Three-year WMAP Observations: Method and Results
... – The temperature at decoupling (where the most of CMB is coming from) was ~3000K, or 0.26 eV. – The temperature at matter-radiation equality was ~9000K, or 0.8 eV. ...
... – The temperature at decoupling (where the most of CMB is coming from) was ~3000K, or 0.26 eV. – The temperature at matter-radiation equality was ~9000K, or 0.8 eV. ...
Measuring the masses of clusters
... –! T ~ 107 – 108 K, emission is from free-free emission (as in groups, but hotter) –! In fact, many distant clusters are now being discovered via x-ray surveys (such as the ROSAT survey) –! Temperatures are not uniform, we see patches of “hot spots” which are not obviously associated with galaxies. ...
... –! T ~ 107 – 108 K, emission is from free-free emission (as in groups, but hotter) –! In fact, many distant clusters are now being discovered via x-ray surveys (such as the ROSAT survey) –! Temperatures are not uniform, we see patches of “hot spots” which are not obviously associated with galaxies. ...
Study of the X-ray Source Population and the Dark Matter
... would indicate that these galaxies are able to retain their compact objects, which are believed to obtain high kick velocities at their birth in asymmetric supernova explosions. Therefore, the search for and the study of X-ray sources in dSph galaxies in the Local Group will enable us to constrain t ...
... would indicate that these galaxies are able to retain their compact objects, which are believed to obtain high kick velocities at their birth in asymmetric supernova explosions. Therefore, the search for and the study of X-ray sources in dSph galaxies in the Local Group will enable us to constrain t ...
Dark Matter: A Brief Review
... wash out too much small-scale structure (see Sec. 4; [19]). In order for lighter gravitinos to be dark matter, one typically must introduce some non-standard cosmology [20]. Heavy gravitinos are, in my opinion, more interesting. If the next-lightest supersymmetric particle (NLSP) is only barely more ...
... wash out too much small-scale structure (see Sec. 4; [19]). In order for lighter gravitinos to be dark matter, one typically must introduce some non-standard cosmology [20]. Heavy gravitinos are, in my opinion, more interesting. If the next-lightest supersymmetric particle (NLSP) is only barely more ...
1 The Milky Way
... lar and the most elliptical orbits are more or less radial. The orbits of stars in the bulge on average stay closer to the centre of the Galaxy. Also, the bulge has a slight net rotation. Inside globular clusters, the stars are buzzing about at random with respect to the centre of the cluster, in mu ...
... lar and the most elliptical orbits are more or less radial. The orbits of stars in the bulge on average stay closer to the centre of the Galaxy. Also, the bulge has a slight net rotation. Inside globular clusters, the stars are buzzing about at random with respect to the centre of the cluster, in mu ...
matter - Osborne High School
... Microscopic Explanation for Properties of Liquids Liquids have an indefinite shape because the particles can slide past one another. Liquids are not easily compressible and have a definite volume because there is little free space between particles. Liquids flow easily because the particles can m ...
... Microscopic Explanation for Properties of Liquids Liquids have an indefinite shape because the particles can slide past one another. Liquids are not easily compressible and have a definite volume because there is little free space between particles. Liquids flow easily because the particles can m ...
Revealing Galactic Scale Bars with the help of Galaxy Zoo
... (Haynes et al. 2011) show that disc galaxies with higher gas content have lower bar fractions. We use a gas deficiency parameter to show that disc galaxies with more/less gas than expected for their stellar mass are less/more likely to host bars. Furthermore, we see that at a fixed gas content there ...
... (Haynes et al. 2011) show that disc galaxies with higher gas content have lower bar fractions. We use a gas deficiency parameter to show that disc galaxies with more/less gas than expected for their stellar mass are less/more likely to host bars. Furthermore, we see that at a fixed gas content there ...
hep-ph - Royal Holloway, University of London
... For some time it has been apparent that the inferred values of the cosmological baryon and dark matter densities are strikingly similar. For example, the latest WMAPdetermined range for the dark matter density, 0.129 > ΩCDM h2 > 0.095, is within a factor of a few of the combined WMAP and big-bang nu ...
... For some time it has been apparent that the inferred values of the cosmological baryon and dark matter densities are strikingly similar. For example, the latest WMAPdetermined range for the dark matter density, 0.129 > ΩCDM h2 > 0.095, is within a factor of a few of the combined WMAP and big-bang nu ...
Lecture Notes
... We now understand that spiral arms ‘trail’ galactic rotation. What is the nature of spiral arms? They cannot represent the same stars (or the same sites of star formation) over time, as this would lead to a ‘winding problem’. Spiral arms must represent a wave phenomenon that progresses through the g ...
... We now understand that spiral arms ‘trail’ galactic rotation. What is the nature of spiral arms? They cannot represent the same stars (or the same sites of star formation) over time, as this would lead to a ‘winding problem’. Spiral arms must represent a wave phenomenon that progresses through the g ...
Chapter 20. Galaxies
... As you worked out in one of your problem set questions (and review the answer sheet if you didn’t get it right!), if we observe v = constant, instead of a falling v, we can infer (assuming that laws of gravity still hold even over the great distances of a galaxy’s radius) that Mr must be growing wit ...
... As you worked out in one of your problem set questions (and review the answer sheet if you didn’t get it right!), if we observe v = constant, instead of a falling v, we can infer (assuming that laws of gravity still hold even over the great distances of a galaxy’s radius) that Mr must be growing wit ...
Probing the stability of superheavy dark matter particles with high
... There is currently mounting evidence for the existence of dark matter (DM) in our Universe from various astronomical and cosmological observations [1]. However, very fundamental properties of the dark matter particle such as the mass or the lifetime are still fairly unconstrained. An important restr ...
... There is currently mounting evidence for the existence of dark matter (DM) in our Universe from various astronomical and cosmological observations [1]. However, very fundamental properties of the dark matter particle such as the mass or the lifetime are still fairly unconstrained. An important restr ...
MACHOs
... Instead of using the total time interval for when magnification starts/ends, we need to pick a value for magnification corresponding to a certain point on the graph. o Before, we were finding the Rm at the point when the magnification was just starting to show a change but using the value for the ...
... Instead of using the total time interval for when magnification starts/ends, we need to pick a value for magnification corresponding to a certain point on the graph. o Before, we were finding the Rm at the point when the magnification was just starting to show a change but using the value for the ...
Dark matter
Dark matter is a hypothetical kind of matter that cannot be seen with telescopes but would account for most of the matter in the universe. The existence and properties of dark matter are inferred from its gravitational effects on visible matter, on radiation, and on the large-scale structure of the universe. Dark matter has not been detected directly, making it one of the greatest mysteries in modern astrophysics.Dark matter neither emits nor absorbs light or any other electromagnetic radiation at any significant level. According to the Planck mission team, and based on the standard model of cosmology, the total mass–energy of the known universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy. Thus, dark matter is estimated to constitute 84.5% of the total matter in the universe, while dark energy plus dark matter constitute 95.1% of the total mass–energy content of the universe.Astrophysicists hypothesized the existence of dark matter to account for discrepancies between the mass of large astronomical objects determined from their gravitational effects, and their mass as calculated from the observable matter (stars, gas, and dust) that they can be seen to contain. Their gravitational effects suggest that their masses are much greater than the observable matter survey suggests. Dark matter was postulated by Jan Oort in 1932, albeit based upon insufficient evidence, to account for the orbital velocities of stars in the Milky Way. In 1933, Fritz Zwicky was the first to use the virial theorem to infer the existence of unseen matter, which he referred to as dunkle Materie 'dark matter'. More robust evidence from galaxy rotation curves was discovered by Horace W. Babcock in 1939, but was not attributed to dark matter. The first hypothesis to postulate ""dark matter"" based upon robust evidence was formulated by Vera Rubin and Kent Ford in the 1960s–1970s, using galaxy rotation curves. Subsequently, many other observations have indicated the presence of dark matter in the universe, including gravitational lensing of background objects by galaxy clusters such as the Bullet Cluster, the temperature distribution of hot gas in galaxies and clusters of galaxies and, more recently, the pattern of anisotropies in the cosmic microwave background. According to consensus among cosmologists, dark matter is composed primarily of a not yet characterized type of subatomic particle.The search for this particle, by a variety of means, is one of the major efforts in particle physics today.Although the existence of dark matter is generally accepted by the mainstream scientific community, some alternative theories of gravity have been proposed, such as MOND and TeVeS, which try to account for the anomalous observations without requiring additional matter. However, these theories cannot account for the properties of galaxy clusters.