共查询到20条相似文献，搜索用时 250 毫秒
1.
E. Ellingson 《Astrophysics and Space Science》2003,285(1):9-18
The galaxy populations in present-day clusters are distinctly different from those of the field, indicating that environment
plays a strong role in galaxy evolution. This review discusses some of the recent observations of moderate to high redshift
clusters. A consistent picture of galaxy evolution in clusters appears to be emerging, which includes a population of galaxies
which formed early in the cluster history, as well as field galaxies which have had their star formation truncated upon falling
into the cluster potential. Galaxy interactions probably play an important role in exhausting star formation in some of these
galaxies. However, there is significant variation in the populations of different cluster samples, with substantial evidence
that some galaxies have their star formation terminated more gradually. This suggests that different mechanisms may dominate
in different clusters, perhaps because of the recent merging history of the clusters. We also present a recent analysis of
population gradients in clusters which suggests that the observed evolution in cluster populations is consistent with a scenario
where changing infall rates drive the fraction of star forming galaxies in clusters, rather than a changing physical mechanism
within the cluster. Thus, galaxy populations may provide a fundamental measure of the growth of large scale structure.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Ram-pressure stripping can remove significant amounts of gas from galaxies that orbit in clusters and massive groups, and thus has a large impact on the evolution of cluster galaxies. In this paper, we reconstruct the present-day distribution of ram pressure and the ram-pressure histories of cluster galaxies. To this aim, we combine the Millennium Simulation and an associated semi-analytic model of galaxy evolution with analytic models for the gas distribution in clusters. We find that about one quarter of galaxies in massive clusters are subject to strong ram pressures that are likely to cause an expedient loss of all gas. Strong ram pressures occur predominantly in the inner core of the cluster, where both the gas density and the galaxy velocity are higher. Since their accretion on to a massive system, more than 64 per cent of galaxies that reside in a cluster today have experienced strong ram pressures of >10−11 dyn cm−2 which most likely led to a substantial loss of the gas. 相似文献
3.
对于星系际弥散恒星的研究是分别从观测、数值模拟和半解析模型这三个方面进行的.现在已经在邻近星系团及中低红移处观测到弥散恒星,甚至在Virgo及Coma星系团中观测到了单个的弥散恒星.观测数据的积累使得人们能够从统计上了解星系际弥散恒星的性质.研究表明星系际弥散恒星围绕着星系团势阱中心呈椭球状对称分布,其在星系团恒星总质... 相似文献
4.
A. D. Romeo N. R. Napolitano G. Covone J. Sommer-Larsen V. Antonuccio-Delogu † M. Capaccioli 《Monthly notices of the Royal Astronomical Society》2008,389(1):13-26
N -body/hydrodynamical simulations of the formation and evolution of galaxy groups and clusters in a Λ cold dark matter (ΛCDM) cosmology are used in order to follow the building-up of the colour–magnitude relation in two clusters and in 12 groups. We have found that galaxies, starting from the more massive, move to the red sequence (RS) as they get aged over times and eventually set upon a 'dead sequence' (DS) once they have stopped their bulk star formation activity. Fainter galaxies keep having significant star formation out to very recent epochs and lie broader around the RS. Environment plays a role as galaxies in groups and cluster outskirts hold star formation activity longer than the central cluster regions. However, galaxies experiencing infall from the outskirts to the central parts keep star formation on until they settle on to the DS of the core galaxies. Merging contributes to mass assembly until z ∼ 1, after which major events only involve the brightest cluster galaxies.
The emerging scenario is that the evolution of the colour–magnitude properties of galaxies within the hierarchical framework is mainly driven by star formation activity during dark matter haloes assembly. Galaxies progressively quenching their star formation settle to a very sharp 'red and dead' sequence, which turns out to be universal, its slope and scatter being almost independent of the redshift (since at least z ∼ 1.5) and environment.
Differently from the DS, the operatively defined RS evolves more evidently with z , the epoch when it changes its slope being closely corresponding to that at which the passive galaxies population takes over the star-forming one: this goes from z ≃ 1 in clusters down to 0.4 in normal groups. 相似文献
The emerging scenario is that the evolution of the colour–magnitude properties of galaxies within the hierarchical framework is mainly driven by star formation activity during dark matter haloes assembly. Galaxies progressively quenching their star formation settle to a very sharp 'red and dead' sequence, which turns out to be universal, its slope and scatter being almost independent of the redshift (since at least z ∼ 1.5) and environment.
Differently from the DS, the operatively defined RS evolves more evidently with z , the epoch when it changes its slope being closely corresponding to that at which the passive galaxies population takes over the star-forming one: this goes from z ≃ 1 in clusters down to 0.4 in normal groups. 相似文献
5.
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
6.
7.
We review here the interplay of cluster and galaxy evolution. As a case study, we consider the Butcher-Oemler effect and propose
that it is the result of the changing rate of cluster merger events in a hierarchical universe. This case study highlights
the need for new catalogs of clusters and groups that possess quantified morphologies. We present such a sample here, namely
the Sloan Digital Sky Survey (SDSS) C4 Catalog, which has been objectively-selected from the SDSS spectroscopic galaxy sample.
We outline here the C4algorithm and present first results based on the SDSS Early Data Release, including an X-ray luminosity-velocity
dispersion (Lx-σv) scaling relationship (as a function of cluster morphology) and the density-SFR relation of galaxies within C4 clusters (Gomez et al., 2003). We also discuss the merger of Coma and the NGC4839 group and
its effect on the galaxy populations in these systems. We finish with a brief discussion of a new sample ofHΔ-selected galaxies
(i.e., k+a, post-starburst galaxies) obtained from the SDSS spectroscopic survey.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
星系团研究涉及面极广，此处仅简介光学研究的若干方面。全文分为两篇，本篇中介绍星系团表、星系团的大尺度分布、星系团的一般性质；第二篇中将介绍团星系的演化、环境与星系形态，并作简要的展望。 相似文献
9.
W. Scott Smith 《Astrophysics and Space Science》1989,157(1-2):215-219
The main purpose of this paper is to present a photometrical evolutionary model for galaxies belonging to rich clusters. This numerical code puts together both cluster dynamics and galaxy photometry in order to obtain theoretical predictions for galaxy evolution, directly comparable with observations. We have specially taken into account the galaxy-cluster interactions and the intrinsic galaxy evolution. 相似文献
10.
Kenji Bekki 《Astrophysics and Space Science》2001,276(2-4):1033-1036
A significant fraction of clusters of galaxies are observed to have substructure, which implies that merging between clusters
and subclusters is a rather common physical process in cluster formation. It still remains unclear how cluster merging affects
the evolution of cluster member galaxies. We report the results of numerical simulations that show the dynamical evolution
of a gas-rich, late-type spiral in a merger between a small group of galaxies and a cluster. The simulations demonstrate that
the time-dependent tidal gravitational field during merging excites non-axisymmetric structure of the galaxy, subsequently
drives efficient transfer of gas to the central region and finally triggers a secondary starburst. This result provides a
close physical relationship between the emergence of starburst galaxies and the formation of substructure in clusters. We
accordingly interpret post-starburst galaxies located near substructure of the Coma Cluster as one observational example indicating
the global tidal effects of group–cluster merging. Our numerical results further suggest a causal link between the observed
excess of blue galaxies in distant clusters and the cluster virialization process through hierarchical merging of subclusters.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
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
12.
星系团研究涉及面极广，此处仅简介光学研究的若干方面，全文分为两篇，前一篇中已知介绍了星系团表，星系团有大尺度分布，星系团的一般性质，本篇中则介绍团星系的演化，环境与星系形态，并作简要的展望。 相似文献
13.
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
14.
A.J. Benson C.S. Frenk C.M. Baugh S. Cole C.G. Lacey 《Monthly notices of the Royal Astronomical Society》2001,327(4):1041-1056
We follow the evolution of the galaxy population in a ΛCDM cosmology by means of high-resolution N -body simulations in which the formation of galaxies and their observable properties are calculated using a semi-analytic model. We display images of the spatial distribution of galaxies in the simulations that illustrate its evolution and provide a qualitative understanding of the processes responsible for the various biases that develop. We consider three specific statistical measures of clustering at and : the correlation length (in both real and redshift space) of galaxies of different luminosity, the morphology–density relation and the genus curve of the topology of galaxy isodensity surfaces. For galaxies with luminosity below L ∗, the correlation length depends very little on the luminosity of the sample, but for brighter galaxies it increases very rapidly, reaching values in excess of 10 h −1 Mpc. The 'accelerated' dynamical evolution experienced by galaxies in rich clusters, which is partly responsible for this effect, also results in a strong morphology–density relation. Remarkably, this relation is already well-established at . The genus curves of the galaxies are significantly different from the genus curves of the dark matter, however this is not a result of genuine topological differences but rather of the sparse sampling of the density field provided by galaxies. The predictions of our model at will be tested by forthcoming data from the 2dF and Sloan galaxy surveys, and those at by the DEEP and VIRMOS surveys. 相似文献
15.
Andrew R. Liddle Pedro T. P. Viana A. Kathy Romer Robert G. Mann 《Monthly notices of the Royal Astronomical Society》2001,325(2):875-880
The redshift evolution of the galaxy cluster temperature function is a powerful probe of cosmology. However, its determination requires the measurement of redshifts for all clusters in a catalogue, which is likely to prove challenging for large catalogues expected from XMM-Newton , which may contain of the order of 2000 clusters with measurable temperatures, distributed around the sky. In this paper we study the apparent cluster temperature, which can be obtained without cluster redshifts. We show that the apparent temperature function itself is of limited use in constraining cosmology, and so concentrate our focus on studying how apparent temperatures can be combined with other X-ray information to constrain the cluster redshift. We also briefly study the circumstances under which the non-thermal spectral features can provide redshift information. 相似文献
16.
R. Vílchez-Gómex G. A. Bruzual R. Pelló R. Domínguez 《Astrophysics and Space Science》2001,276(2-4):757-764
We have developed model predictions for the morphological distribution of cluster galaxies as a function of the cluster-centric
distance and the local galaxy density, using a semi-analytical code. This code allows us to obtain magnitudes and colours
for cluster galaxies at different redshifts, and thus to study in detail the evolution of the colour–magnitude relation of
specific distant clusters.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
The UV upturn phenomenon found in bright elliptical galaxies has notable implications for stellar evolution, galaxy evolution and even for cosmology. The recent space observations of three galaxy clusters made by Brown and his collaborators shed great lights on this field of study. Theoretical models are being improved based on such data. While the core-helium burning stars remain the strongest candidate for the UV upturn, there is a growing concern that the canonical models may be missing important elements, such as binaries. I review the current theoretical understanding and future prospects. 相似文献
18.
Starburst galaxies are extremely luminous objects with an abundance of young massive stars and a disturbed optical morphology.
Famous examples such as the Antennae, involve major mergers, but the starburst phenomenon can also be triggered in a more
gentle, minor merger. Such an event disturbs but does not disrupt the primary galaxy (i.e. the primary will recover from the
interaction without a drastic jump along the Hubble sequence). In such an interaction a significant number of super-star clusters
(SSCs) are formed,which may be the progenitors of present-day globular clusters. The ubiquity of globular cluster systems
among a wide range of galaxy types suggests that these interactions play a significant role in the evolution of ‘normal’ galaxies.
Therefore to understand the formation and evolution of galaxies, it is essential to understand such processes. Here we present
a HST WFPC2 broad-band study of three starburst galaxies with different merger histories.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
19.
Xin-Fa Deng Jun Song Yi-Qing Chen Peng Jiang Ying-Ping Ding 《Astrophysics and Space Science》2014,352(2):833-838
Using two volume-limited Main galaxy samples of the Sloan Digital Sky Survey Data Release 10 (SDSS DR10), we investigate the dependence of the clustering properties of galaxies on stellar velocity dispersion by cluster analysis. It is found that in the luminous volume-limited Main galaxy sample, except at r=1.2, richer and larger systems can be more easily formed in the large stellar velocity dispersion subsample, while in the faint volume-limited Main galaxy sample, at r≥0.9, an opposite trend is observed. According to statistical analyses of the multiplicity functions, we conclude in two volume-limited Main galaxy samples: small stellar velocity dispersion galaxies preferentially form isolated galaxies, close pairs and small group, while large stellar velocity dispersion galaxies preferentially inhabit the dense groups and clusters. However, we note the difference between two volume-limited Main galaxy samples: in the faint volume-limited Main galaxy sample, at r≥0.9, the small stellar velocity dispersion subsample has a higher proportion of galaxies in superclusters (n≥200) than the large stellar velocity dispersion subsample. 相似文献