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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.
| Determination of the Hubble Constant, the Intrinsic Scatter of Luminosities of Type Ia Supernovae, and Evidence for Nonstandard Dust in Other Galaxies
A sample of 109 Type Ia supernovae (SNe Ia) with recession velocity<~30,000 km s-1 is compiled from published SN Ia lightcurves to explore the expansion rate of the local universe. Based on thecolor parameter ΔC12 and the decline rateΔm15, we found that the average absorption-to-reddeningratios for SN Ia host galaxies are RUBVI=4.37+/-0.25,3.33+/-0.11, 2.30+/-0.11, and 1.18+/-0.11, which are systematicallylower than the standard values in the Galaxy. We investigated thecorrelations of the intrinsic luminosity with light-curve decline rate,color index, and SN environmental parameters. In particular, we foundthat SNe Ia in E/S0 galaxies close to the central region are brighterthan those in the outer region, which may suggest a possible metallicityeffect on SN luminosity. The dependence of SN luminosity on galacticenvironment disappears after corrections for the extinction andΔC12. The Hubble diagrams constructed using 73 Hubbleflow SNe Ia yield a 1 σ scatter of <~0.12 mag in BVI bands and~0.16 mag in U band. The luminosity difference between normal SNe Ia andpeculiar objects (including SN 1991bg-like and SN 1991T-like events) hasnow been reduced to within 0.15 mag via ΔC12correction. We use the same precepts to correct the nearby SNe Ia withCepheid distances and found that the fully corrected absolute magnitudesof SNe Ia are MB=-19.33+/-0.06 andMV=-19.27+/-0.05. We deduced a value for the Hubble constantof H0=72+/-6 (total) km s-1 Mpc-1.
| The Hubble Constant from Type Ia Supernovae Calibrated with the Linear and Nonlinear Cepheid Period-Luminosity Relations
It is well known that the peak brightness of Type Ia supernovaecalibrated with Cepheid distances can be used to determine the Hubbleconstant. The Cepheid distances to the host galaxies of the calibratingsupernovae are usually obtained using the period-luminosity (P-L)relation derived from Large Magellanic Cloud (LMC) Cepheids. However,recent empirical studies provide evidence that the LMC P-L relation isnot linear. Here we determine the Hubble constant using both the linearand nonlinear LMC Cepheid P-L relations as calibrating relations to fourgalaxies that hosted Type Ia supernovae. Our results suggest that theobtained values of the Hubble constant are similar. However, a typicalerror of ~0.03 mag has to be added (in quadrature) to the systematicerror for the Hubble constant when the linear LMC P-L relation is used,assuming that the LMC P-L relation is indeed nonlinear. This isimportant to minimize the total error on the Hubble constant in the eraof precision cosmology. The Hubble constants calibrated from the linearand nonlinear LMC P-L relations are H0=74.92+/-2.28(random)+/-5.06(systematic) km s-1 Mpc-1 andH0=74.37+/-2.27(random)+/-4.92(systematic) km s-1Mpc-1, respectively. Hubble constants calculated using theGalactic P-L relation are also presented and briefly discussed.
| Using Line Profiles to Test the Fraternity of Type Ia Supernovae at High and Low Redshifts
Using archival data of low-redshift (z<0.01 Center for Astrophysicsand SUSPECT databases) Type Ia supernovae (SNe Ia) and recentobservations of high-redshift (0.161.7] SNe Ia, which are also subluminous. Inaddition, we give the first direct evidence in two high-z SN Ia spectraof a double-absorption feature in Ca II λ3945, an event alsoobserved, although infrequently, in low-redshift SN Ia spectra (6 out of22 SNe Ia in our local sample). Moreover, echoing the recent studies ofDessart & Hillier in the context of Type II supernovae (SNe II), wesee similar P Cygni line profiles in our large sample of SN Ia spectra.First, the magnitude of the velocity location at maximum profileabsorption may underestimate that at the continuum photosphere, asobserved, for example, in the optically thinner line S II λ5640.Second, we report for the first time the unambiguous and systematicintrinsic blueshift of peak emission of optical P Cygni line profiles inSN Ia spectra, by as much as 8000 km s-1. All the high-z SNeIa analyzed in this paper were discovered and followed up by the ESSENCEcollaboration and are now publicly available.Based in part on observations obtained at the Cerro TololoInter-American Observatory, which is operated by the Association ofUniversities for Research in Astronomy (AURA), Inc., under cooperativeagreement with the National Science Foundation (NSF); the EuropeanSouthern Observatory, Chile (ESO program 170.A-0519) the GeminiObservatory, which is operated by AURA under a cooperative agreementwith the NSF on behalf of the Gemini partnership (the NSF [UnitedStates], the Particle Physics and Astronomy Research Council [UnitedKingdom], the National Research Council [Canada], CONICYT [Chile], theAustralian Research Council [Australia], CNPq [Brazil], and CONICET[Argentina]) (programs GN-2002B-Q-14, GN-2003B-Q-11, and GS-2003B-Q-11)the Magellan Telescopes at Las Campanas Observatory; the MMTObservatory, a joint facility of the Smithsonian Institution and theUniversity of Arizona; and the F. L. Whipple Observatory, which isoperated by the Smithsonian Astrophysical Observatory. Some of the datapresented herein were obtained at the W. M. Keck Observatory, which isoperated as a scientific partnership among the California Institute ofTechnology, the University of California, and the National Aeronauticsand Space Administration. The Observatory was made possible by thegenerous financial support of the W. M. Keck Foundation.
| Low-Luminosity Active Galaxies and Their Central Black Holes
Central black hole masses for 117 spiral galaxies representingmorphological stages S0/a through Sc and taken from the largespectroscopic survey of Ho et al. are derived using Ks-banddata from the Two Micron All Sky Survey. Black hole masses are foundusing a calibrated black hole-Ks bulge luminosity relation,while bulge luminosities are measured by means of a two-dimensionalbulge-disk decomposition routine. The black hole masses are correlatedagainst a variety of parameters representing properties of the nucleusand host galaxy. Nuclear properties such as line width (FWHM [N II]), aswell as emission-line ratios (e.g., [O III]/Hβ, [O I]/Hα, [NII]/Hα, and [S II]/Hα), show a very high degree ofcorrelation with black hole mass. The excellent correlation with linewidth supports the view that the emission-line gas is in virialequilibrium with either the black hole or bulge potential. The very goodemission-line ratio correlations may indicate a change in ionizingcontinuum shape with black hole mass in the sense that more massiveblack holes generate harder spectra. Apart from theinclination-corrected rotational velocity, no excellent correlations arefound between black hole mass and host galaxy properties. Significantdifferences are found between the distributions of black hole masses inearly-, mid-, and late-type spiral galaxies (subsamples A, B, and C) inthe sense that early-type galaxies have preferentially larger centralblack holes, consistent with observations that Seyfert galaxies arefound preferentially in early-type systems. The line width distributionsshow a marked difference among subsamples A, B, and C in the sense thatearlier type galaxies have larger line widths. There are also cleardifferences in line ratios between subsamples A+B and C that likely arerelated to the level of ionization in the gas. Finally, aKs-band Simien & de Vaucouleurs diagram shows excellentagreement with the original B-band relation, although there is a largedispersion at a given morphological stage.
| Ultraluminous X-Ray Sources in Nearby Galaxies from ROSAT High Resolution Imager Observations I. Data Analysis
X-ray observations have revealed in other galaxies a class ofextranuclear X-ray point sources with X-ray luminosities of1039-1041 ergs s-1, exceeding theEddington luminosity for stellar mass X-ray binaries. Theseultraluminous X-ray sources (ULXs) may be powered by intermediate-massblack holes of a few thousand Msolar or stellar mass blackholes with special radiation processes. In this paper, we present asurvey of ULXs in 313 nearby galaxies withD25>1' within 40 Mpc with 467 ROSAT HighResolution Imager (HRI) archival observations. The HRI observations arereduced with uniform procedures, refined by simulations that help definethe point source detection algorithm employed in this survey. A sampleof 562 extragalactic X-ray point sources withLX=1038-1043 ergs s-1 isextracted from 173 survey galaxies, including 106 ULX candidates withinthe D25 isophotes of 63 galaxies and 110 ULX candidatesbetween 1D25 and 2D25 of 64 galaxies, from which aclean sample of 109 ULXs is constructed to minimize the contaminationfrom foreground or background objects. The strong connection betweenULXs and star formation is confirmed based on the striking preference ofULXs to occur in late-type galaxies, especially in star-forming regionssuch as spiral arms. ULXs are variable on timescales over days to yearsand exhibit a variety of long term variability patterns. Theidentifications of ULXs in the clean sample show some ULXs identified assupernovae (remnants), H II regions/nebulae, or young massive stars instar-forming regions, and a few other ULXs identified as old globularclusters. In a subsequent paper, the statistic properties of the surveywill be studied to calculate the occurrence frequencies and luminosityfunctions for ULXs in different types of galaxies to shed light on thenature of these enigmatic sources.
| Chemistry and Star Formation in the Host Galaxies of Type Ia Supernovae
We study the effect of environment on the properties of Type Iasupernovae by analyzing the integrated spectra of 57 local Type Iasupernova host galaxies. We deduce from the spectra the metallicity,current star formation rate, and star formation history of the host andcompare these to the supernova decline rates. Additionally, we comparethe host properties to the difference between the derived supernovadistance and the distance determined from the best-fit Hubble law. Fromthis we investigate possible uncorrected systematic effects inherent inthe calibration of Type Ia supernova luminosities using light-curvefitting techniques. Our results indicate a statistically insignificantcorrelation in the direction of higher metallicity spiral galaxieshosting fainter Type Ia supernovae. However, we present qualitativeevidence suggesting that progenitor age is more likely to be the sourceof variability in supernova peak luminosities than is metallicity. We donot find a correlation between the supernova decline rate and hostgalaxy absolute B magnitude, nor do we find evidence of a significantrelationship between decline rate and current host galaxy star formationrate. A tenuous correlation is observed between the supernova Hubbleresiduals and host galaxy metallicities. Further host galaxyobservations will be needed to refine the significance of this result.Finally, we characterize the environmental property distributions forType Ia supernova host galaxies through a comparison with two larger,more general galaxy distributions using Kolmogorov-Smirnov tests. Theresults show the host galaxy metallicity distribution to be similar tothe metallicity distributions of the galaxies of the NFGS and SDSS.Significant differences are observed between the SN Ia distributions ofabsolute B magnitude and star formation histories and the correspondingdistributions of galaxies in the NFGS and SDSS. Among these is an abruptupper limit observed in the distribution of star formation histories ofthe host galaxy sample, suggesting a Type Ia supernovae characteristicdelay time lower limit of approximately 2.0 Gyr. Other distributiondiscrepancies are investigated and the effects on the supernovaproperties are discussed.
| Cepheid Calibrations from the Hubble Space Telescope of the Luminosity of Two Recent Type Ia Supernovae and a Redetermination of the Hubble Constant
We report observations of two nearby Type Ia supernovae (SNe Ia) forwhich observations of Cepheid variables in the host galaxies have beenobtained with the Hubble Space Telescope: SN 1994ae in NGC 3370 and SN1998aq in NGC 3982. For NCG 3370, we used the Advanced Camera forSurveys to observe 64 Cepheids that yield a distance of 29 Mpc, thefarthest direct measurement of Cepheids. We have measured emission linesfrom H II regions in both host galaxies that providemetallicity-dependent corrections to their period-luminosity relations.These two SNe Ia double the sample of ``ideal'' luminosity calibrators:objects with well-observed and well-calibrated light curves of typicalshape and with low reddening. By comparing them to all similarlywell-measured SNe Ia in the Hubble flow, we find thatH0=73+/-4(statistical)+/-5(systematic) km s-1Mpc-1. A detailed analysis demonstrates that most of the pastdisagreement over the value of H0 as determined from SNe Iais abated by the replacement of past, problematic data by more accurateand precise, modern data.Based on observations with the NASA/ESA Hubble Space Telescope, obtainedat the Space Telescope Science Institute, which is operated by AURA,Inc., under NASA contract NAS 5-26555.
| 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.
| The opacity of spiral galaxy disks. VII. The accuracy of galaxy counts as an extinction probe
The "Synthetic Field Method" (SFM) was introduced by González etal. (1998, ApJ, 506, 152) to calibrate numbers of distant galaxies as aprobe of extinction in a foreground spiral disk. González et al.(2003, AJ, 125, 1182) studied the effect of the foreground disk on thesenumbers using simulations of current and future instruments for fieldsin the LMC, M 31 and NGC 4536, a galaxy in Virgo. They concludedthat: (1) the brighter centers of disks were unsuitable; (2) thegranularity of the disk at a fixed surface brightness is the limitingfactor in the detection of distant galaxies; and (3) the optimumdistance for measurements would be that of the Virgo cluster for thecurrent instruments on board HST. At this distance the foreground diskis smoothed with distance, improving detection of distant backgroundgalaxies. Holwerda et al. (2005a, AJ, 129, 1381) automated the SFM andHolwerda et al. (2005b, AJ, 129, 1396) applied it to a large set ofWFPC2 fields. In this paper, the quality of the extinction measurementin these fields is compared to their distance, granularity, surfacebrightness and structure.
The average surface brightness of theof a field is shown to directly influence the accuracy of the SFM. Thisrestricts meaningful measurements to the disks of spiral galaxies. Largestructures such as spiral arms have a similar effect. The granularity orsmall scale structure in a field influences the detection of distantgalaxies, limiting the SFM measurements in nearby disks. From the trendsin the accuracy and maximum practical field-of-view considerations, theminimum and maximum distance for SFM application, approximately 5 and 35Mpc respectively. Using the same instrument and detection method, therelations with SFM parameters and field characteristics can be used toforgo the synthetic fields altogether. For the wealth of ACS fieldsbecoming available in the archive, these relations can be used to selectthose fields based on expected SFM accuracy.
| Cosmological Results from High-z Supernovae
The High-z Supernova Search Team has discovered and observed eight newsupernovae in the redshift interval z=0.3-1.2. These independentobservations, analyzed by similar but distinct methods, confirm theresults of Riess and Perlmutter and coworkers that supernova luminositydistances imply an accelerating universe. More importantly, they extendthe redshift range of consistently observed Type Ia supernovae (SNe Ia)to z~1, where the signature of cosmological effects has the oppositesign of some plausible systematic effects. Consequently, thesemeasurements not only provide another quantitative confirmation of theimportance of dark energy, but also constitute a powerful qualitativetest for the cosmological origin of cosmic acceleration. We find a ratefor SN Ia of(1.4+/-0.5)×10-4h3Mpc-3yr-1at a mean redshift of 0.5. We present distances and host extinctions for230 SN Ia. These place the following constraints on cosmologicalquantities: if the equation of state parameter of the dark energy isw=-1, then H0t0=0.96+/-0.04, andΩΛ-1.4ΩM=0.35+/-0.14. Includingthe constraint of a flat universe, we findΩM=0.28+/-0.05, independent of any large-scalestructure measurements. Adopting a prior based on the Two Degree Field(2dF) Redshift Survey constraint on ΩM and assuming aflat universe, we find that the equation of state parameter of the darkenergy lies in the range -1.48-1, we obtain w<-0.73 at 95% confidence.These constraints are similar in precision and in value to recentresults reported using the WMAP satellite, also in combination with the2dF Redshift Survey.Based in part on observations with the NASA/ESA Hubble Space Telescope,obtained at the Space Telescope Science Institute, which is operated bythe Association of Universities for Research in Astronomy (AURA), Inc.,under NASA contract NAS 5-26555. This research is primarily associatedwith proposal GO-8177, but also uses and reports results from proposalsGO-7505, 7588, 8641, and 9118.Based in part on observations taken with the Canada-France-Hawaii Telescope, operated by the National Research Council of Canada, le Centre National de la Recherche Scientifique de France, and the University of Hawaii. CTIO: Based in part on observations taken at the Cerro Tololo Inter-American Observatory.Keck: Some of the data presented herein were obtained at the W. M. KeckObservatory, which is operated as a scientific partnership among theCalifornia Institute of Technology, the University of California, and theNational Aeronautics and Space Administration. The Observatory was madepossible by the generous financial support of the W. M. Keck Foundation.UH: Based in part on observations with the University of Hawaii 2.2 mtelescope at Mauna Kea Observatory, Institute for Astronomy, University ofHawaii. UKIRT: Based in part on observations with the United KingdomInfrared Telescope (UKIRT) operated by the Joint Astronomy Centre on behalfof the UK. Particle Physics and Astronomy Research Council. VLT: Based inpart on observations obtained at the European Southern Observatory,Paranal, Chile, under programs ESO 64.O-0391 and ESO 64.O-0404. WIYN: Based in part on observations taken at the WIYN Observatory, a joint facility of the University of Wisconsin-Madison, Indiana University, Yale University, and the National Optical Astronomy Observatories.
| A Search for Active Galactic Nuclei in Sc Galaxies with H II Spectra
We have searched for nuclear radio emission from a statisticallycomplete sample of 40 Sc galaxies within 30 Mpc that are opticallyclassified as star-forming objects, in order to determine whether weakactive galactic nuclei might be present. Only three nuclear radiosources were detected, in NGC 864, NGC 4123, and NGC 4535. Thesegalaxies have peak 6 cm radio powers of ~1020 WHz-1 at arcsecond resolution, while upper limits of thenondetected galaxies typically range from 1018.4 to1020 W Hz-1. The three nuclear radio sources areall resolved and appear to have diffuse morphologies, with linear sizesof ~300 pc. This strongly indicates that circumnuclear star formationhas been detected in these three H II galaxies. Comparisons withprevious 20 cm Very Large Array (VLA) results for the detected galaxiesshow that the extended nuclear radio emission has a flat spectrum in twoobjects and is almost certainly generated by thermal emission from gasionized by young stars in the centers of those galaxies. The 6 cm radiopowers are comparable to predictions for thermal emission that are basedon the nuclear Hα luminosities and imply nuclear star formationrates of 0.08-0.8 Msolar yr-1, while thelow-resolution NRAO VLA Sky Survey implies galaxy-wide star formationrates of 0.3-1.0 Msolar yr-1 in stars above 5Msolar. In a few of the undetected galaxies, the upper limitsto the radio power are lower than predicted from the Hαluminosity, possibly because of overresolution of central star-formingregions. Although the presence of active nuclei powered by massive blackholes cannot be definitively ruled out, the present results suggest thatthey are likely to be rare in these late-type galaxies with H IIspectra.
| Bar Galaxies and Their Environments
The prints of the Palomar Sky Survey, luminosity classifications, andradial velocities were used to assign all northern Shapley-Ames galaxiesto either (1) field, (2) group, or (3) cluster environments. Thisinformation for 930 galaxies shows no evidence for a dependence of barfrequency on galaxy environment. This suggests that the formation of abar in a disk galaxy is mainly determined by the properties of theparent galaxy, rather than by the characteristics of its environment.
| 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.
| Rotation curves and metallicity gradients from HII regions in spiral galaxies
In this paper we study long slit spectra in the region of Hαemission line of a sample of 111 spiral galaxies with recognizable andwell defined spiral morphology and with a well determined environmentalstatus, ranging from isolation to non-disruptive interaction withsatellites or companions. The form and properties of the rotation curvesare considered as a function of the isolation degree, morphological typeand luminosity. The line ratios are used to estimate the metallicity ofall the detected HII regions, thus producing a composite metallicityprofile for different types of spirals. We have found that isolatedgalaxies tend to be of later types and lower luminosity than theinteracting galaxies. The outer parts of the rotation curves of isolatedgalaxies tend to be flatter than in interacting galaxies, but they showsimilar relations between global parameters. The scatter of theTully-Fisher relation defined by isolated galaxies is significantlylower than that of interacting galaxies. The [NII]/Hα ratios, usedas a metallicity indicator, show a clear trend between Z andmorphological type, t, with earlier spirals showing higher ratios; thistrend is tighter when instead of t the gradient of the inner rotationcurve, G, is used; no trend is found with the change in interactionstatus. The Z-gradient of the disks depends on the type, being almostflat for early spirals, and increasing for later types. The[NII]/Hα ratios measured for disk HII regions of interactinggalaxies are higher than for normal/isolated objects, even if all thegalaxy families present similar distributions of Hα EquivalentWidth. Tables 3 and 4 and Figs. 6, 7 and 21 are only available inelectronic form at http://www.edpsciences.org. Table 5 is only availablein electronic form at the 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/393/389 Based on dataobtained Asiago/Ekar Observatory. Also based on observations made withINT operated on the island of La Palma by ING in the SpanishObservatorio del Roque de Los Muchachos of the Instituto deAstrofísica de Canarias.
| BVRI Photometry of Supernovae
We present optical photometry of one Type IIn supernova (1994Y) and nineType Ia supernovae (1993Y, 1993Z, 1993ae, 1994B, 1994C, 1994M, 1994Q,1994ae, and 1995D). SN 1993Y and SN 1993Z appear to be normal SN Iaevents with similar rates of decline, but we do not have data nearmaximum brightness. The colors of SN 1994C suggest that it suffers fromsignificant reddening or is intrinsically red. The light curves of SN1994Y are complicated; they show a slow rise and gradual decline nearmaximum brightness in VRI and numerous changes in the decline rates atlater times. SN 1994Y also demonstrates color evolution similar to thatof the SN IIn 1988Z, but it is slightly more luminous and declines morerapidly than SN 1988Z. The behavior of SN 1994Y indicates a small ejectamass and a gradual strengthening of the Hα emission relative tothe continuum.
| 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.
| Evidence for Asphericity in a Subluminous Type Ia Supernova: Spectropolarimetry of SN 1999by
We present polarization spectra near maximum light for the stronglysubluminous Type Ia supernova SN 1999by that show that the supernova isintrinsically polarized. SN 1999by has an observed, overall level ofpolarization of ~0.3%-0.8%, a rise of the polarization P redward of 6500Å, and a change in polarization across the Si II λ6150feature of about 0.4%. The presentation of the polarization at differentwavelengths in the Q-U plane is shown to be a powerful tool to determinethe overall geometry and the interstellar component. The distribution ofpoints with wavelength using this empirical Q-U plane method revealsthat SN 1999by has a well-defined axis of symmetry and suggests aninterstellar polarization (ISP) vector with PISP=0.3% andposition angle Θ=150deg with an error circle in the Q-Uplane of radius about 0.1%. Synthetic non-LTE spectra for axisymmetricconfigurations based on delayed-detonation models have been computedassuming ellipsoidal geometry. The input ejecta structure andcomposition are based on a Chandrasekhar mass delayed-detonation model.The parameters of the explosion are chosen to reproduce the timeevolution of IR spectra of SN 1999by without further adjustments.Spherical models are then mapped onto ellipsoidal geometries and theaxis ratio, viewing angle, and ISP adjusted to provide the bestagreement with the polarization spectra. Both flux and polarizationspectra can be reasonably well reproduced by models with an asphericityof ~20% observed equator-on. The general properties of the polarizationcan be understood as a consequence of the structure of subluminousmodels. Best fits are obtained for the theoretical models withPISP=0.25% and Θ=140deg, consistent with theempirical method. We discuss our results for this subluminous Type Ia inthe context of ``normally bright'' Type Ia supernovae. For normallybright Type Ia, the photosphere is near the inner iron-rich layers atmaximum light and the ubiquitous iron lines give a rapid variation tothe model polarization spectra. In subluminous models, the photospherenear maximum is in the silicon layers with fewer lines and a smootheroverall polarization spectrum, as observed for SN 1999by. Though dataare sparse, the low upper limits for polarization determined for manynormal events in contrast to the high polarization in SN 1999by maysuggest a relation between the asymmetry we observed and the mechanismthat produces a subluminous Type Ia. Among various mechanisms, rapidrotation of the progenitor white dwarf and/or an explosion during abinary white dwarf merger process are likely candidates to explain theasphericity in SN 1999by.
| The Progenitors of Subluminous Type Ia Supernovae
We find that spectroscopically peculiar subluminous Type Ia supernovae(SNe Ia) come from an old population. Of the 16 subluminous SNe Iaknown, 10 are found in E/S0 galaxies, and the remainder are found inearly-type spiral galaxies. The probability that this is a chanceoccurrence is only 0.2%. The finding that subluminous SNe Ia areassociated with an older stellar population indicates that for asufficiently large look-back time (already accessible in currenthigh-redshift searches) they will not be found. Due to a scarcity in oldpopulations, hydrogen and helium main-sequence stars and He red giantstars that undergo Roche lobe overflow are unlikely to be theprogenitors of subluminous SNe Ia. Earlier findings that overluminousSNe Ia [Δm15(B)<~0.95] come from a young progenitorpopulation are confirmed. The fact that subluminous SNe Ia andoverluminous SNe Ia come from different progenitor populations and alsohave different properties is a prediction of the CO white dwarf mergerprogenitor scenario.
| The formation of galaxy bulges: Spectrophotometric constraints
We have measured Mg2, Fe 5270 and Fe 5335 spectrophotometricindices (LICK system) in the bulge of 89 galaxies, mostly spirals fromthe Héraudeau (\cite{her96}) sample. The indices are reduced to anull velocity dispersion and normalized to an aperture of 0.2h-1 kpc. The mean errors are 0.009 mag on Mg2, and0.3 Å on the iron indices. These measurements almost double theamount of similar data already available on spiral galaxies. Our dataconfirm the existence of the relation between Mg2, andsigma0, the central stellar velocity dispersion; we find aneven tighter relation between Mg2, andVmrot, the maximum rotational velocity of thegalaxy, deduced from HI observations. For the most massive bulges, thesecorrelations may be interpreted as a mass-metallicity relation. However,the presence of young stellar populations, traced by the detection of[OIII] lambda 5007 Å, emission, provides clear evidence that ageeffects do play a role. Since the contribution of the young populationis anti-correlated to the mass of the galaxy, it continues theMg2, vs. sigma0 , relation toward thelow-sigma0, region and globally increases its slope. We alsopresent evidence for a new positive correlation between Fe indices andsigma0, and for a significant correlation between theline-strength indices and the total or disk luminosity. We propose tomodel the whole sequence of bulges within the folowing framework: bulgesare composed of a primary population formed prior to the disk, duringthe initial collapse, and of a secondary population formed during itsevolution. The whole family of bulges can be classified into threeclasses: (A) the bulges dominated by young populations are generallysmall, have ionized gas, low velocity dispersion and low line strengths;(B) the bulges dominated by the primary population lie along themass-metallicity sequence defined for elliptical galaxies; and (C) thebulges where the secondary population is significant are lessMg-over-abundant than (B)-type bulges and deviate from theMg2, vs. sigma0, relation of elliptical galaxies.Based on observations collected at the Observatoire de Haute-Provence.Table 3 is presented in electronic form only at the CDS. Tables 1 and 2are also available form at the CDS, Strasbourg, via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/366/68
| 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.
| On the Relation between Peak Luminosity and Parent Population of Type IA Supernovae: A New Tool for Probing the Ages of Distant Galaxies
We study the properties of Type Ia supernovae (SNe Ia) as functions ofthe radial distance from their host galaxy centers. Using a sample of 62SNe Ia with reliable luminosity, reddening, and decline ratedeterminations, we find no significant radial gradients of SNe Ia peakabsolute magnitudes or decline rates in elliptical+S0 galaxies,suggesting that the diversity of SN properties is not related to themetallicity of their progenitors. We do find that the range inbrightness and light curve width of supernovae in spiral galaxiesextends to brighter, broader values. These results are interpreted assupport for an age, but not metallicity, related origin of the diversityin SNe Ia. If confirmed with a larger and more accurate sample of data,the age-luminosity relation would offer a new and powerful tool to probethe ages and age gradients of stellar populations in galaxies atredshift as high as z~1-2. The absence of significant radial gradientsin the peak (B-V)0 and (V-I)0 colors of SNe Iasupports the reddening correction method of Phillips et al. We find noradial gradient in residuals from the SN Ia luminosity-width relation,suggesting that the relation is not affected by properties of theprogenitor populations and supporting the reliability of cosmologicalresults based upon the use of SNe Ia as distance indicators.
| 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
| A Search for Environmental Effects on Type IA Supernovae
We use integrated colors and B and V absolute magnitudes of Type Iasupernova (SN) host galaxies in order to search for environmentaleffects on the SN optical properties. With the new sample of 44 SNe weconfirm the conclusion by Hamuy et al. that bright events occurpreferentially in young stellar environments. We find also that thebrightest SNe occur in the least luminous galaxies, a possibleindication that metal-poor neighborhoods produce the more luminousevents. The interpretation of these results is made difficult, however,because of the fact that galaxies with younger stellar populations arealso lower in luminosity. In an attempt to remove this ambiguity, we usemodels for the line strengths in the absorption spectrum of fiveearly-type galaxies, in order to estimate metallicities and ages of theSN host galaxies. With the addition of abundance estimates from nebularanalysis of the emission spectra of three spiral galaxies, we findpossible further evidence that luminous SNe are produced in metal-poorneighborhoods. Further spectroscopic observations of the SN hostgalaxies will be necessary to test these results and assist indisentangling the age and metallicity effects on Type Ia SNe.
| 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 I-Band Tully-Fisher Relation for SC Galaxies: 21 Centimeter H I Line Data
A compilation of 21 cm line spectral parameters specifically designedfor application of the Tully-Fisher (TF) distance method is presentedfor 1201 spiral galaxies, primarily field Sc galaxies, for which opticalI-band photometric imaging is also available. New H I line spectra havebeen obtained for 881 galaxies. For an additional 320 galaxies, spectraavailable in a digital archive have been reexamined to allow applicationof a single algorithm for the derivation of the TF velocity widthparameter. A velocity width algorithm is used that provides a robustmeasurement of rotational velocity and permits an estimate of the erroron that width taking into account the effects of instrumental broadeningand signal-to-noise. The digital data are used to establish regressionrelations between measurements of velocity widths using other commonprescriptions so that comparable widths can be derived throughconversion of values published in the literature. The uniform H I linewidths presented here provide the rotational velocity measurement to beused in deriving peculiar velocities via the TF method.
| The I-Band Tully-Fisher Relation for SC Galaxies: Optical Imaging Data
Properties derived from the analysis of photometric I-band imagingobservations are presented for 1727 inclined spiral galaxies, mostly oftypes Sbc and Sc. The reduction, parameter extraction, and errorestimation procedures are discussed in detail. The asymptotic behaviorof the magnitude curve of growth and the radial variation in ellipticityand position angle are used in combination with the linearity of thesurface brightness falloff to fit the disk portion of the profile. TotalI-band magnitudes are calculated by extrapolating the detected surfacebrightness profile to a radius of eight disk scale lengths. Errors inthe magnitudes, typically ~0.04 mag, are dominated by uncertainties inthe sky subtraction and disk-fitting procedures. Comparison is made withthe similar imaging database of Mathewson, Ford, & Buchhorn, both aspresented originally by those authors and after reanalyzing theirdigital reduction files using identical disk-fitting procedures. Directcomparison is made of profile details for 292 galaxies observed incommon. Although some differences occur, good agreement is found,proving that the two data sets can be used in combination with onlyminor accommodation of those differences. The compilation of opticalproperties presented here is optimized for use in applications of theTully-Fisher relation as a secondary distance indicator in studies ofthe local peculiar velocity field.
| BVRI Light Curves for 22 Type IA Supernovae
We present 1210 Johnson/Cousins B, V, R, and I photometric observationsof 22 recent Type Ia supernovae (SNe Ia): SNe 1993ac, 1993ae, 1994M,1994S, 1994T, 1994Q, 1994ae, 1995D, 1995E, 1995al, 1995ac, 1995ak,1995bd, 1996C, 1996X, 1996Z, 1996ab, 1996ai, 1996bk, 1996bl, 1996bo, and1996bv. Most of the photometry was obtained at the Fred Lawrence WhippleObservatory of the Harvard-Smithsonian Center for Astrophysics in acooperative observing plan aimed at improving the database for SNe Ia.The redshifts of the sample range from cz=1200 to 37,000 km s^-1 with amean of cz=7000 km s^-1.
| Central Mg_2 indices for early-type galaxies
We present 210 new measurements of the central absorption line-strength{Mg_2} index for 87 early-type galaxies drawn from the \cite[Prugniel& Simien (1996)]{PS96} sample. 28 galaxies were not observed before.The results are compared to measurements published previously asavailable in HYPERCAT, and rescaled to the Lick system. The meanindividual internal error on these measurements is 0.009m+/-0.003m andthe mean external error is 0.012m+/-0.002m for this series ofmeasurements. Based on observations collected at the Observatoire deHaute-Provence. Tables 1, 3 and 4 are available in electronic form fromthe CDS, Strasbourg (via anonymous ftp to 130.79.128.5). Tables 1 and 3are available from CDS only.
| Stellar kinematic data for the central region of spiral galaxies. II.
We present a second dataset of absorption spectroscopy on the innerregion of spiral galaxies. We have determined the central velocitydispersion for 42 Sa-Sc objects and, for 32 of them, stellar rotationcurves and velocity-dispersion profiles. Some of these profiles arelimited to the bulge, some others do reach a region dominated by theluminosity of the disk. These data are intended to provide basicmaterial for the study of the mass distribution and dynamical status inthe central regions of spiral galaxies. Although no elaboratebulge-and-disk photometric decomposition is performed, we estimate theeffects of limited resolution and contamination by disk light on thecentral velocity dispersion of the bulge. All the material presented inthis paper, in particular the spectra, is available on-line. Based onobservations collected at the Observatoire de Haute-Provence. Tables 2and 3 are presented in electronic form only; Tables 1 through 3 areavailable from the CDS, Strasbourg, via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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