Are Simulations of Cold Dark Matter Consistent with Galactic-Scale Observations at High Redshift?

2001 ◽  
Vol 560 (1) ◽  
pp. L33-L36 ◽  
Author(s):  
Jason X. Prochaska ◽  
Arthur M. Wolfe
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
High Redshift

scholarly journals Small-scale Substructure in Dark Matter Haloes: Where Does Galaxy Formation Come to an End?

2004 ◽  
Vol 220 ◽  
pp. 91-98 ◽  
Author(s):  
J. E. Taylor ◽  
J. Silk ◽  
A. Babul
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Structure Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Small Scale ◽  
Analytic Model ◽  
Model Predictions ◽  
Low Mass

Models of structure formation based on cold dark matter predict that most of the small dark matter haloes that first formed at high redshift would have merged into larger systems by the present epoch. Substructure in present-day haloes preserves the remains of these ancient systems, providing the only direct information we may ever have about the low-mass end of the power spectrum. We describe some recent attempts to model halo substructure down to very small masses, using a semi-analytic model of halo formation. We make a preliminary comparison between the model predictions, observations of substructure in lensed systems, and the properties of local satellite galaxies.

scholarly journals CONSTRAINING TEVES GRAVITY AS EFFECTIVE DARK MATTER AND DARK ENERGY

2007 ◽  
Vol 16 (12a) ◽  
pp. 2055-2063 ◽  
Author(s):  
HONGSHENG ZHAO
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Gravitational Lensing ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Elliptical Galaxies ◽  
Dual Roles ◽  
Acceleration Of The Universe ◽  
The Universe

The phenomena customarily described with the standard ΛCDM model are broadly reproduced by an extremely simple model in TeVeS, Bekenstein's1 modification of general relativity motivated by galaxy phenomenology. Our model can account for the acceleration of the Universe seen at SNeIa distances without a cosmological constant, and the accelerations seen in rotation curves of nearby spiral galaxies and gravitational lensing of high-redshift elliptical galaxies without cold dark matter. The model is consistent with BBN and the neutrino mass between 0.05 eV to 2 eV. The TeVeS scalar field is shown to play the effective dual roles of dark matter and dark energy, with the amplitudes of the effects controlled by a μ function of the scalar field, called the μ essence here. We also discuss outliers to the theory's predictions on multiimaged galaxy lenses and outliers on the subgalaxy scale.

scholarly journals THE EXISTENCE OF AN OLD QUASAR AT z=3.91 AND ITS IMPLICATIONS FOR Λ(t) DEFLATIONARY COSMOLOGIES

2004 ◽  
Vol 13 (07) ◽  
pp. 1321-1325 ◽  
Author(s):  
JOÃO VITAL CUNHA ◽  
ROSE CLÍVIA SANTOS
Keyword(s):  
Dark Matter ◽  
Energy Density ◽  
Total Energy ◽  
Lower Limit ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Observational Constraints ◽  
Total Energy Density ◽  
Lower Limits

We investigate some observational constraints on decaying vacuum cosmologies based on the recently discovered old high redshift quasar APM 08279+5255. This object is located at z=3.91 and has an estimated age of 2–3 Gyr. The class of Λ(t) cosmologies is characterized by a positive β parameter smaller than unity which quantifies the ratio between the vacuum and the total energy density. Assuming the lower limit age (2 Gyr) and that the cold dark matter contributes with Ω M =0.2 we show that β is constrained to be ≥0.07 while for an age of 3 Gyr and Ω M =0.4 the β parameter must be greater than 0.32. Our analysis includes closed, flat and hyperbolic scenarios, and it strongly suggests that there is no age crisis for this kind of Λ(t) cosmologies. Lower limits to the redshift quasar formation are also briefly discussed to the flat case. For Ω M =0.4 we found that the redshift formation is constrained by zf≥8.0.

scholarly journals Scalar Field Models for an Accelerating Universe

2005 ◽  
Vol 201 ◽  
pp. 260-263
Author(s):  
Varun. Sahni
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Accelerating Universe ◽  
Late Time ◽  
Luminosity Distance ◽  
New Class ◽  
Scalar Field Models ◽  
Model Independent

I describe a new class of quintessence+CDM models in which late time scalar field oscillations can give rise to both quintessence and cold dark matter. Additionally, a versatile ansatz for the luminosity distance is used to reconstruct the quintessence equation of state in amodel independentmanner from observations of high redshift supernovae.

scholarly journals Thin Planes of Satellites in ΛCDM are not kinematically coherent

2016 ◽  
Vol 11 (S321) ◽  
pp. 40-41
Author(s):  
Tobias Buck ◽  
Aaron A. Dutton ◽  
Andrea V. Macciò
Keyword(s):  
Dark Matter ◽  
High Resolution ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Large Fraction ◽  
Dark Matter Halo ◽  
Kinematic Structure ◽  
Andromeda Galaxy ◽  
High Incidence ◽  
The One

Recently it has been shown by Ibata et al. (2013) that a large fraction of the dwarf satellite galaxies found in the PAndAS survey (McConnachie et al. 2009) and orbiting the Andromeda galaxy are surprisingly aligned in a thin, extended, and kinematically coherent planar structure. The presence of such a structure seems to challenge the current Cold Dark Matter paradigm of structure formation (Ibata et al. 2014, Pawlowski et al. 2014), which predicts a more uniform distribution of satellites around central objects. We show that it is possible to obtain a thin, extended, rotating plane of satellites resembling the one in Andromeda in cosmological collisionless simulations based on this model. Our new 21 high-resolution simulations (see Buck et al. 2015) show a correlation between the formation time of the dark matter halo and the thickness of the plane of satellites. Our simulations have a high incidence of satellite planes as thin, extended, and as rich as the one in Andromeda and with a very coherent kinematic structure when we select early forming haloes. By tracking the formation of the satellites in the plane we show that they have mainly been accreted onto the main object along thin dark matter filaments at high redshift (Dekel et al. 2009, Libeskind et al. 2009, 2011). Our results show that the presence of a thin, extended, rotating plane of satellites is not a challenge for the Cold Dark Matter paradigm, but actually supports one of the predictions of this paradigm related to the presence of filaments of dark matter around galaxies at high redshift.

scholarly journals High-redshift evolution of optical- and infrared-selected galaxies: a comparison with cold dark matter scenarios

1999 ◽  
Vol 310 (2) ◽  
pp. L27-L32 ◽  
Author(s):  
Adriano Fontana ◽  
Nicola Menci ◽  
Sandro D'Odorico ◽  
Emanuele Giallongo ◽  
Francesco Poli ◽  
...  
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
High Redshift

scholarly journals Cosmological Constraints on the Coupling Model from Observational Hubble Parameter and Baryon Acoustic Oscillation Measurements

Universe ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 57
Author(s):  
Shulei Cao ◽  
Tong-Jie Zhang ◽  
Xinya Wang ◽  
Tingting Zhang
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Hubble Parameter ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Coupling Model ◽  
Acoustic Oscillation ◽  
Baryon Acoustic Oscillation ◽  
Best Fitting ◽  
Age Of The Universe

In the paper, we consider two models in which dark energy is coupled with either dust matter or dark matter, and discuss the conditions that allow more time for structure formation to take place at high redshifts. These models are expected to have a larger age of the universe than that of ΛCDM [universe consists of cold dark matter (CDM) and dark energy (a cosmological constant, Λ)], so it can explain the formation of high redshift gravitationally bound systems which the ΛCDM model cannot interpret. We use the observational Hubble parameter data (OHD) and Hubble parameter obtained from cosmic chronometers method (H(z)) in combination with baryon acoustic oscillation (BAO) data to constrain these models. With the best-fitting parameters, we discuss how the age, the deceleration parameter, and the energy density parameters evolve in the new universes, and compare them with that of ΛCDM.

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