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Scalar potential model of redshift and discrete redshift
On the galactic scale the universe is inhomogeneous and redshift z isoccasionally less than zero. A scalar potential model (SPM) that linksthe galaxy scale z to the cosmological scale z of the Hubble Law ispostulated. Several differences among galaxy types suggest that spiralgalaxies are Sources and that early type, lenticular, and irregulargalaxies are Sinks of a scalar potential field. The morphology-radiusand the intragalactic medium cluster observations support the movementof matter from Source galaxies to Sink galaxies. A cell structure ofgalaxy groups and clusters is proposed to resolve a paradox concerningthe scalar potential like the Olber’s paradox concerning light.For the sample galaxies, the ratio of the luminosity of Source galaxiesto the luminosity of Sink galaxies approaches 2.7 ± 0.1. Anequation is derived from sample data, which is anisotropic andinhomogeneous, relating z of and the distance D to galaxies. Thecalculated z has a correlation coefficient of 0.88 with the measured zfor a sample of 32 spiral galaxies with D calculated using Cepheidvariable stars. The equation is consistent with z < 0 observations ofclose galaxies. At low cosmological distances, the equation reduces to z≈ exp(KD)‑1 ≈ KD, where K is a constant, positive value. Theequation predicts z from galaxies over 18 Gpc distant approaches aconstant value on the order of 500. The SPM of z provides a physicalbasis for the z of particle photons. Further, the SPM qualitativelysuggests the discrete variations in z, which was reported by Tifft[Tifft, W.G., 1997. Astrophy. J. 485, 465] and confirmed by others, areconsistent with the SPM.
| Cepheid Distances to SNe Ia Host Galaxies Based on a Revised Photometric Zero Point of the HST WFPC2 and New PL Relations and Metallicity Corrections
With this paper we continue the preparation for a forthcoming summaryreport of our experiment with the HST to determine the Hubble constantusing Type Ia supernovae as standard candles. Two problems areaddressed. (1) We examine the need for, and determine the value of, thecorrections to the apparent magnitudes of our program Cepheids in the 11previous calibration papers due to sensitivity drifts and chargetransfer effects of the HST WFPC2 camera over the life time of theexperiment from 1992 to 2001. (2) The corrected apparent magnitudes areapplied to all our previous photometric data from which revised distancemoduli are calculated for the eight program galaxies that are parents tothe calibrator Ia supernovae. Two different Cepheid P-L relations areused; one for the Galaxy and one for the LMC. These differ both in slopeand zero point at a fixed period. The procedures for determining theabsorption and reddening corrections for each Cepheid are discussed.Corrections for the effects of metallicity differences between theprogram galaxies and the two adopted P-L relations are derived andapplied. The distance moduli derived here for the eight supernovaeprogram galaxies, and for 29 others, average 0.20 mag fainter (moredistant) than those derived by Gibson et al. and Freedman et al. intheir 2000 and 2001 summary papers for reasons discussed in this paper.The effect on the Hubble constant is the subject of our forthcomingsummary paper.
| An Atlas of Hα and R Images and Radial Profiles of 29 Bright Isolated Spiral Galaxies
Narrowband Hα+[N II] and broadband R images and surface photometryare presented for a sample of 29 bright (MB<-18 mag)isolated S0-Scd galaxies within a distance of 48 Mpc. These galaxies areamong the most isolated nearby spiral galaxies of their Hubbleclassifications as determined from the Nearby Galaxies Catalog.
| Dark and Baryonic Matter in Bright Spiral Galaxies. I. Near-Infrared and Optical Broadband Surface Photometry of 30 Galaxies
We present photometrically calibrated images and surface photometry inthe B, V, R, J, H, and K bands of 25, and in the g, r, and K bands offive nearby bright (B0T<12.5 mag) spiralgalaxies with inclinations of 30°-65° spanning the Hubblesequence from Sa to Scd. Data are from The Ohio State University BrightSpiral Galaxy Survey, the Two Micron All Sky Survey, and the SloanDigital Sky Survey Second Data Release. Radial surface brightnessprofiles are extracted, and integrated magnitudes are measured from theprofiles. Axis ratios, position angles, and scale lengths are measuredfrom the near-infrared images. A one-dimensional bulge/diskdecomposition is performed on the near-infrared images of galaxies witha nonnegligible bulge component, and an exponential disk is fit to theradial surface brightness profiles of the remaining galaxies.Based in part on observations obtained at the Cerro TololoInter-American Observatory, operated by the Association of Universitiesfor Research in Astronomy, Inc., under a cooperative agreement with theNational Science Foundation.
| Constraining Dark Matter Halo Profiles and Galaxy Formation Models Using Spiral Arm Morphology. I. Method Outline
We investigate the use of spiral arm pitch angles as a probe of diskgalaxy mass profiles. We confirm our previous result that spiral armpitch angles (P) are well correlated with the rate of shear (S) in diskgalaxy rotation curves by using a much larger sample (51 galaxies) thanused previously (17 galaxies). We use this correlation to argue thatimaging data alone can provide a powerful probe of galactic massdistributions out to large look-back times. In contrast to previouswork, we show that observed spiral arm pitch angles are similar whenmeasured in the optical (at 0.4 μm) and the near-infrared (at 2.1μm) with a mean difference of 2.3d+/-2.7d. This is then used tostrengthen the known correlation between P and S using B-band images. Wethen use two example galaxies to demonstrate how an inferred shear ratecoupled with a bulge-disk decomposition model and a Tully-Fisher-derivedvelocity normalization can be used to place constraints on a galaxy'sbaryon fraction and dark matter halo profile. We show that ESO 582-G12,a galaxy with a high shear rate (slightly declining rotation curve) at~10 kpc, favors an adiabatically contracted halo, with high initial NFWconcentration (cvir>16) and a high fraction of halobaryons in the form of stars (~15%-40%). In contrast, IC 2522 has a lowshear rate (rising rotation curve) at ~10 kpc and favorsnonadiabatically contracted models with low NFW concentrations(cvir~=2-8) and a low stellar baryon fraction <10%.
| Dark and Baryonic Matter in Bright Spiral Galaxies. II. Radial Distributions for 34 Galaxies
We decompose the rotation curves of 34 bright spiral galaxies intobaryonic and dark matter components. Stellar mass profiles are createdby applying color-M/L relations to near-infrared and optical photometry.We find that the radial profile of the baryonic-to-dark-matter ratio isself-similar for all galaxies, when scaled to the radius at which thecontribution of the baryonic mass to the rotation curve equals that ofthe dark matter (RX). We argue that this is due to thequasi-exponential nature of disks and rotation curves that are nearlyflat after an initial rise. The radius RX is found tocorrelate most strongly with baryonic rotation speed, such that galaxieswith RX measurements that lie further out in their disksrotate faster. This quantity also correlates very strongly with stellarmass, Hubble type, and observed rotation speed; B-band central surfacebrightness is less related to RX than these other galaxyproperties. Most of the galaxies in our sample appear to be close tomaximal disk. For these galaxies, we find that maximum observed rotationspeeds are tightly correlated with maximum rotation speeds predictedfrom the baryon distributions, such that one can create a Tully-Fisherrelation based on surface photometry and redshifts alone. Finally, wecompare our data to the NFW parameterization for dark matter profileswith and without including adiabatic contraction as it is most commonlyimplemented. Fits are generally poor, and all but two galaxies arebetter fit if adiabatic contraction is not performed. In order to havebetter fits, and especially to accommodate adiabatic contraction,baryons would need to contribute very little to the total mass in theinner parts of galaxies, seemingly in contrast with other observationalconstraints.
| A Comparison of Hα and Stellar Scale Lengths in Virgo and Field Spirals
The scale lengths of the old stars and ionized gas distributions arecompared for similar samples of Virgo Cluster members and field spiralgalaxies via Hα and broad R-band surface photometry. While theR-band and Hα scale lengths are, on average, comparable for thecombined sample, we find significant differences between the field andcluster samples. While the Hα scale lengths of the field galaxiesare a factor of 1.14+/-0.07 longer, on average, than their R-band scalelengths, the Hα scale lengths of Virgo Cluster members are, onaverage, 20% smaller than their R-band scale lengths. Furthermore, inVirgo, the scale length ratios are correlated with the size of thestar-forming disk: galaxies with smaller overall Hα extents alsoshow steeper radial falloff of star formation activity. At the sametime, we find no strong trends in scale length ratio as a function ofother galaxy properties, including galaxy luminosity, inclination,morphological type, central R-band light concentration, or bar type. Ourresults for Hα emission are similar to other results for dustemission, suggesting that Hα and dust have similar distributions.The environmental dependence of the Hα scale length placesadditional constraints on the evolutionary process(es) that cause gasdepletion and a suppression of the star formation rate in clusters ofgalaxies.
| The extragalactic Cepheid bias: a new test using the period-luminosity-color relation
We use the Period-Luminosity-Color relation (PLC) for Cepheids to testfor the existence of a bias in extragalactic distances derived from theclassical Period-Luminosity (PL) relation. We calculate the parametersof the PLC using several galaxies observed with the Hubble SpaceTelescope and show that this calculation must be conducted with a PLCwritten in a form where the parameters are independent. The coefficientsthus obtained are similar to those derived from theoretical models.Calibrating with a few unbiased galaxies, we apply this PLC to allgalaxies of the Hubble Space Telescope Key Program (HSTKP) and comparethe distance moduli with those published by the HSTKP team. The newdistance moduli are larger (more exactly, the larger the distance thelarger the difference), consistent with a bias. Further, the bias trendthat is observed is the same previously obtained from two independentmethods based either on the local Hubble law or on a theoretical modelof the bias. The results are quite stable but when we force the PLCrelation closer to the classical PL relation by using unrealisticparameters, the agreement with HSTKP distance moduli is retrieved. Thisalso suggests that the PL relation leads to biased distance moduli. Thenew distance moduli reduce the scatter in the calibration of theabsolute magnitude of supernovae SNIa at their maximum. This may alsosuggest that the relation between the amplitude at maximum and the decayof the light curve Δ m15 may not be as strong asbelieved.
| The Distribution of Bar and Spiral Arm Strengths in Disk Galaxies
The distribution of bar strengths in disk galaxies is a fundamentalproperty of the galaxy population that has only begun to be explored. Wehave applied the bar-spiral separation method of Buta and coworkers toderive the distribution of maximum relative gravitational bar torques,Qb, for 147 spiral galaxies in the statistically well-definedOhio State University Bright Galaxy Survey (OSUBGS) sample. Our goal isto examine the properties of bars as independently as possible of theirassociated spirals. We find that the distribution of bar strengthdeclines smoothly with increasing Qb, with more than 40% ofthe sample having Qb<=0.1. In the context of recurrent barformation, this suggests that strongly barred states are relativelyshort-lived compared to weakly barred or nonbarred states. We do notfind compelling evidence for a bimodal distribution of bar strengths.Instead, the distribution is fairly smooth in the range0.0<=Qb<0.8. Our analysis also provides a first look atspiral strengths Qs in the OSUBGS sample, based on the sametorque indicator. We are able to verify a possible weak correlationbetween Qs and Qb, in the sense that galaxies withthe strongest bars tend to also have strong spirals.
| The extragalactic Cepheid bias: significant influence on the cosmic distance scale
The unique measurements with the Hubble Space Telescope of Cepheidvariable stars in nearby galaxies led to extragalactic distances thatmade the HST Key Project conclude that the Hubble constant isH0 = 72 km s-1 Mpc-1. The idea thatH0 is now known is widely spread among the astronomicalcommunity. Some time ago, we suggested that a strong selection effectmay still exist in the Cepheid method, resulting in too short distances.Using a model similar to traditional bias corrections, we deduce herenew estimates of distances from HST and previous ground-basedobservations which are both affected by this effect, showing the sametrend which starts at different distances. The recent measurement of M83 with the VLT is unbiased. Revisiting the calibration of HSTKP's withour new scale, makes long-range distance criteria more concordant andreduces the value of H0 to ≈60 km s-1Mpc-1. Locally, the corrected Cepheid distances giveHlocal=56 km s-1 Mpc-1 and reduce thevelocity dispersion in the Hubble flow. These numbers are indicative ofthe influence of the suggested Cepheid bias in the context of the HSTKPstudies and are not final values.
| A survey for OB associations in the Sculptor Group spiral galaxy NGC 7793
We report on the results from application of an objective algorithm(PLC) to find OB associations, to B and V images of the Sculptor spiralgalaxy NGC 7793, which were obtained with the ESO VLT and FORSinstrument and basically cover the entire spatial extent of the galaxy.We detected 148 associations. Statistical tests show that less than 6 ofthese detections are caused by randomly concentrated blue stars. In thesize distribution, a sharp peak is observed at a value of about 35microradians, which corresponds to a linear diameter of 135 pc, assuminga distance of 3.91 Mpc to the galaxy. We also find 25 much largerobjects. A second application of the PLC technique shows that 20 of themare stellar complexes consisting of multiple sub-associations withtypical sizes on the order of 130 pc. A comparison of the sizedistribution of the detected OB associations in NGC 7793 with observeddistributions in other galaxies suggests that the conditions in twoSculptor Group galaxies (NGC 300 and NGC 7793) favour the formation oflarge associations. We provide a catalog giving coordinates and physicalparameters for all the associations and stellar complexes we have foundin our survey.
| Bar-induced perturbation strengths of the galaxies in the Ohio State University Bright Galaxy Survey - I
Bar-induced perturbation strengths are calculated for a well-definedmagnitude-limited sample of 180 spiral galaxies, based on the Ohio StateUniversity Bright Galaxy Survey. We use a gravitational torque method,the ratio of the maximal tangential force to the mean axisymmetricradial force, as a quantitative measure of the bar strength. Thegravitational potential is inferred from an H-band light distribution byassuming that the M/L ratio is constant throughout the disc. Galaxiesare deprojected using orientation parameters based on B-band images. Inorder to eliminate artificial stretching of the bulge, two-dimensionalbar-bulge-disc decomposition has been used to derive a reliable bulgemodel. This bulge model is subtracted from an image, the disc isdeprojected assuming it is thin, and then the bulge is added back byassuming that its mass distribution is spherically symmetric. We findthat removing the artificial bulge stretch is important especially forgalaxies having bars inside large bulges. We also find that the massesof the bulges can be significantly overestimated if bars are not takeninto account in the decomposition.Bars are identified using Fourier methods by requiring that the phasesof the main modes (m= 2, m= 4) are maintained nearly constant in the barregion. With such methods, bars are found in 65 per cent of the galaxiesin our sample, most of them being classified as SB-type systems in thenear-infrared by Eskridge and co-workers. We also suggest that as muchas ~70 per cent of the galaxies classified as SAB-types in thenear-infrared might actually be non-barred systems, many of them havingcentral ovals. It is also possible that a small fraction of the SAB-typegalaxies have weak non-classical bars with spiral-like morphologies.
| The dispersion in the Cepheid period-luminosity relation and the consequences for the extragalactic distance scale
Using published Hubble Space Telescope (HST) Cepheid data from 25galaxies, we have found a correlation between the dispersion in theCepheid period-luminosity (P-L) relation and host galaxy metallicity,which is significant at the ~3σ level in the V band. In the I bandthe correlation is less significant, although the tighter intrinsicdispersion of the P-L relation in I may make it harder to detect such acorrelation in the HST sample. One possibility is that low metallicitygalaxies have smaller metallicity gradients than high metallicitygalaxies; if the Cepheid P-L relation has a significant dependence onmetallicity then this might explain the higher P-L dispersion in thehigher metallicity galaxies. A second possibility is that the increasedP-L dispersion is driven by metallicity dispersion but now due to arelation between metallicity and Cepheid colour rather than luminosity.A third possibility is that the increased P-L dispersion is caused by anincrease in the width of the instability strip with metallicity.Whatever the explanation, the high observed dispersions in the HSTCepheid P-L relations have the important consequence that the bias dueto incompleteness in the P-L relation at faint magnitudes is moresignificant than previously thought. Using a maximum likelihoodtechnique which takes into account the effect on the P-L relations oftruncation by consistently defined magnitude completeness limits, werederive the Cepheid distances to the 25 galaxies. In the case of thegalaxies with the highest P-L dispersion at the largest distances, wefind that the published distance modulus underestimates the truedistance modulus by up to ~0.5 mag.When both metallicity and magnitude incompleteness corrections are made,a scale error in the published Cepheid distances is seen in the sensethat the published distance moduli are increasingly underestimated atlarger distances. This results in the average distance modulus to thefour galaxies in the Virgo cluster core increasing from(m-M)0= 31.2 +/- 0.19 to (m-M)0= 31.4 +/- 0.19 ifthe γVI=-0.24 mag dex-1 metallicitycorrection of Kennicutt et al. is assumed. For the 18 HST galaxies withgood Tully-Fisher (TF) distances and (m-M)0 > 29.5 theCepheid-TF distance modulus average residual increases from 0.44 +/-0.09 to 0.63 +/- 0.1 mag with γVI=-0.24. This indicatesa significant scale error in TF distances, which reduces the previousPierce & Tully TF estimate of H0= 85 +/- 10 kms-1 Mpc-1 to H0= 63 +/- 7 kms-1 Mpc-1, assuming γVI=-0.24 anda still uncertain Virgo infall model. Finally, for the eight HSTgalaxies with Type Ia supernovae (SNIa), the metallicity andincompleteness corrected Cepheid distances marginally suggest there maybe a metallicity dependence of SNIa peak luminosity in the sense thatmetal-poor hosts have lower luminosity SNIa. Thus, SNIa Hubble diagramestimates of both H0 and q0 may therefore alsorequire significant corrections for metallicity, once the exact sizes ofthe Cepheid metallicity corrections become better established.
| Massive Star Formation Rates and Radial Distributions from Hα Imaging of 84 Virgo Cluster and Isolated Spiral Galaxies
The massive star formation properties of 55 Virgo Cluster and 29isolated S0-Scd bright (MB<=-18) spiral galaxies arecompared via analyses of R and Hα surface photometry andintegrated fluxes as functions of Hubble type and central R lightconcentration (bulge-to-disk ratio). In the median, the total normalizedmassive star formation rates (NMSFRs) in Virgo Cluster spiral galaxiesare reduced by factors of up to 2.5 compared with isolated spiralgalaxies of the same type or concentration, with a range from enhanced(up to 2.5 times) to strongly reduced (up to 10 times). Within the inner30% of the optical disk, Virgo Cluster and isolated spiral galaxies havesimilar ranges in NMSFRs, with similar to enhanced (up to 4 times)median NMSFRs for Virgo galaxies. NMSFRs in the outer 70% of the opticaldisk are reduced in the median by factors of up to 9 for Virgo Clusterspiral galaxies, with more severely reduced star formation atprogressively larger disk radii. Thus, the reduction in total starformation of Virgo Cluster spiral galaxies is caused primarily byspatial truncation of the star-forming disks. The correlation between HI deficiency and R light central concentration is much weaker than thecorrelation between H I deficiency and Hubble type. The previouslyobserved systematic difference in H I spatial distributions andkinematics between early- and late-type spiral galaxies in the VirgoCluster is at least partially due to the misleading classification ofstripped spiral galaxies as early types. Intraclustermedium-interstellar medium stripping of the gas from spiral galaxies islikely responsible for the truncated star-forming disks of Virgo Clusterspiral galaxies. This effect may be responsible for a significant partof the morphology-density relationship, in that a large fraction ofVirgo Cluster galaxies classified as Sa galaxies are H I-deficientgalaxies with truncated star-forming disks rather than galaxies withlarge bulge-to-disk ratios.
| Classical Cepheids and the Distances of HST Program Galaxies
The distances of HST program galaxies are revised using the PL-relationswe have obtained previously along with a different method from thatemployed by Freedman et al. On the average, the resulting distances tothese galaxies have higher internal accuracies than those obtainedbefore by others. In addition, we have used no corrections formetallicity or for the incompleteness of the samples of classicalcepheids in deriving these distances. Despite this, our distance moduli,with a dispersion of ±0m.395, agree with those of Freedman et al.This indicates that these two effects have little or even no effect forthe samples of classical cepheids in the HST program galaxies.
| Deprojecting spiral galaxies using Fourier analysis. Application to the Ohio sample
We use two new methods developed recently (Barberàet al.\cite{bar03}, A&A, 415, 849), as well as information obtained fromthe literature, to calculate the orientation parameters of the spiralgalaxies in the Ohio State University Bright Galaxy Survey. We comparethe results of these methods with data from the literature, and find ingeneral good agreement. We provide a homogeneous set of mean orientationparameters which can be used to approximately deproject the disks of thegalaxies and facilitate a number of statistical studies of galaxyproperties.Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/421/595
| The extra-galactic Cepheid distance scale from LMC and Galactic period-luminosity relations
In this paper, we recalibrate the Cepheid distance to some nearbygalaxies observed by the HST Key Project and the Sandage-Tammann-Sahagroup. We use much of the Key Project methodology in our analysis butapply new techniques, based on Fourier methods to estimate the mean of asparsely sampled Cepheid light curve, to published extra-galacticCepheid data. We also apply different calibrating PL relations toestimate Cepheid distances, and investigate the sensitivity of thedistance moduli to the adopted calibrating PL relation. We re-determinethe OGLE LMC PL relations using a more conservative approach and alsostudy the effect of using Galactic PL relations on the distance scale.For the Key Project galaxies after accounting for charge transfereffects, we find good agreement with an average discrepancy of -0.002and 0.075 mag when using the LMC and Galaxy, respectively, as acalibrating PL relation. For NGC 4258 which has a geometric distance of29.28 mag, we find a distance modulus of 29.44+/-0.06(random) mag, aftercorrecting for metallicity. In addition we have calculated the Cepheiddistance to 8 galaxies observed by the Sandage-Tammann-Saha group andfind shorter distance moduli by -0.178 mag (mainly due to the use ofdifferent LMC PL relations) and -0.108 mag on average again when usingthe LMC and Galaxy, respectively, as a calibrating PL relation. Howevercare must be taken to extrapolate these changed distances to changes inthe resulting values of the Hubble constant because STS also usedistances to NGC 3368 and 4414 and because STS calibration of SN Ia isoften decoupled from the distance to the host galaxy through their useof differential extinction arguments. We also calculate the distance toall these galaxies using PL relations at maximum light and find verygood agreement with mean light PL distances.However, after correcting for metallicity effects, the differencebetween the distance moduli obtained using the two sets of calibratingPL relations becomes negligible. This suggests that Cepheids in the LMCand Galaxy do follow different PL relations and constrains the sign forthe coefficient of the metallicity correction, gamma , to be negative,at least at the median period log (P) ~ 1.4, of the target galaxies.Full Table 1 is available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/411/361
| The H I Line Width/Linear Diameter Relationship as an Independent Test of the Hubble Constant
The relationship between corrected H I line widths and linear diameters(LW/LD) for spiral galaxies is used as an independent check on the valueof the Hubble constant. After calibrating the Tully-Fisher (TF) relationin both the B and I bands, the B-band relation is used for galaxies ofmorphological/luminosity types Sc I, Sc I.2, Sc I.3, Sab, Sb, Sb I-II,and Sb II to derive the LW/LD relation. We find that for this sample thescatter in the LW/LD is smallest with a Hubble constant of 90-95 kms-1 Mpc-1. Lower values of the Hubble constantproduce a separation in the LW/LD relation that is a function ofmorphological type. Since a Hubble constant of 90-95 is significantlylarger than the final Key Project value of 72 km s-1Mpc-1, a comparison of TF, surface brightness fluctuation(SBF), and fundamental plane (FP) is made. This comparison indicatesthat the Key Project TF distances to 21 clusters may be too large. For asample of 11 clusters, the Key Project TF distances provide anunweighted mean Hubble constant of 77 km s-1Mpc-1, while a combination of the FP, SBF, and our TFdistances for the same 11 clusters gives H0=91 kms-1 Mpc-1. A more subtle result in our data is amorphological dichotomy in the Hubble constant. The data suggest that ScI galaxies follow a Hubble constant of 90-95 while Sb galaxies follow aHubble constant closer to 75 km s-1 Mpc-1.Possible explanations for this result are considered, but it is shownthat this Sb/Sc I Hubble flow discrepancy is also present in the VirgoCluster and is consistent with previous investigations that indicatethat some galaxies carry a component of age-related intrinsic redshift.
| The Visibility of Galactic Bars and Spiral Structure at High Redshifts
We investigate the visibility of galactic bars and spiral structure inthe distant universe by artificially redshifting 101 B-band CCD imagesof local spiral galaxies from the Ohio State University Bright SpiralGalaxy Survey. These local galaxy images represent a much fairerstatistical baseline than the galaxy atlas images presented by Frei etal. in 1995, the most commonly used calibration sample for morphologicalwork at high redshifts. Our artificially redshifted images correspond toHubble Space Telescope I814-band observations of the localgalaxy sample seen at z=0.7, with integration times matching those ofboth the very deep northern Hubble Deep Field (HDF) data and the muchshallower HDF flanking field observations. The expected visibility ofgalactic bars is probed in two ways: (1) using traditional visualclassification and (2) by charting the changing shape of the galaxydistribution in ``Hubble space,'' a quantitative two-parameterdescription of galactic structure that maps closely onto Hubble'soriginal tuning fork. Both analyses suggest that over two-thirds ofstrongly barred luminous local spirals (i.e., objects classified as SBin the Third Reference Catalogue) would still be classified as stronglybarred at z=0.7 in the HDF data. Under the same conditions, most weaklybarred spirals (classified SAB in the Third Reference Catalogue) wouldbe classified as regular spirals. The corresponding visibility of spiralstructure is assessed visually, by comparing luminosity classificationsfor the artificially redshifted sample with the corresponding luminosityclassifications from the Revised Shapley-Ames Catalog. We find that forexposure times similar to that of the HDF, spiral structure should bedetectable in most luminous (MB~M*) low-inclination spiralgalaxies at z=0.7 in which it is present. However, obvious spiralstructure is only detectable in ~30% of comparable galaxies in the HDFflanking field data using the Wide Field Planetary Camera 2. Our studyof artificially redshifted local galaxy images suggests that, whenviewed at similar resolution, noise level, and redshift-correctedwavelength, barred spirals are less common at z~0.7 than they are atz=0.0, although more data are needed to definitively rule out thepossibility that cosmic variance is responsible for much of this effect.
| Local velocity field from sosie galaxies. I. The Peebles' model
Pratton et al. (1997) showed that the velocity field around clusterscould generate an apparent distortion that appears as tangentialstructures or radial filaments. In the present paper we determine theparameters of the Peebles' model (1976) describing infall of galaxiesonto clusters with the aim of testing quantitatively the amplitude ofthis distortion. The distances are determined from the concept of sosiegalaxies (Paturel 1984) using 21 calibrators for which the distanceswere recently calculated from two independent Cepheid calibrations. Weuse both B and I-band magnitudes. The Spaenhauer diagram method is usedto correct for the Malmquist bias. We give the equations for theconstruction of this diagram. We analyze the apparent Hubble constant indifferent regions around Virgo and obtain simultaneously the Local Groupinfall and the unperturbed Hubble constant. We found:[VLG-infall = 208 ± 9 km s-1] [\log H =1.82 ± 0.04 (H ≈ 66 ± 6 km s-1Mpc-1).] The front side and backside infalls can be seenaround Virgo and Fornax. In the direction of Virgo the comparison ismade with the Peebles' model. We obtain: [vinfall} =CVirgo/r0.9 ± 0.2] withCVirgo=2800 for Virgo and CFornax=1350 for Fornax,with the adopted units (km s-1 and Mpc). We obtain thefollowing mean distance moduli: [μVirgo=31.3 ± 0.2(r=18 Mpc )] [μFornax=31.7 ± 0.3 (r=22 Mpc). ] Allthese quantities form an accurate and coherent system. Full Table 2 isonly available 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/393/57
| Calibration of the distance scale from galactic Cepheids. II. Use of the HIPPARCOS calibration
New estimates of the distances of 36 nearby galaxies is presented. Theseare based on the calibration of the V- and I-band Period-Luminosityrelations for galactic Cepheids measured by the HIPPARCOS mission. Thedistance moduli are obtained in a classical way. The statistical biasdue to the incompleteness of the sample is corrected according to theprecepts introduced by Teerikorpi (\cite{Tee87}). We adopt a constantslope (the one obtained with LMC Cepheids). The correction forincompleteness bias introduces an uncertainty that depends on eachgalaxy. On average, this uncertainty is small (0.04 mag) but it mayreach 0.3 mag. We show that the uncertainty due to the correction of theextinction is small (propably less than 0.05 mag). The correlationbetween the metallicity and the morphological type of the host galaxysuggests that we should reduce the application to spiral galaxies inorder to bypass the problem of metallicity. We suspect that the adoptedPL slopes are not valid for all morphological types of galaxies. Thismay induce a mean systematic shift of 0.1 mag on distance moduli. Acomparison with the distance moduli recently published by Freedman etal. (\cite{Fre01}) shows there is a reasonably good agreement with ourdistance moduli. The compilation of raw data is only available inelectronic form at CDS via anonymous ftp to\ cdsarc.u-strasbg.fr(130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/389/19 and on ouranonymous ftp-server www-obs.univ-lyon1.fr (pub/base/CEPHEIDES.tar.gz).
| Calibration of the distance scale from galactic Cepheids. I. Calibration based on the GFG sample
New estimates of the distances of 36 nearby galaxies are presented basedon accurate distances of galactic Cepheids obtained by Gieren et al.(1998) from the geometrical Barnes-Evans method. The concept of``sosie'' is applied to extend the distance determination toextragalactic Cepheids without assuming the linearity of the PLrelation. Doing so, the distance moduli are obtained in astraightforward way. The correction for extinction is made using twophotometric bands (V and I) according to the principles introduced byFreedman & Madore (1990). Finally, the statistical bias due to theincompleteness of the sample is corrected according to the preceptsintroduced by Teerikorpi (1987) without introducing any free parameters(except the distance modulus itself in an iterative scheme). The finaldistance moduli depend on the adopted extinction ratioRV/RI and on the limiting apparent magnitude ofthe sample. A comparison with the distance moduli recently published bythe Hubble Space Telescope Key Project (HSTKP) team reveals a fairagreement when the same ratio RV/RI is used butshows a small discrepancy at large distance. In order to bypass theuncertainty due to the metallicity effect it is suggested to consideronly galaxies having nearly the same metallicity as the calibratingCepheids (i.e. Solar metallicity). The internal uncertainty of thedistances is about 0.1 mag but the total uncertainty may reach 0.3 mag.The table of the Appendix and Table 3 are available in electronic format CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/383/398, and on ouranonymous ftp-server www-obs.univ-lyon1.fr (pub/base/CEPHEIDES.tar.gz).
| Evidence for the extragalactic Cepheid distance bias from the kinematical distance scale
We present new evidence for the extragalactic Cepheid distance bias. Adependence between the Hubble parameter and the absolute Cepheidmagnitude limit for a galaxy may be interpreted as a significant bias inthe derived photometric distances: those from Cepheid samples with abright absolute magnitude limit apparently are underestimated. This maybe caused not only by the dispersion of bar {M} at a fixed Cepheidperiod, but also by the whole amplitude of variation, together with anupper limit in the period of the observed Cepheids, and other factors.If so, then the value of H0 based on methods using Cepheiddistances is expected to be often overestimated (i.e. the distancesunderestimated). We discuss whether the effect could be not real, butrather caused by uncertainties in kinematical distances.
| Predicting the peculiar velocities of nearby PSCz galaxies using the Least Action Principle
We use the Least Action Principle to predict the peculiar velocities ofPSCz galaxies inside cz=2000kms-1. Linear theory is used toaccount for tidal effects to cz=15000kms-1, and we iterategalaxy positions to account for redshift distortions. As the LeastAction Principle is valid beyond linear theory, we can predict reliablepeculiar velocities even for very nearby galaxies (i.e.,cz<=500kms-1). These predicted peculiar velocities arethen compared with the observed velocities of 12 galaxies with Cepheiddistances. The combination of the PSCz galaxy survey (with its large skycoverage and uniform selection) with the accurate Cepheid distancesmakes this comparison relatively free from systematic effects. We findthat galaxies are good tracers of the mass, even at small(<=10h-1Mpc) scales; under the assumption of no biasing,0.25<=β<=0.75 (at 90 per cent confidence). We use thereliable predicted peculiar velocities to estimate the Hubble constantH0 from the local volume without `stepping up' the distanceladder, finding a confidence range of65-75kms-1Mpc-1 (at 90 per cent confidence).
| Final Results from the Hubble Space Telescope Key Project to Measure the Hubble Constant
We present here the final results of the Hubble Space Telescope (HST)Key Project to measure the Hubble constant. We summarize our method, theresults, and the uncertainties, tabulate our revised distances, and givethe implications of these results for cosmology. Our results are basedon a Cepheid calibration of several secondary distance methods appliedover the range of about 60-400 Mpc. The analysis presented here benefitsfrom a number of recent improvements and refinements, including (1) alarger LMC Cepheid sample to define the fiducial period-luminosity (PL)relations, (2) a more recent HST Wide Field and Planetary Camera 2(WFPC2) photometric calibration, (3) a correction for Cepheidmetallicity, and (4) a correction for incompleteness bias in theobserved Cepheid PL samples. We adopt a distance modulus to the LMC(relative to which the more distant galaxies are measured) ofμ0(LMC)=18.50+/-0.10 mag, or 50 kpc. New, reviseddistances are given for the 18 spiral galaxies for which Cepheids havebeen discovered as part of the Key Project, as well as for 13 additionalgalaxies with published Cepheid data. The new calibration results in aCepheid distance to NGC 4258 in better agreement with the maser distanceto this galaxy. Based on these revised Cepheid distances, we find values(in km s-1 Mpc-1) of H0=71+/-2(random)+/-6 (systematic) (Type Ia supernovae), H0=71+/-3+/-7(Tully-Fisher relation), H0=70+/-5+/-6 (surface brightnessfluctuations), H0=72+/-9+/-7 (Type II supernovae), andH0=82+/-6+/-9 (fundamental plane). We combine these resultsfor the different methods with three different weighting schemes, andfind good agreement and consistency with H0=72+/-8 kms-1 Mpc-1. Finally, we compare these results withother, global methods for measuring H0. Based on observationswith the NASA/ESA Hubble Space Telescope, obtained at the SpaceTelescope Science Institute, which is operated by AURA, Inc., under NASAcontract NAS5-26555.
| NICMOS Observations of Extragalactic Cepheids. I. Photometry Database and a Test of the Standard Extinction Law
We present the results of near-infrared observations of extragalacticCepheids made with the Near-Infrared Camera and Multi-ObjectSpectrometer on board the Hubble Space Telescope (HST). The variablesare located in the galaxies IC 1613, IC 4182, M31, M81, M101, NGC 925,NGC 1365, NGC 2090, NGC 3198, NGC 3621, NGC 4496A, and NGC 4536. Allfields were observed in the F160W bandpass; additional images wereobtained in the F110W and F205W filters. Photometry was performed usingthe DAOPHOT II/ALLSTAR package. Self-consistent distance moduli andcolor excesses were obtained by fitting period-luminosity relations inthe H, I, and V bands. Our results support the assumption of a standardreddening law adopted by the HST Key Project on the ExtragalacticDistance Scale. A companion paper will determine true distance moduliand explore the effects of metallicity on the Cepheid distance scale.Based on observations with the NASA/ESA Hubble Space Telescope, obtainedat the Space Telescope Science Institute, operated by AURA, Inc. underNASA contract NAS5-26555.
| A Determination of the Hubble Constant from Cepheid Distances and a Model of the Local Peculiar Velocity Field
We present a measurement of the Hubble constant based on Cepheiddistances to 27 galaxies within 20 Mpc. We take the Cepheid data frompublished measurements by the Hubble Telescope Key Project on theDistance Scale (H0KP). We calibrate the Cepheidperiod-luminosity (PL) relation with data from over 700 Cepheids in theLMC obtained by the OGLE collaboration; we assume an LMC distancemodulus of 18.50 mag (dLMC=50.1 kpc). Using this PLcalibration, we obtain new distances to the H0KP galaxies. Wecorrect the redshifts of these galaxies for peculiar velocities usingtwo distinct velocity field models: the phenomenological model of Tonryet al. and a model based on the IRAS density field and lineargravitational instability theory. We combine the Cepheid distances withthe corrected redshifts for the 27 galaxies to derive H0, theHubble constant. The results are H0=85+/-5 km s-1Mpc-1 (random error) at 95% confidence when the IRAS model isused, and 92+/-5 km s-1 Mpc-1 when thephenomenological model is used. The IRAS model is a better fit to thedata, and the Hubble constant it returns is more reliable. Systematicerror stems mainly from LMC distance uncertainty, which is not directlyaddressed by this paper. Our value of H0 is significantlylarger than that quoted by the H0KP, H0=71+/-6 kms-1 Mpc-1. Cepheid recalibration explains ~30% ofthis difference, and velocity field analysis accounts for ~70%. Wediscuss in detail possible reasons for this discrepancy and futurestudies needed to resolve it.
| Homogenization of the Stellar Population along Late-Type Spiral Galaxies
We present a study of the broadband UBV color profiles for 257 Sbcbarred and nonbarred galaxies, using photoelectric aperture photometrydata from the literature. Using robust statistical methods, we haveestimated the color gradients of the galaxies, as well as the total andbulge mean colors. A comparative photometric study using CCD images wasdone. In our sample, the color gradients are negative (reddish inward)in approximately 59% of the objects, are almost null in 27%, and arepositive in 14%, considering only the face-on galaxies, which representapproximately 51% of the sample. The results do not change, essentially,when we include the edge-on galaxies. As a consequence of this study wehave also found that barred galaxies are overrepresented among theobjects having null or positive gradients, indicating that bars act as amechanism of homogenization of the stellar population. This effect ismore evident in the U-B color index, although it can also be detected inthe B-V color. A correlation between the total and bulge colors wasfound that is a consequence of an underlying correlation between thecolors of bulges and disks found by other authors. Moreover, the meantotal color is the same irrespective of the gradient regime, whilebulges are bluer in galaxies with null or positive gradients, whichindicates an increase of the star formation rate in the central regionsof these objects. We have also made a quantitative evaluation of theamount of extinction in the center of these galaxies. This was doneusing the Wide Field Planetary Camera 2 (WFPC2) and the Near InfraredCamera and Multi-Object Spectrometer (NICMOS) Hubble Space Telescope(HST) archival data, as well as CCD B, V, and I images. We show thatalthough the extinction in the V-band can reach values up to 2 mag inthe central region, it is unlikely that dust plays a fundamental role inglobal color gradients. We found no correlation between color and O/Habundance gradients. This result could suggest that the color gradientsare more sensitive to the age rather than to the metallicity of thestellar population. However, the absence of this correlation may becaused by dust extinction. We discuss this result by considering apicture in which bars are a relatively fast, recurrent phenomenon. Theseresults are not compatible with a pure classical monolithic scenario forbulge and disk formation. On the contrary, they favor a scenario inwhich both these components are evolving in a correlated process inwhich stellar bars play a crucial role. Based partly on observationsmade at the Pico dos Dias Observatory (PDO/LNA-CNPq), Brazil.
| Distances and reddenings of HST galaxies by using theoretical Cepheid PL and PLC relations.
Not Available
| A Database of Tully-Fisher Calibrator Galaxies
We present BVRI surface photometry of spiral galaxies suitable for theabsolute calibration of the Tully-Fisher relation. Galaxies wereobserved at the Fred L. Whipple Observatory (FLWO) 1.2 m, the MountStromlo and Siding Spring Observatory (MSSSO) 1 m, and the Cerro TololoInter-American Observatory (CTIO) 1.5 m telescopes from 1994 to 1999.The surface photometry measurements were carried out using the SFOTOpackage. We also present new derivations of 20% and 50% 21 cm linewidths for most of these galaxies, based on existing profiles.
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