluster.
In a field of 1deg radius centered in the Coma cluster of galaxies, UV(λ=2000A) observations with a 40-cm balloon-borne imagingtelescope (FOCA) have provided a list of 442 UV sources brighter thanm_UV_=18, which are identified in the Godwin et al. (1983) catalogue.254 are identified as galaxies, 178 as star-like objects and 10 asgalaxy-star pairs, unresolved in the UV image. The 254 galaxies fallinto two sub-groups. The galaxies brighter than b=17 define a sequencein the (b-r,m_UV_-b) color-color diagram which is well fitted by themodels of Bruzual & Charlot (1993); most are cluster members. Thegalaxies fainter than b=17 show distinctly (m_UV_-b) colors bluer thanthe former group at the same (b-r); most of them are likely backgroundlate-type galaxies. Notably, a significant fraction of the 178 star-likeobjects have UV magnitudes and colors similar to that of the secondgroup of galaxies; ground-based spectroscopy is required to determinetheir nature and/or membership. In the UV sample, 61 galaxies haveradial velocities consistent with cluster membership. Among them, nearlyhalf are blue (m_UV_-b<1), star-forming galaxies. Their cumulated UVfluxes lead to a star formation rate of ~23h^-2^Msun_/yr.Their velocity distribution shows an unexpected concentration near 7500km/s and a void in the 6000-7000km/s range. The other half contains redgalaxies (m_UV_-b>1) with little or no recent star formation. Allearly-type galaxies brighter than b=14.5 are detected in UV and have amedian color (m_UV_-b)=3.0 in agreement with the representative spectraldistribution of an elliptical compiled from IUE. 17 early-types galaxieswhich have spectroscopic data in the sample of Caldwell et al. (1993)show a correlation between the (m_UV_-b) color and the Hδ(absorption line) equivalent width; some, with (m_UV_-b)<1, wouldimply that the last starburst event is younger than 1 Gyr or that aresidual star-formation is still present. The median UV flux and thefraction of blue star-forming galaxies which are cluster members show anenhancement at ~25'(0.5h^-1^Mpc) from the cluster center, suggestingthat a global physical process might induce star formation in a richcluster such as Coma.
| Cross identification of 238 galaxies and use of a colour magnitude relation in the coma cluster
A catalog of 238 galaxies is obtained by the cross identification ofdata from Kent and Gunn (1982), Godwin and Peach (1977) and Godwin etal. (1983). It contains the radial velocities, bvr magnitudes, colorindices, isophotal radii, and other characteristics of individualgalaxies. This leads to the definition of various samples of radialvelocities complete to various limiting magnitudes depending on radius.The use of a color magnitude relation is discussed to define a class of1340 objects likely to belong to the cluster from their photometry only.
| Far-infrared properties of cluster galaxies
Far-infrared properties are derived for a sample of over 200 galaxies inseven clusters: A262, Cancer, A1367, A1656 (Coma), A2147, A2151(Hercules), and Pegasus. The IR-selected sample consists almost entirelyof IR normal galaxies, with Log of L(FIR) = 9.79 solar luminosities, Logof L(FIR)/L(B) = 0.79, and Log of S(100 microns)/S(60 microns) = 0.42.None of the sample galaxies has Log of L(FIR) greater than 11.0 solarluminosities, and only one has a FIR-to-blue luminosity ratio greaterthan 10. No significant differences are found in the FIR properties ofHI-deficient and HI-normal cluster galaxies.
| Taxonomical analysis of superclusters. II - The A1367/Coma supercluster
The nonhierarchical taxonomical method has been applied to a sample of185 galaxies, complete to m not greater than 15, in the A1367/Comaregion. Once the fore- and background galaxies have been identified, theanalysis of the A1367 cluster shows it composed by two gravitationallybound clumps at essentially the same redshift, 6396 km/s and 6562 km/s,respectively. Central Coma is traced by three different groups whosegravitational binding does not appear clearly. However, accepting theunique dynamical entity of Central Coma, some other neighboring groupswould be part of the cluster. In that case, the average radial velocityand dispersion of the Coma cluster would be 7013 and 423 km/s,respectively. The M/L ratios for the groups evidenced by the taxonomyrange from 13 to 170. The missing mass problem only appears when all thegalaxies in the sample are considered as members of a unique dynamicalstructure. The relationship found in other systems between the redshift,the morphological type and the radioemissivity is also present in thesample.
| The Coma Cluster - Part One - a Catalogue of Magnitudes Colours Ellipticities and Position Angles for 6724 Galaxies in the Field of the Coma Cluster
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983MNRAS.202..113G&db_key=AST
| The dynamics of rich clusters of galaxies. I - The Coma cluster
Self-consistent analytical dynamical models are used to study theendpoint of cluster formation, concentrating on the Coma cluster.Particular attention is paid to the effects of anisotropy in thevelocity dispersion and variations in the energy-distribution functionon the cluster structure, the effect on the core structure of a massivecentral object, the dynamical consequences of morphological segregation,cosmological infall and the edge of a cluster, the distribution of darkmatter in a cluster, and the implications of X-ray observations for thedistribution of gravitating material in a cluster. Radial velocity datais displayed, and new and repeated redshifts are reported for a numberof galaxies in the central regions of the cluster. Cluster membership isdetermined and a velocity-dispersion profile is derived. A compositesurface-density profile is derived, and amazing examples are shown ofmodels with virtually identical surface-density profiles but otherwisecompletely different internal dynamics.
| New radial velocities of galaxies from image-tube spectra.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971AJ.....76..409K&db_key=AST
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
Catalogs and designations:
|
