The LCDM model experiences small scale problems that could be solved by allowing dark matter to have intrinsic thermal velocities, i.e. warm dark matter (WDM). In this talk I discuss the impact of WDM on the 21cm power spectrum, by means of high resolution hydrodynamical N-body simulations of different dark matter (DM) scenarios and different models of neutral hydrogen (HI) spatial distribution. I forecast the bounds that the Square Kilometre Array (SKA) will place on the DM particle mass.
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According to Westfall “The very heart of the new natural philosophy was mechanics, the science of motion. Mechanics required the measurement of a third dimension, time. The creation of the new world of precision was intimately connected to the success of science in learning to measure time.”
On large scales cosmic matter is distributed in a web consistent of clusters, filaments, walls and voids. While the dark-matter skeleton of the cosmic web is closely traced by galaxies and galaxy clusters, the large-scale gaseous distribution is more hardly detected. In particular, the warm-hot intergalactic component (T~10^5-10^7K) where nearly half of the "missing" cosmic baryons should be located, has yet to be firmly detected.
Spectroscopic Observations with Hinode/EIS and IRIS provide us with the opportunity to measure plasma diagnostics (DEM, electron density and flows). These data can be used with imaging data (SDO, Hinode/XRT) to study the temperature distribution of small energetic solar features. Such parameters are crucial for distinuishing between theoretical models. Here we discuss blue-shifted emission seen during small flares by IRIS with the FeXXI (1354A) spectral line, together with electron densities measurements obtained using IRIS OIV and SIV spectral lines (Polito et al, 2016).
La dernière décennie a marqué un tournant dans l'étude du magnétisme des étoiles. Avec ESPaDOnS au CFHT et NARVAL au TBL, une nouvelle génération de spectropolarimètres stellaires a vu le jour, affichant pour la première fois des performances suffisantes pour s'engager dans des mesures systématiques de champs magnétiques dans la quasi-totalité du diagramme de Hertzsprung-Russell, élargissant ainsi radicalement la gamme d'objets accessibles à ces études.
In part one of this seminar, we present a validated method to perform differential emission measure (DEM) inversions on extreme ultraviolet imaging observations of the solar corona taken by the Atmospheric Imaging Assembly onboard NASA’s Solar Dynamics Observatory. We begin with a description of the method and proceed to discuss test cases used for validation.
Investigating the physics of the interstellar medium (ISM) is key to understand how our Galaxy works and evolves. The ISM is the fuel of the Galactic engine, the matter reservoir of the Milky Way to allow for new star formation. This interstellar plasma is a melting pot of cosmic rays, multiphase gas, and dust particles, all tightly coupled with magnetic fields.