共查询到20条相似文献，搜索用时 797 毫秒
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Yang Wang Christian R. Kaiser 《Monthly notices of the Royal Astronomical Society》2008,388(2):677-696
By combining a model for the evolution of the radio luminosity of an individual source with the radio luminosity function, we perform a multidimensional Monte Carlo simulation to investigate the cosmological evolution of the Fanaroff–Riley type II (FR II) radio galaxy population by generating large artificial samples. The properties of FR II sources are required to evolve with redshift in the artificial samples to fit the observations. Either the maximum jet age or the maximum density of the jet environment or both evolve with redshift. We also study the distribution of FR II source properties as a function of redshift. From currently available data we cannot constrain the shape of the distribution of environment density or age, but jet power is found to follow a power-law distribution with an exponent of approximately −2. This power-law slope does not change with redshift out to z = 0.6 . We also find the distribution of the pressure in the lobes of FR II sources to evolve with redshift up to z ∼ 1.2 . 相似文献
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Peter J. Boyce Steven Phillipps J. Bryn Jones Simon P. Driver Rodney M. Smith Warrick J. Couch 《Monthly notices of the Royal Astronomical Society》2001,328(1):277-282
We present the results of a study of the morphology of the dwarf galaxy population in Abell 868, a rich, intermediate-redshift cluster which has a galaxy luminosity function (LF) with a steep faint-end slope . A statistical background subtraction method is employed to study the colour distribution of the cluster galaxies. This distribution suggests that the galaxies contributing to the faint-end of the measured cluster LF can be split into three populations: dwarf irregular galaxies (dIrrs) with dwarf elliptical galaxies (dEs) with and contaminating background giant ellipticals (gEs) with . The removal of the contribution of the background gEs from the counts only marginally lessens the faint-end slope . However, the removal of the contribution of the dIrrs from the counts produces a flat LF . The dEs and the dIrrs have similar spatial distributions within the cluster, except that the dIrrs appear to be totally absent within a central projected radius of about 0.2 Mpc . The number densities of both dEs and dIrrs appear to fall off beyond a projected radius of ≃ 0.35 Mpc. We suggest that the dE and dIrr populations of A868 have been associated with the cluster for similar time-scales, but evolutionary processes such as 'galaxy harassment' tend to fade the dIrr galaxies while having a much smaller effect on the dE galaxies. The harassment would be expected to have the greatest effect on dwarfs residing in the central parts of the cluster. 相似文献
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Volker Springel & Simon D. M. White 《Monthly notices of the Royal Astronomical Society》1998,298(1):143-152
A new method is presented to obtain a non-parametric maximum likelihood estimate of the luminosity function and the selection function of a flux-limited redshift survey. The method parametrizes the selection function as a series of stepwise power laws and allows possible evolution of the luminosity function. We also propose a new technique to estimate the rate of evolution of the luminosity function. This is based on a minimization of the observed large-scale power with respect to the evolutionary model. We use an ensemble of mock surveys extracted from an N -body simulation to verify the power of this method. We apply our estimators to the 1.2-Jy survey of IRAS galaxies. We find a far-infrared luminosity function in good agreement with previously published results and evidence for rather strong evolution. If the comoving number density of IRAS galaxies is assumed to scale ∝ (1 + z ) P , we estimate P = 4.3 ± 1.4. 相似文献
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Roberto De Propris Matthew Colless Simon P. Driver Warrick Couch John A. Peacock Ivan K. Baldry Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Chris Collins Nicholas Cross Gavin B. Dalton George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Edward Hawkins Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve Maddox Darren S. Madgwick Peder Norberg Will Percival Bruce Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2003,342(3):725-737
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We derive deep luminosity functions (LFs) (to M z =−15 ) for galaxies in Abell 1835 ( z = 0.25) and AC 114 ( z = 0.31) , and compare these with the local z ' LF for 69 clusters. The data show that the faint-end upturn, the excess of galaxies above a single Schechter function at M z < −17 , does not exist in the higher redshift clusters. This suggests that the faint-end upturn galaxies have been created recently, by infall into clusters of star-forming field populations or via tidal disruption of brighter objects. 相似文献
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James G. Cresswell Will J. Percival 《Monthly notices of the Royal Astronomical Society》2009,392(2):682-690
It has been known for a long time that the clustering of galaxies changes as a function of galaxy type. This galaxy bias acts as a hindrance to the extraction of cosmological information from the galaxy power spectrum or correlation function. Theoretical arguments show that a change in the amplitude of the clustering between galaxies and mass on large scales is unavoidable, but cosmological information can be easily extracted from the shape of the power spectrum or correlation function if this bias is independent of scale. Scale-dependent bias is generally small on large scales, k < 0.1 h Mpc−1 , but on smaller scales can affect the recovery of Ωm h from the measured shape of the clustering signal, and have a small effect on the Baryon Acoustic Oscillations. In this paper, we investigate the transition from scale-independent to scale-dependent galaxy bias as a function of galaxy population. We use the Sloan Digital Sky Survey Data Release 5 sample to fit various models, which attempt to parametrize the turn-off from scale-independent behaviour. For blue galaxies, we find that the strength of the turn-off is strongly dependent on galaxy luminosity, with stronger scale-dependent bias on larger scales for more luminous galaxies. For red galaxies, the scale dependence is a weaker function of luminosity. Such trends need to be modelled in order to optimally extract the information available in future surveys, and can help with the design of such surveys. 相似文献
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K. I. Caputi R. J. McLure J. S. Dunlop M. Cirasuolo A. M. Schael 《Monthly notices of the Royal Astronomical Society》2006,366(2):609-623
We have selected and analysed the properties of a sample of 2905 Ks < 21.5 galaxies in ∼131 arcmin2 of the Great Observatories Origins Deep Survey (GOODS) Chandra Deep Field South (CDFS), to obtain further constraints on the evolution of Ks -selected galaxies with respect to the results already obtained in previous studies. We made use of the public deep multiwavelength imaging from the optical B through the infrared (IR) 4.5-μm bands, in conjunction with available spectroscopic and COMBO17 data in the CDFS, to construct an optimized redshift catalogue for our galaxy sample. We computed the Ks -band luminosity function and determined that its characteristic magnitude has a substantial brightening and a decreasing total density from z = 0 to 〈 z 〉= 2.5 . We also analysed the colours and number density evolution of galaxies with different stellar masses. Within our sample, and in contrast to what is observed for less massive systems, the vast majority (∼85–90 per cent) of the most massive ( M > 2.5 × 1011 M⊙ ) local galaxies appear to be in place before redshift z ∼ 1 . Around 65–70 per cent of the total assemble between redshifts z = 1 and 3 and most of them display extremely red colours, suggesting that plausible star formation in these very massive systems should mainly proceed in obscured, short-time-scale bursts. The remaining fraction (up to ∼20 per cent) could be in place at even higher redshifts z = 3–4 , pushing the first epoch of formation of massive galaxies beyond the limits of current near-IR surveys. 相似文献
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S. A. Sim D. N. Sauer F. K. Röpke W. Hillebrandt 《Monthly notices of the Royal Astronomical Society》2007,378(1):2-12
We compare observations of the high-redshift galaxy population to the predictions of the galaxy formation model of Croton et al. and De Lucia & Blaizot. This model, implemented on the Millennium Simulation of the concordance Lambda cold dark matter cosmogony, introduces 'radio mode' feedback from the central galaxies of groups and clusters in order to obtain quantitative agreement with the luminosity, colour, morphology and clustering properties of the present-day galaxy population. Here we construct deep light cone surveys in order to compare model predictions to the observed counts and redshift distributions of distant galaxies, as well as to their inferred luminosity and mass functions out to redshift 5. With the exception of the mass functions, all these properties are sensitive to modelling of dust obscuration. A simple but plausible treatment agrees moderately well with most of the data. The predicted abundance of relatively massive (∼ M * ) galaxies appears systematically high at high redshift, suggesting that such galaxies assemble earlier in this model than in the real Universe. An independent galaxy formation model implemented on the same simulation matches the observed mass functions slightly better, so the discrepancy probably reflects incomplete or inaccurate galaxy formation physics rather than problems with the underlying cosmogony. 相似文献
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Ting Lu David G. Gilbank Michael L. Balogh Adam Bognat 《Monthly notices of the Royal Astronomical Society》2009,399(4):1858-1876
The global star formation rate has decreased significantly since z ∼ 1 , for reasons that are not well understood. Red-sequence galaxies, dominating in galaxy clusters, represent the population that have had their star formation shut off, and may therefore be the key to this problem. In this work, we select 127 rich galaxy clusters at 0.17 ≤ z ≤ 0.36 , from 119 deg2 of the Canada–France–Hawaii Telescope Legacy Survey (CFHTLS) optical imaging data, and construct the r '-band red-sequence luminosity functions (LFs). We show that the faint end of the LF is very sensitive to how red-sequence galaxies are selected, and an optimal way to minimize the contamination from the blue cloud is to mirror galaxies on the redder side of the colour–magnitude relation. The LFs of our sample have a significant inflexion centred at , suggesting a mixture of two populations. Combining our survey with low-redshift samples constructed from the Sloan Digital Sky Survey, we show that there is no strong evolution of the faint end of the LF (or the red-sequence dwarf-to-giant ratio) over the redshift range 0.2 ≲ z ≲ 0.4 , but from z ∼ 0.2 to ∼0 the relative number of red-sequence dwarf galaxies has increased by a factor of ∼3, implying a significant build-up of the faint end of the cluster red sequence over the last 2.5 Gyr. 相似文献
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Ignacio Ferreras Thorsten Lisker Anna Pasquali Sadegh Khochfar Sugata Kaviraj 《Monthly notices of the Royal Astronomical Society》2009,396(3):1573-1578
The evolution of number density, size and intrinsic colour is determined for a volume-limited sample of visually classified early-type galaxies selected from the Hubble Space Telescope /Advanced Camera for Surveys images of the Great Observatories Origins Deep Survey (GOODS) North and South fields (version 2). The sample comprises 457 galaxies over 320 arcmin2 with stellar masses above 3 × 1010 M⊙ in the redshift range 0.4 < z < 1.2 . Our data allow a simultaneous study of number density, intrinsic colour distribution and size. We find that the most massive systems (≳3 × 1011 M⊙ ) do not show any appreciable change in comoving number density or size in our data. Furthermore, when including the results from 2dF galaxy redshift survey, we find that the number density of massive early-type galaxies is consistent with no evolution between z = 1.2 and 0, i.e. over an epoch spanning more than half of the current age of the Universe. We find large discrepancies between the predictions of semi-analytic models. Massive galaxies show very homogeneous intrinsic colour distributions, with nearly flat radial colour gradients, but with a significant negative correlation between stellar mass and colour gradient, such that red cores appear predominantly in massive galaxies. The distribution of half-light radii – when compared to z ∼ 0 and z > 1 samples – is compatible with the predictions of semi-analytic models relating size evolution to the amount of dissipation during major mergers. 相似文献