Home     Getting Started     To Survive in the Universe    
Inhabited Sky
    News@Sky     Astro Photo     The Collection     Forum     Blog New!     FAQ     Press     Login  

NGC 4696C



Upload your image

DSS Images   Other Images

Related articles

Structure and kinematics of edge-on galaxy discs - V. The dynamics of stellar discs
In earlier papers in this series we determined the intrinsic stellardisc kinematics of 15 intermediate- to late-type edge-on spiral galaxiesusing a dynamical modelling technique. The sample covers a substantialrange in maximum rotation velocity and deprojected face-on surfacebrightness, and contains seven spirals with either a boxy orpeanut-shaped bulge. Here we discuss the structural, kinematical anddynamical properties. From the photometry we find that intrinsicallymore flattened discs tend to have a lower face-on central surfacebrightness and a larger dynamical mass-to-light ratio. This observationsuggests that, at a constant maximum rotational velocity, lower surfacebrightness discs have smaller vertical stellar velocity dispersions.Although the individual uncertainties are large, we find from thedynamical modelling that at least 12 discs are submaximal. The averagedisc contributes 53 +/- 4 per cent to the observed rotation at 2.2 discscalelengths (hR), with a 1σ scatter of 15 per cent.This percentage becomes somewhat lower when effects of finite discflattening and gravity by the dark halo and the gas are taken intoaccount. Since boxy and peanut-shaped bulges are probably associatedwith bars, the result suggests that at 2.2hR the submaximalnature of discs is independent of barredness. The possibility remainsthat very high surface brightness discs are maximal, as these discs areunderrepresented in our sample. We confirm that the radial stellar discvelocity dispersion is related to the galaxy maximum rotationalvelocity. The scatter in this σ versus vmax relationappears to correlate with the disc flattening, face-on central surfacebrightness and dynamical mass-to-light ratio. Low surface brightnessdiscs tend to be more flattened and have smaller stellar velocitydispersions. The findings are consistent with the observed correlationbetween disc flattening and dynamical mass-to-light ratio and cangenerally be reproduced by the simple collapse theory for disc galaxyformation. Finally, the disc mass Tully-Fisher relation is offset fromthe maximum-disc scaled stellar mass Tully-Fisher relation of the UrsaMajor cluster. This offset, -0.3 dex in mass, is naturally explained ifthe discs of the Ursa Major cluster spirals are submaximal.

Mass Models for Spiral Galaxies from Two-dimensional Velocity Maps
We model the mass distributions of 40 high surface brightness spiralgalaxies inside their optical radii, deriving parameters of mass modelsby matching the predicted velocities to observed velocity maps. We useconstant mass-to-light disk and bulge models, and we have tried fitswith no halo and with three different halo density profiles. The datarequire a halo in most, but not all, cases, while in others the best fitoccurs with negligible mass in the luminous component, which we regardas unphysical. All three adopted halo profiles lead to fits of about thesame quality, and our data therefore do not constrain the functionalform of the halo profile. The halo parameters display large degeneraciesfor two of the three adopted halo functions, but the separate luminousand dark masses are better constrained. However, the fitted disk andhalo masses vary substantially between the adopted halo models,indicating that even high-quality two-dimensional optical velocity mapsdo not provide significant constraints on the dark matter content of agalaxy. We demonstrate that data from long-slit observations are likelyto provide still weaker constraints. We conclude that additionalinformation is needed in order to constrain the separate disk and halomasses in a galaxy.

Flattening and truncation of stellar discs in edge-on spiral galaxies
We analyse the global structure of the old stellar discs in 34 edge-onspiral galaxies. The radial and vertical exponential scale parameters ofthe discs are obtained by applying an improved two-dimensionaldecomposition technique to our I-band photometry. We find a clearincrease in the disc scaleheight with maximum rotational velocity, inaccordance with observations of the stellar velocity dispersions ingalaxy discs. The range and maximum of the intrinsic flattening of thedisc light seem to increase with both maximum rotational velocity andtotal HI mass. We use the disc flattening to estimate the disccontribution to the maximum rotational velocity, resulting in an averageof 57 +/- 22 per cent. The disc light distributions are furtherinvestigated for the presence of radial truncations. We find that theradial light distributions of at least 20 spirals are truncated,corresponding to 60 per cent of the sample. For small scalelengthspirals, which are the most numerous in the local Universe, the resultssuggest that the average ratio of disc truncation radius to discscalelength is at least four.

Tracing the vertical composition of disc galaxies through colour gradients
Optical observations of a statistically complete sample of edge-ondisc-dominated galaxies are used to study the intrinsic vertical colourgradients in the galactic discs, in order to constrain the effects ofpopulation gradients, residual dust extinction and gradients in themetal abundance of the galaxies. For the majority of our samplegalaxies, the colours and colour gradients in the range1.0hz<=|z|<=3.0hz most likely reflect theintrinsic galactic properties (where hz is the verticalscaleheight). It appears that the intrinsic vertical colour gradientsare either non-existent, or small and relatively constant as a functionof position along the major axes of the galaxies. On average, theearlier-type galaxies exhibit smaller vertical (B-I) gradients than thelater types; our results are consistent with the absence of any verticalcolour gradient in the discs of the early-type sample galaxies. In mostgalaxies small-scale variations in the magnitude and even the directionof the vertical gradient are observed: at larger galactocentricdistances they generally display redder colours with increasing zheight, whereas the opposite is often observed in and near the galacticcentres. For a significant fraction of our sample galaxies anothermechanism in addition to the effects of stellar population gradients isrequired to explain the magnitude of the observed gradients. Thenon-zero colour gradients in a significant fraction of our samplegalaxies are likely to be (at least) partially due to residual dustextinction at these z heights, as is also evidenced from the sometimessignificant differences between the vertical colour gradients measuredon either side of the galactic planes. We suggest that initial verticalmetallicity gradients, if any, have probably not been accentuated byaccretion or merging events over the lifetimes of our sample galaxies.On the other hand, they may have weakened any existing verticalmetallicity gradients, although they also may have left the existingcorrelations unchanged.

Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.

Maximum Disk Mass Models for Spiral Galaxies
We present axisymmetric maximum disk mass models for a sample of 74spiral galaxies taken from the southern sky Fabry-Perot Tully-Fishersurvey by Schommer et al. The sample contains galaxies spanning a largerange of morphologies and having rotation widths from 180 km s-1 to 680 km s -1. For each galaxy we have an I-bandimage and a two-dimensional Hα velocity field. We decompose thedisk and bulge by fitting models directly to the I-band image. Thismethod utilizes both the distinct surface brightness profiles and shapesof the projected disk and bulge in the galaxy images. The luminosityprofiles and rotation curves are derived using consistent centers,position angles, and inclinations derived from the photometry andvelocity maps. The distribution of mass is modeled as a sum of disk andbulge components with distinct, constant mass-to-light ratios. No darkmatter halo is included in the fits. The models reproduce the overallstructure of the rotation curves in the majority of galaxies, providinggood fits to galaxies that exhibit pronounced structural differences intheir surface brightness profiles. Of galaxies for which the rotationcurve is measured to R23.5 or beyond 75% are well fitted by amass-traces-light model for the entire region within R23.5.The models for about 20% of the galaxies do not fit well; the failure ofmost of these models is traced directly to nonaxisymmetric structures,primarily bars but also strong spiral arms. The median I-band M/L of thedisk plus bulge is 2.4+/-0.9 h75 in solar units, consistentwith normal stellar populations. These results require either that themass of dark matter within the optical disk of spiral galaxies is smallor that its distribution is very precisely coupled to the distributionof luminous matter.

Galaxy coordinates. II. Accurate equatorial coordinates for 17298 galaxies
Using images of the Digitized Sky Survey we measured coodinates for17298 galaxies having poorly defined coordinates. As a control, wemeasured with the same method 1522 galaxies having accurate coordinates.The comparison with our own measurements shows that the accuracy of themethod is about 6 arcsec on each axis (RA and DEC).

The global structure of galactic discs
A statistical study of global galaxy parameters can help to improve ourunderstanding of galaxy formation processes. In this paper we presentthe analysis of global galaxy parameters based on optical andnear-infrared observations of a large sample of edge-on disc galaxies.We found a correlation between the ratio of the radial to vertical scaleparameter and galaxy type: galaxies become systematically thinner whengoing from type S0 to type Sc, whereas the distribution seems to leveloff for later types. The observed scalelength ratios (and thus theradial colour gradients) largely represent the dust content of thegalaxies. On average, the colour gradients indicated by the scalelengthratios increase from type Sa to at least type Sc. For galaxy types laterthan Sc, the average colour gradient seems to decrease again. Thedistribution of K-band (edge-on) disc central surface brightnesses israther flat, although with a large scatter. However, the latest-typesample galaxies (T>6) show an indication that their average disccentral surface brightnesses may be fainter than those of the earliertypes. This effect is probably not the result of dust extinction.

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.

A catalogue of spatially resolved kinematics of galaxies: Bibliography
We present a catalogue of galaxies for which spatially resolved data ontheir internal kinematics have been published; there is no a priorirestriction regarding their morphological type. The catalogue lists thereferences to the articles where the data are published, as well as acoded description of these data: observed emission or absorption lines,velocity or velocity dispersion, radial profile or 2D field, positionangle. Tables 1, 2, and 3 are proposed in electronic form only, and areavailable from the CDS, via anonymous ftp to cdsarc.u-strasbg.fr (to130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

Optical Rotation Curves and Linewidths for Tully-Fisher Applications
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.2402C&db_key=AST

The I band Tully-Fisher relation for cluster galaxies: data presentation.
Observational parameters which can be used for redshift-independentdistance determination using the Tully-Fisher (TF) technique are givenfor \ntot spiral galaxies in the fields of 24 clusters or groups. I bandphotometry for the full sample was either obtained by us or compiledfrom published literature. Rotational velocities are derived either from21 cm spectra or optical emission line long-slit spectra, and convertedto a homogeneous scale. In addition to presenting the data, a discussionof the various sources of error on TF parameters is introduced, and thecriteria for the assignment of membership to each cluster are given.

Studies of the Centaurus cluster. I. A catalogue of galaxies in the central region of the Centaurus cluster
The central region of the Centaurus cluster was surveyed on a film copyof a high-resolution photographic plate taken with the 100-inch du PontLas Campanas telescope. From visual inspection of the film, a largenumber of cluster galaxy candidates were identified down to a limitingmagnitude of 21.5 in B. Between cluster members and background objectswere distinguished by applying morphological criteria established inprevious studies of the Virgo and Fornax clusters. Following themorphological classification of each member, the images of all 296cluster galaxies on a SRC deep-blue sky survey plate were digitized,processed and analysed with programs written in the image processingpackage MIDAS. Aperture photometry yielded growth curves and totalinstrumental magnitudes of the galaxies. The magnitudes were calibratedwith independent photometric data and subsequently transformed intostandard B-magnitudes. We further established a set of structureparameters for each cluster galaxy: effective surface brightness,effective radius, central exponential surface brightness, and scalelength. For the ellipticals we additionally determined the shapeparameters of the light profiles. The catalogue (CCC) is only availablein electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr( or via http://cdsweb.u-strasbg.fr/Abstract.html

The z-structure of disk galaxies towards the galaxy planes
We present a detailed study of a statistically complete sample of highlyinclined disk galaxies in the near-infrared K' band. Since the K'-bandlight is relatively insensitive to contamination by galactic dust, wehave been able to follow the vertical light distributions all the waydown to the galaxy planes. The mean levels for the sharpness of theK'-band luminosity peaks indicate that the vertical luminositydistributions are more peaked than expected for the intermediate sech(z)distribution, but rounder than exponential. After fitting a generalizedfamily of fitting functions characterised by an exponent 2/n (n = inftyfor exponential, n = 2 for sech and n = 1 for sech(2) ; van der Kruit1988) we find that the mean value for 2/n in the K' band equals<2/n>_{K'} = 0.538, sigma_ {K'} = 0.198. Since projection of notcompletely edge-on galaxies onto the plane of the sky causes verticalluminosity profiles to become rounder, we have performed simulationsthat show that it is possible that all our galaxies can haveintrinsically exponential vertical surface brightness distributions. Wefind that the profile shape is independent of galaxy type, and varieslittle with position along the major axis. The fact that we observe thisin all our sample galaxies indicates that the formation process of thegalaxy disks perpendicular to the galaxy planes is a process intrinsicto the disks themselves. Based on observations obtained at the EuropeanSouthern Observatory, La Silla, Chile

The shape of galaxy disks: how the scale height increases with galactocentric distance.
We present the results of a detailed study of vertical surfacebrightness profiles of edge-on disk galaxies. Although the exponentialdisk scale height is constant to first order approximation, we show thatfor the large majority of galaxies in our sample, the scale heightincreases with distance along the major axis. The effect is strongestfor early-type galaxies, where the increase of the scale height can beas much as a factor of 1.5 per scalelength, but is almost 0 for thelatest-type galaxies. The effect can be understood if early-type diskgalaxies have thick disks with both scale lengths and scale heightslarger than those of the dominant disk component. Its origin appears tobe linked to the processes that have formed the thick disk.

Parameters of 2447 Southern Spiral Galaxies for Use in the Tully-Fisher Relation
I-band luminosities, rotational velocities, and redshifts of 1092 spiralgalaxies have been measured by CCD photometry and Hα spectroscopyusing the 1 m and 2.3 m telescopes at Siding Spring Observatory,respectively. The results are tabulated. Luminosity profiles andHα rotation curves are given for the galaxies. When these resultsare combined with similar data for 1355 spiral galaxies publishedpreviously (Mathewson, Ford, & Buchhorn, hereafter Paper I), itprovides a large, uniform, and unique data set with which to measure,via the Tully-Fisher relation, the peculiar velocities of galaxies inthe local universe to a distance of 11,000 km s^-1^ (Mathewson &Ford). Taking advantage of the opportunity for publishing this data inmachine-readable form, in the CD-ROM, we have also included similar datafor the 1355 galaxies in Paper I.

Rotation Curves of 967 Spiral Galaxies
We present the rotation curves of 967 southern spiral galaxies, obtainedby deprojecting and folding the raw Hα data originally publishedby Mathewson, Ford, & Buchhorn (1992). For 900 objects, we alsopresent, in figures and tables, the rotation curves smoothed on scalescorresponding to 5%-20% of the optical size; of these, 80 meet objectiveexcellence criteria and are suitable for individual detailed massmodeling, while 820, individually less compelling mainly because of themoderate statistics and/or limited extension, are suitable forstatistical studies. The remaining 67 curves suffer from severeasymmetries, small statistics, and large internal scatter that maylargely limit their use in galaxy structure studies. The deprojectedfolded curves, the smoothed curves, and various related quantities areavailable via anonymous ftp at galileo.sissa.it in the directory/users/ftp/pub/psrot.

Measuring galaxy distances from optical rotation curves
A distance indicator for spiral galaxies is described using detailedrotation curves derived from H-alpha velocities fields and I band CCDphotometry. Two-dimensional velocity fields are obtained with an imagingFabry-Perot spectrometer, with a velocity accuracy of better than 10km/s. Rotation curves, based upon rotating disks geometries, are fit tothese velocity fields. The I band photometry profiles, and theindividual rotation curves for 75 galaxies are presented. The extractedcircular velocity is combined with I band magnitudes to form aTully-Fisher relation, with a scatter of about 0.25-0.3 mag. As anexample, the data are used to derive the relative distance modulusbetween the Hydra and Antlia clusters, which yields a peculiar motionfor Antlia of 900 +/- 100 km/s. This confirms previous detections oflarge peculiar motions in the Hydra-Centaurus region.

General study of group membership. II - Determination of nearby groups
We present a whole sky catalog of nearby groups of galaxies taken fromthe Lyon-Meudon Extragalactic Database. From the 78,000 objects in thedatabase, we extracted a sample of 6392 galaxies, complete up to thelimiting apparent magnitude B0 = 14.0. Moreover, in order to considersolely the galaxies of the local universe, all the selected galaxieshave a known recession velocity smaller than 5500 km/s. Two methods wereused in group construction: a Huchra-Geller (1982) derived percolationmethod and a Tully (1980) derived hierarchical method. Each method gaveus one catalog. These were then compared and synthesized to obtain asingle catalog containing the most reliable groups. There are 485 groupsof a least three members in the final catalog.

A southern sky survey of the peculiar velocities of 1355 spiral galaxies
The paper presents data from photometric and spectroscopic observationsof 1355 southern spiral galaxies and uses them to determine theirdistances and peculiar velocities via the Tully-Fisher (TF) relation.I-band CCD surface photometry was carried out using the 1-m and 3.9-mtelescopes at Siding Spring Observatory. H-alpha rotation curves for 965galaxies and 551 H I profiles are presented. The physical parameters,photometric and velocity data, distances, and peculiar velocities of thegalaxies are presented in tabular form. The mean distance, systemicvelocity, and average peculiar velocity of 24 clusters in the sample aregiven. TF diagrams are presented for each cluster.

Peculiar velocities of field spiral galaxies near and beyond the Great Attractor
Peculiar velocities for a sample of 48 late-type spiral galaxies whichare located in the general vicinity of the Great Attractor (GA) aremeasured. Relative distances are derived using the I-band Tully-Fisherrelation. The existence of positive velocity residuals, with amplitude500-2000 km/s in the Hydra-Centaurus region, is confirmed for galaxieslocated at kinematic distances of 20-30 Mpc. Beyond 45 Mpc, there is avery weak signal of negative velocity residuals whose amplitude is verysensitive to the form of the Malmquist correction. However, positivevelocity residuals can be detected in galaxies with distances as largeas 80 Mpc. The origin of these motions is tested by the use of anonlinear spherical infall model which predicts the position of thecaustic surface as a function of distance from the GA. All availablevelocities are used to search for the caustics in redshift space.

Groups of galaxies within 80 Mpc. II - The catalogue of groups and group members
This paper gives a catalog of the groups and associations obtained bymeans of a revised hierarchical algorithm applied to a sample of 4143galaxies with diameters larger than 100 arcsec and redshifts smallerthan 6000 km/s. The 264 groups of galaxies obtained in this way (andwhich contain at least three sample galaxies) are listed, with the looseassociations surrounding them and the individual members of eachaggregate as well; moreover, the location of every entity among 13regions corresponding roughly to superclusters is specified. Finally,1729 galaxies belong to the groups, and 466 to the associations, i.e.,the total fraction of galaxies within the various aggregates amounts to53 percent.

The supergalactic plane redshift survey
Redshift measurements, about 1000 of which are new, are presented for1314 galaxies in a survey toward the apex of the large-scale streamingflow for ellipticals. The velocity histogram shows that the excess ingalaxy number counts in this area is due to a substantial concentrationof galaxies with discrete peaks at V about 3000 km/s and V about 4500km/s. After correction for the sampling function, the centroid of thedensity distribution is found to be near V about 4500 km/s.Normalization to the more extensive SSRS survey, which was selected bythe same criteria, shows that the region studied contains a considerableoverdensity of galaxies from 2000 to 6000 km/s. This result is in goodagreement with the 'great attractor' model suggested by Lynden-Bell etal. (1988) which attributes the peculiar motions of elliptical galaxiesover a large region of space to an extensive mass overdensity whichincludes the Hydra-Centaurus and Pavo-Indus superclusters. The centroidof the density enhancement is also consistent with new data by Dresslerand Faber (1990) of peculiar motions of elliptical and spiral galaxies,both of which show a zero crossing of the Hubble line at approximately4500-5000 km/s.

Determination of the masses of elliptical galaxies and clusters of galaxies with AXAF
The procedures to be used in the determination of the mass and massdistribution of elliptical galaxies and clusters of galaxies, usingspatially resolved X-ray spectra of galaxies and clusters of galaxies tobe obtained by the imaging spectrometers on AXAF, are described. Theprocedures utilize the unique AXAF features of large band width, largefield of view, high angular resolution, long exposure times, and theavailability of sophisticated AXAF instrumentation. The techniquesdescribed involve the measurement of the surface brightness andtemperature profiles of the hot gas trapped in the potential wells ofthese systems. Then, by using the equation of hydrostatic equilibrium,which relates the total mass inside a given radius to the size, absolutetemperature, density gradient, and temperature profile, it will bepossible to infer the mass distribution in these objects to largephysical scales.

Southern Galaxy Catalogue.
Not Available

A catalog of morphological types in 55 rich clusters of galaxies
Data are presented from a study of 55 rich clusters of galaxies. Thedata include positions, morphological types, estimated total magnitudes,bulge sizes, and ellipticities for about 6000 galaxies, as determinedfrom high scale photographic plates. Data reduction procedures aredescribed, and a brief analysis of cluster richness, which indicatesthat Abell richness classes are only rough indicators of total clustermembership, is included.

Corrections to the Reference Catalogue of Bright Galaxies (Third List)
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972PASP...84..462C&db_key=AST

Submit a new article

Related links

  • - No Links Found -
Submit a new link

Member of following groups:

Observation and Astrometry data

Right ascension:12h48m02.60s
Aparent dimensions:2.138′ × 0.355′

Catalogs and designations:
Proper Names   (Edit)
NGC 2000.0NGC 4696C

→ Request more catalogs and designations from VizieR