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Exam 23: Galaxies

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Question 41

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Whether or not a galaxy has a bar is apparently determined by:

A) how fast it is rotating.
B) whether or not it has satellite galaxies with which it is interacting.
C) how much dark matter it has.
D) where it is in its evolutionary journey.

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Question 42

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Which spectral feature originating in a galaxy is used in the Tully-Fisher relation, by measuring its width, to determine the intrinsic luminosity of the galaxy?

A) the 2.3-mm microwave emission line from the molecule CO, which is closely associated with molecular hydrogen
B) the Lyman L $\alpha$ ultraviolet line from atomic hydrogen
C) the 21-cm radio emission line from atomic hydrogen gas
D) the Balmer H $\alpha$ red line from atomic hydrogen

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Question 43

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The Cepheid variables that Hubble observed in M31 had an apparent magnitude of about 18, and thus an apparent brightness relative to the Sun (b/b_Ÿ) of about 1.3 × 10^-18. What approximate periods would these Cepheids need in order to yield a distance to M31 of about 750 kpc?

Type Ia supernovae are frequently used as standard candles for the measurement of distances to galaxies, but they are not all equally luminous. What additional relationship between properties of supernovae is used to determine specific luminosities for individual supernovae?

Gravity is a long-range force, and its effect can be seen in each of the following cases EXCEPT ONE. Which is the EXCEPTION?

Scattering by interstellar dust can affect the results of some standard measuring techniques. Which one of the following is NOT affected by the presence of dust?

According to the Hubble classification scheme, an E6 galaxy:

What is the galaxy content of a rich, irregular cluster of galaxies, like the Hercules Cluster?

Which of the following sequences shows the correct order of galaxy type in terms of the extent of rotational motion, from the least to the most rotation?

Even though the Hubble law for galactic motions indicates that the spectra of all galaxies should show redshift as a consequence of the general expansion of the universe, the Andromeda Galaxy M31 appears to show a blueshift in its spectrum. Why is this?

The Hubble law, representing observations of distant galaxies in the universe, relates which two parameters?

Why is the Tully-Fisher relation NOT used for elliptical galaxies?

The fundamental plane technique for ellipticals can be used to determine galaxies at greater distances than the Tully-Fisher relation that is applied to spirals. Why?

Do the shapes of elliptical galaxies really reflect their true shape?

How does the maser technique work in providing a direct distance measurement to galaxies at intermediate distances (5-10 Mpc range) ?

Scattering by interstellar dust can affect the results of some standard measuring techniques. Which one of the following is NOT affected by the presence of dust?

In the galaxy cluster 1E0657-56, the dark matter seems to have been displaced from the luminous matter during a collision with another cluster. Our understanding of how this might have occurred depends on the premise that:

The Hercules Cluster of galaxies shown in Figure 23-18 (Universe, 11th ed.) is at a distance of 650 million ly from our galaxy. Using a Hubble constant of 23 (km/s) /Mly, at what wavelength will the Balmer H $\alpha$ spectral line, with rest wavelength = 656.3 nm, be seen in the spectrum of a galaxy in this cluster?

Why are RR Lyrae variables NOT used to find distances to distant galaxies?

Which one of the following formulas is not valid when the speed of the object under consideration becomes large-say, 10% of the speed of light?