Abell Clusters Of Galaxies Research Articles

Subclustering and cooling flow in Abell clusters of galaxies

Correlation between the subclustering determined through the application of the wavelet analysis to the optical data and existence of cooling flows observed in the X-ray range are studied. On the basis of eight galaxy clusters with cooling flow and nine non-cooling objects it is shown that substructures are observed in both groups.

Optical luminosity functions of the Abell galaxy cluster ABCG 209 at z = 0.21

We derive the luminosity functions in three bands (BVR) for the rich galaxy cluster ABCG 209 at . The data cover an area of ~78 arcmin2 in the B and R bands, while a mosaic of three pointings was obtained in the V band, covering an area of approximately 160 arcmin2. The galaxy sample is complete to (), () and (). Although the fit of a single Schechter function cannot be rejected in any band, the luminosity functions are better described by a sum of two Schechter functions for bright and faint galaxies, respectively. There is an indication for a presence of a dip in the luminosity functions in the range and . We find a marked luminosity segregation, in the sense that the number ratio of bright–to–faint galaxies decreases by a factor 4 from the center to outer regions. Our analysis supports the idea that ABCG 209 is an evolved cluster, resulting from the merger of two or more sub–clusters.

EGRET Upper Limits on the High‐Energy Gamma‐Ray Emission of Galaxy Clusters

We report EGRET upper limits on the high-energy gamma-ray emission from clusters of galaxies. EGRET observations between 1991 and 2000 were analyzed at positions of 58 individual clusters from a flux-limited sample of nearby X-ray bright galaxy clusters. Subsequently, a coadded image from individual galaxy clusters has been analyzed using an adequately adapted diffuse gamma-ray foreground model. The resulting 2 sigma upper limit for the average cluster is \~ 6 x 10^{-9} cm^{-2} s^{-1} for E > 100 MeV. Implications of the non--detection of prominent individual clusters and of the general inability to detect the X-ray brightest galaxy clusters as a class of gamma-ray emitters are discussed. We compare our results with model predictions on the high-energy gamma-ray emission from galaxy clusters as well as with recent claims of an association between unidentified or unresolved gamma-ray sources and Abell clusters of galaxies and find these contradictory.

Optical and X-Ray Clusters as Tracers of the Supercluster-Void Network. I. Superclusters of Abell and X-Ray Clusters

We study the distribution of Abell and X-ray–selected clusters of galaxies and derive selection functions of these cluster samples. We find that selection functions and percolation properties of Abell clusters of richness class R = 0 and R ≥ 1 are similar; the percolation of X-ray clusters occurs at the same dimensionless radius as the percolation of Abell clusters. We present a new catalog of superclusters of Abell clusters out to a redshift of zlim = 0.13, a catalog of X-ray clusters located in superclusters determined by Abell clusters, and a list of additional superclusters of X-ray clusters. We investigate the distribution of X-ray–selected clusters of galaxies with respect to superclusters determined by Abell clusters of galaxies and show that the distribution of X-ray clusters follows the supercluster-void network determined by Abell clusters. We find that X-ray clusters are more strongly clustered than other clusters: the fraction of X-ray clusters is higher in rich superclusters, and the fraction of isolated X-ray clusters is lower than the fraction of isolated Abell clusters. Poor, non-Abell X-ray clusters follow the supercluster-void network as well: these clusters are embedded in superclusters determined by Abell clusters and populate filaments between them.

A Possible Relationship between Quasars and Clusters of Galaxies

The distribution on the sky of clusters of galaxies shows significant association with relatively nearby, large, active galaxies. The pattern is that of clusters paired equidistant across a central galaxy with the apparent magnitudes and redshifts of their constituent galaxies being closely matched. The clusters and the galaxies in them tend to be strong X-ray and radio emitters, and their redshifts occur at preferred redshift values. The central, low-redshift galaxies often show evidence of ejection in the direction of these higher redshift clusters. In all these respects the clusters resemble closely quasars which have been increasingly shown for the last 34 years to be similarly associated with active parent galaxies. New, especially significant pairings of quasars are presented here, which are, at the same time, associated with Abell clusters of galaxies. It is argued here that, empirically, the quasars are ejected from active galaxies. They evolve to lower redshift with time, forming stars, and fragmenting at the end of their development into clusters of low-luminosity galaxies. The cluster galaxies can be at the same distance as their lower redshift parents because they still retain a component of their earlier, quasar intrinsic redshift.

Peculiarities of the radio emission of very rich Abell clusters

The mutual arrangement of very rich Abell clusters of galaxies influences the radio properties of these clusters, making it possible to explain certain peculiarities of their radio correlation functions.

Seeking the Local Convergence Depth. IV. Tully-Fisher Observations of 35 Abell Clusters

We present Tully-Fisher observations for 35 rich Abell clusters of galaxies. Results from I-band photometry and optical rotation curve work constitute the bulk of this paper. This is the third such data installment of an all-sky survey of 52 clusters in the distance range ~50 to 200 h-1 Mpc. The complete data set provides the basis for determining an accurate Tully-Fisher template relation and for estimating the amplitude and direction of the local bulk flow on a 100 h-1 Mpc scale.

Cluster winds blow along supercluster axes

Within Abell galaxy clusters containing wide-angle tailed radio sources, there is evidence of a ``prevailing wind'' which directs the WAT jets. We study the alignment of WAT jets and nearby clusters to test the idea that this wind may be a fossil of drainage along large-scale supercluster axes. We also test this idea with a study of the alignment of WAT jets and supercluster axes. Statistical test neighbours indicate no alignment of WAT jets towards nearest clusters, but do indicate approximately 98% confidence in alignment with the long axis of the supercluster in which the cluster lies. We find a preferred scale for such superclusters of order 25 Mpc $h^{-1}$.

Seeking the Local Convergence Depth: The Abell Cluster Dipole Flow to 200 [CLC][ITAL]h[/ITAL][/CLC][TSUP]−1[/TSUP] M[CLC]pc[/CLC

We have obtained new Tully-Fisher (TF) peculiar velocity measurements for 52 Abell galaxy clusters distributed throughout the sky between ~50 and 200 h-1 Mpc. The measurements are based on I-band photometry and optical rotation curves for a sample of 522 spiral galaxies, from which an accurate TF template relation has been constructed. Individual cluster TF relations are referred to the template to compute cluster peculiar motions. The reflex motion of the Local Group of galaxies is measured with respect to the reference frame defined by our cluster sample and the distant portion of the Giovanelli et al. cluster set. We find the Local Group motion in this frame to be 565±113 km s-1 in the direction (l, b)=(267°, 26°)±10° when peculiar velocities are weighted according to their errors. After optimizing the dipole calculation to sample equal volumes equally, the vector is 509±195 km s-1 toward (255°, 33°)±22°. Both solutions agree, to within 1 σ or better, with the Local Group motion as inferred from the cosmic microwave background (CMB) dipole. Thus, the cluster sample as a whole moves slowly in the CMB reference frame, its bulk flow being at most 200 km s-1.

The Locations of Gamma‐Ray Bursts Measured by COMPTEL

The COMPTEL instrument on the Compton Gamma Ray Observatory is used to measure the locations of gamma-ray bursts through direct imaging of MeV photons. In a comprehensive search, we have detected and localized 29 bursts observed between 1991 April 19 and 1995 May 31. The average location accuracy of these events is 125 (1 σ), including a systematic error of ~05, which is verified through comparison with Interplanetary Network (IPN) timing annuli. The combination of COMPTEL and IPN measurements results in locations for 26 of the bursts with an average "error box" area of only ~0.3 deg2 (1 σ). We find that the angular distribution of COMPTEL burst locations is consistent with large-scale isotropy and that there is no statistically significant evidence of small-angle autocorrelations. We conclude that there is no compelling evidence for burst repetition since no more than two of the events (or ~7% of the 29 bursts) could possibly have come from the same source. We also find that there is no significant correlation between the burst locations and either Abell clusters of galaxies or radio-quiet quasars. Agreement between individual COMPTEL locations and IPN annuli places a lower limit of ~100 AU (95% confidence) on the distance to the stronger bursts.

Seeking the Local Convergence Depth. I. Tully-Fisher Observations of the Clusters A168, A397, A569, A1139, A1228, and A1983.

We present first results of an all-sky observing program designed to improve the quality of the I band Tully-Fisher (TF) template and to obtain the reflex motion of the Local Group with respect to clusters to z = 0.06. We are obtaining between 5 and 15 TF measurements per cluster on a sample of 50 clusters at intermediate redshifts (0.02 < z < 0.06). Presentation of the data for seven Abell clusters of galaxies is given here. This data incorporates methods for estimating the true inclination of a spiral disk, an observational parameter undervalued for small angular-sized galaxies or for galaxies observed in poor seeing conditions.

Photometry of Brightest Galaxies in Twenty Abell Clusters.

view Abstract Citations References (27) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photometry of Brightest Galaxies in Twenty Abell Clusters. Gaidos, Eric J. Abstract CCD imaging and extractions from the Digitized Sky Survey were used to obtain photometry of the first- and second-ranked galaxies in twenty Abell galaxy clusters selected only on redshift (z < 0.25) and richness (R > 0). For each object, apparent magnitudes were calculated in circular apertures with radii of 5 h(-1) and 10 h(-1) kpc and a total magnitude estimated using an elliptical isophote fitting routine. The distribution of absolute magnitudes in the 10 h(-1) kpc radius aperture is consistent with that found in previous work and can be described by a gaussian with mean <M_1> = -21.54 +/- 0.10 and dispersion sigma_ {M_1} = 0.37 +/- 0.06. There is no evidence for significant luminosity evolution or dependence on cluster properties, although the small size of the sample precludes definitive limits. Publication: The Astronomical Journal Pub Date: August 1997 DOI: 10.1086/118487 Bibcode: 1997AJ....114..474G Keywords: GALAXIES: CLUSTERS: INDIVIDUAL: ABELL; GALAXIES: PHOTOMETRY full text sources ADS | data products SIMBAD (40) NED (20)

Are Gamma-Ray Bursts Indeed Correlated with Abell Clusters of Galaxies?

We study the possible correlation of a selected sample of 87 gamma-ray bursts that can be localized to ≤6 deg2 with 3616 Abell clusters of galaxies (with |b| > 30°) for which we have determined angular sizes. The intention is to confirm whether the bursts are related to Abell clusters of galaxies, as has been claimed by researchers who found a 95% confidence level correlation between Abell clusters and a subsample of 136 events from the BATSE 3B catalog. We find no correlation between the positions of gamma-ray bursts and those of Abell clusters. In fact, the number of observed events toward Abell clusters is even smaller than that expected to occur at random.

An X‐Ray and Optical Study of Matter Distribution in Clusters of Galaxies

A sample of 12 Abell clusters of galaxies has been studied in the optical and X-ray bands. The optical data are derived from automatic photometry based on microdensitometric scans of Palomar Schmidt F-band plates. ROSAT PSPC data were obtained from the public archive. Galaxy density and X-ray luminosity profiles have been constructed and deprojected by parametric and nonparametric techniques to obtain volume density profiles. We find a relation between the gas density ρgas and the galaxy density ρgal consistent with the prediction of the hydrostatic isothermal model. We confirm that more than 70% of the cluster mass is dark within 1.5 Mpc h -->−150 from the cluster center. Outside 250 kpc we find a nearly constant M/LV ratio, which on average is 137 M☉/L☉, implying that the galaxy mass traces the total matter distribution. The dark mass-to-light ratio has a similar behavior. We also find a baryonic fraction fb ≈ 0.2, which, assumed as representative of the cosmic value and compared with nucleosynthesis calculations, constrains the cosmological parameter Ω0 to be smaller than 0.25.

A 20 Centimeter VLA Survey of Abell Clusters of Galaxies. VII. Detailed Radio Images

We present detailed radio images, and models, obtained with the Very Large Array at 20 cm for 199 radio galaxies in Abell clusters of galaxies.

ROSATPSPC Observations of Cool Rich Clusters

We present the results of ROSAT PSPC observations of three cool (kT ≤ 3 keV) Abell clusters of galaxies (A262, A539, and A2589). Spatially resolved X-ray spectroscopy shows that the gas in these clusters is essentially isothermal beyond the central cooling flow region. The PSPC spectra of A262 also show excess soft X-ray absorption above that expected from the galactic hydrogen column density. The excess absorption is not confined to the central cooling flow region but is distributed across the entire field of view with a slight increase in absorption at large radii. We show that this excess absorption coincides with a region of galactic cirrus observed by IRAS. Using the 100 μm flux density toward A262, we derive a column density of molecular gas that is comparable to the column density of atomic gas and can account for the excess absorption. The spatial distribution of the molecular gas is also consistent with the observed variation in soft X-ray absorption across the PSPC field of view. Using the observed density and temperature profiles of the hot gas in these clusters, we determine their gravitating masses from the equation of hydrostatic equilibrium. The anisotropy parameter of the member galaxies is then calculated from the observed line-of-sight velocity dispersion and the X-ray—determined mass. For A262, we find that the early-type galaxies are virialized with a nearly isotropic velocity dispersion, while most of the spiral galaxies cannot be virialized for any value of the anisotropy parameter. There is also a strong alignment between the optical isophotes of the central dominant galaxy, the cluster X-ray isophotes in both A262 and A2589, and the large-scale orientation of the host supercluster. These results are consistent with a formation scenario in which clusters form through the accretion of gas and galaxies along large-scale filaments. We also calculate the entropy profile of the hot gas for a sample of groups, cool clusters, and hot clusters. We find that the gas entropy in cool clusters increases very gradually with radius while rich clusters show a much steeper gradient. The entropy of the core gas (beyond the cooling flow region) is essentially a constant in groups and rich clusters. These results suggest that the diffuse gas in groups and clusters was preheated before, or during, gravitational collapse. The marginal radial increase in the gas entropy in groups indicates that gravitational heating was almost negligible and the gas passed through weak shocks only as it was accreted. The steeper entropy gradient in rich clusters is consistent with the stronger shock heating expected in more massive systems.

A study of radial velocity members of eight rich clusters of galaxies

On the basis of a radial velocity criterion for cluster membership, supplemented by a consideration of surface density distribution, we calculate the distribution parameters and membership probabilities of individual galaxies for 8 Abell clusters of galaxies. The membership determination is shown to be a reasonable and a feasible one, and the distribution of the radial velocity dispersion to be in agreement with the dynamical model. An elongated structure seems to be universal in rich clusters. An obvious relationship between N A and σ c is found from these clusters and the mass to light ratio of rich clusters is found to lie between 100 and 600 h 100 −1, with an average value of 350 h 100 −1.

20 CM VLA Survey of Abell Clusters of Galaxies. VI. Radio/Optical Luminosity Functions

From a statistically complete sample of 188 radio galaxies in Abell clusters, we examine the radio/optical correlations, the FR I/II division, and the univariate and bivariate luminosity functions. As suggested by Owen (1993), the FR I/II division is shown to be a strong function of the optical luminosity of the host galaxy (proportional to L_opt^2). This dependence is also seen in the bivariate luminosity function, which suggests that the evolutionary tracks of radio sources and/or the initial conditions in the source are governed by the host galaxy properties. The probability for detecting radio emission increases with optical luminosity. The optical dependence is clearly separated in the integral luminosity functions which can be used as a constraint to models of FR I radio power evolution. Additionally, the source counts from the integrated univariate radio luminosity function (RLF) are consistent with our suggestion in paper V that radio sources may be a transient phenomenon which occurs in all elliptical galaxies at some time (or several times) over their lifetime. We find no statistically significant differences in the luminosity functions between rich cluster samples and radio sources not selected to reside in clusters. These results suggest that all radio galaxies live in similar environments in that the optical luminosity and the properties of the host galaxy are the most important parameters which affect radio source formation and evolution.

Another Look at the Abell Cluster Inertial Frame Bulk Flow

view Abstract Citations (11) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Another Look at the Abell Cluster Inertial Frame Bulk Flow Graham, Alister W. Abstract Recently, use has been made of the relationship between absolute magnitude and galaxy structure for the first-ranked galaxies in Abell clusters out to 15,000 km s 1, in a determination of a large bulk flow for this volume (see the recent work of Lauer & Postman). The technique uses the logarithmic slope of the galaxy luminosity profile, at 10 h -1 kpc, parameterized by alpha, as an indicator of the galactic structure. In examining this M-alpha relation, it is shown to be similar to a magnitude-radius relation. Fitting a de Vaucouleurs R^{114 }law profile to the Abell brightest cluster galaxy (BCG) sample of Lauer & Postman, the M-log .t'e relationship is used to test for Local Group motion with respect to the Abell cluster inertial reference frame (ACIF), defined by the BCG. A motion of 459 + 371 km s 1 toward 1 = 2030, b = 290 (l 320) is obtained when using the entire sample of 119 BCGs. This differs from the Local Group velocity inferred by the cosmic microwave background dipole, implying that the ACIF has a bulk flow of 738 + 158 km s - I toward 1 = 3300, b = +450 (l 260). Both vectors are consistent with those derived by Lauer & Postman. The BCGs studied are shown to be a very homogeneous set of objects, with their radial size corrected magnitudes having a scatter of only 0.26 mag, making them a powerful tool in measuring galaxy distances and peculiar velocities. Using accurate CCD photometry, the galaxy light profiles are seen to be well fitted by an R^{1 4 }law. The slope of the mu -log re relation, for the BCG, is found to have a value of 2.87. Furthermore, there is negligible evidence for curvature in this bright portion of the fundamental plane. It is shown that use of the M-alpha relation is preferred over the M-log re relation in this type of analysis of bulk flow motion, as it results in considerably smaller error bars. Publication: The Astrophysical Journal Pub Date: March 1996 DOI: 10.1086/176866 Bibcode: 1996ApJ...459...27G Keywords: COSMOLOGY: OBSERVATIONS; GALAXIES: DISTANCES AND REDSHIFTS; GALAXIES: FUNDAMENTAL PARAMETERS; GALAXIES: PHOTOMETRY; COSMOLOGY: LARGE-SCALE STRUCTURE OF UNIVERSE full text sources ADS | data products NED (119) SIMBAD (118)

Observations of High Dispersion Clusters of Galaxies: Constraints on Cold Dark Matter

view Abstract Citations (51) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of High Dispersion Clusters of Galaxies: Constraints on Cold Dark Matter Oegerle, William R. ; Hill, John M. ; Fitchett, Michael J. Abstract We have studied the dynamics of several Abell clusters of galaxies, which were previously reported to have large velocity dispersions, and hence very large masses. In particular, we have investigated the assertion of Frenk et al. (1990) that clusters with intrinsic velocity dispersions ~> 1200 km s^-1^ are extremely rare in the universe, and that large observed dispersions are due to projection effects. We report redshifts for 303 galaxies in the fields of A1775, A2029, A2142, and A2319, obtained with the Nessie multifiber spectrograph at the Mayall 4 m telescope. A1775 appears to be two poor, interacting clusters, separated in velocity space by ~3075 km s^-1^ (in the cluster rest frame). A2029 has a velocity dispersion of 1436 km s^-1^, based on 85 cluster member redshifts. There is evidence that a group or poor cluster of galaxies of slightly different redshift is projected onto (or is merging with) the core of A2029. However, the combined kinematic and x-ray data for A2029 argue for an intrinsically large dispersion for this cluster. Based on redshifts for 103 members of A2142, we find a dispersion of 1280 km s^-1^, and evidence for subclustering. With 130 redshifts in the A2319 field, we have isolated a subcluster ~10' NW of the cD galaxy. After its removal, A2319 has a velocity dispersion of 1324 km s^-1^. The data obtained here have been combined with recent optical and X-ray data for other supposedly high-mass clusters to study the cluster velocity dispersion distribution in a sample of Abell clusters. We find that clusters with true velocity dispersions ~> 1200 km s^-1^ are not extremely rare, but account for ~5% of all Abell clusters with R >= 0. If these clusters are in virial equilibrium, then our results are inconsistent with a high-bias (b~>22), high-density CDM model. Publication: The Astronomical Journal Pub Date: July 1995 DOI: 10.1086/117495 Bibcode: 1995AJ....110...32O Keywords: DARK MATTER; GALAXIES: CLUSTERING; GALAXIES: EVOLUTION full text sources ADS | data products SIMBAD (317) NED (308)