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... As a result, after reionization most hydrogen atoms are kept ionized by the UVB radiation they receive from all the ionizing sources they can see in the Universe. The complexity of processes that set the ionization state of hydrogen depends on the HI column density. At low HI column densities (i.e., ...
... As a result, after reionization most hydrogen atoms are kept ionized by the UVB radiation they receive from all the ionizing sources they can see in the Universe. The complexity of processes that set the ionization state of hydrogen depends on the HI column density. At low HI column densities (i.e., ...
3P33.pdf
... The optical multicolour imaging carried out during the first NOT observing night (taken at March 16.95–17.22 UT) allowed us to construct the optical spectral energy distribution (SED) of the afterglow. Furthermore, including the K -band detection on March 14.3 UT reported by Burud et al. (2002) the ...
... The optical multicolour imaging carried out during the first NOT observing night (taken at March 16.95–17.22 UT) allowed us to construct the optical spectral energy distribution (SED) of the afterglow. Furthermore, including the K -band detection on March 14.3 UT reported by Burud et al. (2002) the ...
cos1+2+3
... • Received at Galaxy B now (tnow ) with λ • λ / λ0 = Rnow /R(t) = 1+z(t) > 1 AS 4022 Cosmology ...
... • Received at Galaxy B now (tnow ) with λ • λ / λ0 = Rnow /R(t) = 1+z(t) > 1 AS 4022 Cosmology ...
AS 4022: Cosmology - ASTRONOMY GROUP – University of St
... • Received at Galaxy B now (tnow ) with λ • λ / λ0 = Rnow /R(t) = 1+z(t) > 1 AS 4022 Cosmology ...
... • Received at Galaxy B now (tnow ) with λ • λ / λ0 = Rnow /R(t) = 1+z(t) > 1 AS 4022 Cosmology ...
ASTRONOMY AND ASTROPHYSICS Elemental abundances of
... damped Lyα systems and the Lyα-forest. We selected quasars with no strong contamination since we are predominantly interested in the emission line flux and profiles. The quasars had to be brighter than 20 mag to achieve a sufficient S/N ratio of at least 20 for the continuum for reasonable integrati ...
... damped Lyα systems and the Lyα-forest. We selected quasars with no strong contamination since we are predominantly interested in the emission line flux and profiles. The quasars had to be brighter than 20 mag to achieve a sufficient S/N ratio of at least 20 for the continuum for reasonable integrati ...
Looking back in time to the big bang theory
... ago, and is still expanding today. The evidence for this is that the spectra from distant stars are red-shifted, meaning that they are moving away from us. Also, the universe has cosmic microwave background radiation, which was caused by the Big Bang. Supporting information There are opportunities f ...
... ago, and is still expanding today. The evidence for this is that the spectra from distant stars are red-shifted, meaning that they are moving away from us. Also, the universe has cosmic microwave background radiation, which was caused by the Big Bang. Supporting information There are opportunities f ...
HST04-Cosmology - Indico
... Expansion of the Universe “The further away galaxies are, the more rapid their recession appears to be” • Velocities measured via redshift; basically the Doppler effect applied to light • Distances typically determined via the use of standard candles (absolute vs. relative brightness) • Leads to Hu ...
... Expansion of the Universe “The further away galaxies are, the more rapid their recession appears to be” • Velocities measured via redshift; basically the Doppler effect applied to light • Distances typically determined via the use of standard candles (absolute vs. relative brightness) • Leads to Hu ...
Galaxy Hunters Article, Cosmology Information, First Star Facts
... the idea that the seeds of galaxy formation—the primordial lumps in the early universe created by dark matter—left tiny temperature variations in the cosmic microwave background, now cooled to a frigid 2.73 degrees above absolute zero. Famed cosmologist Stephen Hawking pronounced the finding the "d ...
... the idea that the seeds of galaxy formation—the primordial lumps in the early universe created by dark matter—left tiny temperature variations in the cosmic microwave background, now cooled to a frigid 2.73 degrees above absolute zero. Famed cosmologist Stephen Hawking pronounced the finding the "d ...
lecture24
... Spiral galaxies have a basic disk shape with the spiral arms in the flat disk. There is a central core containing the bulk of the stars, visible here as bright hubs (99% of the light) from which the spirals radiate. And like the Milky Way, there is a sparsely populated halo of stars. Spirals come wi ...
... Spiral galaxies have a basic disk shape with the spiral arms in the flat disk. There is a central core containing the bulk of the stars, visible here as bright hubs (99% of the light) from which the spirals radiate. And like the Milky Way, there is a sparsely populated halo of stars. Spirals come wi ...
Gamma-ray absorption and pair echos at very high
... to produce electron-positron pairs (γ +γ → e+ +e− ), as long as there is sufficient opacity for energies satisfying the threshold condition Eϵ(1−cos θ) ≥ 2m2e c4 , where θ is the incidence angle of the two photons. The observed spectra of the gamma-ray sources should then exbihit corresponding attenu ...
... to produce electron-positron pairs (γ +γ → e+ +e− ), as long as there is sufficient opacity for energies satisfying the threshold condition Eϵ(1−cos θ) ≥ 2m2e c4 , where θ is the incidence angle of the two photons. The observed spectra of the gamma-ray sources should then exbihit corresponding attenu ...
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... mass density of the universe has roughly doubled since z ~ 1…Intriguingly, the integrated stellar mass of blue galaxies with young stars has not significantly changed since z ~ 1…instead, the growth of the total stellar mass density is dominated by the growth of the total mass in the largely passive ...
... mass density of the universe has roughly doubled since z ~ 1…Intriguingly, the integrated stellar mass of blue galaxies with young stars has not significantly changed since z ~ 1…instead, the growth of the total stellar mass density is dominated by the growth of the total mass in the largely passive ...
The Distribution, Classification, and Color Evolution of Galaxies
... of the galaxy properties, and as a function of cosmic time. The luminosities of galaxies are plotted against their rest-frame colors, as well as redshifts. It is observed that the star-forming processes taking place in a galaxy contribute to its color as a whole. It is therefore hypothesized that yo ...
... of the galaxy properties, and as a function of cosmic time. The luminosities of galaxies are plotted against their rest-frame colors, as well as redshifts. It is observed that the star-forming processes taking place in a galaxy contribute to its color as a whole. It is therefore hypothesized that yo ...
Introduction to Galaxies 5/23/2013 BR: Milky Way Scale The Milky
... centered on a specific point and appear to orbit the center of the Milky Way. The center of the Milky Way is a region of very high star density, most of which is obscured by interstellar gas and dust. Motion of stars that orbit close to the galactic center indicate that this area has about 2.6 milli ...
... centered on a specific point and appear to orbit the center of the Milky Way. The center of the Milky Way is a region of very high star density, most of which is obscured by interstellar gas and dust. Motion of stars that orbit close to the galactic center indicate that this area has about 2.6 milli ...
Redshift
In physics, redshift happens when light or other electromagnetic radiation from an object is increased in wavelength, or shifted to the red end of the spectrum. In general, whether or not the radiation is within the visible spectrum, ""redder"" means an increase in wavelength – equivalent to a lower frequency and a lower photon energy, in accordance with, respectively, the wave and quantum theories of light.Some redshifts are an example of the Doppler effect, familiar in the change of apparent pitches of sirens and frequency of the sound waves emitted by speeding vehicles. A redshift occurs whenever a light source moves away from an observer. Another kind of redshift is cosmological redshift, which is due to the expansion of the universe, and sufficiently distant light sources (generally more than a few million light years away) show redshift corresponding to the rate of increase in their distance from Earth. Finally, gravitational redshift is a relativistic effect observed in electromagnetic radiation moving out of gravitational fields. Conversely, a decrease in wavelength is called blueshift and is generally seen when a light-emitting object moves toward an observer or when electromagnetic radiation moves into a gravitational field. However, redshift is a more common term and sometimes blueshift is referred to as negative redshift.Knowledge of redshifts and blueshifts has been applied to develop several terrestrial technologies such as Doppler radar and radar guns. Redshifts are also seen in the spectroscopic observations of astronomical objects. Its value is represented by the letter z.A special relativistic redshift formula (and its classical approximation) can be used to calculate the redshift of a nearby object when spacetime is flat. However, in many contexts, such as black holes and Big Bang cosmology, redshifts must be calculated using general relativity. Special relativistic, gravitational, and cosmological redshifts can be understood under the umbrella of frame transformation laws. There exist other physical processes that can lead to a shift in the frequency of electromagnetic radiation, including scattering and optical effects; however, the resulting changes are distinguishable from true redshift and are not generally referred to as such (see section on physical optics and radiative transfer).