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تسجيل مستخدم جديدDark sectors of the Universe: A Euclid survey approach
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In this paper we study the consequences of relaxing the hypothesis of the pressureless nature of the dark matter component when determining constraints on dark energy. To this aim we consider simple generalized dark matter models with constant equation of state parameter. We find that present-day low-redshift probes (type-Ia supernovae and baryonic acoustic oscillations) lead to a complete degeneracy between the dark energy and the dark matter sectors. However, adding the cosmic microwave background (CMB) high-redshift probe restores constraints similar to those on the standard $Lambda$CDM model. We then examine the anticipated constraints from the galaxy clustering probe of the future Euclid survey on the same class of models, using a Fisher forecast estimation. We show that the Euclid survey allows us to break the degeneracy between the dark sectors, although the constraints on dark energy are much weaker than with standard dark matter. The use of CMB in combination allows us to restore the high precision on the dark energy sector constraints.
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In this work we study the consequences of allowing non pressureless dark matter when determining dark energy constraints. We show that present-day dark energy constraints from low-redshift probes are extremely degraded when allowing this dark matter
variation. However, adding the cosmic microwave background (CMB) we can recover the $w_{DM} = 0$ case constraints. We also show that with the future Euclid redshift survey we expect to largely improve these constraints; but, without the complementary information of the CMB, there is still a strong degeneracy between dark energy and dark matter equation of state parameters.
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In the last decade, astronomers have found a new type of supernova called `superluminous supernovae (SLSNe) due to their high peak luminosity and long light-curves. These hydrogen-free explosions (SLSNe-I) can be seen to z~4 and therefore, offer the
possibility of probing the distant Universe. We aim to investigate the possibility of detecting SLSNe-I using ESAs Euclid satellite, scheduled for launch in 2020. In particular, we study the Euclid Deep Survey (EDS) which will provide a unique combination of area, depth and cadence over the mission. We estimated the redshift distribution of Euclid SLSNe-I using the latest information on their rates and spectral energy distribution, as well as known Euclid instrument and survey parameters, including the cadence and depth of the EDS. We also applied a standardization method to the peak magnitudes to create a simulated Hubble diagram to explore possible cosmological constraints. We show that Euclid should detect approximately 140 high-quality SLSNe-I to z ~ 3.5 over the first five years of the mission (with an additional 70 if we lower our photometric classification criteria). This sample could revolutionize the study of SLSNe-I at z>1 and open up their use as probes of star-formation rates, galaxy populations, the interstellar and intergalactic medium. In addition, a sample of such SLSNe-I could improve constraints on a time-dependent dark energy equation-of-state, namely w(a), when combined with local SLSNe-I and the expected SN Ia sample from the Dark Energy Survey. We show that Euclid will observe hundreds of SLSNe-I for free. These luminous transients will be in the Euclid data-stream and we should prepare now to identify them as they offer a new probe of the high-redshift Universe for both astrophysics and cosmology.
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The concordance model in cosmology, $Lambda$CDM, is able to fit the main cosmological observations with a high level of accuracy. However, around 95% of the energy content of the Universe within this framework remains still unknown. In this work we f
ocus on the dark matter component and we investigate the generalized dark matter (GDM) model, which allows for non-pressure-less dark matter and a non-vanishing sound speed and viscosity. We first focus on current observations, showing that GDM could alleviate the tension between cosmic microwave background and weak lensing observations. We then investigate the ability of the photometric Euclid survey (photometric galaxy clustering, weak lensing, and their cross-correlations) to constrain the nature of dark matter. We conclude that Euclid will provide us with very good constraints on GDM, enabling us to better understand the nature of this fluid, but a non-linear recipe adapted to GDM is clearly needed in order to correct for non-linearities and get reliable results down to small scales.
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