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|Double Nuclei and ``TDGs": Colliding or Activity of Nucleus Monster?|
It is known that among active galaxies (AG) with strong emission lines (UV-galaxies, Sy 1 and Sy2, Markarian and Kazarian galaxies,Radio-galaxies, QSO's host galaxies and so on) there are large per centof objects with double and multiple nucleus. The common sizes andvolumes of these nuclei are on the order of a few hundred parsecs orkilo-parsecs. In fact these are not double galaxies or clusters ofgalaxies as many of astronomers believe, but just the complicatednucleus of AG. The problem is: what are the nature and the birth ofthese objects? There are in fact two basic suppositions in the subject:(a) The complicated nuclei are the result of merging or colliding of twoor more galaxies, or: (b) They are the results of nuclear activity. Theresults of detailed spectroscopic observations of a number of "tidalgalaxies", carried out with the 5m Palomar telescope, 2.6m telescope ofAmbartsumian Byurakan astrophysical observatory (multi-pupilspectroscopy with Tiger receiver) and 6m telescope of SpecialAstrophysical observatory of Russia are presented. It is shown that inmany cases the "tidal dwarf galaxies "(or actually complicatednucleus) are the result of galactic nuclear activity.
|The UZC-SSRS2 Group Catalog|
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
|Arcsecond Positions of UGC Galaxies|
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
|Kinematics of the Hercules supercluster|
The Hercules supercluster consists of the Abell clusters A2147, A2151,and A2152. Previous studies of the kinematics have been confounded bythe difficulty of correctly assigning galaxies to the individualclusters, which are not well separated. Our study has a total of 468available velocities for galaxies in the region, 175 of them new. Thereare 414 galaxies in the supercluster, about three times the number usedin the previous supercluster study. We verify the existence of the threeindividual clusters and compute their individual dynamical parameters.We investigate several techniques for assigning galaxy membership toclusters in this crowded field. We use the KMM mixture-modelingalgorithm to separate the galaxies into clusters; we find that A2152 hasa higher mean velocity than previous studies have reported. A2147 andA2152 also have lower velocity dispersions: 821 and 715 km/s,respectively. The assignment of galaxies to either A2152 or A2147requires velocity and position information. We study the kinematics ofthe supercluster using the two-body formalism of Beers et al. (1982) andconclude that A2147 and A2151 are probably bound to each other and thatthe supercluster as a whole may also be bound. The mass of thesupercluster, if bound, is (7.6 +/- 2.0) 10 exp 15/h M(solar); with thesupercluster luminosity, (1.4 +/- 0.2) 10 exp 13/sq h L(solar), thisyields 0.34 +/- 0.1.
|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 High-Resolution ROSAT X-Ray Study of the Hercules Cluster|
The well-studied, irregular Hercules cluster of galaxies (Abell 2151)was observed in X-rays with the ROSAT HRI. We find that the X-rayemission is concentrated toward the central subcluster of the system, inagreement with previous Einstein and ROSAT PSPC observations. The X-rayemission in this subcluster divides into two components, whichcorrespond to two groups of galaxies in the region. The center of thebrightest (western) X-ray component coincides with the brightest clustergalaxy (BCG) NGC 6041A, while there is an X-ray peak near the center ofthe poorer eastern component that agrees with the position of anelliptical radio galaxy NGC 6047. The X-ray emission is fairlyirregular, and there are separate X-ray features associated withindividual galaxies including the BCG NGC 6041A. There are two X-rayclumps associated with an interacting peculiar galaxy pair NGC 6040A/B.Gas stripping from the galaxy pair has depleted about 80% of theirneutral hydrogen contents. In addition, the stripped gas may constitutea majority of the X-ray emitting gas in this region, which suggests thatthe gas stripping in this subcluster may be very efficient and is animportant contributing factor to the origin of the hot gas. Theinteraction of the intracluster gas with the radio galaxy NGC 6047 hasalso been investigated. A cooling flow of M = 143 +/- 28 M_sun_ yr^-1^is found in the central subcluster that may have deposited a significantfraction of the cooled gas to the central BCG galaxy NGC 6041A. We alsoprobed the dynamic structure and dark matter distribution in the centralsubcluster. Our data show that, within the central 678 kpc, total darkmatter in this main subcluster is comparable to the total materialcontained in luminous galaxies and X-ray emitting gas in the region.Throughout the paper, we have assumed a Hubble constant of 50 km s^-1^Mpc^-1^ and q_0_ = 0.5.
|The fundamental plane of early-type galaxies: stellar populations and mass-to-light ratio.|
We analyse the residuals to the fundamental plane (FP) of ellipticalgalaxies as a function of stellar-population indicators; these are basedon the line-strength parameter Mg_2_ and on UBVRI broad-band colors, andare partly derived from new observations. The effect of the stellarpopulations accounts for approximately half the observed variation ofthe mass-to-light ratio responsible for the FP tilt. The residual tiltcan be explained by the contribution of two additional effects: thedependence of the rotational support, and possibly that of the spatialstructure, on the luminosity. We conclude to a constancy of thedynamical-to-stellar mass ratio. This probably extends to globularclusters as well, but the dominant factor would be here the luminositydependence of the structure rather than that of the stellar population.This result also implies a constancy of the fraction of dark matter overall the scalelength covered by stellar systems. Our compilation ofinternal stellar kinematics of galaxies is appended.
|The far-infrared-radio relation in cluster spiral galaxies|
We present a study of the far-infrared (FIR) and radio emission in asample of group and cluster spiral galaxies. Galaxies are separated intorich and poor cluster samples based the value of the galaxy-galaxycorrelation coeffiient (Andersen & Owen 1994) of their parentcluster. Galaxies in the rich clusters have lower-FIR-radio ratios thana radio selected sample of field galaxies, while galaxies in poorclusters do not. We find that the degree of radio enhancement withrespect to FIR emission is consistent with a model where the radioemitting interstellar medium (ISM) is compressed by the ram pressure asthe galaxy moves through the intracluster medium. We suggest thatgalaxy-galaxy tidal interactions are important in the poorer clusters,but in general of much less importance in richer clusters.
|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.
|Dark matter and dynamics in the Hercules Cluster (A2151)|
New 21-cm observations of faint spiral galaxies in the Hercules cluster(A2151) are presented in order to investigate the dynamics throughoutthe cluster core, out to a projected radius of 1.8/h Mpc. The globaldynamical mass of Hercules is calculated using the virial theorem andthe projected mass estimator. These masses lie in the range 3-9 x 10 exp14 solar masses. The importance of subclustering in A2151 by eye isexamined via the statistical test of Dressler & Shectman (1988), andby considering the effects of the detected substructure on the dynamicalmass determination. The clumpy distribution is interpreted as a signthat the galaxies in the cluster have not reached dynamical equilibriumin the gravitational potential.
|A catalog of galaxies in Hercules from the Palomar Sky Survey and the Minnesota Automated Plate Scanner|
The development of galaxies catalogs from the Palomar Sky Survey usingthe Minnesota Automated Plate Scanner (APS) is examined. The design andoperation of APS are described. The algorithm used to distinguish starsfrom galaxies is discussed, and the completeness and confusion of thealgorithm as a function of magnitude are estimated. The quality of thephotometric calibration for galaxy magnitudes and surface-brightnessthresholds is evaluated. The relation between the distribution of colorsand morphological types is studied. The luminosity functions forHercules galaxies are calculated and presented. The catalog generatedusing the APS is 80 percent complete; photometry good to 0.23 mag rms ispossible; and J-F colors are good to 0.17 mag rms.
|The distance to the Hercules supercluster. I - Basic data for 220 galaxies in CGCG field 108.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986ApJS...62..255B&db_key=AST
|The evolution of galaxies in clusters. IV - Photometry of 10 low-redshift clusters|
Colors and magnitudes, obtained from Palomar 48 inch (1.2 m) Schmidtplates in the J and F bands, and morphological types are presented forgalaxies in the cores of 10 nearby clusters of galaxies. In the typicalcluster, the sample includes all galaxies within a radius of 1.5 Mpc(assuming H(0) = 50 km/s/Mpc) of the cluster center and brighter than J= 17.5.The accuracy of the photometry varies with cluster, but mostmagnitudes are accurate to 0.10 mag, and typical errors in the colorsare of the same order. As expected, the colors of the elliptical and S0galaxies show a narrow dispersion about a mean color which decreaseswith magnitude. However, the colors of the spiral galaxies are notentirely as expected, having a smaller dispersion than would have beenpredicted from their morphological types.
|1.4 GHz continuum sources in the Hercules cluster|
Observational results are presented of a continuum survey of theHercules Cluster (A2151) near 1.4 GHz. The observations were carried outusing the VLA in the D configuration with a total bandwidth of 25 MHz.Positions and fluxes are given for 65 sources, 21-25 of which areassociated with galaxies. Separation between the radio and opticalpositions of the galaxies was five arcsec for most cases. A group ofthree small rectangles near the classical center of the Hercules Clusteris examined, and it is found that each rectangle contains one opticallybright galaxy and one strongly emitting radio galaxy. It is suggestedthat these regions are physical subcores of A2151 and that they containintergalactic gas. Five sources were found with 1.4 GHz fluxes greaterthan 10 mJy which are not associated with any galaxy. It is conjecturedthat the galaxyless objects are not background objects, but are insteadthe result of a plasma effect in the subcore medium. The radio flux ofthe galaxyless sources correlates well with the 60-micron flux obtainedby IRAS for spiral galaxies. A table is presented which lists thesources associated with galaxies.
|A Westerbork survey of rich clusters of galaxies. IX - The radio luminosity function of the Hercules supercluster at 610 MHz|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979A&A....73...54P&db_key=AST
|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
|Notes on the Hercules Galaxy Cluster|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971PASP...83..320C&db_key=AST
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