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UBVRI Light Curves of 44 Type Ia Supernovae
We present UBVRI photometry of 44 Type Ia supernovae (SNe Ia) observedfrom 1997 to 2001 as part of a continuing monitoring campaign at theFred Lawrence Whipple Observatory of the Harvard-Smithsonian Center forAstrophysics. The data set comprises 2190 observations and is thelargest homogeneously observed and reduced sample of SNe Ia to date,nearly doubling the number of well-observed, nearby SNe Ia withpublished multicolor CCD light curves. The large sample of U-bandphotometry is a unique addition, with important connections to SNe Iaobserved at high redshift. The decline rate of SN Ia U-band light curvescorrelates well with the decline rate in other bands, as does the U-Bcolor at maximum light. However, the U-band peak magnitudes show anincreased dispersion relative to other bands even after accounting forextinction and decline rate, amounting to an additional ~40% intrinsicscatter compared to the B band.
| 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 ISOPHOT 170 μm Serendipity Survey II. The catalog of optically identified galaxies%
The ISOPHOT Serendipity Sky Survey strip-scanning measurements covering≈15% of the far-infrared (FIR) sky at 170 μm were searched forcompact sources associated with optically identified galaxies. CompactSerendipity Survey sources with a high signal-to-noise ratio in at leasttwo ISOPHOT C200 detector pixels were selected that have a positionalassociation with a galaxy identification in the NED and/or Simbaddatabases and a galaxy counterpart visible on the Digitized Sky Surveyplates. A catalog with 170 μm fluxes for more than 1900 galaxies hasbeen established, 200 of which were measured several times. The faintest170 μm fluxes reach values just below 0.5 Jy, while the brightest,already somewhat extended galaxies have fluxes up to ≈600 Jy. For thevast majority of listed galaxies, the 170 μm fluxes were measured forthe first time. While most of the galaxies are spirals, about 70 of thesources are classified as ellipticals or lenticulars. This is the onlycurrently available large-scale galaxy catalog containing a sufficientnumber of sources with 170 μm fluxes to allow further statisticalstudies of various FIR properties.Based on observations with ISO, an ESA project with instruments fundedby ESA Member States (especially the PI countries: France, Germany, TheNetherlands and the UK) and with the participation of ISAS and NASA.Members of the Consortium on the ISOPHOT Serendipity Survey (CISS) areMPIA Heidelberg, ESA ISO SOC Villafranca, AIP Potsdam, IPAC Pasadena,Imperial College London.Full Table 4 and Table 6 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/422/39
| Near-infrared observations of galaxies in Pisces-Perseus. V. On the origin of bulges
We investigate the scaling relations of bulge and disk structuralparameters for a sample of 108 disk galaxies. Structural parameters ofindividual galaxies are obtained from two-dimensional bulge/diskdecomposition of their H-band surface brightness distributions. Bulgesare modelled with a generalized exponential (Sérsic) withvariable integer shape index n. We find that bulge effectivescalelengths reB and luminosity MBincrease with increasing n, but disk properties are independent of bulgeshape. As Hubble type T increases, bulges become less luminous and theirmean effective surface brightness <μeB>gets fainter; disk <μeD> shows a similar,but much weaker, trend. When bulge parameters(<μeB>, reB,MB) are compared with disk ones(<μeD>, reD,MD), they are tightly correlated for n=1 bulges. Thecorrelations gradually worsen with increasing n such that n=4 bulgesappear virtually independent of their disks. The Kormendy relation,<μeB> vs. reB, isshown to depend on bulge shape n; the two parameters are tightlycorrelated in n=4 bulges (r=0.8), and increasingly less so as ndecreases; disk <μeD> andreD are well correlated (r=0.7). Bulge-to-disksize ratios reB/reD areindependent of Hubble type, but smaller for exponential bulges; the meanreB/reD for n=1 bulges is 4times smaller than that for n=4, with a spread which is 9 times smaller.Strongly barred SB galaxies with exponential bulges are more luminousthan their unbarred counterparts. Exponential bulges appear to beclosely related to their underlying disks, while bulges with higher nvalues are less so; n=4 bulges and their disks apparently have norelation. We interpret our results as being most consistent with asecular evolutionary scenario, in which dissipative processes in thedisk are responsible for building up the bulges in most spirals.Based on observations at the TIRGO, NOT, and VATT telescopes. TIRGO(Gornergrat, CH) is operated by IRA-CNR, Arcetri, Firenze. NOT (LaPalma, Canary Islands) is operated by NOTSA, the Nordic ObservatoryScientific Association. VATT (Mt. Graham, AZ) is operated by VORG, theVatican Observatory Research Group.Full Table 1 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/414/905.
| 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.
| The WSRT wide-field H I survey. I. The background galaxy sample
We have used the Westerbork array to carry out an unbiased wide-fieldsurvey for H I emission features, achieving an RMS sensitivity of about18 mJy/Beam at a velocity resolution of 17 km s-1 over 1800deg2 and between -1000 < VHel <+6500 kms-1. The primary data consists of auto-correlation spectrawith an effective angular resolution of 49' FWHM, althoughcross-correlation data were also acquired. The survey region is centeredapproximately on the position of Messier 31 and is Nyquist-sampled over60x 30o in RA x Dec. More than 100 distinct features aredetected at high significance in each of the two velocity regimes(negative and positive LGSR velocities). In this paper we present theresults for our H I detections of external galaxies at positive LGSRvelocity. We detect 155 external galaxies in excess of 8sigma inintegrated H I flux density. Plausible optical associations are foundwithin a 30' search radius for all but one of our H I detections in DSSimages, although several are not previously cataloged or do not havepublished red-shift determinations. Our detection without a DSSassociation is at low galactic latitude. Twenty-three of our objects aredetected in H I for the first time. We classify almost half of ourdetections as ``confused'', since one or more companions is catalogedwithin a radius of 30' and a velocity interval of 400 km s-1.We identify a handful of instances of significant positional offsetsexceeding 10 kpc of unconfused optical galaxies with the associated H Icentroid, possibly indicative of severe tidal distortions or uncatalogedgas-rich companions. A possible trend is found for an excess of detectedH I flux in unconfused galaxies within our large survey beam relative tothat detected previously in smaller telescope beams, both as function ofincreasing distance and increasing gas mass. This may be an indicationfor a diffuse gaseous component on 100 kpc scales in the environment ofmassive galaxies or a population of uncataloged low mass companions. Weuse our galaxy sample to estimate the H I mass function from our surveyvolume. Good agreement is found with the HIPASS BGC results, but onlyafter explicit correction for galaxy density variations with distance.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/406/829 and Fig. 3 is onlyavailable in electronic form at http://www.edpsciences.org
| Classifications of the Host Galaxies of Supernovae
Classifications on the DDO system are given for the host galaxies of 177supernovae (SNe) that have been discovered since 1997 during the courseof the Lick Observatory Supernova Search with the Katzman AutomaticImaging Telescope. Whereas SNe Ia occur in all galaxy types, it isfound, at a high level of statistical confidence, that SNe Ib, Ic, andII are strongly concentrated in late-type galaxies. However, attentionis drawn to a possible exception provided by SN 2001I. This SN IInoccurred in the E2 galaxy UGC 2836, which was not expected to harbor amassive young supernova progenitor.
| 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 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.
| A High Intrinsic Peculiarity Rate among Type IA Supernovae
We have compiled a sample of 45 Type Ia supernovae (SNe Ia) discoveredby the Lick Observatory Supernova Search (LOSS) and the BeijingAstronomical Observatory Supernova Survey (BAOSS), and determined therate of spectroscopically peculiar SNe Ia (i.e., SN 1986G-like, SN1991bg-like, and SN 1991T-like objects) and the luminosity function ofSNe Ia. Because of the nature of the two surveys (distance-limited withsmall baselines and deep limiting magnitudes), nearly all SNe Ia havebeen discovered in the sample galaxies of LOSS and BAOSS; thus, theobserved peculiarity rate and luminosity function of SNe Ia areintrinsic. We find that 36%+/-9% of nearby SNe Ia are peculiar;specifically, the luminosity function of SNe Ia consists of 20% SN1991T-like, 64% normal, and 16% SN 1991bg-like objects. We have comparedour results to those found by earlier studies, and to those found athigh redshift. The apparent dearth of SN 1991T-like objects at highredshift may be due to extinction, and especially to the difficulty ofrecognizing them from spectra obtained past maximum brightness or fromspectra with low signal-to-noise ratios. Implications of the highpeculiarity rate for the progenitor systems of SNe Ia are also brieflydiscussed.
| Supernovae 1999dq, 1999eh, 1999ej, 1999el
IAUC 7304 available at Central Bureau for Astronomical Telegrams.
| Supernovae 1999by, 1999dk, 1999dq
IAUC 7275 available at Central Bureau for Astronomical Telegrams.
| Supernova 1999dq in NGC 976
IAUC 7264 available at Central Bureau for Astronomical Telegrams.
| Supernova 1999dq in NGC 976
IAUC 7250 available at Central Bureau for Astronomical Telegrams.
| Supernova 1999dq in NGC 976
IAUC 7247 available at Central Bureau for Astronomical Telegrams.
| The QDOT all-sky IRAS galaxy redshift survey
We describe the construction of the QDOT survey, which is publiclyavailable from an anonymous FTP account. The catalogue consists ofinfrared properties and redshifts of an all-sky sample of 2387 IRASgalaxies brighter than the IRAS PSC 60-μm completeness limit(S_60>0.6Jy), sparsely sampled at a rate of one-in-six. At |b|>10deg, after removing a small number of Galactic sources, the redshiftcompleteness is better than 98per cent (2086/2127). New redshifts for1401 IRAS sources were obtained to complete the catalogue; themeasurement and reduction of these are described, and the new redshiftstabulated here. We also tabulate all sources at |b|>10 deg with noredshift so far, and sources with conflicting alternative redshiftseither from our own work, or from published velocities. A list of 95ultraluminous galaxies (i.e. with L_60μm>10^12 L_solar) is alsoprovided. Of these, ~20per cent are AGN of some kind; the broad-lineobjects typically show strong Feii emission. Since the publication ofthe first QDOT papers, there have been several hundred velocity changes:some velocities are new, some QDOT velocities have been replaced by moreaccurate values, and some errors have been corrected. We also present anew analysis of the accuracy and linearity of IRAS 60-μm fluxes. Wefind that the flux uncertainties are well described by a combination of0.05-Jy fixed size uncertainty and 8per cent fractional uncertainty.This is not enough to cause the large Malmquist-type errors in the rateof evolution postulated by Fisher et al. We do, however, find marginalevidence for non-linearity in the PSC 60-μm flux scale, in the sensethat faint sources may have fluxes overestimated by about 5per centcompared with bright sources. We update some of the previous scientificanalyses to assess the changes. The main new results are as follows. (1)The luminosity function is very well determined overall but is uncertainby a factor of several at the very highest luminosities(L_60μm>5x10^12L_solar), as this is where the remainingunidentified objects are almost certainly concentrated. (2) Thebest-fitting rate of evolution is somewhat lower than our previousestimate; expressed as pure density evolution with density varying as(1+z)^p, we find p=5.6+/-2.3. Making a rough correction for the possible(but very uncertain) non-linearity of fluxes, we find p=4.5+/-2.3. (3)The dipole amplitude decreases a little, and the implied value of thedensity parameter, assuming that IRAS galaxies trace the mass, isΩ=0.9(+0.45, -0.25). (4) Finally, the estimate of density varianceon large scales changes negligibly, still indicating a significantdiscrepancy from the predictions of simple cold dark matter cosmogonies.
| 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 NICMOS Snapshot Survey of Nearby Galaxies
We present ``snapshot'' observations with the Near-Infrared Camera andMulti-Object Spectrometer (NICMOS) on board the Hubble Space Telescope(HST) of 94 nearby galaxies from the Revised Shapley Ames Catalog.Images with 0.2" resolution were obtained in two filters, a broadbandcontinuum filter (F160W, roughly equivalent to the H band) and anarrowband filter centered on the Paα line (F187N or F190N,depending on the galaxy redshift) with the 51^''x51^'' field of view ofthe NICMOS camera 3. A first-order continuum subtraction is performed,and the resulting line maps and integrated Paα line fluxes arepresented. A statistical analysis indicates that the average Paαsurface brightness in the central regions is highest in early-type(Sa-Sb) spirals.
| Near-infrared observations of galaxies in Pisces-Perseus. I. vec H-band surface photometry of 174 spiral
We present near-infrared, H-band (1.65 $() μm), surface photometry of174 spiral galaxies in the area of the Pisces-Perseus supercluster. Theimages, acquired with the ARNICA camera mounted on various telescopes,are used to derive radial profiles of surface brightness, ellipticities,and position angles, together with global parameters such as H-bandmagnitudes and diameters Radial profiles in tabular form and images FITSfiles are also available upon request from gmorio@arcetri.astro.it.}.The mean relation between H-band isophotal diameter D_{21.5} and theB-band D25 implies a B-H color of the outer disk bluer than3.5; moreover, D_{21.5}/D25 depends on (global) color andabsolute luminosity. The correlations among the various photometricparameters suggest a ratio between isophotal radius D_{21.5}/2 and diskscale length of ~ m3.5 and a mean disk central brightness ~ meq 17.5H-mag arcsec^{-2}. We confirm the trend of the concentration indexC31$ with absolute luminosity and, to a lesser degree, withmorphological type. We also assess the influence of non-axisymmetricstructures on the radial profiles and on the derived parameters. Basedon observations at the TIRGO, NOT, and VATT telescopes. TIRGO(Gornergrat, CH) is operated by CAISMI-CNR, Arcetri, Firenze. NOT (LaPalma, Canary Islands) is operated by NOTSA, the Nordic ObservatoryScientific Association. VATT (Mt. Graham, Az) is operated by VORG, theVatican Observatory Research Group Table 3 and Fig. 4 are only availablein electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html.
| Groups of galaxies. III. Some empirical characteristics.
Not Available
| Bulge-Disk Decomposition of 659 Spiral and Lenticular Galaxy Brightness Profiles
We present one of the largest homogeneous sets of spiral and lenticulargalaxy brightness profile decompositions completed to date. The 659galaxies in our sample have been fitted with a de Vaucouleurs law forthe bulge component and an inner-truncated exponential for the diskcomponent. Of the 659 galaxies in the sample, 620 were successfullyfitted with the chosen fitting functions. The fits are generally welldefined, with more than 90% having rms deviations from the observedprofile of less than 0.35 mag. We find no correlations of fittingquality, as measured by these rms residuals, with either morphologicaltype or inclination. Similarly, the estimated errors of the fittedcoefficients show no significant trends with type or inclination. Thesedecompositions form a useful basis for the study of the lightdistributions of spiral and lenticular galaxies. The object base issufficiently large that well-defined samples of galaxies can be selectedfrom it.
| Catalogue of HI maps of galaxies. I.
A catalogue is presented of galaxies having large-scale observations inthe HI line. This catalogue collects from the literature the informationthat characterizes the observations in the 21-cm line and the way thatthese data were presented by means of maps, graphics and tables, forshowing the distribution and kinematics of the gas. It containsfurthermore a measure of the HI extension that is detected at the levelof the maximum sensitivity reached in the observations. This catalogueis intended as a guide for references on the HI maps published in theliterature from 1953 to 1995 and is the basis for the analysis of thedata presented in Paper II. The catalogue is only available inelectronic form at the CDS via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
| Molecular Gas, Morphology, and Seyfert Galaxy Activity
We probe the cause of the elevated star formation in host galaxies ofSeyfert 2 nuclei compared with Seyfert 1 hosts and with field galaxies.12CO (1--0) observations of a large sample of Seyfert galaxies indicateno significant difference in the total amount of molecular gas as afunction of the Seyfert nuclear type, nor are Seyfert galaxiessignificantly different in this regard from a sample of field galaxiesonce selection effects are accounted for. Therefore, the total amount ofmolecular gas is not responsible for the enhanced star-forming activityin Seyfert 2 hosts. To probe how this gas is being converted moreefficiently into stars in Seyfert 2 hosts than in the other galaxies, weinvestigate the occurrence of bars, interactions, and distortedmorphologies among Seyfert galaxies. We find a significantly higher rateof asymmetric morphologies for Seyfert 2 galaxies with respect toSeyfert 1 galaxies and field galaxies. Relative to field galaxies, theeffect is at a greater than 99.9% confidence level. The presence ofasymmetric morphologies in individual Seyfert galaxies is correlatedwith their tendency to exhibit enhanced star-forming activity. Theseresults suggest that asymmetric morphologies are an important cause forthe link between Seyfert type and star-forming activity: bars anddistortions in Seyfert 2 hosts are likely both to enhance star-formingactivity and to funnel gas into the nuclear region, thus obscuring andpossibly contributing to the feeding of the active nucleus.
| Bias Properties of Extragalactic Distance Indicators. VI. Luminosity Functions of M31 and M101 Look-alikes Listed in the RSA2: H0 Therefrom
Galaxies whose morphologies are similar to M 101 (Sc I) and M3 1 (Sb I-II) are listed in two tables. The selection is made by inspecting directimages of Shapley-Ames galaxies in the recent Carnegie Atlas ofGalaxies. Absolute magnitudes, calculated from redshifts, give meanvalues of
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