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Supernovae 2006dp, 2006dq, 2006dr
IAUC 8731 available at Central Bureau for Astronomical Telegrams.
| Application of iterative blind deconvolution to the reconstruction of LBT LINC-NIRVANA images
Context: .The paper is about methods for multiple image deconvolutionand their application to the reconstruction of the images acquired bythe Fizeau interferometer, denoted LINC-NIRVANA, under development forthe Large Binocular Telescope (LBT). The multiple images of the sametarget are obtained with different orientations of the baseline.Aims: .To propose and develop a blind method for dealing with caseswhere no knowledge or very poor knowledge of the point spread functions(PSF) is available. Methods: .The approach is an iterative onewhere object and PSFs are alternately updated using deconvolutionmethods related to the standard Richardson-Lucy method. It is basicallyan extension, to the multiple image case, of iterative blinddeconvolution methods proposed in the case of a single image.Results: .The method is applied to simulated LBT LINC-NIRVANA images andits limitations are investigated. The algorithm has been implemented inthe module BLI of the software package AIRY (Astronomical ImageReconstruction in interferometrY), available under request. Thepreliminary results we have obtained are promising but an extensivesimulation program is still necessary for a full understanding of theapplicability of the method in the practice of the reconstruction ofLINC-NIRVANA images.
| How large are the bars in barred galaxies?
I present a study of the sizes (semimajor axes) of bars in discgalaxies, combining a detailed R-band study of 65 S0-Sb galaxies withthe B-band measurements of 70 Sb-Sd galaxies from Martin (1995). As hasbeen noted before with smaller samples, bars in early-type (S0-Sb)galaxies are clearly larger than bars in late-type (Sc-Sd) galaxies;this is true both for relative sizes (bar length as fraction ofisophotal radius R25 or exponential disc scalelength h) andabsolute sizes (kpc). S0-Sab bars extend to ~1-10 kpc (mean ~ 3.3 kpc),~0.2-0.8R25 (mean ~ 0.38R25) and ~0.5-2.5h (mean ~1.4h). Late-type bars extend to only ~0.5-3.5 kpc,~0.05-0.35R25 and 0.2-1.5h their mean sizes are ~1.5 kpc, ~0.14R25 and ~0.6h. Sb galaxies resemble earlier-type galaxiesin terms of bar size relative to h; their smallerR25-relative sizes may be a side effect of higher starformation, which increases R25 but not h. Sbc galaxies form atransition between the early- and late-type regimes. For S0-Sbcgalaxies, bar size correlates well with disc size (both R25and h); these correlations are stronger than the known correlation withMB. All correlations appear to be weaker or absent forlate-type galaxies; in particular, there seems to be no correlationbetween bar size and either h or MB for Sc-Sd galaxies.Because bar size scales with disc size and galaxy magnitude for mostHubble types, studies of bar evolution with redshift should selectsamples with similar distributions of disc size or magnitude(extrapolated to present-day values); otherwise, bar frequencies andsizes could be mis-estimated. Because early-type galaxies tend to havelarger bars, resolution-limited studies will preferentially find bars inearly-type galaxies (assuming no significant differential evolution inbar sizes). I show that the bars detected in Hubble Space Telescope(HST) near-infrared(IR) images at z~ 1 by Sheth et al. have absolutesizes consistent with those in bright, nearby S0-Sb galaxies. I alsocompare the sizes of real bars with those produced in simulations anddiscuss some possible implications for scenarios of secular evolutionalong the Hubble sequence. Simulations often produce bars as large as(or larger than) those seen in S0-Sb galaxies, but rarely any as smallas those in Sc-Sd galaxies.
| Disk-bulge decompositions of spiral galaxies in UBVRI
A sample of 26 bright spiral galaxies (Btot < 12.7) withlow to medium inclination and without a bar was observed with UBVRIfilters. The CAFOS focal reducer camera at the Calar Alto 2.2 mtelescope was used. The surface-brightness distributions were fittedusing a 2-dimensional algorithm with corresponding functions for thedisk- and bulge-structure. For the disks an exponential function wasused, for the bulges a Sérsic Rβ law, was appliedwith the concentration parameter β = 1/n as another fit variable.Correlations of the resulting structural parameters of disks and bulgesin UBVRI are investigated, giving clues to the formation history of thebulges.We confirm that the large and bright bulges of early-type spirals aresimilar to elliptical galaxies. They were probably formed prior to thedisks in a monolithic collapse or via early mergers. Late-type spiralshave tiny and faint bulges with disk-like profiles. These bulges wereprobably formed after the disk in secular evolution processes, e.g. froma disk instability. The comparison of the color indices of correspondingspirals and bulges with population synthesis computations support aboveformation scenarios.Tables 2-4 are 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/415/63
| Simulations of normal spiral galaxies
Results from numerical simulations of normal isolated late-type spiralgalaxies are presented; specifically, the galaxy NGC 628 is used as atemplate. The method employs a TREESPH code including stellar particles,gas particles, cooling and heating of the gas, star formation accordingto a Jeans criterion and supernova feedback. A regular spiral disc canbe generated as an equilibrium situation of two opposing actions: on theone hand, cooling and dissipation of the gas; on the other hand, gasheating by the far-ultraviolet field of young stars and supernovamechanical forcing. The disc exhibits small- and medium-scale spiralstructure of which the multiplicity increases as a function of radius.The theory of swing amplification can explain, both qualitatively andquantitatively, the emerging spiral structure. In addition, swingamplification predicts that the existence of a grand-design m= 2 spiralis only possible if the disc is massive. The simulations show that thegalaxy is then unstable to bar formation, confirming the result ofOstriker & Peebles. The occurrence of this bar instability isfurther investigated. A general criterion is derived for the transitionbetween a stable and an unstable bar, depending on the disc masscontribution and the on-disc thickness. It seems that bar stabilitybarely depends on the presence of gas. A detailed quantitative analysisis made of the emerging spiral structure and a comparison is made withobservations. This demonstrates that the structure of the numericalisolated galaxies is not as strong and has a larger multiplicitycompared with the structure of some exemplary real galaxies. It isargued that the suggestion of Kormendy & Norman holds, i.e. that agrand design can only be generated by a central bar or by tidal forcesresulting from an encounter with another galaxy.
| HYPERLEDA. II. The homogenized HI data
After a compilation of HI data from 611 references and new observationsmade in Nançay, we produce a catalog of homogenized HI data for16781 galaxies. The homogenization is made using the EPIDEMIC methodfrom which all data are progressively converted into the adoptedstandard. The result is a catalog giving: 1) the logarithm of twice themaximum rotation velocity, log 2V_Msin i, converted to thesystem of Mathewson et al. (\cite{Mathewson1996}). This quantity isgiven without correction for inclination; 2) the HI magnitude,m21, (area of the 21-cm line width expressed in magnitude)converted to the flux system of Theureau et al. (\cite{Theureau1998});3) the HI velocity, V_HI, expressed with the optical definition (i.e.,using wavelengths instead frequencies). The typical uncertainties are:0.04 for log 2V_Msin i, 0.25 mag for m21 and 9 kms-1 for V_HI.Full Tables \ref{epidemicw}, \ref{epidemicw2}, \ref{epidemicf},\ref{epidemicf2} and Fig. \ref{profiles} are available in electronicform at http://www.edpsciences.org. Full Tables \ref{references},\ref{cataf}, \ref{newdata} and \ref{notes} are available in electronicform at the 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/412/57
| Galaxies with Rows
The results of a search for galaxies with straight structural elements,usually spiral-arm rows (“rows” in the terminology ofVorontsov-Vel'yaminov), are reported. The list of galaxies that possess(or probably possess) such rows includes about 200 objects, of whichabout 70% are brighter than 14m. On the whole, galaxies with rows makeup 6 8% of all spiral galaxies with well-developed spiral patterns. Mostgalaxies with rows are gas-rich Sbc-Scd spirals. The fraction ofinteracting galaxies among them is appreciably higher than amonggalaxies without rows. Earlier conclusions that, as a rule, the lengthsof rows are similar to their galactocentric distances and that theangles between adjacent rows are concentrated near 120° areconfirmed. It is concluded that the rows must be transient hydrodynamicstructures that develop in normal galaxies.
| 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.
| Image restoration methods for the Large Binocular Telescope (LBT)
A complete exploitation of the imaging properties of the Large BinocularTelescope (LBT) will require a generalization of the restoration methodswhich apply to the case of a single image. Several differentobservations must be combined to obtain a high-resolution representationof a given target. The purpose of this paper is to extend to thisproblem some of the most used restoration methods, including linearmethods such as Tikhonov regularization as well as iterativeregularization methods providing positive solution. The proposed methodsare implemented and tested on simulated LBT images of diffuse andpoint-like objects. The results are discussed both from the point ofview of the accuracy and from that of the computational efficiency,because LBT images may contain, in principle, up to 108pixels.
| Application of the OS-EM method to the restoration of LBT images
The Large Binocular Telescope (LBT), which will be available in a fewyears from now, has been designed for high-resolution optical/infraredimaging through coherent cophasing of the two mirrors. The structure ofthe process of image formation in LBT is similar to that in ComputedTomography (CT) so that it is interesting to investigate theapplicability to LBT of image restoration methods developed for CT. Apowerful one is the so-called Expectation Maximization (EM), which isalso known in the astronomical literature as Lucy-Richardson (LR)method. However slow convergence is a drawback of this method. In thecase of CT an accelerated version, based on ordered subsets ofprojection data (OS-EM), has been proposed. In this paper we adapt OS-EMto the problem of restoring LBT images and we show that it provides anacceleration by a factor which is roughly equal to the number ofindependent interferometric images of the same object.
| Small-amplitude density waves in galactic discs with radial gradients
Stellar discs of highly flattened giant galaxies, including that of theMilky Way, are studied by linear theory to determine the stability ofsuch discs against small-amplitude gravity perturbations. In order tounderstand the physics of the problem better, the simplest theoreticalmodel is applied. That is, the local disc is studied by employing themethod of particle orbit theory. In this purely Lagrangian method, anapproximate solution of the Newtonian equations of the motion of starsis obtained using a general technique based upon the perturbationmethod. In the second order of Lindblad's epicyclic theory, expressionsare found for the unperturbed motions of stars in a stationary systemwith an axially symmetric mass distribution. Then, expressions are foundfor the perturbed motions of stars when the small non-axisymmetricgravity perturbation is additionally taken into account. The perturbedterms are obtained as second-order oscillations. To describe the orderedbehaviour of a medium near its quasi-equilibrium state, these equationsfor the trajectories of stars are used to obtain the dispersion relationthat connects the frequency of excited collective oscillations with thewavenumber throughout the disc, including resonant regions. Using thedispersion relation, a new class of gradient microinstabilities of anon-uniformly rotating disc inherent in an inhomogeneous system isdiscussed. The Landau mechanism of excitation of spiral density wavesworks at the corotation resonance between stars and hydrodynamically(Jeans) stable perturbations (e.g. those produced by a bar-likestructure, a spontaneous perturbation and/or a companion galaxy). Aphysical aetiology of the gradient microinstabilities of collisionlessstellar discs is explained. Such instabilities can develop only if theinhomogeneous and non-uniformly rotating disc of stars is Jeans-stable.Certain astronomical implications of the theory for actual galaxies areexplored as well. In particular, the development of these instabilitiesof a stellar disc can result directly in the formation of differentobservable structural features, e.g. spiral arms and collisionlessdynamical relaxation of the system on the Hubble time-scale.
| Quantitative interpretation of the morphology of NGC 1288
We present a quantitative photometry of the bulge and disk of NGC 1288.We deduce from the multiplicity of spiral arms, using arguments ofdensity wave theory, that NGC 1288 must be imbedded in a dark halo.Based on observations collected at the European Southern Observatory,Paranal, Chile (VLT UT1 Commissioning Program).
| Morphological structure and colors of NGC 1232 and NGC 1288
Using the FORS1 focal reducer camera at the VLT UT1 (Antu) a multi-colorsurface photometry has been carried out for the southern Sc galaxies NGC1232 and NGC 1288. Two-dimensional functions for the disk and the bulgewere fitted to the surface-brightness distribution, yielding ahigh-precision disk-bulge decomposition. Nearly linear correlations forthe characteristic scale parameters of disk and bulge in the differentcolors were found, as well as similar correlations for the centralsurface brightness of the disk and the effective surface brightness ofthe bulge. This seems to indicate that there exist connections betweendisk and bulge properties in spiral galaxies and their stellar densityand population distributions. Based on observations collected at theEuropean Southern Observatory, Paranal, Chile (VLT UT1 CommissioningProgram).
| The Durham/UKST Galaxy Redshift Survey - V. The catalogue
We present the radial velocities and blue, optical magnitudes for all ofthe galaxies within the Durham/UKST Galaxy Redshift Survey. Thiscatalogue consists of ~2500 galaxy redshifts to a limiting apparentmagnitude of B_J⋍17 mag, covering a ~1500-deg^2 area around theSouth Galactic Pole. The galaxies in this survey were selected from theEdinburgh/Durham Southern Galaxy Catalogue and were sampled, in order ofapparent magnitude, at a rate of one galaxy in every three. Thespectroscopy was performed at the 1.2-m UK Schmidt Telescope inAustralia using the FLAIR multi-object spectrograph. We show that ourradial velocity measurements made with this instrument have an empiricalaccuracy of +/-150 km s^-1. The observational techniques and datareduction procedures used in the construction of this survey are alsodiscussed. This survey demonstrates that the UKST can be used to make athree-dimensional map of the large-scale galaxy distribution, via aredshift survey to b_J⋍17 mag, over a wide area of the sky.
| The Southern Sky Redshift Survey
We report redshifts, magnitudes, and morphological classifications for5369 galaxies with m_B <= 15.5 and for 57 galaxies fainter than thislimit, in two regions covering a total of 1.70 sr in the southerncelestial hemisphere. The galaxy catalog is drawn primarily from thelist of nonstellar objects identified in the Hubble Space TelescopeGuide Star Catalog (GSC). The galaxies have positions accurate to ~1"and magnitudes with an rms scatter of ~0.3 mag. We compute magnitudes(m_SSRS2) from the relation between instrumental GSC magnitudes and thephotometry by Lauberts & Valentijn. From a comparison with CCDphotometry, we find that our system is homogeneous across the sky andcorresponds to magnitudes measured at the isophotal level ~26 magarcsec^-2. The precision of the radial velocities is ~40 km s^-1, andthe redshift survey is more than 99% complete to the m_SSRS2 = 15.5 maglimit. This sample is in the direction opposite that of the CfA2; incombination the two surveys provide an important database for studies ofthe properties of galaxies and their large-scale distribution in thenearby universe. Based on observations obtained at Cerro TololoInter-American Observatory, National Optical Astronomy Observatories,operated by the Association of Universities for Research in Astronomy,Inc., under cooperative agreement with the National Science Foundation;Complejo Astronomico El Leoncito, operated under agreement between theConsejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; the European Southern Observatory, LaSilla, Chile, partially under the bilateral ESO-ObservatórioNacional agreement; Fred Lawrence Whipple Observatory;Laboratório Nacional de Astrofísica, Brazil; and the SouthAfrican Astronomical Observatory.
| 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.
| Stability of the Stellar Disks of Flat Galaxies. I. A Collisionless, Homogeneous System
A differentially rotating stellar disk, representing highly flattenedgalaxies, is studied by employing the linear kinetic theory to determineits stability against small-amplitude gravity perturbations. Theanalysis is carried out for the special case of an infinitely thin,spatially homogeneous system, taKing into account the effects of random(residual) movements of stars, but neglecting collisions. The influenceof drift motion on the stability of disk oscillations is investigated.This minor motion of a star, whose value may be determined from thehigher order approximation of Lindblad's epicyclic theory, is analogousto the grad B drift of an electrically charged particle in a plasma andis related to the differential rotation of the system. In classicalstellar dynamics, this drift has been known as the asymmetric drift.Within the local approximation of the WKB method, it is shown that adisk rotating differentially could be unstable due to either agravitational Jeans-type instability or an oscillating kinetic-typeinstability (overstability). To suppress Jeans instabilities, ageneralized local stability criterion must be satisfied, which indicatesthat in a differentially rotating disk, nonaxisymmetric perturbationsare more unstable than axisymmetric ones. A Jeans-stable disk is stillunstable to oscillatory growing perturbations. The etiology of thisoscillating instability is the resonant interaction of drifting starswith Jeans-stable waves at the corotation resonance: nonaxisymmetricJeans-stable modes of the differentially rotating disk are modified bydrifts and can become unstable. It is similar to the instability of theCherenkov type (the inverse Landau damping effect) in plasmas, and it isdue to the nature of the differential rotation of the galactic system.The growth rates of the amplitudes of the excited waves areexponentially small, excepting the corotation resonant regions of thesystem. As drift motion always exists in the differentially rotatingdisk, the oscillating instability can be considered to be a long-termgenerating mechanism for propagating density waves, thereby leading tospiral-like patterns in the flat galaxies. It is suggested also thatbecause of the resonant interaction of stars with the gravitationalfield of the oscillatory growing waves, the rate of relaxation of a disktoward equilibrium can be enhanced. This collisionless collectiverelaxation will be accompanied by a secular increase in the stellarvelocity dispersion and a redistribution of the surface mass density toa more peaked distribution. The latter may assist in the formation of acondensed nucleus of a galaxy.
| 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
| The Catalog of Southern Ringed Galaxies
The Catalog of Southern Ringed Galaxies (CSRG) is a comprehensivecompilation of diameters, axis ratios, relative bar position angles, andmorphologies of inner and outer rings, pseudorings, and lenses in 3692galaxies south of declination -17 deg. The purpose of the catalog is toevaluate the idea that these ring phenomena are related to orbitalresonances with a bar or oval in galaxy potentials. The catalog is basedon visual inspection of most of the 606 fields of the Science ResearchCouncil (SRC) IIIa-J southern sky survey, with the ESO-B, ESO-R, andPalomar Sky surveys used as auxiliaries when needed for overexposed coreregions. The catalog is most complete for SRC fields 1-303 (mostly southof declination -42 deg). In addition to ringed galaxies, a list of 859mostly nonringed galaxies intended for comparison with other catalogs isprovided. Other findings from the CSRG that are not based on statisticsare the identification of intrinsic bar/ring misalignment; bars whichunderfill inner rings; dimpling of R'1pseudorings; pointy, rectangular, or hexagonal inner or outer ringshapes; a peculiar polar-ring-related system; and other extreme examplesof spiral structure and ring morphology.
| Inner two-arm symmetry in spiral galaxies
Most galaxies with spiral density waves, including those with multiplelong arms, have two prominent symmetric arms in their inner regions,inside approximately 0.5 R25. Grand-design galaxies, whichhave two prominent arms throughout their disks, also have brighter,narrower, and more continuous arms inside this radius. Based onmeasurements of these morphological features in 173 galaxies, and on ourprevious studies of optical resonance indicators, we propose thatcorotation is optically visible in most spiral galaxies and is locatednear the radius of the endpoints of the highly symmetric part of thespiral arms, approximately midway out in the disk. This places the outerLindbald resonance at approximately R25, or approximately 4scale lengths, for most spiral galaxies. In barred galaxies, the twoinner symmetric arms end at twice the bar radius, independent of the bartype. If large bars end near corotation, then the ends of the twoprominent arms must be beyond corotation in these systems.
| Quantitative Morphology of Bars in Spiral Galaxies
As suggested by numerical simulations, the axis ratio of the bar is afundamental parameter to describe the dynamical evolution of a barredgalaxy. In a first-order approximation considering bars as ellipticalfeatures, visual measurements of bar axis ratios and lengths of 136spiral galaxies were performed on photographs of good linear scale.Despite the limitations affecting such measurements, morphologicalproperties of bars in spirals along the Hubble sequence as well as therelationship between the bar axis ratio and nuclear star formationactivity are studied. It is found that the relative length of bars inearly-type galaxies is, on average, about a factor of 3 larger than thelength observed in late-type spirals. Also, a relation between barlengths and bulge diameters is observed for both early-type andlate-type spirals, confirming results from previous works. Furthermore,although the number of objects is small, there is an apparentcorrelation between the presence of nuclear star formation activity andthe bar axis ratio: about 71% of the starburst galaxies included in thesample have a strong bar (b/a < 0.6). The introduction of thesequantitative parameters in galaxy classification schemes is discussed.
| Integrated photoelectric magnitudes and color indices of bright galaxies in the Johnson UBV system
The photoelectric total magnitudes and color indices published in theThird Reference Catalogue of Bright Galaxies (RC3) are based on ananalysis of approximately equals 26,000 B, 25,000 B-V, and 17,000 U-Bmultiaperture measurements available up to mid 1987 from nearly 350sources. This paper provides the full details of the analysis andestimates of internal and external errors in the parameters. Thederivation of the parameters is based on techniques described by theVaucouleurs & Corwin (1977) whereby photoelectric multiaperture dataare fitted by mean Hubble-type-dependent curves which describe theintegral of the B-band flux and the typical B-V and U-B integrated colorgradients. A sophisticated analysis of the residuals of thesemeasurements from the curves was made to allow for the random andsystematic errors that effect such data. The result is a homogeneous setof total magnitudes BTA total colors(B-V)T and (U-B)T, and effective colors(B-V)e and (U-B)e for more than 3000 brightgalaxies in RC3.
| Galaxy properties in different environments. 1: The sample
This paper presents two galaxy samples, respectively in a high and in alow local density environments, that were generated from the SouthernSky Redshift Survey (SSRS) catalog using objective criteria. Apreliminary comparison of physical properties in these two samplesreveals that galaxies in high-density environments tend to be under ahigher starbursting activity, have a deficiency of the neutral hydrogencontent, present a higher fractional Seyfert population and a higherfraction of barred spirals as well. The present samples are intended tobe used in future spectroscopic observations for more detailedinvestigation.
| Mean morphological types of bright galaxies
The revised Hubble classifications provided in the Third ReferenceCatalogue of Bright Galaxies (RC3) are based on nine lists andcatalogues, both published and unpublished, from five observers. Thispaper describes the procedures that were used to combine theseclassifications into mean classifications including the family, variety,and stage. The best classifications in RC3 are based on large-scalephotographic images taken with 1.5-5 m class reflectors. However, mostof the types in RC3 are based on the small-scale prints, plates, andfilms of the first Palomar Sky Survey and the UK Schmidt IIIa-J SouthernSky Survey. The overlap between the different observers, samples alloweddetermination of the reliability of sky survey types and the effects ofdiameter and inclination on the accuracy of these types. We find thatfor a typical galaxy having isophotal diameter D25approximately = 2 min and inclined by approximately 50 degs, types Tfrom the sky surveys have a mean error (averaged over all of theobservers) of sigma(T) = 0.7 step on the numerical scale of the revisedHubble system. With the new database of classifications, we rederive theclassical relations between Hubble type and integrated colors, surfacebrightnesses, and hydrogen index (hydrogen flux to blue light ratio) fora large sample of galaxies. We also present a table of galaxies which weconsider to be representative examples of each type.
| H0 found by comparing linear diameters of M31 with similar field galaxies
The method of finding a stringent upper limit to H by comparing theknown linear size of M101 with similar field galaxies and requiring thatM101 not be the largest in a distance-limited sample is extended here toSab and Sb galaxies using M31 as the calibrator. In agreement with theearlier result using M101, the upper limit using M31 is H less than 85km/s/Mpc. Because M31 is the nearest Sb spiral, the most probable actualvalue of H is found by equating the known linear diameter of M31 withthe mean of a distance-limited sample of similar galaxies. Data on 60RSA galaxies that are similar to M31 give the most probable value as H =45 +/- 12 km/s/Mpc by this method.
| Complex galactic spiral patterns as a result of the superposition of hydrodynamic modes
A linear analysis of the stability of a thin nonself-gravitating gaseousdisk shows that, in the case of the continuous dependence of rotationvelocity on the radius, a second unstable mode may be excited in ittogether with the well-known centrifugal instability mode. A hypothesisis proposed to the effect that the branching arms of spiral galaxies, aswell as some other observed features of spiral patterns, may be causedby the simultaneous excitation and superposition of both modes.
| Southern Sky Redshift Survey - The catalog
The catalog of radial velocities for galaxies which comprise thediameter-limited sample of the Southern Sky Redshift Survey ispresented. It consolidates the data of observations carried out at theLas Campanas Observatory, Observatorio Nacional, and South AfricanAstronomical Observatory. The criteria used for the sample selection aredescribed, as well as the observational procedures and the techniqueutilized to obtain the final radial velocities. The intercomparisonbetween radial velocity measurements from different telescopes indicatesthat the final data base is fairly homogeneous with a typical error ofabout 40 km/s. The sample is at present 90 percent complete, and themissing galaxies are predominantly objects with very low surfacebrightness for which it is very difficult to obtain optical redshifts.
| Revised supernova rates in Shapley-Ames galaxies
Observations of 855 Shapley Ames galaxies made from November 1, 1980 toOctober 31, 1988, together with improved supernova luminosities, havebeen used to derive the frequency of supernovae of different types, andthe results are presented in tables. From a uniform database of 24supernovae discovered, the following SN rates are found, expressed in SNper century per 10 to the 10th L(B)(solar): SN Ia, 0.3; SN Ib, 0.3; andSN II, 1.0. The present data confirm the relatively high frequency of SNII in late-type galaxies that has been found by many previousinvestigators.
| Inhibition of star formation in SA galaxies
Only 4 percent of Sas in the Revised Shapley-Ames Catalog with B(T) lessthan 12 have an infrared luminosity greater than 10 to the 10th solar.This proportion is about one-sixth of the corresponding one for Sbs andScs. Although the infrared luminosities of most Sa galaxies aredominated by disk emission, the same trend appears in the incidence ofnuclear starbursts. IRAS measurements indicate that no more than threeSas out of the entire RSA sample of 166 galaxies have nuclear starburststhat cannot be associated with interactions or active nuclei. Plots of HI fluxes do not strongly correlate with infrared fluxes. Similarly, forat least the infrared selected Sas, the trend of IR flux with CO flux issimilar to that of later type spiral galaxies. This would imply thatmolecular cloud formation is inhibited in Sas, leading to the lack ofinfrared activity.
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