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1.
Images of the Hubble Ultra Deep Field are analyzed to obtain a catalog of galaxies for which the angular sizes, surface brightness, photometric redshifts, and absolute magnitudes are found. The catalog contains a total of about 4000 galaxies identified at a high signal-to-noise ratio, which allows the cosmological relations angular size—redshift and surface brightness-redshift to be analyzed. The parameters of the evolution of linear sizes and surface brightness of distant galaxies in the redshift interval 0.5–6.5 are estimated in terms of a grid of cosmological models with different density parameters (Ω V ; Ω m ). The distribution of photometric redshifts of galaxies is analyzed and possible superlarge inhomogeneities in the radial distribution of galaxies are found with scale lengths as large as 2000 Mpc.  相似文献   

2.
In this paper, we explore the plausible luminosity evolution of early-type galaxies in different cosmological models by constructing a set of pure luminosity evolution (PLE) models via the choices of the star-formation rate (SFR) parameters and formation redshift z f of galaxies, with the observational constraints derived from the Hubble Space Telescope ( HST  ) morphological number counts for elliptical and S0 galaxies of the Medium Deep Survey (MDS) and the Hubble Deep Field (HDF). We find that the number counts of early-type galaxies can be explained by the pure luminosity evolution models, without invoking exotic scenarios such as merging or introducing an additional population, but the evolution should be nearly passive, with a high z f assumed. The conclusion is valid in all of the three cosmological models we adopt in this paper. We also present the redshift distributions for three bins of observed magnitudes in the F814w passband, to show the redshift at which the objects that dominate the counts at a given magnitude may be found. The predictions of the redshift distribution of 22.5 <  b j  < 24.0 are also presented for comparison with future data.  相似文献   

3.
Clusters of galaxies are the most massive virialized structures in the Universe. Given that the mass function of large-scale structures decreases exponentially at the high-mass end, galaxy clusters are a sensitive probe of its normalization and redshift evolution, and hence of the cosmological parameters that most influence it. It will be discussed to what extent these cosmological parameters, namely the present amplitude of density perturbations, the matter density and a possible cosmological constant, can be constrained using observational data on the present and past abundance of galaxy clusters. Results will be presented based on the available data, as well as expected constraints from the X-ray Cluster Survey (XCS).  相似文献   

4.
This study set out to examine the effect of anisotropy on the various dark energy models by using the observational data, including the Sandage-Loeb test, Strongly gravitationally lensing, observational Hubble data, and Baryon Acoustic Oscillations data. In particular, we consider three cases of dark energy models: the cosmological constant model, which is most favored by current observations, the wCDM model where dark energy is introduced with constant w equation of state parameter and in Chevalier-Polarski-Linder parametrization where ω is allowed to evolve with redshift. With an anisotropy framework, a maximum likelihood method to constrain the cosmological parameters was implemented. With an anisotropic universe, we also study the behavior of different cosmological parameters such as Hubble parameter, EoS parameter, and deceleration parameter of dark energy models mentioned. The results indicate that the Bianchi type I model for the dark energy models are consistent with the combined observational data.  相似文献   

5.
《New Astronomy Reviews》2002,46(2-7):349-351
Our HST WFPC2 survey of 110 BL Lac objects, from six complete X-ray-, radio-, and optically-selected catalogs, probes the host galaxies of low-luminosity radio sources in the redshift range 0<z<1.35. The host galaxies are luminous ellipticals, well matched in radio power and galaxy magnitude to FR I radio galaxies. Similarly, the host galaxies of high luminosity quasars occupy the same region of this plane as FR II radio galaxies (matched in redshift). This strongly supports the unification of radio-loud AGN, and suggests that studying blazars at high redshift is a proxy for investigating less luminous (to us) but intrinsically identical radio galaxies, which are harder to find at high z. Accordingly, the difference between low-power jets in BL Lac objects and high-power jets in quasars can then be related to the FR I/FR II dichotomy; and the evolution of blazar host galaxies or their nuclei (jets) should correspond to the evolution of radio galaxies.  相似文献   

6.
The Tully–Fisher relationship (TFR) has been shown to have a relatively small observed scatter of ∼±0.35 mag implying an intrinsic scatter < ±0.30 mag. However, when the TFR is calibrated from distances derived from the Hubble relation for field galaxies scatter is consistently found to be ±0.64 to ±0.84 mag. This significantly larger scatter requires that intrinsic TFR scatter is actually much larger than ±0.30 mag, that field galaxies have an intrinsic TFR scatter much larger than cluster spirals, or that field galaxies have a velocity dispersion relative to the Hubble flow in excess of 1000 km s−1. Each of these potential explanations faces difficulties and contradicted by available data and the results of previous studies. An alternative explanation is that the measured redshifts of galaxies are composed of a cosmological redshift component predicted from the value of the Hubble constant and a superimposed intrinsic redshift component previously identified in other studies. This intrinsic redshift component may exceed 5000 km s−1 in individual galaxies. In this alternative scenario a possible value for the Hubble constant is 55–60 km s−1 Mpc−1.  相似文献   

7.
Using the multi-band photometric data of all five CANDELS (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey) fields and the near-infrared (F125W and F160W) high-resolution images of HST WFC3 (Hubble Space Telescope Wide Field Camera 3), a quantitative study of morphology and structure of mass-selected galaxies is presented. The sample includes 8002 galaxies with a redshift 1 < z < 3 and stellar mass M*> 1010M⊙. Based on the Convolutional Neural Network (ConvNet) criteria, we classify the sample galaxies into SPHeroids (SPH), Early-Type Disks (ETD), Late-Type Disks (LTD), and IRRegulars (IRR) in different redshift bins. The findings indicate that the galaxy morphology and structure evolve with redshift up to z ～ 3, from irregular galaxies in the high-redshift universe to the formation of the Hubble sequence dominated by disks and spheroids. For the same redshift interval, the median values of effective radii (re) of different morphological types are in a descending order: IRR, LTD, ETD, and SPH. But for the Sérsic index (n), the order is reversed (SPH, ETD, LTD, and IRR). In the meantime, the evolution of galaxy size (re) with the redshift is explored for the galaxies of different morphological types, and it is confirmed that their size will enlarge with time. However, such a phenomenon is not found in the relations between the redshift (1 < z < 3) and the mean axis ratio (b/a), as well as the Sérsic index (n).  相似文献   

8.
In the coming years, a number of projects will start intensive supernovæsearches resulting in an increase of the current statistics by a factor of 10. At low redshift, the Nearby Supernova Factory will detect and follow spectrophotometricly ～ 400 of SNe Ia with a redshift at z ～ 0.05, and improve our understanding of the intrinsic properties of SNe Ia. At high redshift, the large imager Megacam at the Canada-France-Hawaii Telescope running in a survey mode, will make it possible to detect and follow a large amount of high redshift supernovae. Using Megacam during 5 years ～ 1000 Type Ia SNe will be detected, at z ranging from 0.3 to 1.2, and ～ 700 will be used for measuring the cosmological parameters via the Hubble diagram. They will provide a measurement of the cosmic equation of state parameter w. A first test run search was done last spring at the CFHT, using the current imager: the `CFH 12k'. Detection procedure and preliminary results are presented in this article.  相似文献   

9.
We present results of an investigation of clustering evolution of field galaxies between a redshift of z ∼ 1 and the present epoch. The current analysis relies on a sample of ∼ 14000 galaxies in two fields of the COMBO 17 survey. The redshift distribution extends to z ∼ 1. The amplitude of the three-dimensional correlation function can be estimated by means of the projected correlation function w(r p ). The validity of the deprojection was tested on the Las Campanas Redshift Survey (LCRS). In a flat cosmology with non-zero cosmological constant for bright galaxies (M B ≤-18) the clustering growth is proportional to (1+z) -2. However, the measured clustering evolution clearly depends on Hubble type. While locally the clustering strength of early type galaxies is equal to that of the bright galaxies, at high redshifts they are much stronger clustered, and thus the clustering has to evolve much more slowly. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

10.
Deep and high-resolution radio observations of the Hubble Deep Field and flanking fields have shown the presence of two distant edge-darkened FR I radio galaxies, allowing for the first time an estimate of their high-redshift space density. If it is assumed that the space density of FR I radio galaxies at     is similar to that found in the local Universe, then the chance of finding two FR I radio galaxies at these high radio powers in such a small area of sky is < 1 per cent. This suggests that these objects were significantly more abundant at     than at present, effectively ruling out the possibility that FR I radio sources undergo no cosmological evolution. We suggest that FR I and FR II radio galaxies should not be treated as intrinsically distinct classes of objects, but that the cosmological evolution is simply a function of radio power with FR I and FR II radio galaxies of similar radio powers undergoing similar cosmological evolutions. Since low-power radio galaxies have mainly FR I morphologies and high-power radio galaxies have mainly FR II morphologies, this results in a generally stronger cosmological evolution for the FR IIs than the FR Is. We believe that additional support from the V / V max test for evolving and non-evolving population of FR IIs and FR Is respectively is irrelevant, since this test is sensitive over very different redshift ranges for the two classes.  相似文献   

11.
At the beginning of a series of papers concerning reality of various suggested cosmological evolutionary effects, the counts of quasars are examined. The recently reported counts of optically selected quasars (Green and Schmidt, 1978) probably have been biased by the use of distance-dependent morphological criteria of selection. The influence of this bias is to mimic cosmological evolution. The application of theK-correction for the counts of quasars is discussed. TheK-corrected, presumably unbiased counts of objects with ultraviolet excess and broad emission lines, including quasars and type 1 Seyfert galaxies, give the slopeb=0.6, i.e. a uniform radial distribution. Correctness of the latter sampling of data is dependent on the solution of the redshift problem and presupposes an inverse correlation between luminosity and intrinsic redshift.  相似文献   

12.
The Fundamental plane provides a sensitive tool to measure the change in the M/L ratio of early type galaxies with redshift. The evolution of the M/L ratio is a function of the star formation history. It depends on the IMF, the formation redshift, and cosmology. Some model examples are shown, and a first result on the cluster Abell 665 at z=0.18 is given. The measurements confirm the cosmological surface brightness dimming, and imply an evolution of the (red) L/M ratio ∝ (1 + z)1.8±0.7. More data are needed to extend this result to higher redshifts, and to test the underlying assumptions. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

13.
The most accurate data on galaxy types, corrected apparent magnitudes and redshifts as given in the Sandage-TammanRevised Shapley-Ames catalog are analyzed. It is shown that Sb galaxies of the same luminosity class as M31 and M81 define a narrow Hubble relation withH 0=65 –6 +15 km s–1 Mpc–1.In contrast, Sc galaxies deviate strongly towars higher redshift from a linear, log redshift—apparent magnitude relation. Not all this deviation can be selection effect due to increasing volume sampled at increasing redshift (Malmquist bias). Physical associations of groups of galaxies in theRSA Catalog are used to establish the existence of various amounts of excess (non-velocity) redshifts among Sc and allied types of galaxies.Independent distances fromHi line width — luminosity criterion (Tully-Fisher) are analyzed. It is shown that this criterion gives much smaller distances than redshifts do for galaxies which deviate above the Hubble line. Unless the Tully-Fisher relation gives too small distances for more luminous galaxies, this confirms the excess redshift to be intrinsic to the Galaxy. But it is next demonstrated, that for low redshift galaxies, there is no discrepancy between redshift and Tully-Fisher distance even though there is a wide range of absolute magnitudes.If Tully-Fisher distances are accepted, the onlly alternative to having a Hubble constant which increases strongly with distance is to have a component of the higher redshift Sc's contributed by a non-recessional redshift. Streaming motions would have to be large, increase with distance and be always in the receding sence. It is shown here that the Sc's which deviate most from the Hubble relation and have the largest discrepancies with Tully-Filsher distances lie predominantly in the sky toward very nearby groups of galaxies. If they were at these closer distances the discordant galaxies, mostly ScI's, would have dwarfish physical properties but not so unprecedented as the large sizes which result from redshift distances.Finally the interaction of specific high redshift ScI's with nearby galaxies is presented as an independent proof that ScI's are generally small, low luminosity galaxies. This result furnishes insight into the long standing puzzle of how apparently distant ScI's can interact with nearby galaxies such as in Stephan's Quintet, Seyfert's Sextet and NGC 4151/4156.  相似文献   

14.
The dependence of the formation redshift of clusters of galaxies on the cosmological constant is discussed on the basis of recent measurements of gravitational masses and radii from X-ray astronomy techniques. For a flat CDM model with several different values of the cosmological constant, the cluster number density as a function of the redshift is calculated. Comparing the calculated number density at z − 0 with the observed value limits the spectrum parameter Γ to the range 0.15–0.32. We also show that if Γ and/or ΩΛ were larger, many more clusters of galaxies would have been formed at high redshifts.  相似文献   

15.
Om diagnostic is a useful geometric method to differentiate between different cosmological models without the accurate current value of matter density. We investigate the Om diagnostic for viscous Cardassian universe and find that the model can be easily distinguished from LCDM. We also investigate the influence of the bulk viscosity coefficient τ on the evolutive behavior of Om with respect to redshift z. According to the value of Om(z=0) for viscous Cardassian models, we obtain the current value of equation of state w k0.  相似文献   

16.
A submillimetre survey of the star formation history of radio galaxies   总被引：1，自引：0，他引：1  
We present the results of the first major systematic submillimetre survey of radio galaxies spanning the redshift range 1< z <5. The primary aim of this work is to elucidate the star formation history of this sub class of elliptical galaxies by tracing the cosmological evolution of dust mass. Using SCUBA on the JCMT, we have obtained 850-μm photometry of 47 radio galaxies to a consistent rms depth of 1 mJy, and have detected dust emission in 14 cases. The radio galaxy targets have been selected from a series of low-frequency radio surveys of increasing depth (3CRR, 6CE, etc.), in order to allow us to separate the effects of increasing redshift and increasing radio power on submillimetre luminosity. Although the dynamic range of our study is inevitably small, we find clear evidence that the typical submillimetre luminosity (and hence dust mass) of a powerful radio galaxy is a strongly increasing function of redshift; the detection rate rises from ≃15 per cent at z <2.5 to ≳75 per cent at z >2.5, and the average submillimetre luminosity rises at a rate ∝(1+ z )3 out to z ≃4. Moreover, our extensive sample allows us to argue that this behaviour is not driven by underlying correlations with other radio galaxy properties such as radio power, radio spectral index, or radio source size/age. Although radio selection may introduce other more subtle biases, the redshift distribution of our detected objects is in fact consistent with the most recent estimates of the redshift distribution of comparably bright submillimetre sources discovered in blank field surveys. The evolution of submillimetre luminosity found here for radio galaxies may thus be representative of massive ellipticals in general.  相似文献   

17.
We present a study of the baryonic fraction in galaxy clusters aimed at constraining the cosmological parameters Ωm, ΩLgr; and the ratio between the pressure and density of the `dark' energy, w. We use results on the gravitating mass profiles of a sample of nearby galaxy clusters observed with the BeppoSAX X-ray satellite (Ettori, De Grandi and Molendi, 2002)to set constraints on the dynamical estimate of Ωm. We then analyze Chandra observations of a sample of eight distant clusters with redshift in the range 0.72 and 1.27 and evaluate the geometrical limits on the cosmological parameters Ωm, ΩΛ and w by requiring that the gas fraction remains constant with respect to the look-back time. By combining these two independent probability distributions and using a priori distributions on both Ωb and H 0 peaked around primordial nucleosynthesis and HST-Key Project results respectively, we obtain that, at 95.4 per cent level of confidence, (i) w < —0.54, (ii)Ωm = 0.34+0.11 —0.05, ΩΛ = 1.50+0.24 —1.13 for w = — 1 (corresponding to the case for a cosmological constant), and (iii) Ωm = 1 —ΩΛ = 0.33+0.06 —0.05 for a flat Universe. This paper summarizes the work in press at Astronomy & Astrophysics by Ettori, Tozzi and Rosati (astro-ph/0211335).  相似文献   

18.
We present the results of optical identifications and spectroscopic redshift measurements for galaxy clusters from the second Planck catalogue of Sunyaev–Zeldovich sources (PSZ2) located at high redshifts, z ≈ 0.7?0.9. We used the data of optical observations with the Russian–Turkish 1.5-mtelescope (RTT-150), the Sayan Observatory 1.6-m telescope, the Calar Alto 3.5-m telescope, and the 6-m SAO RAS telescope (BTA). The spectroscopic redshift measurements were obtained for seven galaxy clusters, including one cluster, PSZ2 G126.57+51.61, from the cosmological sample of the PSZ2 catalogue. In the central regions of two clusters, PSZ2 G069.39+68.05 and PSZ2 G087.39?34.58, we detected arcs of strong gravitational lensing of background galaxies, one of which is at redshift z = 4.262. The data presented below roughly double the number of known galaxy clusters in the second Planck catalogue of Sunyaev–Zeldovich sources at high redshifts, z ≈ 0.8.  相似文献   

19.
One of the key goals of NASA’s astrophysics program is to answer the question: How did galaxies evolve into the spirals and elliptical galaxies that we see today? We describe a space mission concept called Galaxy Evolution Spectroscopic Explorer (GESE) to address this question by making a large spectroscopic survey of galaxies at a redshift, z～1 (look-back time of ～8 billion years). GESE is a 1.5-m space telescope with an ultraviolet (UV) multi-object slit spectrograph that can obtain spectra of hundreds of galaxies per exposure. The spectrograph covers the spectral range, 0.2–0.4 μm at a spectral resolving power, R～500. This observed spectral range corresponds to 0.1–0.2 μm as emitted by a galaxy at a redshift, z=1. The mission concept takes advantage of two new technological advances: (1) light-weighted, wide-field telescope mirrors, and (2) the Next-Generation MicroShutter Array (NG-MSA) to be used as a slit generator in the multi-object slit spectrograph.  相似文献   

20.
New expressions for ON and NS calibrations (we call them ON11 and NS11 calibrations) for the determination of oxygen and nitrogen abundances in HII regions are proposed. New criteria for the division of HII regions into three classes (hot, warm, and cold) are also proposed. ON11 and NS11 calibrations provide more accurate determination of oxygen and nitrogen abundances from integrated emission spectra, in comparison with ON and NS calibrations. Oxygen and nitrogen abundances are estimated for a sample of 57 470 SDSS galaxies using ON11 and NS11 calibrations. Strongline flux measurements for SDSS spectra of these galaxies are taken from the MPA/JHU catalog. A ??mass-metallicity?? diagram for several redshift ranges is constructed. It is found that the interstellar medium of galaxies with high masses log(M/M ??) > 11.3 was hardly enriched with either oxygen or nitrogen over the last 4 Gyrs (corresponding to the redshift interval z = 0?C0.4). This indicates that an active stage of star formation in massive galaxies was completed more than 4 Gyrs ago. For galaxies of lower masses, changes in oxygen and nitrogen abundances over the time period under consideration increase as galaxy mass decreases.  相似文献   

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