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HI content in galaxies in loose groups
Gas deficiency in cluster spirals is well known and ram-pressurestripping is considered the main gas removal mechanism. In some compactgroups too gas deficiency is reported. However, gas deficiency in loosegroups is not yet well established. Lower dispersion of the membervelocities and the lower density of the intragroup medium in small loosegroups favour tidal stripping as the main gas removal process in them.Recent releases of data from the HI Parkes All-Sky Survey (HIPASS) andcatalogues of nearby loose groups with associated diffuse X-ray emissionhave allowed us to test this notion. In this paper, we address thefollowing questions: (i) do galaxies in groups with diffuse X-rayemission statistically have lower gas content compared to the ones ingroups without diffuse X-ray emission? (ii) does HI deficiency vary withthe X-ray luminosity, LX, of the loose group in a systematicway? We find that (i) galaxies in groups with diffuse X-ray emission, onaverage, are HI deficient, and have lost more gas compared to those ingroups without X-ray emission; the latter are found not to havesignificant HI deficiency; (ii) no systematic dependence of the HIdeficiency with LX is found. Ram-pressure-assisted tidalstripping and evaporation by thermal conduction are the two possiblemechanisms to account for this excess gas loss.
| Why Are Radio Galaxies Prolific Producers of Type Ia Supernovae?
An analysis of SN Ia events in early-type galaxies from the database ofCappellaro and coworkers provides conclusive evidence that the rate ofSNe Ia in radio-loud galaxies is about 4 times higher than the ratemeasured in radio-quiet galaxies, i.e., SN Ia rate(radio-loudgalaxies)=0.43+0.19-0.14h275 SNu as compared to SN Ia rate(radio-quietgalaxies)=0.11+0.06-0.03h275 SNu. The actual value of the enhancement islikely to be in the range ~2-7 (P~10-4). This finding puts onrobust empirical grounds the results obtained by Della Valle &Panagia on the basis of a smaller sample of SNe. We analyze the possiblecauses of this result and conclude that the enhancement of the SN Iaexplosion rate in radio-loud galaxies has the same origin as their beingstrong radio sources, but there is no causal link between the twophenomena. We argue that repeated episodes of interaction and/or mergersof early-type galaxies with dwarf companions, on timescales of about 1Gyr, are responsible for both inducing strong radio activity observed in~14% of early-type galaxies and supplying an adequate number of SN Iaprogenitors to the stellar population of elliptical galaxies.
| Reddening, Absorption, and Decline Rate Corrections for a Complete Sample of Type Ia Supernovae Leading to a Fully Corrected Hubble Diagram to v < 30,000 km s-1
Photometric (BVI) and redshift data corrected for streaming motions arecompiled for 111 ``Branch-normal,'' four 1991T-like, seven 1991bg-like,and two unusual supernovae of Type Ia (SNe Ia). Color excessesE(B-V)host of normal SNe Ia, due to the absorption of thehost galaxy, are derived by three independent methods, giving excellentagreement leading to the intrinsic colors at maximum of(B-V)00=-0.024+/-0.010 and (V-I)00=-0.265+/-0.016if normalized to a common decline rate of Δm15=1.1. Thestrong correlation between redshift absolute magnitudes (based on anarbitrary Hubble constant of H0=60 km s-1Mpc-1), corrected only for the extrinsic Galactic absorption,and the derived E(B-V)host color excesses leads to thewell-determined yet abnormal absorption-to-reddening ratios ofRBVI=3.65+/-0.16, 2.65+/-0.15, and 1.35+/-0.21.Comparison with the canonical Galactic values of 4.1, 3.1, and 1.8forces the conclusion that the law of interstellar absorption in thepath length to the SN in the host galaxy is different from the localGalactic law, a result consistent with earlier conclusions by others.Improved correlations of the fully corrected absolute magnitudes (on thesame arbitrary Hubble constant zero point) with host galaxymorphological type, decline rate, and intrinsic color are derived. Werecover the result that SNe Ia in E/S0 galaxies are ~0.3 mag fainterthan in spiral galaxies for possible reasons discussed in the text. Thenew decline rate corrections to absolute magnitudes are smaller thanthose by some authors for reasons explained in the text. The fourspectroscopically peculiar 1991T-type SNe are significantly overluminousas compared to Branch-normal SNe Ia. The overluminosity of the seven1999aa-like SNe is less pronounced. The seven 1991bg types in the sampleconstitute a separate class of SNe Ia, averaging in B 2 mag fainter thanthe normal Ia. New Hubble diagrams in B, V, and I are derived out to~30,000 km s-1 using the fully corrected magnitudes andvelocities, corrected for streaming motions. Nine solutions for theintercept magnitudes in these diagrams show extreme stability at the0.02 mag level using various subsamples of the data for both low andhigh extinctions in the sample, proving the validity of the correctionsfor host galaxy absorption. We shall use the same precepts for fullycorrecting SN magnitudes for the luminosity recalibration of SNe Ia inthe forthcoming final review of our Hubble Space Telescope Cepheid-SNexperiment for the Hubble constant.
| Redshift-Distance Survey of Early-Type Galaxies: Spectroscopic Data
We present central velocity dispersions and Mg2 line indicesfor an all-sky sample of ~1178 elliptical and S0 galaxies, of which 984had no previous measures. This sample contains the largest set ofhomogeneous spectroscopic data for a uniform sample of ellipticalgalaxies in the nearby universe. These galaxies were observed as part ofthe ENEAR project, designed to study the peculiar motions and internalproperties of the local early-type galaxies. Using 523 repeatedobservations of 317 galaxies obtained during different runs, the dataare brought to a common zero point. These multiple observations, takenduring the many runs and different instrumental setups employed for thisproject, are used to derive statistical corrections to the data and arefound to be relatively small, typically <~5% of the velocitydispersion and 0.01 mag in the Mg2 line strength. Typicalerrors are about 8% in velocity dispersion and 0.01 mag inMg2, in good agreement with values published elsewhere.
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| 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
| Supernovae in isolated galaxies, in pairs and in groups of galaxies
In order to investigate the influence of environment on supernova (SN)production, we have performed a statistical investigation of the SNediscovered in isolated galaxies, in pairs and in groups of galaxies. 22SNe in 18 isolated galaxies, 48 SNe in 40 galaxy members of 37 pairs and211 SNe in 170 galaxy members of 116 groups have been selected andstudied. We found that the radial distributions of core-collapse SNe ingalaxies located in different environments are similar, and consistentwith those reported by Bartunov, Makarova & Tsvetkov. SNe discoveredin pairs do not favour a particular direction with respect to thecompanion galaxy. Also, the azimuthal distributions inside the hostmembers of galaxy groups are consistent with being isotropics. The factthat SNe are more frequent in the brighter components of the pairs andgroups is expected from the dependence of the SN rates on the galaxyluminosity. There is an indication that the SN rate is higher in galaxypairs compared with that in groups. This can be related to the enhancedstar formation rate in strongly interacting systems. It is concludedthat, with the possible exception of strongly interacting systems, theparent galaxy environment has no direct influence on SN production.
| Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
| Supernova Type Ia Luminosities, Their Dependence on Second Parameters, and the Value of H0
A sample of 35 Type Ia supernovae (SNe Ia) with good to excellentphotometry in B and V, minimum internal absorption, and1200
| 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.
| Groups of galaxies. III. Some empirical characteristics.
Not Available
| The Universality of the Fundamental Plane of E and S0 Galaxies: Spectroscopic Data
We present central velocity dispersion measurements for 325 early-typegalaxies in eight clusters and groups of galaxies, including newobservations for 212 galaxies. The clusters and groups are the A262,A1367, Coma (A1656), A2634, Cancer, and Pegasus Clusters and the NGC 383and NGC 507 Groups. The new measurements were derived frommedium-dispersion spectra that cover 600 Å centered on the Mg I btriplet at lambda ~ 5175 Å. Velocity dispersions were measuredusing the Tonry & Davis cross-correlation method, with a typicalaccuracy of 6%. A detailed comparison with other data sources is made.
| The Universality of the Fundamental Plane of E and S0 Galaxies: Sample Definition and I-Band Photometric Data
As part of a project to compare the fundamental plane and Tully-Fisherdistance scales, we present here I-band CCD photometry for 636early-type galaxies in eight clusters and groups of galaxies. These arethe A262, A1367, Coma (A1656), A2634, Cancer and Pegasus Clusters, andthe NGC 383 and NGC 507 Groups. Sample selection, cluster properties,and cluster membership assignment criteria are discussed. We presentphotometric parameters that are used in the fundamental plane relation,the effective radius r_e, and the effective surface brightness mu_e, asderived from a r^1/4 fit to the observed radial photometric profile ofeach galaxy. A comparison with similar data found in the literature forthe Coma Cluster shows that large systematic uncertainties can beintroduced in the measurement of r_e and mu_e by the particular methodused to derive those parameters. However, the particular combination ofthese two parameters that enters in the fundamental plane relation is aquantity that can be measured with high accuracy.
| 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.
| Explosion Models for Type IA Supernovae: A Comparison with Observed Light Curves, Distances, H 0, and Q 0
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...457..500H&db_key=AST
| Photoelectric UBV Photometry of Galaxies in the Clusters Pegasus I, Pegasus II, Abell 262, Abell 1367, and Abell 2197-9
This paper presents photoelectric UBV multiaperture photometry of 144galaxies, 139 of which are associated with six nearby bright clusters.The observations were made at the McDonald Observatory from 1986September to 1987 November and were part of the production of the ThirdReference Catalogue of Bright Galaxies (RC3). The observations were usedto compute total magnitudes and color indices published in RC3. Theobservations can also be used to calibrate CCD images.
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| The Hubble Diagram for Supernovae of Type Ia. II. The Effect on the Hubble Constant of a Correlation between Absolute Magnitude and Light Decay Rate
New Hubble diagrams in B and V are derived for supernovae of type Ibased on light curves from the archive literature plus 13 new lightcurves with superior modern photometry observed in the CerroTololo/University of Chile program (Hamuy et al, 1995). The sample isrestricted to SNe Ia whose light curves are defined by photometrybeginning 5 days or less after maximum light and with (B - V)max <0.5 mag. Supernovae of known type Ib or Ic are also excluded. Theresulting Hubble diagrams, extending to redshifts of 30,00 km s^- 1^,have dispersions in absolute magnitude of 0.34 mag in B and 0.33 mag inV, confirming that spectroscopically "normal" (Branch et al. 1993) SNeIa are among the best standard candles known. A solution for the slopeof the Hubble diagram gives n(B) = 0.977 +/- 0.025 and n(V) = 1.020 +/-0.024 for the exponent in ν~D^n^, proving linearity of the expansionfield to a high level. The residuals in magnitude from the ridge line ofthe Hubble diagram are compared with the light decay rate during thefirst 15 days to test the correlation between the two suggested byPskovskii and by Phillips. The strongest possible correlation using theextant data has a slope 3 times smaller than that derived by Phillips,and 2 times smaller than suggested by Hamuy et al., leading to adecrease of less than 10% in the distance scale based on the present(1995) SNe Ia calibration by means of three supernovae whose distancesare known from Cepheids in their parent galaxies. Applying the maximumpossible correction to M(max) for a Psko'vskii- Phillips effect wouldgive Hubble constants of H_0_(B)<= 54 +/- 4 km s^-1^ Mpc^-1^, andH_0_(V) <= 59 +/- 4 km s^-1^ Mpc^-1^, where the errors are internal.It is argued that the absence of measurable bias effects in the Hubblediagrams shows that the three local (nearest) SNe Ia presentlycalibrated via Cepheid distances cannot all be overluminous relative tothe average of more distant SNe. If they are underluminous, which mustbe the case by the statistics of the Malmquist effect if the largedispersion in M(max) for SNe Ia claimed by Hamuy et al. applies to thecalibrators, then the value of H_0_ = 52 km s^-1^ Mpc^-1^ given by Sahaet al. is an upper limit to the Hubble constant.
| The Peak Brightness of Supernovae in the U Band and the Hubble Constant
The peak magnitudes of Type I supernovae in the U band can be used toanswer various questions relating to supernovae and the Hubble constant:(1) Well-observed normal Type Ia supernovae are placed in a color-colordiagram along the extinction line of (B - V) = 1.25(U - B) + 0.15 with ascatter of 0.1 mag in each color. (2) The peak B - V colors measured atthe Asiago Observatory are far from this relation, hence supporting theearlier conclusions that these data are unreliable. (3) The intrinsic B- V at B peak of normal Type Ia events is 0.00 +/- 0.04 or perhapsslightly redder, hence implying that these are good standard candles.(4) The dereddened absolute magnitude in the U band at the time of Bpeak is -18.88 +/- 0.15 for H0 = 75. (5) The U- and H-band light curvesof SN 1972E yield low values for the Hubble constant.
| The blue anbd visual absolute magnitude distributions of Type IA supernovae
Tully-Fisher (TF), surface brightness fluctuation (SBF), and Hubble lawdistances to the parent galaxies of Type Ia supernovae (SNs Ia) are usedin order to study the SN Ia blue and visual peak absolute magnitude(MB and MV) distributions. We propose twoobjective cuts, each of which produces a subsample with small intrinsicdispersion in M. One cut, which can be applied to either band,distinguishes between a subsample of bright events and a smallersubsample of dim events, some of which were extinquished in the parentgalaxy and some of which were intrinsically subluminous. The brightevents are found to be distributed with an observed dispersions of 0.3less than or approximately = Sigmaobs less than orapproximately = 0.4 about a mean absolut magnitude (M-barB orM-barV). Each of the dim SNs was spectroscopically peculiarand/or had a red B-V color; this motivates the adoption of analternative cut that is based on B-V rather than on M. To wit, SNs Iathat are both known to have -0.25 less than B-V less than + 0.25 and notknown to be spectroscopically peculiar show observational dispersion ofonly Sigmaobs(MB) =Sigmaobs(MV) = 0.3. Because characteristicsobservational errors produce Sigmaerr(M) greater than 0.2,theintrinsic dispersion among such SNs Ia is Sigmaint(M) lessthan or approximately = 0.2. The small observational dispersionindicates that SNs Ia, the TF relation, and SBFs all good relativedistances to those galaxies that produce SNs Ia. The conflict betweenthose who use SNs Ia in order to determine the value of the Hubbleconstant (H0) and those who use TF and SBF distances todetermine H0 results from discrepant calibrations.
| Integrated photoelectric magnitudes and color indices of bright galaxies in the Johnson UBV system
The photoelectric total magnitudes and color indices published in theThird Reference Catalogue of Bright Galaxies (RC3) are based on ananalysis of approximately equals 26,000 B, 25,000 B-V, and 17,000 U-Bmultiaperture measurements available up to mid 1987 from nearly 350sources. This paper provides the full details of the analysis andestimates of internal and external errors in the parameters. Thederivation of the parameters is based on techniques described by theVaucouleurs & Corwin (1977) whereby photoelectric multiaperture dataare fitted by mean Hubble-type-dependent curves which describe theintegral of the B-band flux and the typical B-V and U-B integrated colorgradients. A sophisticated analysis of the residuals of thesemeasurements from the curves was made to allow for the random andsystematic errors that effect such data. The result is a homogeneous setof total magnitudes BTA total colors(B-V)T and (U-B)T, and effective colors(B-V)e and (U-B)e for more than 3000 brightgalaxies in RC3.
| Type IA supernovae in Lyon groups of galaxies
Two galaxies with observed type Ia supernovae have been identified ineach of three Lyon groups of galaxies not associated with the Virgocluster. The difference of well-determined apparent magnitudes atlight-curve maximum of the supernovae in each group is delta B less thanor equal to 0.2 mag. delta V less than or equal to 0.2 mag. Previously,Branch and Tammann found that the observed apparent magnitudes atmaximum light for type Ia supernovae in three galaxies, each with twoobserved supernovae, are nearly identical. The consistency of these twoindependent results further suggests that the set of all type Iasupernovae contains a large subset of 'standard candles.'
| A comparison of calculated and observed monochromatic Type IA supernova light curves
The calculated monochromatic (B and V) light curves of a set of Type Iasupernova models are compared with the observed monochromatic lightcurves of 13 Type Ia supernovae (SNIa). The set consists of 11 Type Iasupernova models including deflagrations, detonations, delayeddetonations, pulsating delayed detonations and tamped detonations. Thetheoretical light curves have been calculated using our recentlydeveloped light curve model. The model incorporates a detailed equationof state with an elaborate treatment of the ionization balance, animplicit grey Local Thermodynamic Equilibrium (LTE) radiation transportscheme based on the moment equations, a total energy equation for thegas and the radiation field, expansion opacities, and a Monte Carlogamma-ray deposition scheme. To evolve the structure of the underlyingexplosion models homologous expansion is assumed. We find that fastrising light curves (e.g., SN 1972E, SN 1981B and SN 1986G) can bereproduced best by delayed detonation models, and that slowly rising(tmax greater than or approximately equal to 17 days) lightcurves (e.g., SN 1984A and SN 1990N) cannot be reproduced by standarddetonation, deflagration or delayed detonation models. In order toobtain an acceptable agreement with observations for slowly rising lightcurves explosion models are required where the C/O white dwarf issurrounded by an unburnt extended envelope of typically 0.2 to 0.4 solarmass. Our interpretation of the light curves is also favored from theexpansion velocities observed in the spectra of the slowly rising SNIa.Based on a comparison of theoretical light curves and observationaldata, the distances of the parent galaxies have been determined. We showthat SNeIa allow for a measurement of the value of the Hubble constantprovided individual fits are used and if they are located at distanceslarger than 15 Mpc, because only then they are in the 'Hubble' flow.Taking this restriction into account a Hubble constant of H = 66 +/- 10km/(secMpc) can be derived within a 2 sigma error.
| A revised catalog of CfA1 galaxy groups in the Virgo/Great Attractor flow field
A new identification of groups and clusters in the CfA1 Catalog ofHuchra et al. is presented, using a percolation algorithm to identifydensity enhancements. It is shown that in the resulting catalog,contamination by interlopers is significantly reduced. The Schechterluminosity function is redetermined, including the Malmquist bias.
| The Hubble diagram in V for supernovae of Type IA and the value of H(0) therefrom
The Hubble diagram for Type I supernovae is derived in V and issummarized from the literature in B and in m(pg). The ridge lineequation of the diagram in V and the calibration of the absolutemagnitudes at maximum are presented. The intrinsic (B - V) color at Bmaximum light is 0.09 +/- 0.04 mag. The Virgo Cluster distance isderived and found to be 23.9 +/- 2.4 Mpc. This Virgo distance gives thecosmic value of the Hubble constant to be H(0) = 47 +/- 5 km/sec perMpc.
| Type IA supernovae as standard candles
The distribution of absolute blue magnitudes among Type Ia supernovae(SNs Ia) is studied. Supernovae were used with well determined apparentmagnitudes at maximum light and parent galaxies with relative distancesdetermined by the Tully-Fisher or Dn - sigma techniques. The meanabsolute blue magnitude is given and the observational dispersion isonly sigma(MB) 0.36, comparable to the expected combined errors indistance, apparent magnitude, and extinction. The mean (B-V) color atmaximum light is 0.03 +/- 0.04, with a dispersion sigma(B-V) = 0.20. TheCepheid-based distance to IC 4182, the parent galaxy of the normal andunextinguished Type Ia SN 1937C, leads to a Hubble constant of H(0) + 51+/- 12 km/s Mpc. The existence of a few SNs Ia that appear to have beenreddened and dimmed by dust in their parent galaxies does not seriouslycompromise the use of SNs Ia as distance indicators.
| General study of group membership. II - Determination of nearby groups
We present a whole sky catalog of nearby groups of galaxies taken fromthe Lyon-Meudon Extragalactic Database. From the 78,000 objects in thedatabase, we extracted a sample of 6392 galaxies, complete up to thelimiting apparent magnitude B0 = 14.0. Moreover, in order to considersolely the galaxies of the local universe, all the selected galaxieshave a known recession velocity smaller than 5500 km/s. Two methods wereused in group construction: a Huchra-Geller (1982) derived percolationmethod and a Tully (1980) derived hierarchical method. Each method gaveus one catalog. These were then compared and synthesized to obtain asingle catalog containing the most reliable groups. There are 485 groupsof a least three members in the final catalog.
| The Local Group Motion Towards Virgo and the Microwave Background
The peculiar motion of the Local Group is determined from 15 clusterswhose relative distances are known with minimum bias. The resultinglocal motion is 745 +/- 106 kms^-1^ towards l = 273^deg^, b = 3^deg^.This 7σ signal is in perfect statistical agreement with the motioninferred from the dipole of the cosmic microwave background. The mediandistance of 6400 km s^-1^ of the 15 clusters sets an upper limit to thecomoving volume. - The three-dimensional peculiar motions of theclusters become 587 km s^-1^, if allowance is made for a 5 percent errorof the cluster distances. The value compares well with the 489 km s^-1^motion of the Virgo complex with respect to the cosmic microwavebackground. - The data imply a local slow-down of the expansion fielddue to the Virgo cluster of v_VC_ = 239 +/- 40 km s^-1^. An almostidentical value, i.e. v_VC_ = 233 +/- 44 km s^-1^, is independentlydetermined using the relative distances of the Virgo, UMa, and Fornaxclusters and of eight nearby supernovae of type Ia. - These results donot require the adoption of any zero-point of the extragalactic distancescale.
| The rate of supernovae. I - The data base, the recipe and the uncertainties
Because the determination of SN rates is vulnerable to the small numberstatistics of homogeneous samples, the data bases of two independent SNsearches were merged in order to build up the largest data base everused for SN rate determinations. Using a software specially developedfor the analysis of these materials, the individual control times wereestimated for each galaxy and in turn the SN rates for samples ofgalaxies extracted from different catalogs were estimated. Theuncertainties in the input parameters were quantitatively estimated byseveral tests. It is found that the assumption of the limiting discoverymagnitude is crucial. Contrary to previous belief, it is shown that thedispersion of the absolute SN magnitude at maximum is not particularlyimportant for the SN rates determined from the samples, whereasuncertainties about the shape of the light curve are more serious. Therate of SNe was computed for four galaxy samples extracted fromdifferent catalogs. It is shown that the SNe rate reflects thedifferences among the galaxy parameters reported by different catalogs.
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