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Hα surface photometry of galaxies in the Virgo cluster. IV. The current star formation in nearby clusters of galaxies
Hα +[NII] imaging observations of 369 late-type (spiral) galaxiesin the Virgo cluster and in the Coma/A1367 supercluster are analyzed,covering 3 rich nearby clusters (A1367, Coma and Virgo) and nearlyisolated galaxies in the Great-Wall. They constitute an opticallyselected sample (mp<16.0) observed with ~ 60 %completeness. These observations provide us with the current(T<107 yrs) star formation properties of galaxies that westudy as a function of the clustercentric projected distances (Theta ).The expected decrease of the star formation rate (SFR), as traced by theHα EW, with decreasing Theta is found only when galaxies brighterthan Mp ~ -19.5 are considered. Fainter objects show no orreverse trends. We also include in our analysis Near Infrared data,providing information on the old (T>109 yrs) stars. Puttogether, the young and the old stellar indicators give the ratio ofcurrently formed stars over the stars formed in the past, or``birthrate'' parameter b. For the considered galaxies we also determinethe ``global gas content'' combining HI with CO observations. We definethe ``gas deficiency'' parameter as the logarithmic difference betweenthe gas content of isolated galaxies of a given Hubble type and themeasured gas content. For the isolated objects we find that b decreaseswith increasing NIR luminosity. In other words less massive galaxies arecurrently forming stars at a higher rate than their giant counterpartswhich experienced most of their star formation activity at earliercosmological epochs. The gas-deficient objects, primarily members of theVirgo cluster, have a birthrate significantly lower than the isolatedobjects with normal gas content and of similar NIR luminosity. Thisindicates that the current star formation is regulated by the gaseouscontent of spirals. Whatever mechanism (most plausibly ram-pressurestripping) is responsible for the pattern of gas deficiency observed inspiral galaxies members of rich clusters, it also produces the observedquenching of the current star formation. A significant fraction of gas``healthy'' (i.e. with a gas deficiency parameter less than 0.4) andcurrently star forming galaxies is unexpectedly found projected near thecenter of the Virgo cluster. Their average Tully-Fisher distance isfound approximately one magnitude further away (muo = 31.77)than the distance of their gas-deficient counterparts (muo =30.85), suggesting that the gas healthy objects belong to a cloudprojected onto the cluster center, but in fact lying a few Mpc behindVirgo, thus unaffected by the dense IGM of the cluster. Based onobservations taken at the Observatorio Astronómico Nacional(Mexico), the OHP (France), Calar Alto and NOT (Spain) observatories.Table \ref{tab4} is only available in electronic form athttp://www.edpsciences.org
| 1.65 ^mum (H-band) surface photometry of galaxies. IV. observations of 170 galaxies with the Calar Alto 2.2 m telescope
We present near-infrared (H band) surface photometry of 170 galaxies,obtained in 1997 using the Calar Alto 2.2 m telescope equipped with theNICMOS3 camera MAGIC. The majority of our targets are selected amongbright members of the Virgo cluster, however galaxies in the A262 andCancer clusters and in the Coma/A1367 supercluster are also included.This data set is aimed at complementing the NIR survey in the Virgocluster discussed in \cite[Boselli et al. (1997)]{B97} and in the ComaSupercluster, presented in Papers I, II and III of this series.Magnitudes at the optical radius, total magnitudes, isophotal radii andlight concentration indices are derivedTables 1 and 2 (full version) 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.Based on observations taken at the Calar Alto Observatory, operated bythe Max-Planck-Institut für Astronomie (Heidelberg) jointly withthe Spanish National Commission for Astronomy.
| 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
| 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 Star Formation Properties of Disk Galaxies: Hα Imaging of Galaxies in the Coma Supercluster
We present integrated Hα measurements obtained from imagingobservations of 98 late-type galaxies, primarily selected in the Comasupercluster. These data, combined with Hα photometry from theliterature, include a magnitude-selected sample of spiral (Sa to Irr)galaxies belonging to the ``Great Wall'' complete up to m_p = 15.4, andthus composed of galaxies brighter than M_p = -18.8 (H_0 = 100 km s^-1Mpc^-1). The frequency distribution of the Hα equivalent width,determined for the first time from an optically complete sample, isapproximately Gaussian, peaking at EW ~ 25 Å. We find that, at thepresent limiting luminosity, the star formation properties of spiral +Irr galaxy members of the Coma and A1367 Clusters do not differsignificantly from those of the isolated ones belonging to the GreatWall. The present analysis confirms the well-known increase of thecurrent massive star formation rate (SFR) with Hubble type. Moreover,perhaps a more fundamental anticorrelation exists between the SFR andthe mass of disk galaxies: low-mass spirals and dwarf systems havepresent SFRs ~50 times higher than giant spirals. This result isconsistent with the idea that disk galaxies are coeval, evolving as``closed systems'' with exponentially declining SFR, and that the massof their progenitor protogalaxies is the principal parameter governingtheir evolution. Massive systems having high initial efficiency ofcollapse, or a short collapse timescale, have retained little gas tofeed the present epoch of star formation. These findings support theconclusions of Gavazzi & Scodeggio, who studied the color-massrelation of a local galaxy sample, and agree with the analysis by Cowieet al., who traced the star formation history of galaxies up to z >1. Based on observations made at the Observatorio AstronómicoNacional (OAN), San Pedro Mártir, B.C., of the UniversidadNacional Autónoma de México (UNAM).
| 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.
| The molecular gas content of spiral galaxies in the Coma/A1367 supercluster.
We present ^12^CO(J=1-0) line observations of 73 spiral galaxies mostlyin the Coma/A1367 supercluster. From these data, combined with dataavailable in the literature, we extract the first complete, opticallyselected sample (m_pg_<15.2) of 37 isolated and of 27 clustergalaxies. Adopting a standard conversion factor X=N(H_2_)/I(CO), weestimate that the molecular hydrogen content of isolated spiral galaxiesis, on average, 20% of the atomic hydrogen reservoir, significantlylower than previous estimates based on samples selected by FIR criteria,thus biased towards CO rich objects. We show that the frequencydistributions of the CO deficiency parameter, defined as the differencebetween the expected and the observed molecular gas content of a galaxyof given luminosity (or linear diameter), computed separately forcluster and isolated galaxies, are not significantly different,indicating that the environment does not affect the molecular gascontent of spiral discs. A well defined relationship exists betweenM_i_(H_2_) and the star formation activity in bright galaxies, while itis weaker at lower luminosities. We interpret this finding as indicatingthat CO emission traces relatively well the H_2_ mass only in high-massgalaxies, such as the Milky Way. On the other hand, in low-mass spiralsthe higher far-UV radiation field produced by young O-B stars and thelower metallicity cause the photodissociation of the diffuse moleculargas, weakening the expected relationship between star formation and theCO emission. The conversion factor between the CO line intensity and theamount of molecular hydrogen being ill-determined and variable with theUV flux and abundances, it is difficult to assess the relationshipbetween the star formation and the amount of molecular hydrogen.
| 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.
| 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.
| Kinematics and dynamics of the MKW/AWM poor clusters
We report 472 new redshifts for 416 galaxies in the regions of the 23poor clusters of galaxies originally identified by Morgan, Kayser, andWhite (MKW), and Albert, White, and Morgan (AWM). Eighteen of the poorclusters now have 10 or more available redshifts within 1.5/h Mpc of thecentral galaxy; 11 clusters have at least 20 available redshifts. Basedon the 21 clusters for which we have sufficient velocity information,the median velocity scale is 336 km/s, a factor of 2 smaller than foundfor rich clusters. Several of the poor clusters exhibit complex velocitydistributions due to the presence of nearby clumps of galaxies. We checkon the velocity of the dominant galaxy in each poor cluster relative tothe remaining cluster members. Significantly high relative velocities ofthe dominant galaxy are found in only 4 of 21 poor clusters, 3 of whichwe suspect are due to contamination of the parent velocity distribution.Several statistical tests indicate that the D/cD galaxies are at thekinematic centers of the parent poor cluster velocity distributions.Mass-to-light ratios for 13 of the 15 poor clusters for which we havethe required data are in the range 50 less than or = M/LB(0)less than or = 200 solar mass/solar luminosity. The complex nature ofthe regions surrounding many of the poor clusters suggests that thesegroupings may represent an early epoch of cluster formation. Forexample, the poor clusters MKW7 and MKWS are shown to be gravitationallybound and likely to merge to form a richer cluster within the nextseveral Gyrs. Eight of the nine other poor clusters for which simpletwo-body dynamical models can be carried out are consistent with beingbound to other clumps in their vicinity. Additional complex systems withmore than two gravitationally bound clumps are observed among the poorclusters.
| A CCD survey of galaxies. IV. Observations with the 2.1 M telescope at San Pedro Martir.
Continuing a CCD survey of galaxies belonging or projected onto the Comaand Hercules Superclusters, to the A262 and Cancer clusters, we presentisophote maps and photometric profiles in the Johnson system of 111galaxies (67 in the V and B bands, 42 only in V, 2 only in B) obtainedwith the 2.1 m telescope at San Pedro Martir (Baja California, Mexico).
| 21 centimeter study of spiral galaxies in the Coma supercluster. II - Evidence for ongoing gas stripping in five cluster galaxies
High-sensitivity 21 cm observations of 73 galaxies in the Comasupercluster are presented. Seventeen new redshifts are reported. Threegalaxies in A1367 and two in the Coma Cluster are found with remarkablyasymmetrical H I spectra indicating uneven gas distribution in theirdisks. This unstable configuration is interpreted as being due toongoing dynamical gas stripping taking place on time scales shorter thanthose required for differential rotation to redistribute the gas, i.e.,a few times 100 million yr. This suggests that spiral galaxies arecontinuously supplied to the clusters from the surrounding supercluster.
| Near-infrared observations of galaxies in the Coma supercluster
Near-IR magnitudes have been obtained for 136 galaxies in the Coma/A1367supercluster region, and near-IR colors (J-H) and (H-K) for 90 and 87objects, respectively. The near-IR colors are contained in a small rangeand do not depend on morphological types, galaxy inclination, orenvironment. Optical-to-IR colors depend strongly on a galaxy'smorphological type and inclination. There is a dependence of therelative excess of radio, and to a lesser degree, of far-IR emission onrecent star formation activity. The magnitude-line width relation forgalaxies in Coma and A1367 obtained with these data has a larger spreadthan previously found with smaller samples. The data suggest a distancemodulus to Coma of about 35, regardless of the choice of primarycalibrators.
| Uncertainties in 21 centimeter redshifts. I - Data
High-precision data on the 21-cm redshifts, profile widths, and shapesfor 625 galaxies are presented. Each galaxy is listed in across-identification and morphology table. High-resolution spectra arealso given for each galaxy. Internal redshift consistency is roughly 1km/s for galaxies for which the S/N is above 15. No systematic effectshave been found which might influence the observed redshift quantizationat 72.5 km/s or its submultiples.
| A statistical study of companions to Seyfert galaxies
Comparison of a large sample of nearby Seyfert galaxies with a controlsample of normal spirals reveals only marginal evidence that Seyfertspossess an excess of comparably sized companions. It is shown that theexcess of companions near Seyferts noted by Dahari (1984) is primarilydue to low-luminosity galaxies that would have been eliminated asbackground by the present technique. Seyferts are found to be in sparserenvironments than radio galaxies both with or without strong emissionlines in their nuclear spectra.
| 21 centimeter study of spiral galaxies in the Coma supercluster
High-sensitivity, 21 cm line observations of 130 galaxies in theComa/A1367 Supercluster region are presented and used to study thelarge-scale distribution of galaxies in the direction of the ComaSupercluster and the H I content in spiral galaxies as a function of thelocal galaxy density. Groups of galaxies are found to form aquasi-continuous structure that connects the Local Supercluster to theComa Supercluster. This structure is composed of real filaments only inthe vicinity of the Coma Cluster. Spiral galaxies in the surveyed groupsand multiple systems have H I content not dissimilar from that ofisolated galaxies. Galaxies within about 1 Abell radius from the ComaCluster contain about three times less hydrogen on average than isolatedgalaxies. There is a strong tendency for galaxies that are more severelyH I-depleted to be redder and of earlier Hubble type. In the ComaCluster a considerable fraction of late-type, blue galaxies have largedeficiency parameters.
| 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.
| Radio continuum survey of the Coma/A1367 supercluster. II - 1.5 GHz observations of 396 CGCG galaxies
1.5 GHz VLA radio continuum observations of 396 relatively isolated CGCGgalaxies in the Coma/A1367 supercluster yielded the detection of 95objects. These observations, added to the ones presented in previouspapers, form a complete sample of optically selected objects with m(p)equal to or less than 15.3. Two wide-angle-tailed sources have beenfound in smaller groups within the supercluster.
| Gas deficiency in cluster galaxies - A comparison of nine clusters
The available 21 cm line data in the literature for galaxies in nineclusters is combined with new high-sensitivity observations of 51galaxies in five of the nine clusters in order to test fordiscriminating circumstances between those clusters which show H Ideficiency among their spiral population and those which do not. An H Ideficiency for the complete cluster sample is derived employing acomparison sample of galaxies chosen from the Catalog of IsolatedGalaxies. The deficiency and its radial dependence is summarized foreach cluster and a composite. A comparison of the environments indifferent clusters leads to the conclusion that the occurrence of H Ideficiency is correlated with the presence of a hot X-ray intraclustermedium, and that an ongoing interaction process is active through thecores of X-ray clusters.
| Face-on galaxies
A 21 cm survey of about 200 face-on galaxies using the 305 m Areciboradio telescope is reported. The narrowest profiles for everymorphological type are presented. The data are consistent with anintegral velocity dispersion of about 8 km/s in every morphologicaltype. When combined with the results of other studies, the presentresults indicate that the gas dispersion appears to be a universalnumber, broadly independent of morphological type, absolute magnitude,and position within a galaxy. Two direct consequences follow from theuniversality of an isotropic velocity distribution: (1) the 'missingmass' component within galaxies necessarily resides in the halo, and (2)small galaxies may only maintain an H I distribution through galaxy-widerandom motions, provided that the appropriate dispersion is thecanonical one.
| A survey of galaxy redshifts. IV - The data
The complete list of the best available radial velocities for the 2401galaxies in the merged Zwicky-Nilson catalog brighter than 14.5mz and with b (II) above +40 deg or below -30 deg ispresented. Almost 60 percent of the redshifts are from the CfA surveyand are accurate to typically 35 km/s.
| 21 centimeter observations of supercluster galaxies - The bridge between Coma and A1367
21 cm observations of galaxies in the region of the Coma-A1367supercluster are presented. It is shown that galaxies near the clustercenter are hydrogen deficient, while galaxies which are in between thetwo clusters have a normal hydrogen content. A crossing time of about1.7 x 10 to the 9th yr is defined by the radius of the region oftransition between deficient and nondeficient galaxies and the cluster'svelocity dispersion. The gas removed by stripping is a small fraction ofthe gas observed in the X-ray region.
| Radial Velocities of Ring-Shaped Galaxies - Part Two
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