scholarly journals Constraints on cold dark matter theories from observations of massive x-ray-luminous clusters of galaxies at high redshift

1995 ◽  
Vol 445 ◽  
pp. L77 ◽  
Author(s):  
G. A. Luppino ◽  
I. M. Gioia
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Clusters Of Galaxies ◽  
X Ray

scholarly journals NIKA: a mm camera for Sunyaev-Zel’dovich science in clusters of galaxies

2020 ◽  
Vol 228 ◽  
pp. 00016
Author(s):  
J.F. Macías-Pérez ◽  
R. Adam ◽  
P. Ade ◽  
P. André ◽  
A. Andrianasolo ◽  
...  
Keyword(s):  
Dark Matter ◽  
Angular Resolution ◽  
High Redshift ◽  
Radial Pressure ◽  
Pressure Profile ◽  
Field Of View ◽  
Dual Band ◽  
Clusters Of Galaxies ◽  
The Universe

Clusters of galaxies, the largest bound objects in the Universe, constitute a cosmological probe of choice, which is sensitive to both dark matter and dark energy. Within this framework, the Sunyaev-Zel’dovich (SZ) effect has opened a new window for the detection of clusters of galaxies and for the characterization of their physical properties such as mass, pressure and temperature. NIKA, a KID-based dual band camera installed at the IRAM 30-m telescope, was particularly well adapted in terms of frequency, angular resolution, field-of-view and sensitivity, for the mapping of the thermal and kinetic SZ effect in high-redshift clusters. In this paper, we present the NIKA cluster sample and a review of the main results obtained via the measurement of the SZ effect on those clusters: reconstruction of the cluster radial pressure profile, mass, temperature and velocity.

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 Dark matter and X-ray halo in early-type galaxies and clusters of galaxies

2009 ◽  
Vol 5 (H15) ◽  
pp. 89-90
Author(s):  
Takaya Ohashi
Keyword(s):  
Dark Matter ◽  
Clusters Of Galaxies ◽  
Large Scatter ◽  
Early Type ◽  
Matter Distribution ◽  
X Ray ◽  
Galaxy Groups ◽  
Hot Gas ◽  
Luminous Galaxies ◽  
Dark Matter Distribution

X-ray observations reveal extended halos around early-type galaxies which enable us to trace the dark matter distribution around the galaxies (see Mathews and Brighenti 2003 for a review). X-ray luminosities, LX of massive early-type galaxies are 1040−1042 erg s−1 in 0.3–2 keV. The correlation plot between LX and B-band luminosity LB shows a large scatter in the sense that LX varies by 2 orders of magnitudes for the same LB, in the brightest end (log LB ≳ 10.5). The amount of the X-ray hot gas in early-type galaxies is typically a few % of the stellar mass, in contrast to clusters of galaxies which hold ~5 times more massive gas than stars. Matsushita (2001) showed that X-ray luminous galaxies are characterized by extended X-ray halo with a few tens of re, similar to the scale of galaxy groups, so the presence of group-size potentials would be strongly linked with the problem of large LX scatter.

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 Quasars as standard candles

2020 ◽  
Vol 642 ◽  
pp. A150 ◽  
Author(s):  
E. Lusso ◽  
G. Risaliti ◽  
E. Nardini ◽  
G. Bargiacchi ◽  
M. Benetti ◽  
...  
Keyword(s):  
Cold Dark Matter ◽  
High Redshift ◽  
Full Description ◽  
X Rays ◽  
Hubble Diagram ◽  
X Ray ◽  
Flux Limit ◽  
Cold Dark Matter Model ◽  
Systematic Effects ◽  
The Stability

We present a new catalogue of ∼2400 optically selected quasars with spectroscopic redshifts and X-ray observations from either Chandra or XMM–Newton. The sample can be used to investigate the non-linear relation between the ultraviolet (UV) and X-ray luminosity of quasars as well as to build a Hubble diagram up to a redshift of z ∼ 7.5. We selected sources that are neither reddened by dust in the optical and UV nor obscured by gas in the X-rays, and whose X-ray fluxes are free from flux-limit-related biases. After checking for any possible systematics, we confirm, in agreement with our previous works, that the X-ray to UV relation provides distance estimates matching those from supernovae up to z ∼ 1.5, and its slope shows no redshift evolution up to z ∼ 5. We provide a full description of the methodology for testing cosmological models, further supporting a trend whereby the Hubble diagram of quasars is well reproduced by the standard flat cold dark matter model up to z ∼ 1.5–2, but strong deviations emerge at higher redshifts. Since we have minimised all non-negligible systematic effects and proven the stability of the LX − LUV relation at high redshifts, we conclude that an evolution of the expansion rate of the Universe should be considered as a possible explanation for the observed deviation, rather than some systematic (redshift-dependent) effect associated with high-redshift quasars.

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