The Sun moves in a near-circular orbit about the Galactic center with a speed of 200 km/s at an orbital radius of 8 kpc. Which approximation(s) is/are needed so that from these numbers alone we can constrain the total mass of the Milky Way inside of the Solar orbit?
What is meant by "wind mass loading factor" when talking about galactic winds?
How does cosmic reionization affect the baryon content of halos of different size?
In the prevailing picture of galaxy formation, what feedback channels dominate the regulation of star formation in low- and high-mass halos?
The lowest metallicity star known in the Milky Way has [Fe/H] = -7.3. What exactly does that number express?
Consider Fig 5.20 in Sect 5.3 of Sparke & Gallagher and estimate the total mass of NGC 7331 enclosed within 20 kpc, expressed in solar masses.
2.7e11
The rotation curves of disc galaxies are often approximately "flat" at large radii. What does this imply for the density law at those radii?
If the rotation curve v(r) of a disc galaxy in its inner few kpc increases roughly linearly with radius, what does this imply for the angular speed omega(r) and for the density distribution of the galaxy at these radii?
For which of the following astrophysical aspects is the Tully-Fisher relation (TFR) relevant?
Which of the following properties characterise an "effective potential"?
How does a planar orbit that can be described by the epicycle approximation look like for an external (non-rotating) observer?
What is the ratio of epicycle to orbital frequencies needed to describe Keplerian motion?
1
Which of the following statements the phenomenon of "asymmetric drift" are correct?
Which of the following statements about the vertical motions (in z direction) in a galactic disc are correct?
Which statements are essential for a complete formulation of the virial theorem (VT) applied to a stellar system such as a galaxy?
What is/are the main problem(s) occuring when the concept of the "singular isothermal sphere" is applied to describe real systems?
Which physical principle determines the temporal evolution of an expanding supernova remnant?
The radial velocity dispersion of a star cluster is measured to be 10 km/s. If we approximate the cluster as a homogeneous sphere with a radius of 10 pc in virial equilibrium, estimate the mass of the cluster (expressed in solar masses).
1.34e6
Consider an idealised elliptical galaxy made entire of stars of the same mass and spectral type. In what way would the integrated spectrum of this galaxy differ from that of a single star?
Consider two elliptical galaxies at the same distance. One has a velocity dispersion of 100 km/s, the other one of 200 km/s. What ratio of luminosities do you expect (brighter/fainter)?
16
Why can it be ruled out that the observed flattening of elliptical galaxies is generally due to rotation?
Which of the following statements describe real differences between a "loop orbit" and a "box orbit"?
Which of the following statements gives a sufficiently precise definition of the "radius of influence" of a supermassive black hole to allow calculate it?
Predict the mass of the central black hole for an elliptical galaxy with L = 1e11 L_sun (solar luminosities). Result must be given as the decadal logarithm of the mass in solar masses.
9.15
Why does a prevalence of box orbits in an elliptical galaxy make it more difficult to detect a possible supermassive black hole in the centre of that galaxy?
Which of the following statements about the relation between isochrones and stellar evolution tracks are correct?
What is approximately the mass limit for the oldest currently existing main sequence stars, assuming that such stars have ages of 1.3e10 years? Give the result in solar masses.
0.91
Why would a parametrisation of the IMF as a single power law be unphysical without explicitly stated lower and upper mass limits?
Explain why the present-day mass function of stars in the (extended) solar neighbourhood has a much steeper high-mass slope than the IMF.
Question 4Answer
Why are binary stars a big problem for constraining the IMF through observations?
Which specific feature(s) in the HRD can be used to estimate the age of an SSP?
Which of the following statements about strengths and weaknesses of theoretical spectral libraries compared to empirical ones are correct?
Does changing the IMF in a stellar population model lead to different stellar mass estimates?
How large is the fractional contribution of main sequence stars to the total flux at 500nm, for a typical present-day star-forming galaxy observed today? Obtain this number by visual estimation from Fig. 5 in the Conroy review (= Sect 4.3 of the lecture notes).
0.5
Which part(s) of the spectral energy distribution of a galaxy are sensitive to the recent star formation rate, and why?
Which of the following elements are "alpha elements"?
Why do low-mass stars (below 0.5 solar masses or so) not contribute to the chemical evolution of galaxies?
Why are stellar winds in main sequence stars not relevant for the chemical evolution of galaxies, despite the high mass loss rates of massive stars?
What is the exact physical meaning of the yield parameter p in chemical evolution models?
Why is the solution for Z(t) in the closed box model with constant star formation efficiency unphysical, strictly speaking?
Suppose the differential distribution of metallicities for an ensemble of stars is a Gaussian normal distribution centred on Z_1 with a dispersion of sigma_Z. What is then the fraction of stars with metallicities Z < (Z_1 - sigma_Z)?
0.16
How does the (differential) stellar metallicity distribution depend on the star formation history?
Which of the following modifications to the Simple Closed Box model can fix the G-Dwarf problem?
What is the asymptotic value for Z(t) in the accreting box model, assuming a yield p = 0.03?
0.03
Summing up all the starlight in the Coma cluster of galaxies gives a luminosity of about 8e12 solar luminosities. The velocity dispersion of the cluster is 1000 km/s, its radius is roughly 1 Mpc. Calculate the mass-to-light ratio of the cluster under the assumption that it is fully virialised.
87
Which of the following arguments are needed (or not needed) to conclude that the X-rays emitting hot gas in galaxy clusters provides evidence for dark matter?
What is the meaning of a value of xi(r) = 100 for the two-point correlation function?
Adopting the power-law approximation for the two-point correlation function of galaxies, which parameter combination specifies the case of "no clustering at all"?
The velocity dispersion of the Milky Way is about 130 km/s. What would be its Einstein radius if observed from far away as gravitational lens, assuming it to be placed halfway (in angular diameter distances) between observer and background source? Give the result in arcseconds
Which observational measurements can break the "mass-sheet degeneracy" in gravitational lensing?
Which of the following statements about weak lensing are correct?
Which of the following properties are essential for a dark matter concentration to be called a halo?
The ratio of stellar to halo masses has a pronounced maximum at M_h ~ 1e12 solar masses and is much smaller for both low- and high-mass haloes. Which of the following mechanisms are believed to contribute to this?
Estimate roughly the star formation efficiency, given as ratio between stellar mass formed and available gas mass, for galaxies with halo masses of ~1e11 solar masses.
0.02
Suppose that 1000 core-collapse supernovae exploded in a galaxy within a very short time, leading to a large outflow breaking out into the circumgalactic medium where the density is only ~0.001 particles/cm3. How far (approximately) will the superbubble shell have expanded after 10 Myrs? Give the result in pc
1758
Which quantity is called the mass-loading factor?
Which are the main physical effects of feedback leading to quench star formation in a galaxy?
When a satellite galaxy orbits a host galaxy approximated as a singular isothermal sphere, how does its dynamical friction deceleration dv/dr depend on the distance r to the host?
Consider a dry merger resulting from a parabolic encounter of two virialised galaxies with mass ratio M2/M1 = 1:2 and velocity dispersion ratio sigma2/sigma1 = 1:2**(2/3). What is the radius of the merger product, expressed as ratio to the radius r1 of the primary progenitor?
1.71
What is the limiting exponent alpha in the Schechter formula for the galaxy luminosity function for which the total luminosity density becomes infinite when integrated from L = 0?
2
Which of the following statements are correct
At what age of the Universe, roughly, was 10% of the present-day stellar mass in the Universe assembled? Result must be given as a single number in Gyrs, without units. You may estimate the answer visually from an appropriate figure in the Lecture Notes
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