Contenuti
Immagini
Carica la tua immagine
DSS Images Other Images
Articoli relazionati
Discovery of a Solitary Dwarf Galaxy in the APPLES Survey
During the APPLES parallel campaign, the Hubble Space Telescope (HST)Advanced Camera for Surveys has resolved a distant stellar system, whichappears to be an isolated dwarf galaxy. It is characterized by acircularly symmetric distribution of stars with an integrated magnitudemF775W=20.13+/-0.02, a central surface brightnessμF775W~=21.33+/-0.18 mag arcsec-2, and ahalf-light radius of ~=1.8". The ACS and VLT spectra show no evidence ofionized gas and appear to be dominated by a 3 Gyr old stellarpopulation. The OB spectral type derived for two resolved stars in thegrism data and the systemic radial velocity (Vhel~=670 kms-1) measured from the VLT data give a fiducial distance of~=9+/-2 Mpc. These findings, with the support of the spatial morphology,would classify the system among the dwarf spheroidal (dSph) galaxies.Following IAU rules, we have named this newly discovered galaxy APPLES1. An intriguing peculiarity of APPLES 1 is that the properties (age andmetallicity) of the stellar content so far detected are similar to thoseof dSph galaxies in the Local Group, where star formation is thought tobe driven by galaxy interactions and mergers. Yet, APPLES 1 seems not tobe associated with a major group or cluster of galaxies. Therefore,APPLES 1 could be the first example of a field dSph galaxy withself-sustained and regulated star formation, and therefore would make aninteresting test case for studies of the formation and evolution ofunperturbed dSph galaxies.
| The column density distribution function at z= 0 from HI selected galaxies
We have measured the column density distribution function, f(NHI), at z= 0 using 21-cm HI emission from galaxies selected from ablind HI survey. f(NH I) is found to be smaller and flatterat z= 0 than indicated by high-redshift measurements of damped Lymanα (DLA) systems, consistent with the predictions of hierarchicalgalaxy formation. The derived DLA number density per unit redshift,dNDLA/dz= 0.058, is in moderate agreement with valuescalculated from low-redshift QSO absorption line studies. We use twodifferent methods to determine the types of galaxies which contributemost to the DLA cross-section: comparing the power-law slope off(NH I) to theoretical predictions and analysingcontributions to dNDLA/dz. We find that comparison of thepower-law slope cannot rule out spiral discs as the dominant galaxy typeresponsible for DLA systems. Analysis of dNDLA/dz however, ismuch more discriminating. We find that galaxies with log MHI< 9.0 make up 34 per cent of dNDLA/dz Irregular andMagellanic types contribute 25 per cent; galaxies with surfacebrightness account for 22 per cent and sub-L* galaxiescontribute 45 per cent to dNDLA/dz. We conclude that a largerange of galaxy types give rise to DLA systems, not just large spiralgalaxies as previously speculated.
| The mass distribution in the innermost regions of spiral galaxies
We use high-spatial resolution ( ~ 100 pc) rotation curves of 83 spiralgalaxies to investigate the mass distribution of their innermost kpc. Weshow that in this region the luminous matter completely accounts for thegravitational potential and no dark component is required. The derivedI-band disk mass-to-light ratios Y_I agree well with those obtained frompopulation synthesis models and correlate with color in a similar way.We find strict upper limits of ~ 10^7 M_Sun for the masses of compactbodies at the center of spirals ruling out that these systems host theremnants of the quasar activity.
| The 1.0 Megaparsec Galaxy Pair Sample in Low-Density Regions
Using complete redshift catalogs, we have compiled a list of galaxypairs based solely on a pair's projected separation, rp, andvelocity difference, ΔV. We have made high-velocity precision H Iobservations of each galaxy in the sample and have reported these in theliterature. Due to the nature of the redshift catalogs, we are able toquantitatively evaluate the effects of isolation and number density ofsurrounding galaxies on each pair in the sample. For the close galaxypairs (rp<100 kpc), the degree of isolation (a measure ofthe number of near neighbors) has little effect on the median ΔV.This median is about 55 km s-1 for the 25 close pairs (ifmedium-density close pairs are omitted ΔV is even smaller, but thedifference is not statistically significant). The effect of isolation isstrong for the entire sample of galaxy pairs with separations as largeas 1.0 Mpc. For these larger separation pairs, relaxation of strictisolation requirements introduces small groups into the sample, whichdramatically increases the median ΔV. We find little evidence ofan increase in the median ΔV with decreasing rp, norwith increasing total luminosity. For our isolated pairs in low-densityregions, the overall median ΔV is only 30 km s-1. Forsimilar separations and isolation criteria, galaxy satellites withlarger luminosity ratios (i.e., less dynamical friction) in higherdensity regions have ΔV approximately twice as large. Weconjecture that our orbits are highly eccentric, so that the indirecteffect of dynamical friction leads to predominantly small ΔV.However, the halos of our galaxies may also be of low density (althoughhighly extended).
| 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.
| Box- and peanut-shaped bulges. I. Statistics
We present a classification for bulges of a complete sample of ~ 1350edge-on disk galaxies derived from the RC3 (Third Reference Catalogue ofBright Galaxies, de Vaucouleurs et al. \cite{rc3}). A visualclassification of the bulges using the Digitized Sky Survey (DSS) inthree types of b/p bulges or as an elliptical type is presented andsupported by CCD images. NIR observations reveal that dust extinctiondoes almost not influence the shape of bulges. There is no substantialdifference between the shape of bulges in the optical and in the NIR.Our analysis reveals that 45% of all bulges are box- and peanut-shaped(b/p). The frequency of b/p bulges for all morphological types from S0to Sd is > 40%. In particular, this is for the first time that such alarge frequency of b/p bulges is reported for galaxies as late as Sd.The fraction of the observed b/p bulges is large enough to explain theb/p bulges by bars. Partly based on observations collected at ESO/LaSilla (Chile), DSAZ/Calar Alto (Spain), and Lowell Observatory/Flagstaff(AZ/U.S.A.). Tables 6 and 7 are only available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The QDOT all-sky IRAS galaxy redshift survey
We describe the construction of the QDOT survey, which is publiclyavailable from an anonymous FTP account. The catalogue consists ofinfrared properties and redshifts of an all-sky sample of 2387 IRASgalaxies brighter than the IRAS PSC 60-μm completeness limit(S_60>0.6Jy), sparsely sampled at a rate of one-in-six. At |b|>10deg, after removing a small number of Galactic sources, the redshiftcompleteness is better than 98per cent (2086/2127). New redshifts for1401 IRAS sources were obtained to complete the catalogue; themeasurement and reduction of these are described, and the new redshiftstabulated here. We also tabulate all sources at |b|>10 deg with noredshift so far, and sources with conflicting alternative redshiftseither from our own work, or from published velocities. A list of 95ultraluminous galaxies (i.e. with L_60μm>10^12 L_solar) is alsoprovided. Of these, ~20per cent are AGN of some kind; the broad-lineobjects typically show strong Feii emission. Since the publication ofthe first QDOT papers, there have been several hundred velocity changes:some velocities are new, some QDOT velocities have been replaced by moreaccurate values, and some errors have been corrected. We also present anew analysis of the accuracy and linearity of IRAS 60-μm fluxes. Wefind that the flux uncertainties are well described by a combination of0.05-Jy fixed size uncertainty and 8per cent fractional uncertainty.This is not enough to cause the large Malmquist-type errors in the rateof evolution postulated by Fisher et al. We do, however, find marginalevidence for non-linearity in the PSC 60-μm flux scale, in the sensethat faint sources may have fluxes overestimated by about 5per centcompared with bright sources. We update some of the previous scientificanalyses to assess the changes. The main new results are as follows. (1)The luminosity function is very well determined overall but is uncertainby a factor of several at the very highest luminosities(L_60μm>5x10^12L_solar), as this is where the remainingunidentified objects are almost certainly concentrated. (2) Thebest-fitting rate of evolution is somewhat lower than our previousestimate; expressed as pure density evolution with density varying as(1+z)^p, we find p=5.6+/-2.3. Making a rough correction for the possible(but very uncertain) non-linearity of fluxes, we find p=4.5+/-2.3. (3)The dipole amplitude decreases a little, and the implied value of thedensity parameter, assuming that IRAS galaxies trace the mass, isΩ=0.9(+0.45, -0.25). (4) Finally, the estimate of density varianceon large scales changes negligibly, still indicating a significantdiscrepancy from the predictions of simple cold dark matter cosmogonies.
| Very Wide Galaxy Pairs of the Northern and Southern Sky
We present highly accurate observations of the 21 cm line of hydrogen ingalaxies made at the Arecibo and Parkes Observatories. The galaxiesobserved have been identified, through rigorous selection criteriaapplied to the CfA and SSRS catalogs, as being members of pairs withprojected separations of up to 1.5 Mpc (H0 = 75 km s-1 Mpc-1). Theseobservations form the completion of the Chengalur-Nordgren galaxy pairsample with data previously published by Chengalur, Nordgren andcolleagues. The new selection criteria used in this paper are anextension to larger projected separations of the criteria usedpreviously. Forty-nine new galaxies are observed, while H I is detectedin 41 of them. With the addition of these galaxies, the completed samplehas highly accurate H I velocities for a total of 219 galaxies.
| 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.
| 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
| Homogeneous Velocity-Distance Data for Peculiar Velocity Analysis. III. The Mark III Catalog of Galaxy Peculiar Velocities
This is the third in a series of papers in which we assemble and analyzea homogeneous catalog of peculiar velocity data. In Papers I and II, wedescribed the Tully-Fisher (TF) redshift-distance samples thatconstitute the bulk of the catalog and our methodology for obtainingmutually consistent TF calibrations for these samples. In this paper, wesupply further technical details of the treatment of the data andpresent a subset of the catalog in tabular form. The full catalog, knownas the Mark III Catalog of Galaxy Peculiar Velocities, is available inaccessible on-line databases, as described herein. The electroniccatalog incorporates not only the TF samples discussed in Papers I andII but also elliptical galaxy Dn- sigma samples originally presentedelsewhere. The relative zero pointing of the elliptical and spiral datasets is discussed here. The basic elements of the Mark III Catalog arethe observables for each object (redshift, magnitude, velocity width,etc.) and inferred distances derived from the TF or Dn- sigma relations.Distances obtained from both the forward and inverse TF relations aretabulated for the spirals. Malmquist bias--corrected distances arecomputed for each catalog object using density fields obtained from theIRAS 1.2 Jy redshift survey. Distances for both individual objects andgroups are provided. A variety of auxiliary data, including distancesand local densities predicted from the IRAS redshift surveyreconstruction method, are tabulated as well. We study the distributionsof TF residuals for three of our samples and conclude that they are wellapproximated as Gaussian. However, for the Mathewson et al. sample wedemonstrate a significant decrease in TF scatter with increasingvelocity width. We test for, but find no evidence of, a correlationbetween TF residuals and galaxy morphology. Finally, we derivetransformations that map the apparent magnitude and velocity width datafor each spiral sample onto a common system. This permits theapplication of analysis methods that assume that a unique TF relationdescribes the entire sample.
| 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
| An Atlas of Hubble Space Telescope Ultraviolet Images of Nearby Galaxies
We present an atlas of UV (~2300 A) images, obtained with the HubbleSpace Telescope (HST) Faint Object Camera, of the central 22" x 22" of110 galaxies. The observed galaxies are an unbiased selectionconstituting about one-half of a complete sample of all large (D >6') and nearby (V < 2000 km s^-1^) galaxies. This is the firstextensive UV imaging survey of normal galaxies. The data are useful forstudying star formation, low-level nuclear activity, and UV emission byevolved stellar populations in galaxies. At the HST resolution (~0.05"),the images display an assortment of morphologies and UV brightnesses.These include bright nuclear point sources, compact young star clustersscattered in the field or arranged in circumnuclear rings, centrallypeaked diffuse light distributions, and galaxies with weak or undetectedUV emission. We measure the integrated ~2300 A flux in each image,classify the UV morphology, and examine trends between these parametersand the optical properties of the galaxies.
| 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.
| Recalibration of the H-0.5 magnitudes of spiral galaxies
The H-magnitude aperture data published by the Aaronson et al.collaboration over a 10 year period is collected into a homogeneous dataset of 1731 observations of 665 galaxies. Ninety-six percent of thesegalaxies have isophotal diameters and axial ratios determined by theThird Reference Cataloque of Bright Galaxies (RC3; de Vaucouleurs et al.1991), the most self-consistent set of optical data currently available.The precepts governing the optical data in the RC3 are systematicallydifferent from those of the Second Reference Catalogue (de Vaucouleurs,de Vaucouleurs, & Corwin 1976), which were used by Aaronson et al.for their original analyses of galaxy peculiar motions. This in turnleads to systematic differences in growth curves and fiducialH-magnitudes, prompting the present recalibration of the near-infraredTully-Fisher relationship. New optically normalized H-magnitude growthcurves are defined for galaxies of types SO to Im, from which new valuesof fiducial H-magnitudes, Hg-0.5, are measured forthe 665 galaxies. A series of internal tests show that these fourstandard growth curves are defined to an accuracy of 0.05 mag over theinterval -1.5 less than or equal to log (A/Dg) less than orequal to -0.2. Comparisons with the Aaronson et al. values of diameters,axial ratios, and fiducial H-magnitudes show the expected differences,given the different definitions of these parameters. The values ofHg-0.5 are assigned quality indices: a qualityvalue of 1 indicates an accuracy of less than 0.2 mag, quality 2indicates an accuracy of 0.2-0.35 mag, and quality 3 indicates anaccuracy of more than 0.35 mag. Revised values of corrected H I velocitywidths are also given, based on the new set of axial ratios defiend bythe RC3.
| A Preliminary Classification Scheme for the Central Regions of Late-Type Galaxies
The large-scale prints in The Carnegie Atlas of Galaxies have been usedto formulate a classification scheme for the central regions oflate-type galaxies. Systems that exhibit small bright central bulges ordisks (type CB) are found to be of earlier Hubble type and of higherluminosity than galaxies that do not contain nuclei (type NN). Galaxiescontaining nuclear bars, or exhibiting central regions that are resolvedinto individual stars and knots, and galaxies with semistellar nuclei,are seen to have characteristics that are intermediate between those oftypes CB and NN. The presence or absence of a nucleus appears to be auseful criterion for distinguishing between spiral galaxies andmagellanic irregulars.
| Total and effective colors of 501 galaxies in the Cousins VRI photometric system
Total color indices (V-R)T, (V-I)T and effectivecolor indices (V-R)e, (V-I)e in the Cousins VRIphotometric system are presented for 501 mostly normal galaxies. Thecolors are computed using a procedure outlined in the Third ReferenceCatalogue of Bright Galaxies (RC3) whereby standard color curvesapproximated by Laplace-Gauss integrals are fitted to observedphotoelectric multiaperture photometry. 11 sources of such photometrywere used for our analysis, each source being assigned an appropriateweight according to a rigorous analysis of residuals of the data fromthe best-fitting standard color curves. Together with the integrated B-Vand U-B colors provided in RC3, our analysis widens the range ofwavelength of homogeneously defined colors of normal galaxies of allHubble types. We present color-color and color-type relations that canbe modeled to understand the star formation history of galaxies.
| 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.
| On the size and formation mechanism of the largest star-forming complexes in spiral and irregular galaxies
The average diameters of the largest star complexes in most of thespiral and irregular galaxies in the Sandage and Bedke Atlas of Galaxieswere measured from the Atlas photographs. The complex diametersDc correlate with galaxy magnitude as Dc = 0.18 -0.14MB, which has about the same slope as the correlation forthe largest H II regions studied by Kennicutt. There is no obviouscorrelation between Dc and either Hubble type or spiral armclass at a given magnitude. The variation of Dc withMB closely matches the expected variation in thecharacteristic length of the gaseous gravitational instabilityconsidering that the rotation curve varies with MB and thatthe stability parameter Q is about 1 in the outer regions of the disk.This match corresponds to an effective velocity dispersion of 6.1 km/sthat is about the same for all spiral and irregular galaxies.
| Dynamics of the Pavo-Indus and Grus clouds of galaxies
A study of groups of galaxies in the above regions was carried out byselecting a sample extending one magnitude deeper than previous work inthe area, complete down to 15 mag. We report new redshift determinationsfor 58 galaxies in the region and 13 other miscellaneous galaxies, basedon La Silla observations. Using a total of 266 galaxies with measuredredshifts in the Pavo-Indus and Grus clouds, we perform a new analysisof groupings following a well-tested algorithm. A total of 18 groups issingled out, most of them known from previous work, even though a fewadditional members are added. For all the groups, we have calculateddynamical parameters and M/L ratios. All groups are found to be boundaggregates, but only one group can be virialized. For the six mostpopulated examples, having at least five members, we also calculateseveral mass estimators and discuss the wide range of observed M/Lratios, which extends from nine to nearly 500 M(solar)/L(solar). Weintroduce two parameters to measure the presence of either a dominantgalaxy or internal subcondensations, respectively, and test whether anycorrelation with the M/L ratios can be detected. No clear correlationsare found.
| 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.
| Nearby galaxy flows modeled by the light distribution - Distances, model, and the local velocity anomaly
Tables giving measured galaxy distances used to construct a map ofobserved peculiar velocities, and giving a grid of the distribution oflight used to construct a map of expected peculiar velocities arepresented. A preferred model was developed which yielded a best fitbetween these maps, and this model was used to generate output kinematicdistances which are recorded for groups and individual galaxies withV0 of less than 3000 km/s. In terms of the ratio ofpeculiar-to-systemic velocities, the local velocity anomaly is the mostimportant perturbation involving substantial numbers of galaxies forthis case. The ratio of these quantities in this case is larger than forthe more famous cases of the Virgocentric or Great Attractorperturbations. Maps which illustrate the fit of the present mass modelto the velocity data in the local region are provided. A graphicaldemonstration of the relative importance of large-scale streaming tolocal motions within the context of this model is presented.
| 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 proportion of ultraluminous IRAS galaxies in interacting systems.
Not Available
| The proportion of ultraluminous IRAS galaxies in interacting systems
A sample consisting of 41 ultraluminous IRAS galaxies with far-infraredluminosities greater than 10 exp 12 solar luminosities is examined, aswell as a control sample of 41 low-luminosity IRAS galaxies withluminosities less than 10 exp 9.7. Their images on the film copies ofthe SERC Sky Survey were scanned with a pixel size of 5 microns over asquare area of typically 6.72 arcsec to the side. The density contourmaps and the sky survey material show that the proportion ofultraluminous IRAS galaxies which are interacting or merger systems, 61+/-12 percent, is much higher than that of low-luminosity ones (10 +/-5percent), but still well short of the 100 percent suggested in severalrecent reports. This result supports the conclusion that galaxyinteraction or merging is more common at high-IR luminosity, but it isprobably not the only cause of their activity.
| 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.
| Gaseous content of galaxies inside groups
The gaseous content of a sample constituted of 84 Sb and 95 Sc galaxiesinside groups has been analyzed. After correcting for the luminosityeffect, no gas deficiency was found for those galaxies in spite of aspan of about 2 orders of magnitude in the galaxy density. Anyintergalactic gas present in the considered groups must have densitiessmaller than 0.0003/cu cm.
| A catalog of southern groups of galaxies
A catalog of groups of galaxies identified in the southern Galactic capis presented. This catalog was constructed utilizing the group-findingalgorithm developed by Huchra and Geller (1982) to analyze galaxysamples with well-defined selection criteria and complete velocityinformation.
|
Sottometti un nuovo articolo
Link relazionati
Sottometti un nuovo link
Membro dei seguenti gruppi:
|
Osservazione e dati astrometrici
Cataloghi e designazioni:
|
