Found 42 talks width keyword dark matter

I will review some theoretical ideas in Cosmology different to the standard "Big Bang": the Quasi-steady State model, Plasma Cosmology model, non-cosmological redshifts, alternatives to non-baryonic dark matter and/or dark energy, and others. Some open problems of Cosmology within the standard model will also be summarized.

In the first part of this talk I will present a historical review of the CMB observations, one of the most powerful cosmological probes. Following the first talk of this series, where Jose Alberto described the basic parameters that define the standard cosmological model, I will here summarize the constraints to these parameters that have been derived from these observations. I will also describe the current challenges in this field, in particular the detection of the inflation's B-mode signal through CMB polarization observations, as well as the experiments that have been developed worldwide to this aim, including IAC's QUIJOTE. In the second part, I will focus on the so-called ``missing baryon problem'', i.e. the fact that the half of the expected baryon content of the local universe remains yet undetected. I will describe the theoretical studies that provide hints on where these baryons could be located, and the observational efforts that have been undertaken in this regard.

This is the first talk of a series of four aimed to discuss about Cosmology. Here, I will review the basic concepts of the standard cosmological model, which will be further discussed in the following talks, as well as the observational evidence in support of the Lambda-CDM model. As the subject is very broad, I will focus the discussion on topics related with inflation, dark matter and dark energy. Moreover, I will mainly discuss large scale structure probes.

The extragalactic background light (EBL) is of fundamental importance both for understanding the entire process of galaxy evolution and for gamma-ray astronomy, but the overall spectrum of the EBL between 0.1 and 1000 microns has never been determined directly from galaxy spectral energy distribution (SED) observations over a wide redshift range. Galaxy SED-type fractions from z=0.2-1 are estimated from a multi-wavelength sample from the AEGIS collaboration that allows a new determination of the evolving EBL. Then, the transparency of the Universe to very high energy (VHE) gamma-ray photons is derived. We find the maximum transparency of the Universe allowed by the standard framework. This result challenges current VHE observations of high redshift blazars. A solution to this problem is discussed utilizing VHE spectra of the highest redshift blazars assuming the existence of a plausible dark matter candidate known as axion-like particle.

Dark Matter in Galaxies is an important subject of current astrophysical research. I will concentrate on spiral galaxies, and first give an overview of the subject from the standpoint of a radioastronomer with a long involvement in the subject. This includes a historical introduction and a review of some of the present-day debates. The currently popular Lambda-CDM model has problems on the scale of galaxies. In a second part I will address more specifically the problem that we still do not know how much dark matter there is in spiral galaxies, and how it is distributed. This is due to the fact that the M/L of the visible matter is poorly constrained and that there is a 'conspiracy' between the dark and the baryonic material. I will present various dynamical methods that have been proposed to constrain the dark matter mass distribution and discuss their advantages and disadvantages.

The distribution of matter in galaxies of different luminosities and Hubble types, as inferred from observations, plays an important role in cosmology, extragalactic astrophysics, astroparticle physics, as well as in a number of issues in high-energy astrophysics, galactic astronomy, star formation and evolution and general relativity. Not withstanding the general successes of the ΛCDM model in explaining the structure and evolution of the universe, there is a growing conviction that the structural properties of the dark and luminous components in galaxies hold important clues about the nature of dark matter and about the processes that are responsible for galaxy formation. This talk is part of an international initiative known as "Dark Matter Awareness Week".The overall purpose of this event is to increase the awareness of the phenomenology of the mass discrepancy phenomenon in galaxies amongst the many scientists currently working with a theoretical, observational, experimental and simulation approach on issues involving dark matter or its alternatives. The content of the talk will be at the level of a journal club talk with an important dose of review.

Recent observations of the rotation curve of M31 show a rise of the outer part that cannot be understood in terms of standard dark matter models or perturbations of the galactic disc by M31's satellites. In this talk, we show a possible explanation of this dynamical feature based on the influence of the magnetic field within the thin disc. We have considered standard mass models for the luminous mass distribution, a Navarro-Frenk-White model to describe the dark halo, and we have added up the contribution to the rotation curve of a magnetic field in the disc. We have found a significant improvement of the fit in the outer part when magnetic effects are considered. Our best-fit requires a field strength of ~ 4μG which is compatible with the observations of the magnetic fields in M31.