Contents
Images
Upload your image
DSS Images Other Images
Related articles
Hα surface photometry of galaxies in nearby clusters
We present the Hα imaging observations of 273 late-type galaxiesin the nearby rich galaxy clusters Virgo, A 1367, Coma, Cancer, Herculesand in the Great Wall, carried out primarily with the 2.1 m telescope ofthe San Pedro Martir Observatory (SPM) and with the ESO/3.6 m telescope.We derived the Hα+[NII] fluxes and equivalent widths. The Hαsurvey reached completion for an optically selected sample of nearbygalaxies in and outside rich clusters. Taking advantage of thecompleteness of the data set, the dependence of Hα properties onthe Hubble type was determined for late-type galaxies in the Virgocluster. Differences in the gaseous content partly account for the largescatter of the Hα EW within each Hubble-type class. We studied theradial distributions of the Hα EW around Coma+A 1367 and the Virgoclusters in two luminosity bins. Luminous galaxies show a decrease intheir average Hα EW in the inner ~1 virial radius, whilelow-luminosity galaxies do not show this trend.
| Stellar populations in local star-forming galaxies - II. Recent star formation properties and stellar masses
We present the integrated properties of the stellar populations in theUniversidad Complutense de Madrid (UCM) Survey galaxies. Applying thetechniques described in the first paper of this series, we derive ages,burst masses and metallicities of the newly formed stars in our samplegalaxies. The population of young stars is responsible for the Hαemission used to detect the objects in the UCM Survey. We also infertotal stellar masses and star formation rates in a consistent way takinginto account the evolutionary history of each galaxy. We find that anaverage UCM galaxy has a total stellar mass of ~1010Msolar, of which about 5 per cent was formed in aninstantaneous burst that occurred about 5 Myr ago, and subsolarmetallicity. Less than 10 per cent of the sample shows massivestarbursts involving more than half of the total mass of the galaxy.Several correlations are found among the derived properties. The burststrength is correlated with the extinction and with the integratedoptical colours for galaxies with low obscuration. The current starformation rate is correlated with the gas content. A stellarmass-metallicity relation is also found. Our analysis indicates that theUCM Survey galaxies span a broad range in properties between those ofgalaxies completely dominated by current/recent star formation and thoseof normal quiescent spirals. We also find evidence indicating that starformation in the local Universe is dominated by galaxies considerablyless massive than L*.
| Stellar populations in local star-forming galaxies - I. Data and modelling procedure
We present an analysis of the integrated properties of the stellarpopulations in the Universidad Complutense de Madrid (UCM) Survey ofHα-selected galaxies. In this paper, the first of a series, wedescribe in detail the techniques developed to model star-forminggalaxies using a mixture of stellar populations, and taking into accountthe observational uncertainties. We assume a recent burst of starformation superimposed on a more evolved population. The effects of thenebular continuum, line emission and dust attenuation are taken intoaccount. We also test different model assumptions, including the choiceof specific evolutionary synthesis model, initial mass function, starformation scenario and the treatment of dust extinction. Quantitativetests are applied to determine how well these models fit ourmultiwavelength observations for the UCM sample. Our observations spanthe optical and near-infrared, including both photometric andspectroscopic data. Our results indicate that extinction plays a keyrole in this kind of study, revealing that low- and high-obscuredobjects may require very different extinction laws and must be treateddifferently. We also demonstrate that the UCM Survey galaxies are bestdescribed by a short burst of star formation occurring within aquiescent galaxy, rather than by continuous star formation. A detaileddiscussion on the inferred parameters, such as the age, burst strength,metallicity, star formation rate, extinction and total stellar mass forindividual objects, is presented in Paper II of this series.
| Spatial Analysis of the Hα Emission in the Local Star-forming UCM Galaxies
We present a photometric study of the Hα emission in theUniversidad Complutense de Madrid (UCM) Survey galaxies. This workcomplements our previously published spectroscopic data. We study thelocation of the star-forming knots, their intensity and concentration,and the relationship of these properties with those of the host galaxy.We also estimate that the amount of Hα emission that arises fromthe diffuse ionized gas is about 15%-30% of the total Hα flux fora typical UCM galaxy. This percentage seems to be independent of theHubble type. Conversely, we find that an ``average'' UCM galaxy harborsa star formation event with 30% of its Hα luminosity arising froma nuclear component. The implications of these results for higherredshift studies are discussed, including the effects of galaxy size andthe depth of the observations. A correlation between the star formationrate and the Balmer decrement is observed, but such correlation breaksdown for large values of the extinction. Finally, we recalculate theHα luminosity function and star formation rate density of thelocal universe using the new imaging data. Our results point out that,on average, spectroscopic observations detected about one-third of thetotal emission-line flux of a typical UCM galaxy. The new valuesobtained for the Hα luminosity density and the star formation ratedensity of the local universe are 1039.3+/-0.2 ergss-1 Mpc-3 andρSFR=0.016+0.007-0.004Msolar yr-1 Mpc-3 (H0=50 kms-1 Mpc-1, ΩM=1.0, Λ=0).The corresponding values for the ``concordance cosmology''(H0=70 km s-1 Mpc-1,ΩM=0.3, Λ=0.7) are 1039.5+/-0.2 ergss-1 Mpc-3 andρSFR=0.029+0.008-0.005Msolar yr-1 Mpc-3.
| Spectroscopy of KISS Emission-Line Galaxy Candidates. I. MDM Observations
Spectroscopic observations for 351 emission-line galaxy candidates fromthe KPNO International Spectroscopic Survey (KISS) have been obtainedusing the MDM Observatory 2.4 m telescope on Kitt Peak. KISS is anongoing wide-field objective-prism survey for extragalacticemission-line objects, which has cataloged over 2200 emission-linegalaxy (ELG) candidates to date. Spectroscopic follow-up observationsare being carried out to study the characteristics of the surveyobjects. The observational data presented here include redshifts,reddening estimates, line equivalent widths, Hα line fluxes, andemission-line ratios. The galaxies have been classified based on theiremission-line characteristics. The procedure for selecting the ELGcandidates in KISS is found to be very reliable: 95% of the candidatesin this sample are verified to have emission lines. A comparison ofobjective-prism survey data-redshifts, Hα line fluxes, andequivalent widths-with the long-slit measurements shows good overallagreement.
| 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.
| Compact groups in the UZC galaxy sample
Applying an automatic neighbour search algorithm to the 3D UZC galaxycatalogue (Falco et al. \cite{Falco}) we have identified 291 compactgroups (CGs) with radial velocity between 1000 and 10 000 kms-1. The sample is analysed to investigate whether Tripletsdisplay kinematical and morphological characteristics similar to higherorder CGs (Multiplets). It is found that Triplets constitute lowvelocity dispersion structures, have a gas-rich galaxy population andare typically retrieved in sparse environments. Conversely Multipletsshow higher velocity dispersion, include few gas-rich members and aregenerally embedded structures. Evidence hence emerges indicating thatTriplets and Multiplets, though sharing a common scale, correspond todifferent galaxy systems. Triplets are typically field structures whilstMultiplets are mainly subclumps (either temporarily projected orcollapsing) within larger structures. Simulations show that selectioneffects can only partially account for differences, but significantcontamination of Triplets by field galaxy interlopers could eventuallyinduce the observed dependences on multiplicity. Tables 1 and 2 are onlyavailable in electronic at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/391/35
| 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).
| The KPNO International Spectroscopic Survey. II. Hα-selected Survey List 1
The KPNO International Spectroscopic Survey (KISS) is a newobjective-prism survey for extragalactic emission-line objects. Itcombines many of the features of previous slitless spectroscopic surveyswith the advantages of modern CCD detectors and is the first purelydigital objective-prism survey for emission-line galaxies. Here wepresent the first list of emission-line galaxy candidates selected fromour red spectral data, which cover the spectral range 6400 to 7200Å. In most cases, the detected emission line is Hα. Thecurrent survey list covers a 1°-wide strip located atδ=29°30' (B1950.0) and spanning the right ascension range12h15m to 17h0m. An area of62.2 deg2 is covered. A total of 1128 candidate emission-lineobjects have been selected for inclusion in the survey list (18.1deg-2). We tabulate accurate coordinates and photometry foreach source, as well as estimates of the redshift and emission-line fluxand equivalent width based on measurements of the digitalobjective-prism spectra. The properties of the KISS emission-linegalaxies are examined using the available observational data.
| Optical photometry of the UCM lists I and II. II. B band surface photometry and morphological discussion
We present Johnson B surface photometry for the UCM Survey galaxies.One-dimensional bulge-disk decomposition is attempted, discussing onfitting functions and computational procedures. The results from thisdecomposition, jointly with concentration indices and an asymmetrycoefficient, are employed to study the morphological properties of thesegalaxies. We also compare our results with the previous morphologicalclassification established using Gunn r imaging data and with othersamples of galaxies. No major statistical differences in morphology arefound between red and blue data, although some characteristics such assize and luminosity concentration vary. We find a correlation betweenluminosity and size. Several parameters are used to segregate theobjects according to their morphological type. Tables 2 and 3 are alsoavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/365/370
| Star formation properties of Universidad Complutense de Madrid survey galaxies
We present new near-infrared J and K imaging data for 67 galaxies fromthe Universidad Complutense de Madrid (UCM) survey used in thedetermination of the SFR density of the local Universe by Gallego et al.This is a sample of local star-forming galaxies with redshift lower than0.045, and they constitute a representative subsample of the galaxies inthe complete UCM survey. From the new data, complemented with our ownGunn-r images and long-slit optical spectroscopy, we have measuredintegrated K-band luminosities, r-J and J-K colours, and Hαluminosities and equivalent widths. Using a maximum likelihood estimatorand a complete set of evolutionary synthesis models, these observationsallow us to estimate the strength of the current (or most recent) burstof star formation, its age, the star formation rate and the totalstellar mass of the galaxies. An average galaxy in the sample has astellar mass of 5×1010Msolar and isundergoing (or has recently completed) a burst of star formationinvolving about 2per cent of its total stellar mass. We identify twoseparate classes of star-forming galaxies in the UCM sample:low-luminosity, high-excitation galaxies (Hiilike) and relativelyluminous spiral galaxies (starburst disc-like). The former show higherspecific star formation rates (SFRs per unit mass) and burst strengths,and lower stellar masses than the latter. With regard to their specificstar formation rates, the UCM galaxies are intermediate objects betweennormal quiescent spirals and the most extreme Hii galaxies.
| 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%.
| Luminosity versus Phase-Space-Density Relation of Galaxies Revisited
We reexamined the correlation between the BTmagnitude and the phase-space-density parameterw=(D225vc)-1 of galaxies forthe Virgo, the Coma, the Fornax, and the Perseus clusters in an effortto better understand the physical underpinning of the fundamental plane.A tight correlation (BT=alog w+b) common to differentmorphological types of galaxies (E, S0, S) was found for the Virgo andthe Coma clusters, with a=1.87+/-0.10 and 1.33+/-0.11, respectively. Aninvestigation using only E galaxies was made for the four clusters. Theresults indicated that the empirical linear relation might be commonamong the Coma, the Fornax, and the Perseus clusters, with the VirgoCluster showing deviation. This relation, which is another way toproject the fundamental plane, has an expression insensitive to themorphology and may be suitable for treating galaxies of differentmorphological types collectively.
| 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
| Optical photometry of the UCM Lists I and II I. The data
We present Johnson B CCD photometry for the whole sample of galaxies ofthe Universidad Complutense de Madrid (UCM) Survey Lists I and II. Theyconstitute a well-defined and complete sample of galaxies in the LocalUniverse with active star formation. The data refer to 191 S0 to Irrgalaxies at an averaged redshift of 0.027, and complement the alreadypublished Gunn r, J and K photometries. In this paper the observationaland reduction features are discussed in detail, and the new colourinformation is combined to search for clues on the properties of thegalaxies, mainly by comparing our sample with other surveys. Tables 1and 3 are also available in electronic form at the CDS via anonymous ftpto 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
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
| 21 CM H1 Line Spectra of Galaxies in Nearby Clusters
A compilation of HI line fluxes, systemic velocities and line widths ispresented for \Ndet detected galaxies, mostly in the vicinities of 30nearby rich clusters out to a redshift of z ~ .04, specifically for usein applications of the Tully-Fisher distance method. New 21 cm HI lineprofiles have been obtained for ~ 500 galaxies in 27 Abell clustersvisible from Arecibo. Upper limits are also presented for \Nnod galaxiesfor which HI emission was not detected. In order to provide ahomogeneous line width determination optimized for Tully-Fisher studies,these new data are supplemented by the reanalysis of previouslypublished spectra obtained both at Arecibo and Green Bank that areavailable in a digital archive. Corrections for instrumental broadening,smoothing, signal-to-noise and profile shape are applied, and anestimate of the error on the width is given. When corrected forturbulent broadening and viewing angle, the corrected velocity widthspresented here will provide the appropriate line width parameter neededto derive distances via the Tully-Fisher relation.
| The I band Tully-Fisher relation for cluster galaxies: data presentation.
Observational parameters which can be used for redshift-independentdistance determination using the Tully-Fisher (TF) technique are givenfor \ntot spiral galaxies in the fields of 24 clusters or groups. I bandphotometry for the full sample was either obtained by us or compiledfrom published literature. Rotational velocities are derived either from21 cm spectra or optical emission line long-slit spectra, and convertedto a homogeneous scale. In addition to presenting the data, a discussionof the various sources of error on TF parameters is introduced, and thecriteria for the assignment of membership to each cluster are given.
| A Moderate-Resolution Spectral Atlas of Carbon Stars: R, J, N, CH, and Barium Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..105..419B&db_key=AST
| Survey for Emission-Line Galaxies: Universidad Complutense de Madrid List 2
A low-dispersion objective-prism survey for low-redshift emission-linegalaxies (ELGs) is being carried out by the Universidad Complutense deMadrid with the Schmidt telescope at the German-Spanish Observatory ofCalar Alto (Almeria, Spain). A 4^deg^ full-aperture prism, whichprovides a dispersion of 1950 A mm^-1^, and IIIa-F emulsion combinationhas been used to search for ELGs selected by the presence of Hαemission in their spectra. A compilation of descriptions and positions,along with finding charts, is presented for 103 emission-line objects.This is the second list, which contains objects located in a region ofthe sky covering 201.4 deg^2^ in seven fields near α = 15^h^ andδ = 25^deg^.
| Observations of a complete sample of Hα emission-line galaxies. Long-slit spectroscopy of galaxies in UCM lists 1 and 2.
Spectroscopic observations for the full sample of Hα emission-linegalaxy candidates (ELGs) from the Universidad Complutense de Madridobjective-prism survey Lists 1 and 2 have been obtained in order toinvestigate fully the properties of the survey constituents as well asthe selection characteristics and completeness limits of the surveyitself. The spectroscopic data include redshifts, line fluxes,equivalent widths, emission-line ratios, optical reddening estimates andsynthesized color indexes. We find that 74% of the objects in thissample do exhibit emission lines. We compare our observational data withparameters given in the published survey lists in order to assess theusefulness of the latter. The different emission-line galaxies have beenclassified according to their spectra in several groups. Gray-scaleimages of the CCD spectra near the main emission lines, spatial profilesat the continuum and the line for [OIII] λ5007 and Hαlines, as well as plots of the coadded spectra of selected galaxies arepresented, and a number of peculiar objects are described.
| Photometric and morphological analysis of UCM galaxies. I. Observations and reductions. Morphological classifications.
We present the results of Thuan & Gunn r CCD imaging observations ofthe Universidad Complutense de Madrid (UCM) sample of emission-linegalaxies (ELGs), selected by the presence of Hα emission inlow-resolution objective prism spectra. In this work we characterizephotometrically and morphologically a total of 212 objects from the UCMsurvey. This Paper presents the observations and basic reductions, andlists a set of photometric parameters calculated for each UCM object. Inaddition, for the first time in a ELGs sample, we have determined themorphological classification of the objects using simultaneously fivedifferent criteria.
| 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).
| Colors, luminosities, and masses of disk galaxies. 2: Environmental dependenceis
The B-band and near-infrared (H) luminosity functions of spiral galaxiesare derived for the Coma and A1367 clusters and for a referencepopulation of 'field' galaxies in the Coma supercluster. They areconsistent at the bright end, but they differ significantly at the faintend, indicating an overdensity of spirals with blue color (B-H less than3.0) and faint H luminosity (H greater than -21.5) in clusters withrespect to the field. These objects have disturbed morphology andpeculiar velocities significantly larger than the rest of the clustersample. We discuss these results in the framework of a possibleenvironmental dependence of galaxy evolution, and we conclude thatenhanced current star formation in cluster spiral galaxies might occurdue to molecular gas collapse stimulated by the ram-pressure mechanism.
| 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.
| Tests of the Tully-Fisher relation. 1: Scatter in infrared magnitude versus 21 CM width
We examine the precision of the Tully-Fisher relation (TFR) using asample of galaxies in the Coma region of the sky, and find that it isgood to 5% or better in measuring relative distances. Total magnitudesand disk axis ratios are derived from H and I band surface photometry,and Arecibo 21 cm profiles define the rotation speeds of the galaxies.Using 25 galaxies for which the disk inclination and 21 cm width arewell defined, we find an rms deviation of 0.10 mag from a linear TFRwith dI/d(log Wc) = -5.6. Each galaxy is assumed to be at adistance proportional to its redshift, and an extinction correction of1.4(1-b/a) mag is applied to the total I magnitude. The measured scatteris less than 0.15 mag using milder extinction laws from the literature.The I band TFR scatter is consistent with measurement error, and the 95%CL limits on the intrinsic scatter are 0-0.10 mag. The rms scatter usingH band magnitudes is 0.20 mag (N = 17). The low width galaxies havescatter in H significantly in excess of known measurement error, but thehigher width half of the galaxies have scatter consistent withmeasurement error. The H band TFR slope may be as steep as the I bandslope. As the first applications of this tight correlation, we note thefollowing: (1) the data for the particular spirals commonly used todefine the TFR distance to the Coma cluster are inconsistent with beingat a common distance and are in fact in free Hubble expansion, with anupper limit of 300 km/s on the rms peculiar line-of-sight velocity ofthese gas-rich spirals; and (2) the gravitational potential in the disksof these galaxies has typical ellipticity less than 5%. The publisheddata for three nearby spiral galaxies with Cepheid distancedeterminations are inconsistent with our Coma TFR, suggesting that theselocal calibrators are either ill-measured or peculiar relative to theComa Supercluster spirals, or that the TFR has a varying form indifferent locales.
| The Dynamics of the Outer Regions of the Coma Cluster
We apply the spherical infall model to compare the observed distributionof radial velocities of galaxies around Coma with predictions that arebased on optical and X-ray overdensity profiles. Two optically selectedgalaxy catalogues, the CfA redshift survey and a UKST plate scanned withthe APM, are used to determine the overdensity profile of the cluster.The two sets of predicted caustics in the angular separation-redshiftdiagram are compared with a radial velocity catalogue which we haveextended significantly in the range between 10 and 40 from the centre ofthe Coma cluster. In total, we have measured 98 new redshifts. Despitealmost doubling the number of radial velocities in this interval, wefail to find the caustics with any degree of certainty. Using recentX-ray-based density profiles of Coma, we derive an independentprediction of the caustics in redshift space. The velocities predictedusing these X-ray profiles are in general agreement with the observedvelocity distribution. We also investigate the effect that non-sphericalmass distributions have on the velocity field in the halo. For avelocity field that is constant on concentric ellipsoids, we show thatthe caustics are blurred, providing a natural explanation of why we donot see the caustics in Coma.
| Tully-Fisher distances to M31-like galaxies in the Coma cluster
Newly observed H I 21 cm linewidths for eight galaxies and morphologicaltypes for 33 galaxies are combined with data in the literature toconstruct a homogeneous magnitude-limited sample of spiral galaxies inthe Coma cluster. From this sample, we identify the seven Coma M31-likegalaxies, i.e. the spiral members with inclinations larger than -44 degand deprojected linewidths larger than -440 km/s. The distance moduli ofthese seven galaxies obtained by application of a blue-band Tully-Fisher(TF) relation are used to measure the distance to the Coma cluster. Ourresult, which is free of 'Malmquist' bias at the 3 sigma level, is adistance modulus of micron(0) = 34.4 +/- 0.2, which corresponds to aHubble constant H(0) of about 90 km/s Mpc. The observed rms dispersionof blue-band TF distance moduli for the seven Coma M31-like galaxies is0.14 mag, which is consistent with observational uncertainties alone,i.e. no intrinsic dispersion of the blue-band TF relation has beendetected above the observational rms noise level of 0.14 mag. This smallscatter is a specific result of our strict selection criteria adopted atthe onset of the analysis.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
Catalogs and designations:
|
