The first generation of stars in the Λ cold dark matter cosmology

We have performed a large set of high-resolution cosmological simulations using smoothed particle hydrodynamics to study the formation of the first luminous objects in the Lambda cold dark matter cosmology. We follow the collapse of primordial gas clouds in eight early structures and document the scatter in the properties of the first star-forming clouds. Our first objects span formation redshifts from   z ∼ 10  to ∼50 and cover an order of magnitude in halo mass. We find that the physical properties of the central star-forming clouds are very similar in all of the simulated objects despite significant differences in formation redshift and environment. This suggests that the formation path of the first stars is largely independent of the collapse redshift; the physical properties of the clouds have little correlation with spin, mass or assembly history of the host halo. The collapse of protostellar objects at higher redshifts progresses much more rapidly due to the higher densities, which accelerates the formation of molecular hydrogen, enhances initial cooling and shortens the dynamical time-scales. The mass of the star-forming clouds cover a broad range, from a few hundred to a few thousand solar masses, and exhibit various morphologies: some have disc-like structures which are nearly rotational supported; others form flattened spheroids; still others form bars. All of them develop a single protostellar 'seed' which does not fragment into multiple objects up to the moment that the central gas becomes optically thick to H₂ cooling lines. At this time, the instantaneous mass accretion rate on to the centre varies significantly from object to object, with disc-like structures having the smallest mass accretion rates. The formation epoch and properties of the star-forming clouds are sensitive to the values of cosmological parameters.     

On quasar host galaxies as tests of non-cosmological redshifts

Despite a general consensus in the astronomical community that all quasars are located at the distances implied by their redshifts, a number of observations still challenge this interpretation, possibly indicating that some subpopulation of quasars may harbour significant redshift components not related to the expansion of the Universe. It has been suggested that these objects may have been ejected from local galaxies and are likely to evolve into new galaxies themselves. Here, a test of such exotic scenarios is proposed, based on the spectral energy distribution of the galaxies hosting quasars with suspected ejection origin. Provided that the time-scales over which the ejected objects manifest themselves as quasars is short, one would in the framework of the ejection scenarios expect to find either no quasar host galaxy, a pseudo-host consisting of gas ionized by the quasar, or a host galaxy consisting of young stars only. It is argued that the spectral energy distributions corresponding to the last two options should differ significantly from that of most quasar host galaxies detected at low redshift so far, thus providing a potential test of the claimed existence of ejected quasars. A minimal implementation of this test, involving optical and near-infrared broad-band photometry, is suggested.     

Astronomical redshifts of highly ionized regions

Astronomical or cosmological redshifts are an observable property of extragalactic objects and have historically been wholly attributed to the recessional velocity of that object. The question of other, or intrinsic, components of the redshift has been highly controversial since it was first proposed. This paper investigates one theoretical source of intrinsic redshift that has been identified. The highly ionized regions of Active Galactic Nuclei (AGN) and Quasi-Stellar Objects (QSO) are, by definition, plasmas. All plasmas have electromagnetic scattering characteristics that could contribute to the observed redshift. To investigate this possibility, one region of a generalized AGN was selected, the so called Broad Line Region (BLR). Even though unresolvable with current instrumentation, physical estimates of this region have been published for years in the astronomical literature. These data, selected and then averaged, are used to construct an overall model that is consistent with the published data to within an order of magnitude. The model is then subjected to a theoretical scattering investigation. The results suggest that intrinsic redshifts, derivable from the characteristics of the ambient plasma, may indeed contribute to the overall observed redshift of these objects.     

Absorption line redshifts of QSOs in relation to their emission line redshifts

Analysis of the recent data indicate that absorption line redshifts of QSOs are significantly correlated to their emission line redshifts. It is concluded that the absorption lines originate in materials intrinsic to the QSOs.     

The effect of a relative infinity on cosmological redshifts

We present anon-general relativistic cosmological model with the following features.

All cosmological objects appear to be receding from each other. There are two mathematically distinct types of objects.

Type I objects have apparent magnitudes and apparent angular diameters comparable to those for standard FLRW models. Their redshifts are bounded; this bound is at least 3.

Type II objects can have unlimited redshifts. They appear significantly smaller than Type I objects with the same redshift, and (for redshifts greater than 1) appear brighter (and more so for larger redshifts).

The model is an extension of classical de Sitter spacetime in which the location of infinity is allowed to be relative.     

The formation of ultracompact dwarf galaxies

Recent spectroscopic observations of galaxies in the Fornax Cluster reveal nearly unresolved 'star-like' objects with redshifts appropriate to the Fornax Cluster. These objects have intrinsic sizes of ≈100 pc and absolute B -band magnitudes in the range  −14< M _B<−11.5 mag  and lower limits for the central surface brightness   μ _B≳23 mag arcsec⁻²  , and so appear to constitute a new population of ultracompact dwarf galaxies (UCDs). Such compact dwarfs were predicted to form from the amalgamation of stellar superclusters (by Kroupa) , which are rich aggregates of young massive star clusters (YMCs) that can form in collisions between gas-rich galaxies. Here we present the evolution of superclusters in a tidal field. The YMCs merge on a few supercluster crossing times. Superclusters that are initially as concentrated and massive as knot S in the interacting Antennae galaxies evolve to merger objects that are long-lived and show properties comparable to the newly discovered UCDs. Less massive superclusters resembling knot 430 in the Antennae may evolve to ω Cen-type systems. Low-concentration superclusters are disrupted by the tidal field, dispersing their surviving star clusters while the remaining merger objects rapidly evolve into the   μ _B− M _B  region populated by low-mass Milky Way dSph satellites.     

Detecting the most distant (z>7) objects with ALMA

Detecting and studying objects at the highest redshifts, out to the end of Cosmic Reionization at z>7, is clearly a key science goal of ALMA. ALMA will in principle be able to detect objects in this redshift range both from high-J (J>7) CO transitions and emission from ionized carbon, [CII], which is one of the main cooling lines of the ISM. ALMA will even be able to resolve this emission for individual targets, which will be one of the few ways to determine dynamical masses for systems in the Epoch of Reionization. We discuss some of the current problems regarding the detection and characterization of objects at high redshifts and how ALMA will eliminate most (but not all) of them.     

Three-dimensional quantized time in cosmology

Starting from a model of 3-d time in units of the Planck energy, it is possible to model fundamental particles and forces. Masses are associated with 3-d volumes of time; forces are related to 4-d space-time structures from which the fine structure constant can be derived. Fundamental particles may then be assembled into larger objects, up to galaxies, within which special relativity is satisfied. The component parts of an object retain a common quantized temporal structure which appears to link the spatially distributed parts together. The flow of time is associated with a flow of the common temporal structure within a general 3-d temporal space. Each galaxy evolves along a 1-d timeline such that within a given galaxy standard 4-d space-time physics is satisfied. The model deviates from ordinary physics by associating different galaxies with independent timelines within a general 3-d temporal space. These timelines diverge from a common origin and can have different flow rates for different classes of objects. The common origin is consistent with standard cosmology. The radius of temporal space replaces the standard radius of curvature in describing redshifts seen when photons transfer between objects on different timelines. Redshift quantization, discordant redshifts, and other observed cosmological phenomena are natural consequences of this type of model.     

Properties of BL Lac Objects with Redshift < 0.2

We present a large sample which includes 82 BL Lac objects with redshifts below 0.2 from recent literature. We find strong correlations in both flux and luminosity between the radio (5 GHz) and optical bands (5500 A). The correlations in other bands are very weak. Five TeV BL Lacs and two suspect sources are found to have similar properties as high-frequency-peaked BL Lacs (HBLs). Our results suggest that both the radio and optical emissions are from the same radiation mech anism in the SSC model. The TeV BL Lac candidates should be HBLs or HBL-like objects with small redshifts.     

Abschätzung von Quasarmassen

The masses of quasi-stellar objects having absorption lines with redshifts larger than the redshifts of the corresponding emission lines are attributed to gas clouds which are moving radially against the quasar. Other forces than the gravitational attraction of the quasars are neglected. The average of the mass of a quasi-stellar object is 5 ⋅ 10¹² 𝔐 ⊙.     

The changing interstellar medium of massive elliptical galaxies and cosmic evolution of radio galaxies and quasars

The recently discovered apparent dramatic expansion in the effective radii of massive elliptical galaxies from   z ≃ 2  to ≃0.1 has been interpreted in terms of either galaxy mergers or the rapid loss of cold gas due to active galactic nuclei (AGN) feedback. In examining the latter case, we have quantified the extent of the expansion, which is uncertain observationally, in terms of the star formation parameters and time of the expulsion of the cold gas. In either case, the large global decrease in stellar density should translate into a major drop in the interstellar medium density and pressure with cosmic epoch. These cosmological changes are expected to have a major influence on the gas accretion mode, which will shift from 'cold' thin disc accretion at high redshifts towards 'hot' Bondi fed Advection Dominated Accretion Flow (ADAF) accretion at low redshifts. The decline of angular momentum inflow would then lead to a spin down of the black hole, for which we have calculated more precise time-scales; a value of about 0.2 Gyr is typical for a  10⁹ M_⊙  central black hole. These results have implications for the different cosmological evolutionary patterns found for the luminosity functions of powerful and weak radio galaxies.     

Anomalous redshifts and the variable mass hypothesis

There are several observations of extragalactic objects that do not appear to be consistent with the cosmological hypothesis that their redshifts arise from the expansion of the universe. These phenomena are looked at in a spacetime framework that is wider in its scope than general relativity. This framework directly incorporates the Machian notion of intertia and is conformally invariant. The consequence of this approach is that the mass of a particle may not stay constant. Two alternative viewpoints are presented to explain how large redshifts could arise from emission of radiation by particles of low masses.     

Cosmology and cosmogony in a cyclic universe

In this paper we discuss the properties of the quasi-steady state cosmological model (QSSC) developed in 1993 in its role as a cyclic model of the universe driven by a negative energy scalar field. We discuss the origin of such a scalar field in the primary creation process first described by F. Hoyle & J. V. Narlikar forty years ago. It is shown that the creation processes which take place in the nuclei of galaxies are closely linked to the high energy and explosive phenomena, which are commonly observed in galaxies at all redshifts. The cyclic nature of the universe provides a natural link between the places of origin of the microwave background radiation (arising in hydrogen burning in stars), and the origin of the lightest nuclei (H, D, He³ and He⁴). It also allows us to relate the large scale cyclic properties of the universe to events taking place in the nuclei of galaxies. Observational evidence shows that ejection of matter and energy from these centers in the form of compact objects, gas and relativistic particles is responsible for the population of quasi-stellar objects (QSOs) and gamma-ray burst sources in the universe. In the later parts of the paper we briefly discuss the major unsolved problems of this integrated cosmological and cosmogonical scheme — the understanding of the origin of the intrinsic redshifts, and the periodicities in the redshift distribution of the QSOs.     

Evidence for Intrinsic Redshifts in Normal Spiral Galaxies

The Tully–Fisher Relationship (TFR) is utilized to identify anomalous redshifts in normal spiral galaxies. Three redshift anomalies are identified in this analysis: (1) several clusters of galaxies are examined, in which late type spirals have significant excess redshifts relative to early-type spirals in the same clusters; (2) galaxies of morphology similar to ScI galaxies are found to have a systematic excess redshift relative to the redshifts expected if the Hubble Constant is 72 km s⁻¹ Mpc⁻¹; (3) individual galaxies, pairs, and groups are identified which strongly deviate from the predictions of a smooth Hubble flow. These redshift deviations are significantly larger than can be explained by peculiar motions and TFR errors. It is concluded that the redshift anomalies identified in this analysis are consistent with previous claims for large non-cosmological (intrinsic) redshifts.     

On the largest angular size-redshift diagram for quasars

The envelope function in the largest angular size-redshift diagram for quasars is shown to be a consequence of the distribution of their redshifts and to have no intrinsic physical significance.     

X选BL Lac天体的某些性质(Ⅱ)

本文对X射线选择BLLac天体（XBLs）的完备样品进行了较细致的研究，讨论了该样品各观测量的分布、最新发现的几例X射线和ROSAT选择的BLLac天体的Hubble关系及BLLac天体的红移起源问题．     

Combining optical and X-ray observations of galaxy clusters to constrain cosmological parameters

Galaxy clusters present unique advantages for cosmological study.Here we collect a new sample of 10 lensing galaxy clusters with X-ray observations to constrain cosmological parameters.The redshifts of the lensing clusters lie between 0.1 and 0.6,and the redshift range of their arcs is from 0.4 to 4.9.These clusters are selected carefully from strong gravitational lensing systems which have both X-ray satellite observations and optical giant luminous arcs with known redshifts.Giant arcs usually appear in th...     

Old high-redshift galaxies and primordial density fluctuation spectra

We have discovered a population of extremely red galaxies at z  ≃ 1.5 which have apparent stellar ages of ≳ 3 Gyr, based on detailed spectroscopy in the rest-frame ultraviolet. In order for galaxies to have existed at the high collapse redshifts indicated by these ages, there must be a minimum level of power in the density fluctuation spectrum on galaxy scales. This paper compares the required power with that inferred from other high-redshift populations: damped Lyα absorbers and Lyman-limit galaxies at z  ≃ 3.2. If the collapse redshifts for the old red galaxies are in the range z _c ≃ 6–8, there is general agreement between the various tracers on the required inhomogeneity on 1-Mpc scales. This level of small-scale power requires the Lyman-limit galaxies to be approximately ν ≃ 3.0 fluctuations, implying a very large bias parameter b  ≃ 6. If the collapse redshifts of the red galaxies are indeed in the range z _c = 6–8 required for power spectrum consistency, their implied ages at z  ≃ 1.5 are between 3 and 3.8 Gyr for essentially any model universe of current age 14 Gyr. The age of these objects as deduced from gravitational collapse thus provides independent support for the ages estimated from their stellar populations. Such early-forming galaxies are rare, and their contribution to the cosmological stellar density is consistent with an extrapolation to higher redshifts of the star formation rate measured at z  < 5; there is no evidence for a general era of spheroid formation at extreme redshifts.     

The spectra of three newly discovered high-redshift quasars

Spectra of three high-redshift quasars discovered on low-dispersion objective prism plates were obtained. We present the emission line identifications and redshifts of the objects. Equivalent widths, line widths and low-resolution line profiles are given characterizing the quasar emission region. The Lyα and CIV equivalent widths indicate that the considered quasars are luminous objects at high redshift. Both these equivalent widths are too low by a factor 4, whereas the N V/Lyα ratio is 5 times larger than predicted by the photoionisation models. The line profiles are compared with logarithmic, electron-scattering and Gaussian profiles. In all the spectra rich absorption line systems are evident.