排序方式： 共有128条查询结果，搜索用时 15 毫秒
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Mark Vogelsberger Amina Helmi Volker Springel Simon D. M. White Jie Wang Carlos S. Frenk Adrian Jenkins Aaron Ludlow Julio F. Navarro 《Monthly notices of the Royal Astronomical Society》2009,395(2):797-811
We study predictions for dark matter (DM) phase-space structure near the Sun based on high-resolution simulations of six galaxy haloes taken from the Aquarius project. The local DM density distribution is predicted to be remarkably smooth; the density at the Sun differs from the mean over a best-fitting ellipsoidal equidensity contour by less than 15 per cent at the 99.9 per cent confidence level. The local velocity distribution is also very smooth, but it differs systematically from a (multivariate) Gaussian distribution. This is not due to the presence of individual clumps or streams, but to broad features in the velocity modulus and energy distributions that are stable in both space and time and reflect the detailed assembly history of each halo. These features have a significant impact on the signals predicted for weakly interacting massive particle and axion searches. For example, weakly interacting massive particles recoil rates can deviate by ∼10 per cent from those expected from the best-fitting multivariate Gaussian models. The axion spectra in our simulations typically peak at lower frequencies than in the case of multivariate Gaussian velocity distributions. Also in this case, the spectra show significant imprints of the formation of the halo. This implies that once direct DM detection has become routine, features in the detector signal will allow us to study the DM assembly history of the Milky Way. A new field, 'DM astronomy', will then emerge. 相似文献
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Juan E. González C. G. Lacey C. M. Baugh C. S. Frenk A. J. Benson 《Monthly notices of the Royal Astronomical Society》2009,397(3):1254-1274
The huge size and uniformity of the Sloan Digital Sky Survey (SDSS) make possible an exacting test of current models of galaxy formation. We compare the predictions of the galform semi-analytical galaxy formation model for the luminosities, morphologies, colours and scalelengths of local galaxies. galform models the luminosity and size of the disc and bulge components of a galaxy, and so we can compute quantities which can be compared directly with SDSS observations, such as the Petrosian magnitude and the Sérsic index. We test the predictions of two published models set in the cold dark matter cosmology: the Baugh et al. model, which assumes a top-heavy initial mass function (IMF) in starbursts and superwind feedback, and the Bower et al. model, which uses active galactic nucleus feedback and a standard IMF. The Bower et al. model better reproduces the overall shape of the luminosity function, the morphology–luminosity relation and the colour bimodality observed in the SDSS data, but gives a poor match to the size–luminosity relation. The Baugh et al. model successfully predicts the size–luminosity relation for late-type galaxies. Both models fail to reproduce the sizes of bright early-type galaxies. These problems highlight the need to understand better both the role of feedback processes in determining galaxy sizes, in particular the treatment of the angular momentum of gas reheated by supernovae, and the sizes of the stellar spheroids formed by galaxy mergers and disc instabilities. 相似文献
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R. E. Angulo C. M. Baugh C. S. Frenk C. G. Lacey 《Monthly notices of the Royal Astronomical Society》2008,383(2):755-776
We assess the detectability of baryonic acoustic oscillation (BAO) in the power spectrum of galaxies using ultralarge volume N -body simulations of the hierarchical clustering of dark matter and semi-analytical modelling of galaxy formation. A step-by-step illustration is given of the various effects (non-linear fluctuation growth, peculiar motions, non-linear and scale-dependent bias) which systematically change the form of the galaxy power spectrum on large scales from the simple prediction of linear perturbation theory. Using a new method to extract the scale of the oscillations, we nevertheless find that the BAO approach gives an unbiased estimate of the sound horizon scale. Sampling variance remains the dominant source of error despite the huge volume of our simulation box (=2.41 h −3 Gpc3 ) . We use our results to forecast the accuracy with which forthcoming surveys will be able to measure the sound horizon scale, s , and, hence constrain the dark energy equation of state parameter, w (with simplifying assumptions and without marginalizing over the other cosmological parameters). Pan-STARRS could potentially yield a measurement with an accuracy of Δ s / s = 0.5–0.7 per cent (corresponding to Δ w ≈ 2–3 per cent), which is competitive with the proposed WFMOS survey ( Δ s / s = 1 per cent Δ w ≈ 4 per cent). Achieving Δ w ≤ 1 per cent using BAO alone is beyond any currently commissioned project and will require an all-sky spectroscopic survey, such as would be undertaken by the SPACE mission concept under proposal to ESA. 相似文献
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The 2dF Galaxy Redshift Survey: the bias of galaxies and the density of the Universe 总被引：1，自引：0，他引：1
Licia Verde Alan F. Heavens Will J. Percival Sabino Matarrese Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Matthew Colless Chris Collins Warrick Couch Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve Maddox Darren Madgwick Peder Norberg John A. Peacock Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,335(2):432-440
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A. J. Benson C. S. Frenk C. G. Lacey C. M. Baugh S. Cole 《Monthly notices of the Royal Astronomical Society》2002,333(1):177-190
We use a self-consistent model of galaxy formation and the evolution of the intergalactic medium to study the effects of the reionization of the Universe at high redshift on the properties of satellite galaxies like those seen around the Milky Way. Photoionization suppresses the formation of small galaxies, so that surviving satellites are preferentially those that formed before the Universe reionized. As a result, the number of satellites expected today is about an order of magnitude smaller than the number inferred by identifying satellites with subhaloes of the same circular velocity in high-resolution simulations of the dark matter. The resulting satellite population has an abundance similar to that observed in the Local Group, although the distribution of circular velocities differs somewhat from the available data. We explore many other properties of satellite galaxies, including their gas content, metallicity and star formation rate, and find generally good agreement with available data. Our model predicts the existence of many as yet undetected satellites in the Local Group. We quantify their observability in terms of their apparent magnitude and surface brightness, and also in terms of their constituent stars. A near-complete census of the Milky Way's satellites would require imaging to V ≈20 and to a surface brightness fainter than 26 V -band magnitudes per square arcsecond. Satellites with integrated luminosity V =15 should contain of order 100 stars brighter than B =26 , with central stellar densities of a few tens per square arcminute. Discovery of a large population of faint satellites would provide a strong test of current models of galaxy formation. 相似文献
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Roberto De Propris Warrick J. Couch Matthew Colless Gavin B. Dalton Chris Collins Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Nicholas Cross Kathryn Deeley Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve Maddox Darren Madgwick Stephen Moody Peder Norberg John A. Peacock Will Percival Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,329(1):87-101
We have carried out a study of known clusters within the 2dF Galaxy Redshift Survey (2dFGRS) observed areas and have identified 431 Abell, 173 APM and 343 EDCC clusters. Precise redshifts, velocity dispersions and new centroids have been measured for the majority of these objects, and this information is used to study the completeness of these catalogues, the level of contamination from foreground and background structures along the cluster's line of sight, the space density of the clusters as a function of redshift, and their velocity dispersion distributions. We find that the Abell and EDCC catalogues are contaminated at the level of about 10 per cent, whereas the APM catalogue suffers only 5 per cent contamination. If we use the original catalogue centroids, the level of contamination rises to approximately 15 per cent for the Abell and EDCC catalogues, showing that the presence of foreground and background groups may alter the richness of clusters in these catalogues. There is a deficiency of clusters at that may correspond to a large underdensity in the Southern hemisphere. From the cumulative distribution of velocity dispersions for these clusters, we derive a space density of clusters of This result is used to constrain models for structure formation; our data favour low-density cosmologies, subject to the usual assumptions concerning the shape and normalization of the power spectrum. 相似文献