Luminosity Segregation Research Articles

The luminosity of galactic components and morphological segregation

view Abstract Citations (21) References (32) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Luminosity of Galactic Components and Morphological Segregation Solanes, Jose M. ; Salvador-Sole, Eduard ; Sanroma, Manuel Abstract We analyze the luminosity of the bulge and disk components of disk galaxies and their possible correlations with morphological type and local density. We show that galaxies of different types are located in distinct bands in the B/D vs total-luminosity diagram, which seem to be insensitive to the particular galaxy environment. This allows one to infer the typical bulge luminosity function (BLF) of disk galaxies of different types from their respective total luminosity functions (LF). Furthermore, it allows a better characterization of morphological segregation (MS) among disk galaxies. MS would reveal their tendency to have bigger B/D's with increasing local density. Contrary to previous results obtained from the same catalog, no evidence is found of any bulge luminosity segregation. Instead, disks appear to be less luminous with increasing local density. This should cause a slight total luminosity antisegregation among disk galaxies, which is, in fact, not inconsistent with the recently reported opposite trend. Indeed, the observed behavior depends on whether the sample of galaxies analyzed is total- or bulge-magnitude limited. Publication: The Astronomical Journal Pub Date: September 1989 DOI: 10.1086/115179 Bibcode: 1989AJ.....98..798S Keywords: Disk Galaxies; Galactic Bulge; Luminosity; Galactic Radiation; Morphology; Statistical Distributions; Astrophysics; GALAXIES: STRUCTURE full text sources ADS | data products SIMBAD (3) NED (1)

A quadratic programming technique for modeling gravitating systems

view Abstract Citations (94) References (45) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Quadratic Programming Technique for Modeling Gravitating Systems Dejonghe, Herwig Abstract This paper presents a general method that produces analytic distribution functions for gravitating systems. A typical model fits photometric and kinematical data and is a superposition of components. The coefficients of the linear combination are determined by a quadratic programming technique. We give an explicit example for systems with spherical symmetry, and subsequently we apply the method to the Coma Cluster of galaxies. Statistically significant fits are obtained using only a small number of components. This technique is also a dynamical mass estimator. We obtain masses between 1.7 x 10^15^h^-1^_50_ M_sun_ and 5 x 10^15^h^-1^_50_ M_sun_ within 5h^-1^_50_ Mpc, and find some evidence for luminosity segregation in the orbital structure. Publication: The Astrophysical Journal Pub Date: August 1989 DOI: 10.1086/167689 Bibcode: 1989ApJ...343..113D Keywords: Astronomical Models; Computational Astrophysics; Galactic Clusters; Gravitation; Quadratic Programming; Astronomical Photometry; Celestial Mechanics; Galactic Mass; Luminosity; Symmetry; Astrophysics; ANALYTICAL METHODS; GALAXIES: CLUSTERING; STARS: STELLAR DYNAMICS full text sources ADS | data products SIMBAD (1)

The distribution of cluster members in the vicinity of a central dominant galaxy

view Abstract Citations (36) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Distribution of Cluster Members in the Vicinity of a Central Dominant Galaxy Merrifield, Michael R. ; Kent, Stephen M. Abstract The projected distribution of cluster members within 250 h^-1^ kpc of a central dominant galaxy is investigated by stacking CCD images of 29 clusters of galaxies. The radial distribution of the projected galaxy number density is well described by an exponential profile with an e-folding length of approximately 100 h^-1^ kpc. The shape of the profile is characteristic of the effects of dynamical friction and suggests that this force may have played a significant role in cluster evolution. However, there is no evidence for the luminosity segregation that might be expected to accompany such evolution. The central density for the core profile appears to be only weakly correlated with the overall cluster richness. The dynamics of this projected profile are investigated for a range of credible mass distributions, and existing redshift measurements are shown to be consistent with an isotropic velocity distribution. The high central density associated with this cusped distribution explains the presence of at least 50% of the observed "multiple nuclei" projected within 10 h^-1^ kpc of the center of the dominant galaxy. In view of the bias aperture containing maximum luminosity, and uncertainties in the effective limiting magnitude to which existing surveys of multiple nuclei have been made, this population could be responsible for most of the observed occurrences of multiple nuclei. However, calculations indicate that the high density and low velocities of galaxies in the cluster core may lead to a sufficiently high rate of collisions between cluster members and the central dominant galaxy to produce a significant population of multiple nuclei which are in the process of merging with the underlying central galaxy. Publication: The Astronomical Journal Pub Date: August 1989 DOI: 10.1086/115151 Bibcode: 1989AJ.....98..351M Keywords: Cosmology; Galactic Clusters; Background Radiation; Classifications; Maximum Likelihood Estimates; Spatial Distribution; Velocity Distribution; Astrophysics; GALAXIES: CLUSTERING full text sources ADS | data products SIMBAD (30) NED (29)

Linear clusters of galaxies - A194

New measurements for 160 redshifts and previous measurements for 108 other redshifts are presented for galaxies within 5 deg of A194. The galaxy distribution in A194 is shown to be inconsistent with a spherically symmetric King model. A mass-to-light ratio is derived using the virial theorem which is lower than the mean for the groups in the CfA redshift survey (Huchra and Geller, 1982; Geller, 1984). A nonparametric test for galaxy-cluster alignment and a Chi-squared test are used to search for alignment of galaxy major axes with the axis of A194. Evidence for neither luminosity segregation nor significant differences in the velocity or surface distributions of galaxies as a function of morphological type is found.

Field effects on the luminosity segregation analysis of distant clusters of galaxies

view Abstract Citations (18) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Field Effects on the Luminosity Segregation Analysis of Distant Clusters of Galaxies Dominguez-Tenreiro, R. ; del Pozo-Sanz, R. Abstract A method to remove field effects on the determination of the intergalactic distance distribution function in distant galaxy clusters is presented. This method is applied to Butcher, Oemler, and Wells's observations of the A1758 cluster in order to analyze its luminosity segregation. It is shown that field galaxies strongly mask the luminosity segregation of the brightest galaxies of this cluster, in which a critical magnitude appears, m_c_, such that no significant segregation is observed at any scale for galaxies fainter than m_c_. Publication: The Astrophysical Journal Pub Date: January 1988 DOI: 10.1086/165927 Bibcode: 1988ApJ...324..677D Keywords: Cosmology; Galactic Clusters; Galactic Evolution; Luminosity; Many Body Problem; Gravitational Fields; Mass Distribution; Mass To Light Ratios; Spatial Distribution; Astrophysics; GALAXIES: CLUSTERING full text sources ADS | data products SIMBAD (1) NED (1)

Void probabilities in the galaxy distribution - Scaling and luminosity segregation

A method for estimating the void probability function (VPF) from any volume- and absolute magnitude-limited galaxy catalog is developed and applied to three volume- and magnitude-limited subclasses from the CfA catalog which involve different luminosity classes. The VPF is calculated for each subclass and the count probability of finding N galaxies in a volume V is calculated for N = 1 to 4, successively. It is shown that each of the samples obeys a scaling invariance predicted by the class of hierarchical models, suggesting that this property applies to the whole galaxy distribution. This result permits a comparison of the VPFs for the three samples, and is it shown that bright galaxies are more clustered than faint ones in the samples studied. Estimations of the two-point correlation functions show that bright and faint galaxies appear to obey a universal distribution. 24 references.

Dark matter influence on velocity dispersion profiles of clusters of galaxies

We have performed a series ofN-body experiments including the effects of a massive dominant background which follows Schuster's density law in order to simulate clusters of galaxies in which a smoothly distributed dark component is present. The existence of this background is inferred from the weak luminosity segregation observed in clusters which, however, show several characteristics of well-relaxed systems. The comparison of the velocity dispersion profiles of three clusters of galaxies (Coma, Perseus, and Virgo) with those obtained in the numerical experiments allows us to place some constraints on both the distribution and amount of distributed dark material in these clusters. The profiles are rather insensitive to variations in the ratio of the background mass to the mass attached to galaxies (Mb/Mg), but exhibit a strong dependence on their relative concentration. We conclude that highly concentrated background models are not consistent with observations. We find a maximum value for the ratio of the gravitational radius of the galaxies and the background (Rg/Rb) (approximately 0.6) and using previous results (Navarroet al., 1986) we conclude that virial theorem masses underestimate the total mass (Mb+Mg) of the clusters. As a final result, we derive a minimum value for theMb/Mg ratio. All these conclusions could apply in general if Coma, Perseus, and Virgo constitute a fair sample of the rich clusters of galaxies in the Universe.

Luminosity Segregation in Distant Galaxy Clusters

Angular separation-magnitude plots drawn from deep photometry of galaxies in distant clusters show evidence for luminosity segregation which cannot be accounted for by field contamination. This segregation, interpreted in terms of dynamical friction, allows one to determine (M/L)g, the mass-to-light ratio of galaxies from their velocity dispersion. In A370 (z=0.37) more than 30 velocities have been measured by multi-aperture spectroscopy, leading to (M/L)g ∼70. Values greater than 100 are found in 5 other distant clusters by deriving the velocity dispersion from the richness. The luminosity segregation, observed even inside each of the clumps of 3C299, could result either from dynamical friction inside the clumps or from some early environmental influence.

Investigation of photometric and geometric parameters of galaxies in clusters. I. The cluster A 2065

The results are given of analysis of a photograph of the cluster A 2065 obtained with the 2.6-m telescope of the Byurakan Astrophysical Observatory in the photographic band. The magnitudes were integrated down to the isophote corresponding to m/sub pg/ = 25 from a square second of arc. The completeness limit of the sample is 19/sup m/.5, and the number of galaxies down to this limit is 132. The values obtained for the parameters of the Schechter function are a* = -125 and M/sub pg/* = -20.45 and for the Abell function s/sub 1/ = 1.1 and s/sub 2/ = 0.36. Luminosity segregation of the galaxies is observed only within a magnitude of the brightest galaxy. The ellipticities and position angles of the major axes of the galaxies have been determined. The observed ellipticity does not depend on the luminosity, diameter, or position of the galaxy in a cluster. Various statistical criteria reveal that there is a preferred orientation of the major axes. This direction is perpendicular to the orientation of the central double galaxy and to the direction along which the cluster is elongated

Galaxy distribution in Butcher-Oemler clusters

The galaxy distribution in six Butcher-Oemler clusters is analyzed in order to obtain separate core radii for the blue galaxies and for the red E-sequence galaxies. By fitting these distributions with isothermal spheres via maximum-likelihood techniques, the core radius for the blue galaxies is shown to be nearly three times that of the red galaxies. While the general trend of the blue/red galaxy segregation was noticed by Butcher and Oemler, the analysis is presented here places this result on firm statistical ground. A test for luminosity segregation gives only marginally significant results, while a comparison of differential luminosity functions shows that blue galaxies, in their quiescent state, are likely to be about 1 mag fainter than red E-sequence galaxies. When combined with each other, the two previous results imply that mass segregation cannot explain the broad blue galaxy distribution. A discussion of dynamical considerations particularly the relative velocity dispersions of blue and red galaxies - is included to show how the blue/red galaxy segregation might arise.

Evidence for cannibalism in the 0004.8–3450 cluster of galaxies

The analysis of the luminosity segregation in the 0004.8–3450 cluster of galaxies is made which reinforces the assumption of merging mechanisms.

Counts of galaxies in seven distant clusters

This paper presents counts of galaxies in each of seven distant clusters with redshifts between 0.17 and 0.46. Luminosity segregation is found in two of the clusters. The data is inconclusive as regards color segregation.

The Cluster of Galaxies Abell 1413

view Abstract Citations (20) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Cluster of Galaxies Abell 1413 Noonan, Thomas W. Abstract The cluster Abell 1413 at a redshift of 0.143 shows an effect which may be interpreted as a luminosity segregation, indicating that this property probably persists over look-back times of order 0.14 of the inverse of the Hubble constant. The cluster has the same richness as the Coma cluster but only about 60% as the radius, unless what appears to be the brightest member is really a foreground galaxy. Publication: The Astronomical Journal Pub Date: February 1972 DOI: 10.1086/111237 Bibcode: 1972AJ.....77....9N full text sources ADS | data products NED (1)