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 An Atlas of Hα and R Images and Radial Profiles of 29 Bright Isolated Spiral GalaxiesNarrowband Hα+[N II] and broadband R images and surface photometryare presented for a sample of 29 bright (MB<-18 mag)isolated S0-Scd galaxies within a distance of 48 Mpc. These galaxies areamong the most isolated nearby spiral galaxies of their Hubbleclassifications as determined from the Nearby Galaxies Catalog. A Comparison of Hα and Stellar Scale Lengths in Virgo and Field SpiralsThe scale lengths of the old stars and ionized gas distributions arecompared for similar samples of Virgo Cluster members and field spiralgalaxies via Hα and broad R-band surface photometry. While theR-band and Hα scale lengths are, on average, comparable for thecombined sample, we find significant differences between the field andcluster samples. While the Hα scale lengths of the field galaxiesare a factor of 1.14+/-0.07 longer, on average, than their R-band scalelengths, the Hα scale lengths of Virgo Cluster members are, onaverage, 20% smaller than their R-band scale lengths. Furthermore, inVirgo, the scale length ratios are correlated with the size of thestar-forming disk: galaxies with smaller overall Hα extents alsoshow steeper radial falloff of star formation activity. At the sametime, we find no strong trends in scale length ratio as a function ofother galaxy properties, including galaxy luminosity, inclination,morphological type, central R-band light concentration, or bar type. Ourresults for Hα emission are similar to other results for dustemission, suggesting that Hα and dust have similar distributions.The environmental dependence of the Hα scale length placesadditional constraints on the evolutionary process(es) that cause gasdepletion and a suppression of the star formation rate in clusters ofgalaxies. Star Formation in H I-selected Galaxies. II. H II Region PropertiesA sample of 69 galaxies with radial velocities less than 2500 kms-1 was selected from the H I Parkes All Sky Survey (HIPASS)to deduce details about star formation in nearby disk galaxies selectedwith no bias to optical surface brightness selection effects. Broadband(B and R) and narrowband (Hα) images were obtained for all ofthese objects. More than half of the sample galaxies are late-type,dwarf disks (mostly Sc and Sm galaxies). We have measured the propertiesof the H II regions on Hα continuum-subtracted images, using theHIIphot package developed by Thilker et al. All but one of the galaxiescontained at least one detectable H II region. Examination of theproperties of the H II regions in each galaxy revealed that thebrightest regions in higher surface brightness galaxies tend to be moreluminous than those in lower surface brightness galaxies. A higherfraction (referred to as the diffuse fraction) of the Hα emissionfrom lower surface brightness galaxies comes from diffuse ionized gas. HII region luminosity functions (LFs) co-added according to surfacebrightness show that the shapes of the LFs for the lowest surfacebrightness galaxies are different from those for typical spiralgalaxies. This discrepancy could be caused by the lowest surfacebrightness galaxies having somewhat episodic star formation or by themforming a relatively larger fraction of their stars outside of dense,massive molecular clouds. In general, the results imply that theconditions under which star formation occurs in lower surface brightnessgalaxies are different than in more typical, higher surface brightnessspiral galaxies. Star Formation in H I-Selected Galaxies. I. Sample CharacteristicsA sample of 69 galaxies with radial velocities of less than 2500 kms-1 was selected from the H I Parkes All-Sky Survey (HIPASS)and imaged in broadband B and R and narrowband Hα, to deducedetails about star formation in nearby disk galaxies while avoidingsurface brightness selection effects. The sample is dominated bylate-type, dwarf disks (mostly Sc and Sm galaxies) with exponential diskscale lengths of ~1-5 kpc. The HIPASS galaxies, on average, have lowerstar formation rates (SFRs), are bluer, and have lower surfacebrightness than an optically selected sample. H II regions were detectedin all but one of the galaxies. Many galaxies had as few as two to fiveH II regions. The galaxies' Hα equivalent widths, colors, and SFRsper unit of H I mass are best explained by young mean ages (~3-5 Gyr,according to Schmidt-law models) with star formation histories in whichthe SFRs were higher in the past. Comparison of the surface brightnesscoverage of the HIPASS galaxies with that of an optically selectedsample shows that such a sample may miss ~10% of the local galaxy numberdensity and could possibly miss as much as 3%-4% of the SFR density. Theamount lower surface brightness galaxies contribute to the totalluminosity density may be insignificant, but this conclusion is somewhatdependent on how the fluxes of these objects are determined. Double-barred galaxies. I. A catalog of barred galaxies with stellar secondary bars and inner disksI present a catalog of 67 barred galaxies which contain distinct,elliptical stellar structures inside their bars. Fifty of these aredouble-barred galaxies: a small-scale, inner or secondary bar isembedded within a large-scale, outer or primary bar. I providehomogenized measurements of the sizes, ellipticities, and orientationsof both inner and outer bars, along with global parameters for thegalaxies. The other 17 are classified as inner-disk galaxies, where alarge-scale bar harbors an inner elliptical structure which is alignedwith the galaxy's outer disk. Four of the double-barred galaxies alsopossess inner disks, located in between the inner and outer bars. Whilethe inner-disk classification is ad-hoc - and undoubtedly includes someinner bars with chance alignments (five such probable cases areidentified) - there is good evidence that inner disks form astatistically distinct population, and that at least some are indeeddisks rather than bars. In addition, I list 36 galaxies which may bedouble-barred, but for which current observations are ambiguous orincomplete, and another 23 galaxies which have been previously suggestedas potentially being double-barred, but which are probably not. Falsedouble-bar identifications are usually due to features such as nuclearrings and spirals being misclassified as bars; I provide someillustrated examples of how this can happen.A detailed statistical analysis of the general population of double-barand inner-disk galaxies, as represented by this catalog, will bepresented in a companion paper.Tables \ref{tab:measured} and \ref{tab:deproj} are only available inelectronic form at http://www.edpsciences.org On the 3D dynamics and morphology of inner ringsWe argue that inner rings in barred spiral galaxies are associated withspecific 2D and 3D families of periodic orbits located just beyond theend of the bar. These are families located between the inner radialultraharmonic 4:1 resonance and corotation. They are found in the upperpart of a type-2 gap of the x1 characteristic, and can account for theobserved ring morphologies without any help from families of thex1-tree. Due to the evolution of the stability of all these families,the ring shapes that are favoured are mainly ovals, as well as polygonswith corners' on the minor axis, on the sides of the bar. On the otherhand, pentagonal rings, or rings of the NGC 7020-type hexagon, should beless probable. The orbits that make the rings belong in their vastmajority to 3D families of periodic orbits and orbits trapped aroundthem. A new catalogue of ISM content of normal galaxiesWe have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of normality''. Thedefinition of a normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5 An H I/Optical Atlas of Isolated GalaxiesWe present an H I and optical survey of 41 extremely isolated galaxiesin an attempt to search for the gaseous remnants of the galaxy formationprocess, predicted to exist by hierarchical models of galaxy formation.By observing extremely isolated, quiescent, nonpeculiar galaxies weminimize the chances that any extragalactic H I found will be anothergalaxy, tidal debris, or ejecta from a galactic fountain or superwind.We have obtained new and archival data from the VLA and ATCA in a searchfor H I clouds down to MHI~107 Msolararound these galaxies. We found 13 H I-rich companions around 10 of the41 galaxies surveyed. Optical imaging finds spatially coincident starsassociated with all 13 companions. We find that the isolated galaxieshave properties fairly similar to those of field galaxies, while thecompanions are similar to dwarf irregular galaxies. The presence ofstars in all 13 companions suggests that H I clouds without starsdiscovered by other authors around field galaxies are not primordial andmost likely have either a tidal or ejecta origin. A Catalog of H I-Selected Galaxies from the South Celestial Cap Region of SkyThe first deep catalog of the H I Parkes All Sky Survey (HIPASS) ispresented, covering the south celestial cap (SCC) region. The SCC areais ~2400 deg2 and covers δ<-62°. The average rmsnoise for the survey is 13 mJy beam-1. Five hundredthirty-six galaxies have been cataloged according to their neutralhydrogen content, including 114 galaxies that have no previous catalogedoptical counterpart. This is the largest sample of galaxies from a blindH I survey to date. Most galaxies in optically unobscured regions of skyhave a visible optical counterpart; however, there is a small populationof low-velocity H I clouds without visible optical counterparts whoseorigins and significance are unclear. The rms accuracy of the HIPASSpositions is found to be 1.9′. The H I mass range of galaxiesdetected is from ~106 to ~1011 Msolar.There are a large number of late-type spiral galaxies in the SCC sample(66%), compared with 30% for optically selected galaxies from the sameregion in the NASA Extragalactic Database. The average ratio of H I massto B luminosity of the sample increases according to optical type, from1.8 Msolar/Lsolar for early types to 3.2Msolar/Lsolar for late-type galaxies. The HI-detected galaxies tend to follow the large-scale structure traced bygalaxies found in optical surveys. From the number of galaxies detectedin this region of sky, we predict the full HIPASS catalog will contain~5000 galaxies, to a peak flux density limit of ~39 mJy (3 σ),although this may be a conservative estimate as two large voids arepresent in the region. The H I mass function for this catalog ispresented in a subsequent paper. Analysis of the distribution of HII regions in external galaxies. IV. The new galaxy sample. Position and inclination anglesWe have compiled a new sample of galaxies with published catalogs of HIIregion coordinates. This sample, together with the former catalog ofGarcía-Gómez & Athanassoula (\cite{gga1}), will formthe basis for subsequent studies of the spiral structure in discgalaxies. In this paper we address the problem of the deprojection ofthe galaxy images. For this purpose we use two deprojection methodsbased on the HII region distribution and compare the results with thevalues found in the literature using other deprojection methods. Takinginto account the results of all the methods, we propose optimum valuesfor the position and inclination angles of all the galaxies in oursample. Tables 2 and 3 are only available in electronic form athttp://www.edpsciences.org A Dust-penetrated Classification Scheme for Bars as Inferred from Their Gravitational Force FieldsThe division of galaxies into barred'' (SB) and normal'' (S) spiralsis a fundamental aspect of the Hubble galaxy classification system. Thistuning fork'' view was revised by de Vaucouleurs, whose classificationvolume recognized apparent bar strength'' (SA, SAB, SB) as acontinuous property of galaxies called the family.'' However, the SA,SAB, and SB families are purely visual judgments that can have littlebearing on the actual bar strength in a given galaxy. Until veryrecently, published bar judgments were based exclusively on blue lightimages, where internal extinction or star formation can either mask abar completely or give the false impression of a bar in a nonbarredgalaxy. Near-infrared camera arrays, which principally trace the oldstellar population in both normal and barred galaxies, now facilitate aquantification of bar strength in terms of their gravitationalpotentials and force fields. In this paper, we show that the maximumvalue, Qb, of the ratio of the tangential force to the meanaxisymmetric radial force in a barred disk galaxy is a quantitativemeasure of the strength of a bar. Qb does not measure barellipticity or bar shape but rather depends on the actual forcing due tothe bar embedded in its disk. We show that a wide range of true barstrengths characterizes the category SB,'' while the de Vaucouleurscategory SAB'' corresponds to a narrower range of bar strengths. Wepresent Qb values for 36 galaxies, and we incorporate our barclasses into a dust-penetrated classification system for spiralgalaxies. Ultraviolet Signposts of Resonant Dynamics in the Starburst-ringed SAB Galaxy M94 (NGC 4736)The dynamic orchestration of star-birth activity in the starburst-ringedgalaxy M94 (NGC 4736) is investigated using images from the UltravioletImaging Telescope (UIT; far-ultraviolet [FUV] band), Hubble SpaceTelescope (HST; near-ultraviolet [NUV] band), Kitt Peak 0.9 m telescope(Hα, R, and I bands), and Palomar 5 m telescope (B band), alongwith spectra from the International Ultraviolet Explorer (IUE) and theLick 1 m telescope. The wide-field UIT image shows FUV emission from (1)an elongated nucleus, (2) a diffuse inner disk, where Hα isobserved in absorption, (3) a bright inner ring of H II regions at theperimeter of the inner disk (R=48"=1.1 kpc), and (4) two 500 pc sizeknots of hot stars exterior to the ring on diametrically opposite sidesof the nucleus (R=130"=2.9 kpc). The HST Faint Object Camera imageresolves the NUV emission from the nuclear region into a bright core anda faint 20" long minibar'' at a position angle of 30°. Optical andIUE spectroscopy of the nucleus and diffuse inner disk indicates a~107-108 yr old stellar population from low-levelstar-birth activity blended with some LINER activity. Analysis of theHα-, FUV-, NUV-, B-, R-, and I-band emissions, along with otherobserved tracers of stars and gas in M94, indicates that most of thestar formation is being orchestrated via ring-bar dynamics, involvingthe nuclear minibar, inner ring, oval disk, and outer ring. The innerstarburst ring and bisymmetric knots at intermediate radius, inparticular, argue for bar-mediated resonances as the primary drivers ofevolution in M94 at the present epoch. Similar processes may begoverning the evolution of the core-dominated'' galaxies that havebeen observed at high redshift. The gravitationally lensed `PretzelGalaxy'' (0024+1654) at a redshift of ~1.5 provides an importantprecedent in this regard. Near-infrared probing of embedded structures in starburst and Seyfert galaxiesSurface photometry in the J and K' bands of 15 southernSeyfert or starburst galaxies is presented. The detailed centralmorphology and structural properties of these objects were analyzed byfitting ellipses to isophotes. New central peculiar structures have beenidentified like, for instance, three double-barred systems (ESO215-G031; ESO 320-G030; ESO 443-G017), one object with a nested nuclearspiral structure at the center of a primary bar (NGC 5135), one objectwith a nuclear bar without evidence of a large-scale bar (NGC 4941), andone galaxy with a likely dissolved secondary bar within a primary one(ESO 508-G005). The J-K' radial profile proved to bereasonably well linked with the presence of a starburst, but not withthe Seyfert activity. For significant starbursts, the centralJ-K' value is 0.3 - 1.5 magnitude larger than the disc one.Based on observations collected at the European Southern Observatory, LaSilla, Chile (ESO programme 59.A--0773). Resonance Rings and Galaxy MorphologyRings of star formation are a common phenomenon of early to intermediateHubble type disk galaxies. Most rings form by gas accumulation atresonances, usually under the continuous action of gravity torques froma bar pattern, but sometimes in response to a mild tidal interactionwith a nearby companion. In either case, a resonance is a very specialplace in any galaxy where star formation can be enhanced and may proceedeither as a starburst or continuously over a long time period. Thisarticle describes the characteristic morphologies of bar-driven andtidally-driven resonance rings. Total magnitude, radius, colour indices, colour gradients and photometric type of galaxiesWe 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. The Distribution and Properties of H II Regions in Early-to-Intermediate Hubble Type Ringed GalaxiesThis paper presents a study of the H II regions in 32 ringed andpseudo-ringed galaxies having Hubble types in the range S0 + to Sc. Theobjective is to illustrate the distributions of H II regions in classicexamples of ringed galaxies and to relate the observed properties toresonance theory. The sample is selected from the Catalog of SouthernRinged Galaxies and includes examples covering a range of ring andgalaxy morphological properties. We find that the distribution ofHα luminosity around inner rings is sensitive to the intrinsicshape of the rings. Extremely oval inner rings show a greaterconcentration of H II regions near the intrinsic ring major axiscompared to more circular rings. Nuclear rings are present in several ofthe sample galaxies and show a range of morphological properties, from adouble nuclear ring in NGC 1317 to an irregular feature in NGC 1433. Wefind also that in galaxies in which an R_1_ outer ring is prominent inthe continuum image, the H II regions follow an R^'^_2_ morphology. Inseveral cases, the observed distribution of H II regions stronglysupports the idea that the rings are linked to specific orbitalresonances with the bar. H II region luminosity functions have beenderived for all of the sample galaxies. The functions can be representedby power laws whose exponents are very similar to those found fornonringed galaxies. In a few cases, a luminous nuclear ring produces asecondary peak in the luminosity function. One galaxy shows a break inthe luminosity function similar to that observed in other galaxies byKennicutt, Edgar, & Hodge. The most unusual Hα distribution inthe sample was found in the large outer-ringed galaxy NGC 1291. Theprimary bar, lens, and secondary bar regions of this SO/a galaxy arefilled with a wispy pattern of ionized gas filaments very reminiscent ofwhat is seen in the bulge of M31. Disc galaxies with multiple triaxial structures. II. JHK surface photometry and numerical simulations.We present detailed JHK surface photometry with ellipse fits of 13galaxies selected from previous optical observations as likelycandidates for having a secondary bar or a triaxial bulge within theprimary bar. We have found 7 double-barred galaxies, 3 double-barredgalaxies with an additional intermediate structure with twistedisophotes, and 3 galaxies with a bar and central twisted isophotes. Aglobal analysis of the structural parameter characteristics in the I-and K-bands is presented. Various numerical models of galaxies with barswithin bars are also analysed using the ellipse fitting technique andcompared to the observations. A thorough review of the possiblehypotheses able to explain this phenomenon is given with emphasis on themost likely ones. The Catalog of Southern Ringed GalaxiesThe 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. Integrated photoelectric magnitudes and color indices of bright galaxies in the Johnson UBV systemThe 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. Disc galaxies with multiple triaxial structures. I. BVRI and Hα surface photometry.We present a BVRI survey of 36 galaxies selected as candidates forhaving a misaligned secondary bar or a triaxial bulge inside the primarybar. Fifteen galaxies have also been observed in Hα. A positivedetection of more than one triaxial structure has been found in 22galaxies shared out as follows: 13 double-barred galaxies, 3triple-barred galaxies, 3 double-barred galaxies with an additionalstructure with twisted isophotes, and 3 galaxies with a bar and astructure with twisted isophotes. Triaxial deformation(s) have beenfound in 6 galaxies classified as unbarred in RC3. The number of Seyfertnuclei amongst double-barred systems is high (6 over 13). Photometrically distinct nuclei in elliptical and early-type disks galaxies.Not Available Pattern speed domains in ringed disk galaxies from observational and simulational databasesNew test-particle simulations have been carried out to learn more aboutthe secular evolution and morphology of the gaseous and stellardistributions in barred galaxies. We verify the previous results of M.P. Schwarz that gas clouds will tend to collect into ring-like patternsnear major orbit resonances, owing to gravity torques. However, weimprove on these results in several ways. Firstly, we use more gasclouds (10000 vs 2000) than Schwarz and track individual clouds todetermine when they collide, rather than using a collision box as didSchwarz. Secondly, besides Schwarz's isochrone rotation curve, we alsouse a flat rotation curve. Thirdly, we consider more bar pattern speedsand strengths than did Schwarz. Finally, unlike Schwarz and othersimulators, we have a large database of images and color index maps ofnearly 140 ringed galaxies that can be compared to the simulations toevaluate their significance. We confirm the two types of outer Lindbladresonance rings that Schwarz discovered, but find that their existenceis not due so much to the initial density distribution of gas clouds asto pattern speed and the time interval since the bar potential wasimposed. The simulations and the images lead us to suggest that we candivide barred galaxies according to the resonances which the bar patternspeed and rotation curve allow in the disk. We illustrate specificgalaxies that we believe belong to fast, medium, and slow bar patternspeed 'domains' and match them to particular simulation frames. We alsodiscuss alternative hypotheses in which the pattern speed is such thatall resonances are present but the gas has been depleted or wasdistributed differently in various galaxies to produce the threeclassification domains. Mean morphological types of bright galaxiesThe 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. Metric characteristics of nuclear rings and related features in spiral galaxiesThe metric properties of nuclear rings, pseudorings, spirals, and barsare discussed in the context of resonance theory and are used to gaugethe range of sizes for such features. The nuclear rings and pseudoringsof strongly barred SB and SAB galaxies have a wide range in lineardiameter; the mean diameter is about 1.1 kpc for a sample of 20 objects.We suggest that there are clear analogs of the nuclear rings of stronglybarred spirals in both weakly barred (SAB) and nonbarred (SA) spirals.The size ratios of nuclear rings with respect to outer rings andpseudorings, as well as morphological characteristics, are bestexplained if outer rings and pseudorings are linked to the outerLindblad resonance, and nuclear rings, pseudorings, and spirals arelinked to the inner Lindblad resonance. Nuclear bars are oftenassociated with nuclear rings and spirals, but also can existindependently of such features. We present a list of 13 double-barredgalaxies and discuss the significance of the phase angle of the nuclearbar with respect to the primary bar. On the transparency of the inner regions of early-type spiral galaxiesSurface photometry of 17 inclined Sa-Sb galaxies with prominent bulgesfrom the ESO-LV Data Base has been analyzed with the aim of detectingthe possible effects of a hypothetical absorbing layer bisecting thecentral bulge. Our method is based on looking for an asymmetry betweenthe photometric profiles of the two semi-minor axes, and iscomplementary to the surface brightness inclination test which, forearly spirals with bright bulges, is confused by the very presence ofthese bulges. None of the galaxies in our sample shows evidence of acontinuous, near-opaque layer reaching the very center. Our conclusionsare strengthened by two additional, well-studied objects, M 31 and M104; our results indicate a lower obscuration in the central regions ofearly spirals with strong bulges compared to later types, and contributeto discriminate between competing models of light obscuration withingalactic disks. Southern Sky Redshift Survey - The catalogThe 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. Southern Galaxy Catalogue.Not Available The dependence on distance and redshift of the velocity vectors of the sun, the Galaxy, and the Local Group with respect to different extragalactic frames of referenceThe solar apex S is confirmed to move steadily from S-prime toS-asterisk, when the mean redshift of the reference frame increases fromsmall to large values, on the basis of a new analysis of the solarmotion and Hubble ratio. Most of the change takes place in the 0-4000km/sec interval. The velocity vectors increase steadily, and thedirections of the apexes drift progressively as the mean distance orredshift of the reference frame increases. The frame of referencedefined by galaxies at z greater than 0.01 is essentially at rest withrespect to background radiation, suggesting that any intrinsic dipolaranisotropy of the background radiation is probably less than about0.0001. Objectively determined pitch angles of spiral galaxies in the light of competing theories concerning the spiral structureSubjective criteria play a more important part in studies of galaxiesthan in other areas of astrophysics. Problems arise in connection withthe determination of the pitch angle. This parameter represents acrucial quantity for each theory of the spiral structure. Adetermination of the pitch angle on the basis of a procedure which is asobjective as possible can, therefore, make a contribution towards adecision with respect to the competing theories of the spiral structure.The present investigation is concerned with such a determination. Thedigitizing of galaxy images on the Schmidt plates of the ESO(B) Surveyis discussed, and an objective determination of the pitch angle isdescribed. The two competing theories regarding spiral formation,including the density wave theory reported by Lin et al. (1969) and theconcept of stochastic self propagating star formation considered byGerola and Seiden (1978), are evaluated on the basis of the obtainedpitch angle data. It is found that the agreement between theory andempirical data is significantly more satisfactory in the case of theconcept of stochastic star formation. Inner ring structures in galaxies as distance indicators. III - Distances to 453 spiral and lenticular galaxiesAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983ApJS...51..149B&db_key=AST
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