Chapter 31: Galaxies and the Universe
... have no way to get outside of the galaxy and look down on the disk. Astronomers have used hydrogen atoms to discover the spiral arms. Hydrogen atoms in a very low-density gas can emit radiation at a wavelength of 21 cm. The use of this hydrogen emission for mapping the spiral arms of our galaxy has ...
... have no way to get outside of the galaxy and look down on the disk. Astronomers have used hydrogen atoms to discover the spiral arms. Hydrogen atoms in a very low-density gas can emit radiation at a wavelength of 21 cm. The use of this hydrogen emission for mapping the spiral arms of our galaxy has ...
The mass of the Milky Way: Limits from a newly assembled set of
... Honma & Sofue 1997), is still uncertain because its determination requires knowledge of accurate distances to these tracers (Fich & Tremaine 1991). Also, interstellar gas can be traced ...
... Honma & Sofue 1997), is still uncertain because its determination requires knowledge of accurate distances to these tracers (Fich & Tremaine 1991). Also, interstellar gas can be traced ...
Revisiting the Hubble sequence in the SDSS DR7
... As pointed out in Sect. 3, there is a critical point in our approach, since the classified sample contains lots of galaxies fainter than the limiting magnitude of the training sample. Therefore, it is very important to check that these faint galaxies are not systematically misclassified just because ...
... As pointed out in Sect. 3, there is a critical point in our approach, since the classified sample contains lots of galaxies fainter than the limiting magnitude of the training sample. Therefore, it is very important to check that these faint galaxies are not systematically misclassified just because ...
A New Assessment of Dark Matter in the Milky Way Galaxy
... For many years, it has been known that the observed rotation rates of spiral galaxies dier greatly ...
... For many years, it has been known that the observed rotation rates of spiral galaxies dier greatly ...
Galaxy Pairs in the Sloan Digital Sky Survey
... We use a sample of close galaxy pairs selected from the Sloan Digital Sky Survey Data Release 4 (SDSS DR4) to investigate in what environments galaxy mergers occur and how the results of these mergers depend on differences in local galaxy density. The galaxies are quantified morphologically using tw ...
... We use a sample of close galaxy pairs selected from the Sloan Digital Sky Survey Data Release 4 (SDSS DR4) to investigate in what environments galaxy mergers occur and how the results of these mergers depend on differences in local galaxy density. The galaxies are quantified morphologically using tw ...
Early-type dwarf galaxies in clusters - ARI
... Early-type dwarf (dE) galaxies play a key role in understanding galaxy cluster evolution. Their low mass and low density make them more susceptible to physical effects than giant galaxies, and they are a large population, outnumbering all other galaxy types in dense environments by far. They are thu ...
... Early-type dwarf (dE) galaxies play a key role in understanding galaxy cluster evolution. Their low mass and low density make them more susceptible to physical effects than giant galaxies, and they are a large population, outnumbering all other galaxy types in dense environments by far. They are thu ...
The half-light radius distribution of LBGs and their
... • The half-light radius of LBGs have been measured; • Their distribution can be well fitted by log-normal, • There exists an correlation between r_ff and SFR --- imply that the star forming regions are disk-like; • Star formation timescale is about 0.3Gyr • Duty cycle effect is important for LBGs -- ...
... • The half-light radius of LBGs have been measured; • Their distribution can be well fitted by log-normal, • There exists an correlation between r_ff and SFR --- imply that the star forming regions are disk-like; • Star formation timescale is about 0.3Gyr • Duty cycle effect is important for LBGs -- ...
The XXL Survey - I. Scientific motivations − XMM
... In other words, our philosophy is that complete and uncontaminated cluster samples cannot be defined by a single parameter such as a flux limit. Rather, cosmological cluster samples are surface brightness and signal-to-noise limited and thus are selected in a two-dimensional parameter space of flux ...
... In other words, our philosophy is that complete and uncontaminated cluster samples cannot be defined by a single parameter such as a flux limit. Rather, cosmological cluster samples are surface brightness and signal-to-noise limited and thus are selected in a two-dimensional parameter space of flux ...
The Current Status of Galaxy Formation
... where α = e2 /(h̄c) and αg = Gm2p /e2 are the electromagnetic and gravitational fine structure constants. For a cooling function Λ(T ) ∝ T β , over the relevant temperature range (105 − 107 K), one can take β ≈ −1/2 for a low metallicity plasma (Gnat & Sternberg, 2007). The result is that one finds ...
... where α = e2 /(h̄c) and αg = Gm2p /e2 are the electromagnetic and gravitational fine structure constants. For a cooling function Λ(T ) ∝ T β , over the relevant temperature range (105 − 107 K), one can take β ≈ −1/2 for a low metallicity plasma (Gnat & Sternberg, 2007). The result is that one finds ...
Environment and self-regulation in galaxy formation
... 2.3 Kinematics and Lick line index measurements The kinematics of gas and stars are determined for all 48,023 objects, using the code GANDALF developed by Sarzi et al. (2006). Stellar population and emission line templates are fitted simultaneously to the galaxy spectrum. The outcome are emission li ...
... 2.3 Kinematics and Lick line index measurements The kinematics of gas and stars are determined for all 48,023 objects, using the code GANDALF developed by Sarzi et al. (2006). Stellar population and emission line templates are fitted simultaneously to the galaxy spectrum. The outcome are emission li ...
Galaxy Formation
... • galaxies are receding from us with speed proportional to their distance • expansion is the same for all observers 2. The microwave background radiation ...
... • galaxies are receding from us with speed proportional to their distance • expansion is the same for all observers 2. The microwave background radiation ...
stochastic star formation and a (nearly) uniform stellar
... for numerous astrophysical problems, is commonly assumed to be invariant with time and with galactic properties. This ansatz follows from a lack of evidence for its variation, despite searches covering a wide range of environments (e.g., Kroupa 2001; Chabrier 2003; Bastian et al. 2010), more than fr ...
... for numerous astrophysical problems, is commonly assumed to be invariant with time and with galactic properties. This ansatz follows from a lack of evidence for its variation, despite searches covering a wide range of environments (e.g., Kroupa 2001; Chabrier 2003; Bastian et al. 2010), more than fr ...
Antlia, the Machine Pneumatique
... the Greek word for pump. It is difficult even to visualise a pump-shape amongst the star-formation with Antlia containing no stars brighter than magnitude 4.2. This southern treasure however, should by no means be underestimated. To start with, it hosts a huge number of galaxies. ...
... the Greek word for pump. It is difficult even to visualise a pump-shape amongst the star-formation with Antlia containing no stars brighter than magnitude 4.2. This southern treasure however, should by no means be underestimated. To start with, it hosts a huge number of galaxies. ...
Morphology and dynamics of the cosmic web Aragón Calvo
... • Both the spin vector and the major axis of inertia of haloes located in walls lie in the plane of the wall. • The spin vector of haloes points in the direction perpendicular to the filament in which they are located (at least until masses of a few times 1011 M h−1 (AragónCalvo et al., 2007), lat ...
... • Both the spin vector and the major axis of inertia of haloes located in walls lie in the plane of the wall. • The spin vector of haloes points in the direction perpendicular to the filament in which they are located (at least until masses of a few times 1011 M h−1 (AragónCalvo et al., 2007), lat ...
Weak gravitational lensing
While the presence of any mass bends the path of light passing near it, this effect rarely produces the giant arcs and multiple images associated with strong gravitational lensing. Most lines of sight in the universe are thoroughly in the weak lensing regime, in which the deflection is impossible to detect in a single background source. However, even in these cases, the presence of the foreground mass can be detected, by way of a systematic alignment of background sources around the lensing mass. Weak gravitational lensing is thus an intrinsically statistical measurement, but it provides a way to measure the masses of astronomical objects without requiring assumptions about their composition or dynamical state.