G. Boerner

Max Planck Institute for Astrophysics, Arching, Bavaria, Germany

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Publications (108)347.49 Total impact

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    Hong Guo, Cheng Li, Y. P. Jing, G. Boerner
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    ABSTRACT: We measure the three-point correlation function (3PCF) of the SDSS DR7 main sample galaxies in both redshift and projected spaces on scales up to $40\mpchi$. The dependence of the 3PCF on stellar mass and color is explored in different scales and triangle shapes. We find a weak but significant stellar mass dependence. More massive galaxies generally have higher amplitudes of the 3PCF, but lower amplitudes of the reduced 3PCF. The reduced 3PCF in both redshift and projected spaces only has mild shape dependence on small scales ($<2\mpchi$), regardless of stellar mass and color. The shape dependence of the reduced 3PCF does not correlate with the stellar mass on small scales. On large scales, the shape dependence of the reduced 3PCF is stronger for lower-mass galaxies. The reduced 3PCF in the projected space shows weaker shape dependence but stronger stellar mass and color dependence, indicating that the redshift-space distortion reduces the dependence on galaxy properties. Red galaxies have higher amplitudes of the reduced 3PCF than those of the blue galaxies, implying that the nonlinear bias is important for the dependence on color.
    The Astrophysical Journal 03/2013; · 6.73 Impact Factor
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    ABSTRACT: A large amount of observations have constrained cosmological parameters and the initial density fluctuation spectrum to a very high accuracy. However, cosmological parameters change with time and the power index of the power spectrum varies with mass scale dramatically in the so-called concordance Lambda CDM cosmology. Thus, any successful model for its structural evolution should work well simultaneously for various cosmological models and different power spectra. We use a large set of high-resolution N-body simulations of a variety of structure formation models (scale-free, standard CDM, open CDM, and Lambda CDM) to study the mass accretion histories (MAHs), the mass and redshift dependence of concentrations and the concentration evolution histories of dark matter halos. We find that there is significant disagreement between the much-used empirical models in the literature and our simulations. According to two simple but tight correlations we find from the simulation results, we develop new empirical models for both the MAHs and the concentration evolution histories of dark matter halos, and the latter can also be used to predict the mass and redshift dependence of halo concentrations. These models are accurate and universal: the same set of model parameters works well for different cosmological models and for halos of different masses at different redshifts and the model predictions are highly accurate even when the histories are traced to very high redshift. These models are also simple and easy to implement. A web calculator and a user-friendly code to make the relevant calculations are available from http://www.shao.ac.cn/dhzhao/mandc.html . We explain why Lambda CDM halos on nearly all mass scales show two distinct phases in their evolution histories.
    The Astrophysical Journal 11/2008; 707. · 6.73 Impact Factor
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    ABSTRACT: By comparing semi-analytic galaxy catalogues with data from the Sloan Digital Sky Survey (SDSS), we show that current galaxy formation models reproduce qualitatively the dependence of galaxy clustering and pairwise peculiar velocities on luminosity, but some subtle discrepancies with the data still remain. The comparisons are carried out by constructing a large set of mock galaxy redshift surveys that have the same selection function as the SDSS Data Release Four (DR4). The mock surveys are based on two sets of semi-analytic catalogues presented by Croton et al. and Kang et al. From the mock catalogues, we measure the redshift-space projected two-point correlation function wp(rp), the power spectrum P(k) and the pairwise velocity dispersion (PVD) in Fourier space sigma12(k) and in configuration space sigma12(rp), for galaxies in different luminosity intervals. We then compare these theoretical predictions with the measurements derived from the SDSS DR4. On large scales and for galaxies brighter than L*, both sets of mock catalogues agree well with the data. For fainter galaxies, however, both models predict stronger clustering and higher pairwise velocities than observed. We demonstrate that this problem can be resolved if the fraction of faint satellite galaxies in massive haloes is reduced by ~30 per cent compared to the model predictions. A direct look into the model galaxy catalogues reveals that a significant fraction (15 per cent) of faint galaxies (-18 < M0.1r - 5 log10h < -17) reside in haloes with Mvir > 1013 Msolar, and this population is predominantly red in colour. These faint red galaxies are responsible for the high PVD values of low-luminosity galaxies on small scales.
    Monthly Notices of the Royal Astronomical Society 01/2007; · 5.52 Impact Factor
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    ABSTRACT: (abridged)We use a sample of ~200,000 galaxies drawn from the Sloan Digital Sky Survey to study how clustering depends on properties such as stellar mass (M*), colour (g-r), 4000A break strength (D4000), concentration index (C), and stellar surface mass density (\mu_*). We find that more massive galaxies cluster more strongly than less massive galaxies, with the difference increasing above the characteristic stellar mass of the Schechter mass function. When divided by physical quantities, galaxies with redder colours, larger D4000, higher C and larger \mu_* cluster more strongly. The clustering differences are largest on small scales and for low mass galaxies. At fixed stellar mass,the dependences of clustering on colour and 4000A break strength are similar. Different results are obtained when galaxies are split by concentration or surface density. The dependence of w(r_p) on g-r and D4000 extends out to physical scales that are significantly larger than those of individual dark matter haloes (> 5 Mpc/h). This large-scale clustering dependence is not seen for the parameters C or \mu_*. On small scales (< 1 Mpc/h), the amplitude of the correlation function is constant for ``young'' galaxies with 1.1 < D4000< 1.5 and a steeply rising function of age for ``older'' galaxies with D4000>1.5. In contrast, the dependence of the amplitude of w(r_p) on concentration on scales less than 1 Mpc/h is strongest for disk-dominated galaxies with C<2.6. This demonstrates that different processes are required to explain environmental trends in the structure and in star formation history of galaxies. Comment: 17 pages, 14 figures; reference updated and text slightly changed to match the published version; Tables 5 and 6 are available at http://www.mpa-garching.mpg.de/~leech/papers/clustering/
    Monthly Notices of the Royal Astronomical Society 09/2005; · 5.52 Impact Factor
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    ABSTRACT: (abridged) We present measurements of the pairwise velocity dispersion (PVD) for different classes of galaxies in the Sloan Digital Sky Survey. For a sample of about 200,000 galaxies, we study the dependence of the PVD on galaxy properties such as luminosity, stellar mass (M_*), colour (g-r), 4000A break strength (D4000), concentration index (C), and stellar surface mass density (\mu_*). The luminosity dependence of the PVD is in good agreement with the results of Jing & B\"orner (2004) for the 2dFGRS catalog. The value of \sigma_{12} measured at k=1 h/Mpc decreases as a function of increasing galaxy luminosity for galaxies fainter than L*, before increasing again for the most luminous galaxies in our sample. Each of the galaxy subsamples selected according to luminosity or stellar mass is divided into two further subsamples according to colour, D4000, C and \mu_*. We find that galaxies with redder colours and higher D4000, C, and \mu_* values have larger PVDs on all scales and at all luminosities/stellar masses. The dependence of the PVD on parameters related to recent star formation(colour, D4000) is stronger than on parameters related to galaxy structure (C, \mu_*), especially on small scales and for faint galaxies. The reddest galaxies and galaxies with high surface mass densities and intermediate concentrations have the highest pairwise peculiar velocities, i.e. these move in the strongest gravitational fields. We conclude that the faint red population located in rich clusters is responsible for the high PVD values that are measured for low-luminosity galaxies on small scales. Comment: 14 pages, 13 figures; reference updated and text slightly changed to match the published version; data of measurements of power spectrum and PVD available at http://www.mpa-garching.mpg.de/~leech/papers/clustering/
    Monthly Notices of the Royal Astronomical Society 09/2005; · 5.52 Impact Factor
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    ABSTRACT: We investigate the influence of radiative effects on supersonic wind accretion onto gravitating objects. The accreting matter is assumed to be optically thin. The physical mechanisms taken into account include cooling due to free-free and free-bound transitions, the Compton heating via X-ray scattering on electrons and the inverse Compton cooling in the regions where the temperature of the matter becomes sufficiently large to be able to transfer part of its internal energy to photons. A wide range of determining parameters was covered, including the values applicable to the Vela X-1 binary system, but our main emphasis is on the study of the effects of radiative processes on the behavior of accretion flows. It is shown that the applicability of polytropic accretion models is very limited and the actual accretion rate can be considerably lower than that provided by the Bondi–Hoyle–Lyttleton formula. The detailed consideration of the realistic radiative effects proved to be of great importance in our understanding of the accretion phenomenon, since they can substantially affect it both qualitatively and quantitatively.
    Astronomy and Astrophysics 01/2005; 441:863-872. · 5.08 Impact Factor
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    Weipeng Lin, G. Börner, H. J. Mo
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    ABSTRACT: We present semi-analytic models and monte-carlo simulations of QSO Lyalpha absorption line systems which originate in gaseous galactic halos, galaxy disks, and satellite halos around central galaxies. The relation between the properties of predicted absorption lines and those of galaxies has been investigated. Using a model with galactic halos, satellites, and hi disks of spirals, 60 % of the observed strong Lyalpha lines and all of the Lyman-limit systems can be predicted. The models predict wr ∝ rho-alpha lbbeta (1+z)-gamma with alpha ˜ 0.5, beta ˜ 0.15, gamma ˜ 0.5. For strong Lyalpha lines the average covering factor within 250 h-1 kpc is ˜ 0.36, with an average absorption radius of ˜ 150 h-1 kpc for a galaxy halo, in good agreement with observations. Using mock imaging and spectroscopic surveys, selection effects are found to be able to strengthen the anti-correlation between line width and projected distance. The models were also applied to quasar metal absorption lines and more realistic absorption spectra with noise were simulated.
    Proceedings of the International Astronomical Union 01/2005; 1.
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    X Kang, Y P Jing, H J Mo, G Börner
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    ABSTRACT: We model the galaxy formation in a series of high-resolution N-body simu-lations using the semi-analytical approach. Unlike many earlier investigations based on semi-analytical models, we make use of the subhalos resolved in the N-body simulations to follow the mergers of galaxies in dark halos, and we show that this is pivotal in modeling correctly the galaxy luminosity function at the bright end and the bimodal nature of galaxy color distribution. Merger of galax-ies based on subhalos also results in many more bright red galaxies at high z. The semi-analytical model we adopt is similar to those used in earlier semi-analytical studies, except that we consider the effect of a prolonged cooling in small halos and that we explicitly follow the chemical enrichment in the interstellar medium. We use our model to make predictions for the properties of the galaxy popula-tion at low redshift and compare them with various current observations. We find that our model prediction can match the luminosity functions of galaxies in various wavebands. The shape of the luminosity function at bright end is well reproduced if galaxy mergers are modeled with the merger trees of subhalos and the steep faint-end slope can be moderated if the gas cooling time in low-mass ha-los is comparable to the age of the universe. The same model can also match the observed bimodal distribution of galaxy color, the color-magnitude relation for elliptical galaxies in clusters, the metallicity-luminosity relation and metallicity-rotation velocity relation of spiral galaxies, and the gas fraction in present-day spiral galaxies. We also identify areas where further improvement of the model is required.
    09/2004;
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    Y. P. Jing, G. Boerner
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    ABSTRACT: We present the first determination of the pairwise velocity dispersion of galaxies at different luminosity with the final release of the Two-Degree Field Galaxy Redshift Survey (2dFGRS). Our result surprisingly shows that the random velocities of the faint galaxies are very high, around $ 700 \kms$, reaching similar values as the brightest galaxies. At intermediate luminosities slightly brighter than the characteristic luminosity $M_\star$, the velocities exhibit a well defined steep minimum near $ 400 \kms$. The result challenges the current halo model of galaxies of Yang et al. that was obtained by matching the clustering and luminosity function of 2dFGRS, and can be an important constraint in general on theories of galaxy formation, e.g., the semi-analytical model. Combining the observed luminosity dependence of clustering, our result implies that quite a fraction of faint galaxies are in massive halos of galaxy clusters as the brightest ones, but most of the $M_\star$ galaxies are in galactic halos. Comment: 5 pages, 2 figures, talk at IAUC 195, in the proceedings "Outskirts of Galaxy Clusters: intense life in the suburbs" A. Diaferio ed
    Proceedings of the International Astronomical Union 06/2004;
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    Y. P. Jing, G. Boerner
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    ABSTRACT: We present the first determination of the pairwise velocity dispersion (PVD) for galaxies in different luminosity intervals using the final release of the Two-Degree Field Galaxy Redshift Survey (2dFGRS). We have discovered quite surprisingly that the relative velocities of the faint galaxies at small separation are very high, around $700 \kms$, reaching similar values as the brightest galaxies. At intermediate luminosities $M^*-1$ ($M^*$ is the characteristic luminosity of the Schechter function), the relative velocities exhibit a well defined steep minimum near $400 \kms$. This result has been derived using a novel method to determine the real space power spectrum and the PVD from the redshift space power spectrum of the 2dFGRS. Both quantities can be determined quite reliably. We have taken the parameter $\beta$ equal to 0.45. But we have also checked that the results are changed very little, if we allow a variation of $\beta$ with luminosity. The result is a challenge to the current halo model of galaxies of Yang et al. that was obtained by matching the clustering and luminosity function of the 2dFGRS, but cannot reproduce the luminosity dependence of the PVD. It may also be an mportant constraint in general on theories of galaxy formation, such as semi-analytical models and hydro/N-body simulations of galaxy formation. Combined with the observed luminosity dependence of clustering, our result implies that a substantial fraction of faint galaxies, as well as the brightest ones, are in massive halos of galaxy cluster size, but most of the $M^*$ galaxies are in galactic halos. Comment: 30 pages, 9 figures, ApJ (in press). A much more detailed discussion on the halo model as well as on the SDSS galaxy-galaxy lensing
    The Astrophysical Journal 06/2004; · 6.73 Impact Factor
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    Y. P. Jing, G. Boerner
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    ABSTRACT: In a detailed analysis of the three point correlation function (3PCF) for the 2dF Galaxy Redshift Survey we have accurately measured the 3PCF for galaxies of different luminosity. The 3PCF amplitudes [$\Qsu$ or $\Qrpu$] of the galaxies generally decrease with increasing triangle size and increase with the shape parameter $v$, in qualitative agreement with the predictions for the clustering of dark matter in popular hierarchical CDM models. The 2dFGRS results agree well with the results of Jing & B\"orner for the Las Camapanas Redshift Survey (LCRS), though the measurement accuracy is greatly improved in the present study. The dependence of the 3PCF on luminosity is not significant, but there seems to be a trend for the brightest galaxy sample to have a lower amplitude than the fainter ones. Comparing the measured 3PCF amplitudes [$\Qsu$ or $\Qrpu$] to the prediction of a WMAP concordance model, we find that the measured values are consistently lower than the predicted ones for dark matter. This is most pronounced for the brightest galaxies, for which about one-half of the predicted $Q$ value provides a good description of $\Qrpu$ for the 2dFGRS data. For a less luminous sample, the $Q$ values are also smaller than in the dark matter model on small scales, but on scales larger than $s=8 \mpc$ and $r_p=3.25 \mpc$ they reach the model values. We discuss implications for current theories of galaxy formation. Comment: 39 pages, 18 figures, ApJ, published version; minor changes to the previous version
    The Astrophysical Journal 11/2003; · 6.73 Impact Factor
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    ABSTRACT: Using a combination of N-body simulations with different resolutions, we study in detail how the concentrations of cold dark matter (CDM) halos depend on halo mass at different redshifts. We confirm that halo concentrations at the present time depend strongly on halo mass, but our results also show marked differences from the predictions of some early empirical models. Our main result is that the mass dependence of the concentrations becomes weaker at higher redshifts, and at z >~ 3 halos of mass greater than 10^{11} Msun/h all have a similar median concentration, c ~ 3.5. While the median concentrations of low-mass halos grow significantly with time, those of massive halos change only little with redshifts. These results are quantitatively in good agreement with the empirical model proposed by Zhao et al. which shows that halos in the early fast accretion phase all have similar concentrations. Comment: 11 pages, including 2 figures and 1 table, publicated in ApJL, the first paper stating the zero mass-dependence of concentrations for massive and/or high redshift dark matter halos, which are still in the fast growth phase, quoted by the second version of ; v2: references corrected to be the same as the published version
    The Astrophysical Journal 09/2003; · 6.73 Impact Factor
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    Kohji Yoshikawa, Y. P. Jing, Gerhard Börner
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    ABSTRACT: We present velocity statistics of galaxies and their biases inferred from the statistics of the underlying dark matter using a cosmological hydrodynamic simulation of galaxy formation in low-density and spatially flat cold dark matter cosmogony. We find that the pairwise velocity dispersion (PVD) of all galaxies is significantly lower than that of the dark matter particles, and that the PVD of the young galaxies is lower than that of the old types, and even of all galaxies together, especially at small separations. These results are in reasonable agreement with the recent measurements of PVDs in the Las Campanas redshift survey, the PSCz catalogue and the SDSS data. We also find that the low PVD of young galaxies is due to the effects of dynamical friction as well as the different spatial distribution. We also consider the mean infall velocity and the POTENT density reconstruction that are often used to measure the cosmological parameters, and investigate the effects of spatial bias and dynamical friction. In our simulation, the mean infall velocity of young galaxies is significantly lower than that of all the galaxies or of the old galaxies, and the dynamical bias becomes important on scales less than 3Mpc/h. The mass density field reconstructed from the velocity field of young galaxies using the POTENT-style method suffers in accuracy both from the spatial bias and the dynamical friction on the smoothing scale of R_s=8Mpc/h. On the other hand, in the case of R_s=12Mpc/h, which is typically adopted in the actual POTENT analysis, the density reconstruction based on various tracers of galaxies is reasonably accurate. Comment: 29 pages, 11 figures, accepted for publication in the ApJ
    The Astrophysical Journal 03/2003; · 6.73 Impact Factor
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    ABSTRACT: In this paper, we analyse in detail the mass-accretion histories and structural properties of dark haloes in high-resolution N-body simulations. We model the density distribution in individual haloes using the Navarro–Frenk–White (NFW) profile. For a given halo, there is a tight correlation between its inner-scale radius rs and the mass within it, Ms, for all its main progenitors. Using this correlation, one can predict quite well the structural properties of a dark halo at any time in its history from its mass-accretion history, implying that the structure properties and the mass-accretion history are closely correlated. The predicted growing rate of concentration c with time tends to increase with decreasing mass-accretion rate. The build-up of dark haloes in cold dark matter (CDM) models generally consists of an early phase of fast accretion (where the halo mass Mh increases with time much faster than the expansion rate of the Universe) and a late phase of slow accretion (where Mh increases with time approximately as the expansion rate). These two phases are separated at a time when c∼ 4 and the typical binding energy of the halo is approximately equal to that of a singular isothermal sphere with the same circular velocity. Haloes in the two accretion phases show systematically different properties, for example, the circular velocity vh increases rapidly with time in the fast accretion phase but remains almost constant in the slow accretion phase, the inner properties of a halo, such as rs and Ms increase rapidly with time in the fast accretion phase but change only slowly in the slow accretion phase, the inner circular velocity vs is approximately equal to vh in the fast accretion phase but is larger in the slow accretion phase. The potential well associated with a halo is built up mainly in the fast accretion phase, while a large amount of mass can be accreted in the slow accretion phase without changing the potential well significantly. We discuss our results in connection with the formation of dark haloes and galaxies in hierarchical models.
    Monthly Notices of the Royal Astronomical Society 01/2003; 339(1):12 - 24. · 5.52 Impact Factor
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    R. Casas-Miranda, H. J. Mo, G. Börner
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    ABSTRACT: Using high-resolution N -body simulations, we test two theoretical models, based either on spherical or on ellipsoidal collapse model, for the higher order moments of the dark matter halo distribution in cold dark matter (CDM) models. We find that a theoretical model based on spherical collapse describes accurately the simulated counts-in-cells moments for haloes of several mass ranges. It appears that the model using ellipsoidal collapse instead of spherical collapse in defining dark haloes is unable to improve the models for the higher order moments of halo distribution, for haloes much smaller than M * (the mass scale on which the fluctuation of the density field has a rms about 1). Both models are particularly accurate for the descendants of haloes selected at high redshift, and so are quite useful in interpreting the high- order moments of galaxies. As an application we use the theoretical model to predict the higher order moments of the Lyman break galaxies observed at z approximate to 3 and their descendants at lower redshifts.
    Monthly Notices of the Royal Astronomical Society 01/2003; · 5.52 Impact Factor
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    ABSTRACT: The influence of radiative effects on the accretion onto stellar magnetospheres is investigated by performing global 2- and 2.5-dimensional simulations on the basis of high-resolution numerical schemes with the application of irregular grids adapted to the shape of the magnetopause. The latter is represented by an impermeable, contracted dipole magnetic field surface with polar holes. Accreting matter is assumed to be optically thin. The physical mechanisms which are taken into account include cooling due to free-free and free-bound transitions, the Compton heating via X-ray scattering on electrons, and the inverse Compton cooling in the regions where the temperature of the matter becomes sufficiently large to be able to transfer part of its internal energy to photons. Depending on the determining parameters, both steady-state solutions with a system of discontinuities and unsteady flows with expanding shock waves can be obtained. It is shown that efficient cooling of the matter can substantially facilitate the penetration of the matter through the polar holes. The detailed consideration of the realistic radiative effects proved to be of great importance in our understanding of the accretion phenomenon, since they can substantially affect it both qualitatively and quantitatively.
    Astronomy and Astrophysics 01/2003; · 5.08 Impact Factor
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    ABSTRACT: Accretion onto neutron stars and black holes is the main energy supply in galactic X-ray sources. The angular momentum captured by the X-ray star from the optical companion's wind with velocity V_{infty} and the binary period P is proportional to V^{-4}_{infty}P^{-1} [4]. If V_{infty} is high or the binary components are widely separated, the angular momentum is not sufficient for the accretion disk formation at distances of the Alfvén radius where the magnetic pressure of the star is balanced by the dynamic pressure of infalling matter, and the accretion at large distances from the star becomes nearly spherically symmetric. This occurs, for example, in some X-ray sources with a massive companion star where long-periodic pulsars are observed [1], [3].
    01/2003; -1:473.
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    Xi Kang, Y. P. Jing, H. J. Mo, G. Börner
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    ABSTRACT: We use N-body simulations to test the predictions of redshift distortion in the power spectrum given by the halo model in which the clustering of dark matter particles is considered as a result both of the clustering of dark haloes in space and of the distribution of dark matter particles in each individual dark halo. The predicted redshift distortion depends sensitively on several model parameters in a different way from the real-space power spectrum. An accurate model of the redshift distortion can be constructed if the following properties of the halo population are modelled accurately: the mass function of dark haloes, the velocity dispersion among dark haloes, and the non-linear nature of halo bias on small scales. The model can be readily applied to interpreting the clustering properties and velocity dispersion of different populations of galaxies once a cluster-weighted bias (or equivalently an halo occupation number model) is specified for the galaxies. Some non-trivial bias features observed from redshift surveys of optical galaxies and of IRAS galaxies relative to the standard low-density cold dark matter model can be easily explained in the cluster weighted bias model. The halo model further indicates that a linear bias can be a good approximation only for k≤ 0.1 h Mpc−1.
    Monthly Notices of the Royal Astronomical Society 10/2002; 336(3):892 - 900. · 5.52 Impact Factor
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    ABSTRACT: The stochasticity in the distribution of dark haloes in the cosmic density field is reflected in the distribution function PV(Nh|δm), which gives the probability of finding Nh haloes in a volume V with mass density contrast δm. We study the properties of this function using high-resolution N-body simulations, and find that PV(Nh|δm) is significantly non-Poisson. The ratio between the variance and the mean goes from ∼1 (Poisson) at 1+δm≪1 to <1 (sub-Poisson) at 1+δm∼1 to >1 (super-Poisson) at 1+δm≫1. The mean bias relation is found to be well described by halo bias models based on the Press–Schechter formalism. The sub-Poisson variance can be explained as a result of halo exclusion, while the super-Poisson variance at high δm may be explained as a result of halo clustering. A simple phenomenological model is proposed to describe the behaviour of the variance as a function of δm. Galaxy distribution in the cosmic density field predicted by semi-analytic models of galaxy formation shows similar stochastic behaviour. We discuss the implications of the stochasticity in halo bias to the modelling of higher order moments of dark haloes and of galaxies.
    Monthly Notices of the Royal Astronomical Society 06/2002; 333(4):730 - 738. · 5.52 Impact Factor
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    W. P. Lin, G. Börner, H. J. Mo
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    ABSTRACT: In this paper we present semi-analytic models and Monte Carlo simulations of quasi-stellar object (QSO, quasar) Ly absorption-line systems that originate in gaseous galactic haloes, galaxy discs and dark matter (DM) satellites around big central haloes. The aim is to estimate the number density per unit redshift of Ly absorption lines related to galaxies, and to investigate the properties of the predicted galaxy–absorber systems, such as equivalent widths Wr, projected distances ρ, galaxy luminosities LB, as well as absorber redshifts z. It is found that, for strong Ly absorption lines galactic haloes and satellites can explain ∼20 per cent and 40 per cent of the line number density of the HST QSO Absorption Line Key Project respectively. The population of DM satellites is adopted from recent numerical simulations by Klypin et al. If big galaxies indeed possess such large numbers of DM satellites and they possess gas, these satellites may play an important role for strong Ly lines. However, the predicted number density of Lyman-limit systems by satellites is ∼0.1 (per unit redshift), which is four times smaller than that by halo clouds. Including galactic haloes, satellites and H i discs of spirals, the predicted number density of strong lines can be as much as 60 per cent of the HST result. The models can also predict all of the observed Lyman-limit systems. For strong lines the average covering factor within 250 h−1 kpc is estimated to be ∼0.36, which is in good agreement with observations. Also, the effective absorption radius of a galaxy (with unit covering factor) is estimated to be ∼150 h−1 kpc. There exist correlations of Wr versus ρ, LB and z. The models predict with and To compare with the results of imaging and spectroscopic surveys, we study the selection effects of selection criteria similar to the surveys. We simulate mock observations through known QSO lines of sight and find that selection effects can statistically tighten the dependence of linewidth on projected distance. This result confirms previous suggestions in the literature. After applying selection criteria, the models can predict similar distributions of Wr, ρ, LB, absolute magnitudes and absorber redshifts to those of imaging and spectroscopic surveys. Finally we find that the total redshift interval of the present observations (∼5) is not large enough for the models to reveal the real relationships if adopting the selection criteria. An adequate total redshift interval might be ∼10. This may reconcile contradictory conclusions about the anticorrelation of equivalent widths versus projected distances by different authors.
    Monthly Notices of the Royal Astronomical Society 04/2002; 319(2):517 - 538. · 5.52 Impact Factor

Publication Stats

1k Citations
347.49 Total Impact Points

Institutions

  • 1975–2005
    • Max Planck Institute for Astrophysics
      Arching, Bavaria, Germany
  • 1998–2004
    • Chinese Academy of Sciences
      • Graduate School
      Peping, Beijing, China
    • The University of Tokyo
      • Department of Physics
      Edo, Tōkyō, Japan
  • 2002
    • Peking University
      Peping, Beijing, China
  • 2001
    • Northeast Institute of Geography and Agroecology
      • Department of Physics
      Peping, Beijing, China
  • 1988–1999
    • Tianjin Normal University
      T’ien-ching-shih, Tianjin Shi, China
  • 1996
    • University of Tuebingen
      Tübingen, Baden-Württemberg, Germany
  • 1993
    • Space Telescope Science Institute
      Baltimore, Maryland, United States
    • Universität Basel
      Bâle, Basel-City, Switzerland
  • 1991
    • Technion - Israel Institute of Technology
      H̱efa, Haifa District, Israel
  • 1987
    • Nagoya University
      Nagoya, Aichi, Japan
  • 1978
    • University of Cologne
      • Institute for Theoretical Physics
      Köln, North Rhine-Westphalia, Germany