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Quantitative Morphology of Galaxies in the Core of the Coma Cluster
We present a quantitative morphological analysis of 187 galaxies in aregion covering the central 0.28 deg2 of the Coma Cluster.Structural parameters from the best-fitting Sérsicr1/n bulge plus, where appropriate, exponential disk model,are tabulated here. This sample is complete down to a magnitude of R=17mag. By examining the recent compilation by Edwards et al. of galaxyredshifts in the direction of Coma, we find that 163 of the 187 galaxiesare Coma Cluster members and that the rest are foreground and backgroundobjects. For the Coma Cluster members, we have studied differences inthe structural and kinematic properties between early- and late-typegalaxies and between the dwarf and giant galaxies. Analysis of theelliptical galaxies reveals correlations among the structural parameterssimilar to those previously found in the Virgo and Fornax Clusters.Comparing the structural properties of the Coma Cluster disk galaxieswith disk galaxies in the field, we find evidence for an environmentaldependence: the scale lengths of the disk galaxies in Coma are 30%smaller. An analysis of the kinematics shows marginal differencesbetween the velocity distributions of elliptical galaxies withSérsic index n<2 (dwarfs) and those with n>2 (giants), thedwarf galaxies having a greater (cluster) velocity dispersion. Finally,our analysis of all 421 background galaxies in the catalog of Edwards etal. reveals a nonuniform distribution in redshift with contrasts indensity of ~3, characterized by a void extending from ~10,000 to ~20,000km s-1, and two dense and extended structures centered at~20,000 and ~47,000 km s-1.
| A Comparison of the Galaxy Populations in the Coma and Distant Clusters: The Evolution of k+a Galaxies and the Role of the Intracluster Medium
The spectroscopic properties of galaxies in the Coma Cluster arecompared with those of galaxies in rich clusters at z~0.5, toinvestigate the evolution of the star formation history in clusters.Luminous galaxies with MV<=-20 andpoststarburst/post-star-forming (k+a) spectra that constitute asignificant fraction of galaxies in distant cluster samples are absentin Coma, where spectacular cases of k+a spectra are found instead atMV>-18.5 and represent a significant proportion of thecluster dwarf galaxy population. A simple inspection of their positionson the sky indicates that this type of galaxy does not show apreferential location within the cluster, but the bluest and strongestlined group of k+a galaxies lie in projection toward the central 1.4 Mpcof Coma and have radial velocities significantly higher than the clustermean. We find a striking correlation between the positions of theseyoung and strong poststarburst galaxies and substructure in the hotintracluster medium (ICM) identified from XMM-Newton data, with thesegalaxies lying close to the edges of two infalling substructures. Thisresult strongly suggests that the interaction with the dense ICM couldbe responsible for the quenching of the star formation (thus creatingthe k+a spectrum) and, possibly, for any previous starburst. Theevolution with redshift of the luminosity distribution of k+a galaxiescan be explained by a ``downsizing effect,'' with the maximumluminosity/mass of actively star-forming galaxies infalling ontoclusters decreasing at lower redshift. We discuss the possible physicalorigin of this downsizing effect and the implications of our results forcurrent scenarios of environmental effects on the star formation ingalaxies.Based on observations made with the William Herschel Telescope operatedon the island of La Palma by the Isaac Newton Group in the SpanishObservatorio del Roque de los Muchachos of the Instituto de Astrofisicade Canarias.
| Stellar populations in early-type Coma cluster galaxies - I. The data
We present a homogeneous and high signal-to-noise ratio data set (meanS/N ratio of ~60 Å-1) of Lick/IDS stellar populationline indices and central velocity dispersions for a sample of 132 bright(bj<= 18.0) galaxies within the central 1°(≡1.26h-1 Mpc) of the nearby rich Coma cluster (A1656). Ourobservations include 73 per cent (100 out of 137) of the totalearly-type galaxy population (bj<= 18.0). Observationswere made with the William Herschel 4.2-m telescope and theAUTOFIB2/WYFFOS multi-object spectroscopy instrument (resolution of~2.2-Å FWHM) using 2.7-arcsec diameter fibres (≡0.94h-1 kpc). The data in this paper have well-characterizederrors, calculated in a rigorous and statistical way. Data are comparedwith previous studies and are demonstrated to be of high quality andwell calibrated on to the Lick/IDS system. Our data have median errorsof ~0.1 Å for atomic line indices, ~0.008 mag for molecular lineindices and 0.015 dex for velocity dispersions. This work provides awell-defined, high-quality baseline at z~ 0 for studies of medium- tohigh-redshift clusters. Subsequent papers will use this data set toprobe the stellar populations (which act as fossil records of galaxyformation and evolution) and the spectrophotometric relations of thebright early-type galaxies within the core of the Coma cluster.
| A Photometric and Spectroscopic Study of Dwarf and Giant Galaxies in the Coma Cluster. II. Spectroscopic Observations
This is the second paper in a series studying the photometric andspectroscopic properties of galaxies of different luminosities in theComa Cluster. We present the sample selection, spectroscopicobservations, and completeness functions. To study the spectralproperties of galaxies as a function of their local environment, twofields were selected for spectroscopic observations to cover both thecore (Coma 1) and outskirts (i.e., southwest of the core and centered onNGC 4839; Coma 3) of the cluster. To maximize the efficiency ofspectroscopic observations, two subsamples were defined, consisting of``bright'' and ``faint'' galaxies, both drawn from magnitude-limitedparent samples. Medium-resolution spectroscopy (6-9 Å) was thencarried out for a total of 490 galaxies in both fields (302 in Coma 1and 188 in Coma 3), using the WYFFOS multifiber spectrograph on theWilliam Herschel Telescope. The galaxies cover a range of 122. The completeness functions for our sampleare calculated. These show that the bright sample is 65% complete atR<17 mag, becoming increasingly incomplete toward fainter magnitudes,while the faint sample follows a monotonically decreasing completenessfunction at R>19 mag. Based on observations made with the WilliamHerschel Telescope, operated on the island of La Palma by the IsaacNewton Group in the Spanish Observatorio del Roque de los Muchachos ofthe Instituto de Astrofisica de Canarias.
| VLA HI Imaging of the brightest spiral galaxies in Coma. II. The HI Atlas and deep continuum imaging of selected early type galaxies
In the first paper of this series we used HI observations of the 19brightest spirals in Coma to analyze the dynamical state of the cluster.In this paper we present the detailed HI distribution and kinematics ofthe spirals that were detected in HI, and radio continuum data for asample of star forming and post starburst galaxies in Coma. We discussthe importance of ICM-ISM interactions to explain the observed HImorphology. A rough comparison of observed HI sizes with predicted HIsizes from simulations by Abadi et al. (\cite{Abadi99}) gives reasonableagreement. We use the results on radio continuum emission to estimatethe star formation rate in the PSB galaxies we pointed at. The radiocontinuum emission in the 11 so called post starburst galaxies,identified by Caldwell et al. (\cite{Caldwell93}) in the cluster, isweak. Eight of the 11 were not detected down to a 3 sigma upper limit of0.6 mJy. This sets an upper limit to the star formation rate in thesegalaxies of less than 0.2 Msun,yr-1. The threedetected post starburst galaxies have a star formation rate of less thanone solar mass per year. Thus none of the post starburst galaxies inComa are dust enshrouded starbursts. Appendix is only available inelectronic form at http://www.edpsciences.org
| VLA H I Imaging of the Brightest Spiral Galaxies in Coma
We have obtained 21 cm images of 19 spiral galaxies in the Coma cluster,using the VLA in its C and D configurations. The sample selection wasbased on morphology, brightness, and optical diameters of galaxieswithin one Abell radius (1.2d). The H I-detected, yet deficient galaxiesshow a strong correlation in their H I properties with projecteddistance from the cluster center. The most strongly H I-deficient(DefH I>0.4) galaxies are located inside a radius of 30'(~0.6 Mpc) from the center of Coma, roughly the extent of the centralX-ray emission. These central galaxies show clear asymmetries in their HI distribution and/or shifts between the optical and 21 cm positions.Another 12 spirals were not detected in H I with typical H I mass upperlimits of 108 Msolar. Seven of the 12nondetections are located in the central region of Coma, roughly within30' from the center. The other nondetections are to the east andsouthwest of the center. We looked for seven so-called blue diskgalaxies in Coma in H I and detected six. These galaxies are relativelyclose to the central region of Coma. The nondetected one is the closestto the center. The six detected blue galaxies are mildly H I deficient.We did a more sensitive search for H I from 11 of the 15 knownpoststarburst galaxies in Coma. None were detected with typical H I masslimits between 3 and 7x107 Msolar. Our resultspresent and enhance a picture already familiar for well-studiedclusters. H I poor galaxies (deficient ones and nondetections) areconcentrated toward the center of the cluster. The H I morphology of thecentral galaxies with optical disks extending beyond the H I disks isunique to cluster environments and strongly suggests an interaction withthe intergalactic medium (IGM). A new result in Coma is the clumpydistribution of gas deficiency. In the cluster center the deficientgalaxies are to the east while the nondetections are to the west. In theouter parts the gas rich galaxies are north of Coma, nondetected spiralsare found in the NGC 4944 group to the east, and the NGC 4839 group isto the southwest. This supports recent findings that merging of groupsis ongoing in the center of Coma, farther out the NGC 4944 and NGC 4839must have passed at least once through the core, and the galaxies to thenorth have yet to fall in.
| Extensive near-infrared (H-band) photometry in Coma
We present extensive and accurate photometry in the near-infrared H bandof a complete sample of objects in an area of about 400arcmin2 toward the Coma cluster of galaxies. The sample,including about 300 objects, is complete down to H ~ 17 mag, the exactvalue depending on the type of magnitude (isophotal, aperture, Kron) andthe particular region studied. This is six magnitudes below thecharacteristic magnitude of galaxies, well into the dwarfs' regime atthe distance of the Coma cluster. For each object (star or galaxy) weprovide aperture magnitudes computed within five different apertures,the magnitude within the 22 mag arcsec-2 isophote, the Kronmagnitude and radius, magnitude errors, as well as the coordinates, theisophotal area, and a stellarity index. Photometric errors are 0.2 magat the completness limit. This sample is meant to be the zero-redshiftreference for evolutionary studies of galaxies. Based on observationscollected with the Telescope Bernard Lyot, at the Pic du MidiObservatory, operated by INSU (CNRS).
| On the Origins of Starburst and Poststarburst Galaxies in Nearby Clusters
Hubble Space Telescope (HST) Wide Field Planetary Camera 2 images in B(F450W) and I (F814W) have been obtained for three starburst (SB) andtwo poststarburst (PSB) galaxies in the Coma Cluster and for three suchgalaxies in the cluster DC 048-52. V (F555W) and I images for anadditional PSB galaxy in Coma have been extracted from the HST archive.Six of these galaxies were previously classified as E/S0 on the basis ofground-based images, two as Sa, and the other as an irregular. The HSTimages reveal these SB/PSB galaxies to be heterogeneous in morphology.Nevertheless, a common theme is that many of them, especially the SBgalaxies, tend to have centralized spiral structure that appears simplyas a bright ``bulge'' on ground-based images. In addition, while somePSB galaxies exhibit distinct spiral structure, on the whole they havesmoother morphologies than the SB galaxies. The morphologies andluminosity profiles are generally consistent with substantialstarbursts, in the form of centralized spiral structure (the SBgalaxies), that fade into smoother morphologies (the PSB galaxies), withlingering spectroscopic evidence for past central starbursts. Animportant point is that the PSB galaxies retain disks; i.e., they havenot evolved into spheroidal systems. While the morphologies revealed inthe HST images are heterogeneous, and thus may not fit well into asingle picture, we see evidence in several cases that the morphologiesand centralized star formation have been driven by external tidalperturbations. We discuss several physical mechanisms for inducing starformation in cluster galaxies with a view toward explaining theparticular morphologies seen in the HST images.
| Characteristics of KISO Ultraviolet Excess Galaxies
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.1758T&db_key=AST
| 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.
| Morphological classification and structural parameters for early-type galaxies in the Coma cluster.
We present the results of an isophotal shape analysis of three samplesof galaxies in the Coma cluster. Quantitative morphology, together withstructural and photometric parameters, is given for each galaxy. Specialemphasis has been placed on the detailed classification of early-typegalaxies. The three samples are: i) a sample of 97 early-type galaxiesbrighter than m_B_=17.00 falling within one degree from the center ofthe Coma cluster; these galaxies were observed with CCD cameras, mostlyin good to excellent resolution conditions; ii) a magnitude completesample of 107 galaxies of all morphological types down to m_B_=17.00falling in a circular region of 50arcmin diameter, slightly offcenteredto the North-West of the cluster center; the images for this and thenext sample come from digitized photographic plates; iii) a completecomparison sample of 26 galaxies of all morphological types down tom_R_=16.05 (or m_B_=~17.5), also in a region of 50arcmin diameter, butcentered 2.6degrees West of the cluster center. The reliability of ourmorphological classifications and structural parameters of galaxies,down to the adopted magnitude limits, is assessed by comparing theresults on those galaxies for which we had images taken with differentinstrumentation and/or seeing conditions, and by comparing our resultswith similar data from other observers.
| Galaxy Properties at the North Galactic Pole. I. Photometric Properties on Large Spatial Scales
A two-color study of the galaxies detected on POSS-I in a 289 squaredegree region centered on the North Galactic Pole is presented. We use avariety of mapping techniques to characterize the large-scale spatialdistribution of galaxies. The depth and sample size of this new surveyallows, for the first time, the isolation of large photometricsubsamples of galaxies in high- and low-density environments on thescale of superclusters. Our principal finding is a statisticallysignificant difference between the mean photometric properties of thesesubsamples in the sense that galaxies in the high-density Coma andfilament environments have redder colors and larger concentrationindices than galaxies drawn from low-density interfilament regions.These results are in accord with the known morphology-density relation.Thus, appropriately chosen photometric and morphological parameters, inconcert with a galaxy surface density map, can be used to selectstructures from the projected galaxy distribution which correspond toregions of high density. An illustration of this point is our discoveryof a concentration of blue galaxies identified in our maps near the coreof the Coma cluster. This feature is comprised of early-type galaxieswhich exhibit signs of current or recent star formation. These resultsare predicated on relations between morphological type and photometricparameters derived from APS scans of POSS-I. We therefore discuss theimage calibration procedures used to compile our catalog of physicallysignificant photometric parameters. We demonstrate the morphologicaltype dependence among quantities such as mean color and imageconcentration index, and the lack of such a dependence for mean surfacebrightness.
| 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.
| Star formation in early-type galaxies in the Coma cluster
The Hydra bench spectrograph on the 4 m telescope at Kitt Peak is usedto obtain multifiber spectra of 125 early-type galaxies in the Comacluster of galaxies. About one-third of all galaxies in a field locatedabout 40 arcmin SW of the center of the cluster exhibits enhanced Balmerabsorption lines or emission lines, indicative of recent star formationor nuclear activity. In contrast, very few such galaxies are found inthe central field of the cluster. It is argued that the anomalousspectral features cannot arise from morphological misidentifications. Itis suggested that an environmental process similar to that frequentlyfound in clusters at moderate redshift is occurring at the present epochin the outskirts of the Coma cluster.
| 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.
| The evolution of galaxies in clusters. IV - Photometry of 10 low-redshift clusters
Colors and magnitudes, obtained from Palomar 48 inch (1.2 m) Schmidtplates in the J and F bands, and morphological types are presented forgalaxies in the cores of 10 nearby clusters of galaxies. In the typicalcluster, the sample includes all galaxies within a radius of 1.5 Mpc(assuming H(0) = 50 km/s/Mpc) of the cluster center and brighter than J= 17.5.The accuracy of the photometry varies with cluster, but mostmagnitudes are accurate to 0.10 mag, and typical errors in the colorsare of the same order. As expected, the colors of the elliptical and S0galaxies show a narrow dispersion about a mean color which decreaseswith magnitude. However, the colors of the spiral galaxies are notentirely as expected, having a smaller dispersion than would have beenpredicted from their morphological types.
| 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.
| A catalog of morphological types in 55 rich clusters of galaxies
Data are presented from a study of 55 rich clusters of galaxies. Thedata include positions, morphological types, estimated total magnitudes,bulge sizes, and ellipticities for about 6000 galaxies, as determinedfrom high scale photographic plates. Data reduction procedures aredescribed, and a brief analysis of cluster richness, which indicatesthat Abell richness classes are only rough indicators of total clustermembership, is included.
| Properties of the redshift-magnitude bands in the Coma cluster.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973ApJ...179...29T&db_key=AST
| The Correlation of Redshift with Magnitude and Morphology in the Coma Cluster
Abstract image available at:http://adsabs.harvard.edu/abs/1972ApJ...175..613T
| Photographic brightness profiles of Coma Cluster galaxies. I. Catalogue of program galaxies.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1967AJ.....72..398R&db_key=AST
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