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Maximum feedback and dark matter profiles of dwarf galaxies
The observed rotation curves of dark matter-dominated dwarf galaxiesindicate low-density cores, contrary to the predictions of CDM models. Apossible solution of this problem involves stellar feedback. A strongbaryonic wind driven by vigorous star formation can remove a largefraction of the gas, causing the dark matter to expand. Using bothnumerical and analytical techniques, we explore the maximum effect ofthe feedback with an instantaneous removal of the gaseous disc. Theenergy input depends on the compactness of the disc, hence the specificangular momentum of the disc. For the plausible cosmological parametersand a wide range of the disc angular momenta, the feedback isinsufficient to destroy the central halo cusp, while the inner densityis lowered only by a modest factor of 2 to 6. Any realistic modelling ofthe feedback would have even lesser impact on dark matter. We find thatno star formation effect can resolve the problems of CDM cusps.
| A catalogue of helium abundance indicators from globular cluster photometry
We present a survey of helium abundance indicators derived from acomprehensive study of globular cluster photometry in the literature.For each of the three indicators used, we conduct a thorough erroranalysis, and identify systematic errors in the computationalprocedures. For the population ratio RNHBNRGB, wefind that there is no evidence of a trend with metallicity, althoughthere appears to be real scatter in the values derived. Although thisindicator is the one best able to provide useful absolute heliumabundances, the mean value is Y~0.20, indicating the probable presenceof additional systematic error. For the magnitude difference from thehorizontal branch to the main sequence Δ and the RR Lyraemass-luminosity exponent A, it is only possible to determine relativehelium abundances reliably. This is due to continuing uncertainties inthe absolute metallicity scale for Δ, and uncertainty in the RRLyrae temperature scale for A. Both indicators imply that the heliumabundance is approximately constant as a function of [Fe/H]. Accordingto the A indicator, both Oosterhoff I and II group clusters haveconstant values independent of [Fe/H] and horizontal branch type. Inaddition, the two groups have slopes dlog/d[Fe/H]that are consistent with each other, but significantly smaller than theslope for the combined sample.
| 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.
| 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.
| The Catalog of Southern Ringed Galaxies
The Catalog of Southern Ringed Galaxies (CSRG) is a comprehensivecompilation of diameters, axis ratios, relative bar position angles, andmorphologies of inner and outer rings, pseudorings, and lenses in 3692galaxies south of declination -17 deg. The purpose of the catalog is toevaluate the idea that these ring phenomena are related to orbitalresonances with a bar or oval in galaxy potentials. The catalog is basedon visual inspection of most of the 606 fields of the Science ResearchCouncil (SRC) IIIa-J southern sky survey, with the ESO-B, ESO-R, andPalomar Sky surveys used as auxiliaries when needed for overexposed coreregions. The catalog is most complete for SRC fields 1-303 (mostly southof declination -42 deg). In addition to ringed galaxies, a list of 859mostly nonringed galaxies intended for comparison with other catalogs isprovided. Other findings from the CSRG that are not based on statisticsare the identification of intrinsic bar/ring misalignment; bars whichunderfill inner rings; dimpling of R'1pseudorings; pointy, rectangular, or hexagonal inner or outer ringshapes; a peculiar polar-ring-related system; and other extreme examplesof spiral structure and ring morphology.
| 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.
| The Galactic globular cluster system - Empirical relationship between light-to-mass ratio and metallicity
The light-to-mass ratio A of the ab-type RR Lyrae stars in a wide sampleof Galactic globular cluster is calculated using the period and the blueamplitude of the light curve. It is shown that the average A(12) dependson the metallicity as well as the horizontal-branch (HB) morphology ofthe cluster, in full agreement with the predictions of synthetic HBmodels at constant helium. If clusters with not extremely blue HB aretaken into account, then the average A(12)-(Fe/H) relationship has aslope of about -0.05. If the clusters with very blue HB are includedthen the resulting slope turns out to be steeper and closer to the valuefound in the field. Such a result would confirm the suggestion that manymetal-poor variables in the field are highly evolved stars from the blueside of the RR Lyrae gap. The whole globular cluster system seems togenerally follow on average the same A-(Fe/H) correlation found for theLub variables in the field.
| 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.
| A wide angle redshift survey of the Hydra-Centaurus region
Spectroscopic observations of 266 galaxies in the Hya-Cen region arereported. Redshift data obtained at 350-700 nm with dispersion 21 nm/mmusing the UNIT spectrograph and RPCS detector on the 1.9-m RadcliffeReflector telescope at SAO during March 1985, May 1986, and March 1987are presented in tables and graphs and briefly characterized. It isshown that the Hya supercluster is separated from the Cen superclusterby a large void at right ascension 11 h 40 min, declination -35 deg, andradial velocity 5200 km/sec; a bridge of galaxies at velocity about 3200km/sec connects the two superclusters.
| Formation and Evolution of the Galaxy
Not Available
| Colors and the evolution of amorphous galaxies
UBVRI and H-alpha photometric observations are presented for 16amorphous galaxies and a comparison sample of Magellanic irregular (Im)and Sc spiral galaxies. These data are analyzed in terms ofstar-formation rates and histories in amorphous galaxies. Amorphousgalaxies have mean global colors and star-formation rates per unit areathat are similar to those in giant Im systems, despite differences inspatial distributions of star-forming centers in these two galacticstructural classes. Amorphous galaxies differ from giant Im systems inhaving somewhat wider scatter in relationships between B - V and U - Bcolors, and between U - B and L(H-alpha)/L(B). This scatter isinterpreted as resulting from rapid variations in star-formation ratesduring the recent past, which could be a natural consequence of theconcentration of star-forming activity into centrally located,supergiant young stellar complexes in many amorphous galaxies. While theunusual spatial distribution and intensity of star formation in someamorphous galaxies is due to interactions with other galaxies, severalamorphous galaxies are relatively isolated and thus the processes mustbe internal. The ultimate evolutionary fate of rapidly evolvingamorphous galaxies remains unknown.
| Accurate optical positions for the centers of galactic globular clusters
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986AJ.....91..312S&db_key=AST
| Southern Galaxy Catalogue.
Not Available
| X-ray illumination of globular cluster puzzles
Globular clusters are thought to be among the oldest objects in theGalaxy, and provide, in this connection, important clues for determiningthe age and process of formation of the Galaxy. The presentinvestigation is concerned with puzzles relating to the X-ray emissionof globular clusters, taking into account questions regarding thelocation of X-ray emitting clusters (XEGC) unusually near the galacticplane and/or galactic center. An adopted model is discussed for thenature, formation, and lifetime of X-ray sources in globular clusters.An analysis of the available data is conducted in connection with asearch for correlations between binary formation time scales, centralrelaxation times, galactic locations, and X-ray emission. The positivecorrelation found between distance from galactic center and two-bodybinary formation time for globular clusters, explanations for thiscorrelation, and the hypothesis that X-ray sources in globular clustersrequire binary star systems provide a possible explanation of theconsidered puzzles.
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