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1.
We analyze the data presented in a previous paper by Gyulzadyan and Petrosian, and discuss the results of a statistical investigation
of the relationship between SBS galaxies and Zwicky clusters. The main results are that SBS galaxies follow the overall galaxy
distribution in clusters and they do not avoid any type of Zwicky cluster. There is a significantly higher probability of
finding SBS galaxies occurring in medium compact clusters than in open clusters. They also follow the well-established morphology-density
relation. Earlier morphological type, higher luminosity, larger linear size, and redder SBS galaxies tend to be found in clusters
with higher compactness, or in more compact regions of the clusters. The number distribution of SBS galaxies in Zwicky open
clusters probably follows the distribution of normal galaxies. The number distribution of SBS galaxies in medium compact and
compact clusters shows two-maxima structure.
Published in Astrofizika, Vol. 52, No. 2, pp. 225–236 (May 2009). 相似文献
2.
Observations of quasars suggest that compact quasars with flat radio spectra belong to the class of dwarf galaxies and extended quasars with steep spectra to the one of bright galaxies. This can be seen also in the associations of quasars with clusters of galaxies, compact quasars occurring in nearby clusters and extended quasars in distant clusters. 相似文献
3.
本文在星系有偏袒形成的冷暗物质模型框架下,假定星系都在红移～5时形成,研究了星系群和星系团的形成对星系演化的影响。由示冷暗物质模型中各种不同尺度扰动的幅度相近,星系群和星系团的维里化与星系的维里化在时间上比较接近,在星系群或星系团的维里化过程中获得巨大维里速度的星系仍然富有气体,因此,当它们因为频繁的互相碰撞,或者因为进入星系团中心区的稠密星系际介质受到巨大冲压,或者是被附近射电星系的喷流所产生的高压茧状体所包容,都可能激发活动性,造成恒星的爆发性形成.高红移星系团中观测到的B-O效应和高红移射电星系的光学像与射电喷流同轴向现象都可以据此得到解释. 相似文献
4.
B. N. G. Guthrie 《Astrophysics and Space Science》1977,52(1):177-188
Clusters of galaxies in which radio emission at low frequencies (178 MHz) has been detected were classified on the Bautz-Morgan (BM) system according to the dominance of the brightest galaxy. Radio sources with steep low-frequency spectra occur in clusters of all BM types but more often in rich clusters; the distributions of BM types for clusters with high and low spectral indices between 38 and 178 MHz are similar. Glass copies of Mount Palomar Sky Survey plates were measured to determine the distribution of the ten brightest galaxies in clusters without dominant galaxies. Some clusters were found to have central cores of bright galaxies which may reflect mass segregation of galaxies due to dynamical friction. The bright galaxies in such cores may later merge to form dominant cD galaxies. The positions of the cD galaxies and cores of bright galaxies are often at projected distances <200 kpc from the low-frequency radio emission. The low-frequency spectrum of radio emission associated with a cD galaxy may be either steep or normal, but the low-frequency spectrum from a core of bright galaxies is usually steep. A steep spectrum may develop when a radio source is confined by hot gas in a cluster over a long period (109 yr). Confinement would probably occur for radio sources associated with bright galaxies in the cores of clusters and cD galaxies in clusters. However, cD galaxies may have recurrent radio outbursts so that steep spectra are not always observed. 相似文献
5.
The location of galaxies in 377 rich Abell galaxy clusters is discussed. We compared the distributions of galaxies in the sample containing all galaxies with the sample compiled from the 20 brightest objects. Counts in circular sectors with angle width equal to 30î show isotropy. Only in the case of BM I clusters and the coordinate system related to the cluster major axis did we find anisotropic distributions. We investigated also the distributions of galaxy position angles within clusters exhibiting isotropy. The structure position angles for both samples have been studied as well. They appeared to be different. The difference in location of galaxies in the case of cD clusters, as well as the more elliptical shape and different position angles of samples containing bright galaxies is observed. 相似文献
6.
K. -H. Schmidt 《Astrophysics and Space Science》1975,34(1):23-31
The existence of intergalactic dust has been proved by the following observational facts: the decrease of the numbers of distant galaxies and clusters of galaxies behind the central regions of near clusters of galaxies; the different distributions of RR Lyrae stars and galaxies near ι Microscopii (Hoffmeister's cloud); the dependence of colour excesses of galaxies on supergalactic coordinates as well as on the surface density of bright galaxies; the colour index vs redshift correlation of quasistellar objects. The densities of intergalactic dust are estimated to be between 5×10?30 g cm?3 (near the centers of clusters of galaxies) and 2×10?34 g cm?3 (in general intergalactic space). The grains may be formed either in the early phases of the Universe (25相似文献
7.
With the advent of the new generation wide-field cameras it became possible to survey in an unbiased mode galaxies spanning a variety of local densities, from the core of rich clusters, to compact and loose groups, down to filaments and voids. The sensitivity reached by these instruments allowed to extend the observation to dwarf galaxies, the most “fragile” objects in the universe. At the same time models and simulations have been tailored to quantify the different effects of the environment on the evolution of galaxies. Simulations, models, and observations consistently indicate that star-forming dwarf galaxies entering high-density environments for the first time can be rapidly stripped from their interstellar medium. The lack of gas quenches the activity of star formation, producing on timescales of \({\sim }\)1 Gyr quiescent galaxies with spectro-photometric, chemical, structural, and kinematical properties similar to those observed in dwarf early-type galaxies inhabiting rich clusters and loose groups. Simulations and observations consistently identify ram pressure stripping as the major effect responsible for the quenching of the star-formation activity in rich clusters. Gravitational interactions (galaxy harassment) can also be important in groups or in clusters whenever galaxies have been members since early epochs. The observation of clusters at different redshifts combined with the present high infalling rate of galaxies onto clusters indicate that the quenching of the star-formation activity in dwarf systems and the formation of the faint end of the red sequence is a very recent phenomenon. 相似文献
8.
A correlation analysis is made of the spatial distribution of galaxies in the Coma, Bridge, and A1367 clusters, which form
the Coma supercluster. The scale of the clustering of galaxies and the variation in their density distribution with the main
parameters of the galaxies– luminosity, morphological type, and observed H I deficiency in the 21 cm line– are evaluated.
The mass-to-luminosity ratios are computed for the spiral galaxies in the Coma, Bridge, and A1367 clusters. It is suggested
that a larger fraction of hypothetical dark matter may be concentrated in the spiral galaxies which predominantly populate
the subclusters previously identified by us within these clusters than in the spiral galaxies observed in the peripheral regions
of the clusters. 相似文献
9.
F. W. Baier 《Astronomische Nachrichten》1976,297(6):295-300
The structures of compact groups of galaxies are compared with the structures of rich clusters of galaxies. It was established that there are structural similarities between these two types of clusters of galaxies. It is imaginable that these structures are typical for all such complexes of galaxies and that the different structures are due to different initial conditions at the beginning of their evolution. For a final answer on this question it is necessary to accumulate more observational material with respect to the distribution of galaxies in such clusters. As part of a larger programme the present paper contains the derived number-density distributions and core radii for ten clusters. 相似文献
10.
Jens Bicker U. Fritze-von Alvensleben K.J. Fricke 《Astrophysics and Space Science》2003,284(2):463-466
The galaxy population in rich local galaxy clusters shows a ratio of one quarter elliptical galaxies, two quarters S0 galaxies,
and one quarter spiral galaxies. Observations of clusters at redshift 0.5 show a perspicuously different ratio, the dominant
galaxy type are spiral galaxies with a fraction of two quarters while the number of S0 galaxies decreases to a fraction of
one quarter (Dressler et al. 1997). This shows an evolution of the galaxy population in clusters since redshift 0.5 and it
has been suspected that galaxy transformation processes during the infall into a cluster are responsible for this change.
These could be merging, starburst or ram-pressure stripping. We use our evolutionary synthesis models to describe various
possible effects of those interactions on the star formation of spiral galaxies infalling into clusters. We study the effects
of starbursts of various strengths as well as of the truncation of star formation at various epochs on the color and luminosity
evolution of model galaxies of various spectral types. As a first application we present the comparison of our models with
observed properties of the local S0 galaxy population to constrain possible S0 formation mechanisms in clusters. Application
to other types of galaxies is planned for the future.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
11.
12.
A. M. Newsam I. M. McHardy L. R. Jones K. O. Mason 《Monthly notices of the Royal Astronomical Society》1999,310(1):255-261
At the faint end of the deepest X-ray surveys, a population of X-ray luminous galaxies is seen. In this paper, we present the results of a cross-correlation between the residual, unresolved X-ray photons in a very deep X-ray survey and the positions of faint galaxies, in order to examine the importance of these objects at even fainter flux levels. We measure a significant correlation on all angular scales up to ∼1 arcmin. This signal could account for a significant fraction of the unresolved X‐ray background, approximately 35 per cent if the clustering is similar to optically selected galaxies. However, the angular form of the correlation is seen to be qualitatively similar to that expected for clusters of galaxies and the X-ray emission could be associated with hot gas in clusters or with QSOs within galaxy clusters rather than emission from individual faint galaxies. The relative contribution from each of these possibilities cannot be determined with the current data. 相似文献
13.
We analyze the properties of the clusters of galaxies in the region of the Ursa Major (UMa) supercluster using observational data from SDSS and 2MASS catalogs. The region studied includes a supercluster (with a galaxy and cluster overdensity of 3 and 15, respectively) and field clusters inside the 150-Mpc diameter surrounding region. The total dynamical mass of 10 clusters of galaxies in UMa is equal to 2.25 × 1015 M ⊙, and the mass of 11 clusters of galaxies in the UMa neighborhood is equal to 1.70 × 1015 M ⊙. The fraction of early-type galaxies brighter than M K * + 1 in the virialized regions of clusters is, on the average, equal to 70%, and it is virtually independent on the mass of the cluster. The fraction of these galaxies and their average photometric parameters are almost the same both for UMa clusters and for the clusters located in its surroundings. Parameters of the clusters of galaxies, such as infrared luminosities up to a fixed magnitude, the mass-to-luminosity ratio, and the number of galaxies have almost the same correlations with the cluster mass as in other samples of galaxies clusters. However, the scatter of these parameters for UMa member clusters is twice smaller than the corresponding scatter for field clusters, possibly, due to the common origin of UMa clusters and synchronized dynamical evolution of clusters in the supercluster. 相似文献
14.
R. M. González Delgado V. M. Muñoz Marín E. Pérez H. R. Schmitt R. Cid Fernandes 《Astrophysics and Space Science》2009,320(1-3):61-67
Nuclear stellar clusters are a common phenomenon in spirals and in starburst galaxies, and they may be a natural consequence of the star formation processes in the central regions of galaxies. HST UV imaging of a few Seyfert 2 galaxies have resolved nuclear starbursts in Seyfert 2 revealing stellar clusters as the main components of the extended emission. However, we do not know whether stellar clusters are always associated with all types of nuclear activity. We present HST NUV and optical images to study the role that stellar clusters play in different types of AGNs. Also with these images, we study the circumnuclear dust morphology as a probe of the circumnuclear environment of AGNs. 相似文献
15.
Y. Fukazawa K. Makishima T. Tamura K. Nakazawa H. Ezawa Y. Ikebe K. Kikuchi T. Ohashi 《Monthly notices of the Royal Astronomical Society》2000,313(1):21-31
We measured metal abundances of the intracluster medium in the central regions of 34 nearby clusters of galaxies, using ASCA data. Clusters that have a sharp X-ray emission centred on a cD galaxy are commonly found to exhibit a central increment in the Fe abundance, which is more pronounced in lower temperature clusters; +(0.1–0.2) solar at kT >5 keV, compared with +(0.2–0.3) solar at 1.5< kT <4 keV. These central excess metals are thought to be ejected from cD galaxies. Several low-temperature cD type clusters also show significant Si abundance increase by +(0.1–0.2) solar at the central region. Compared with the Si-rich abundances observed in the outer regions of rich clusters, the Si to Fe abundance ratio of central excess metals tends to be near the solar ratio, implying that type Ia products from cD galaxies are dominant for the central excess metals. On the other hand, some other clusters do not show the central Fe abundance increase. As these clusters tend to contain two or three central giant galaxies, it is suggested that galaxy interactions have removed the central abundance increase. 相似文献
16.
K. Rudnicki 《Astronomische Nachrichten》1976,297(6):317-322
A morphological box for the space distribution of galaxies and dark matter as the consequence of various types of cosmogonical hypotheses is presented. A short review of concepts of clustering of galaxies is given. One has to distinguish between the phenomena of “clusters of galaxies” and of “clustering of galaxies”. The second notion is more general. The investigations of KIANG , FLIN , and PEEBLES speak in favour of general clustering rather than overal existence of individual clusters. Individuals such as our Supergalaxy, Coma cluster etc. seem rather to be exceptional features. 相似文献
17.
The HI content of galaxies in the Eridanus group is studied using the GMRT observations and the HIPASS data. A significant
HI deficiency up to a factor of 2–3 is observed in galaxies in the high galaxy density regions. The HI deficiency in galaxies
is observed to be directly correlated to the local projected galaxy density, and inversely correlated to the line-of-sight
radial velocity. Furthermore, galaxies with larger optical diameters are predominantly in the lower galaxy density regions.
It is suggested that the HI deficiency in Eridanus is due to tidal interactions. In some galaxies, evidences of tidal interactions
are seen. An important implication is that significant evolution of galaxies can take place in the group environment. In the
hierarchical way of formation of clusters via mergers of groups, a fraction of the observed HI deficiency in clusters could
have originated in groups. The co-existence of S0s and severely HI deficient galaxies in the Eridanus group suggests that
tidal interaction is likely to be an effective mechanism for transforming spirals to S0s. 相似文献
18.
Fumiaki Nakata Richard G. Bower Michael L. Balogh David J. Wilman 《Monthly notices of the Royal Astronomical Society》2005,357(2):679-686
We investigate the evolution of the star formation rate in cluster galaxies. We complement data from the Canadian Network for Observational Cosmology 1 (CNOC1) cluster survey (0.15 < z < 0.6) with measurements from galaxy clusters in the Two-degree Field (2dF) galaxy redshift survey (0.05 < z < 0.1) and measurements from recently published work on higher-redshift clusters, up to almost z = 1 . We focus our attention on galaxies in the cluster core, i.e. galaxies with r < 0.7 h −1 70 Mpc . Averaging over clusters in redshift bins, we find that the fraction of galaxies with strong [O ii ] emission is ≲20 per cent in cluster cores, and the fraction evolves little with redshift. In contrast, field galaxies from the survey show a very strong increase over the same redshift range. It thus appears that the environment in the cores of rich clusters is hostile to star formation at all the redshifts studied. We compare this result with the evolution of the colours of galaxies in cluster cores, first reported by Butcher and Oemler. Using the same galaxies for our analysis of the [O ii ] emission, we confirm that the fraction of blue galaxies, which are defined as galaxies 0.2 mag bluer in the rest-frame B – V than the red sequence of each cluster, increases strongly with redshift. Because the colours of galaxies retain a memory of their recent star formation history, while emission from the [O ii ] line does not, we suggest that these two results can best be reconciled if the rate at which the clusters are being assembled is higher in the past, and the galaxies from which it is being assembled are typically bluer. 相似文献
19.
Hubble Space Telescope observations of distant clusters have suggested a steep increase in the proportion of S0 galaxies between clusters at high redshifts and similar systems at the present day. It has been proposed that this increase results from the transformation of the morphologies of accreted field galaxies from spirals to S0s. We have simulated the evolution of the morphological mix in clusters based on a simple phenomenological model where the clusters accrete a mix of galaxies from the surrounding field, the spiral galaxies are transformed to S0s (through an unspecified process) and are added to the existing cluster population. We find that in order to reproduce the apparently rapid increase in the ratio of S0 galaxies to ellipticals in the clusters, our model requires that: (1) the galaxy accretion rate has to be high (typically, more than half of the present-day cluster population must have been accreted since z ∼0.5) , and (2) most of the accreted spirals, with morphological types as late as Scdm, must have transformed to S0s. Although the latter requirement may be difficult to meet, it is possible that such bulge-weak spirals have already been 'pre-processed' into the bulge-strong galaxies prior to entering the cluster core and are eventually transformed into S0s in the cluster environment. On the basis of the evolution of the general morphological mix in clusters our model suggests that the process responsible for the morphological transformation takes a relatively long time (∼ 1–3 Gyr) after the galaxy has entered the cluster environment. 相似文献
20.
E. H. Nikogossian 《Astrophysics》2001,44(3):305-314
The hierarchical and dynamical structure of three clusters of galaxies, A 2634, A 1983, and DC 0428-53, is investigated. Based on their example, we can say that the central cD galaxies play the leading role in clusters, affecting the course of their evolution. Radio and x-ray galaxies are not always part of the substructure. The morphological composition of various hierarchical subgroups depends on the stage of evolution. Clusters have a tendency to be oriented in the direction toward the nearest neighbor. 相似文献