Exam 20: Galaxies

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A) the black hole only produces a jet in one direction
B) of relativistic beaming
C) the other side is inside the black hole's event horizon
D) of dust obscuration
E) of dark matter that blocks the light from one side of the jet

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An AGN of any type (e.g., Seyferts or qu...

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A) Spiral galaxies still have ongoing star formation whereas elliptical galaxies do not.
B) Spiral galaxies are sometimes very thin in appearance whereas elliptical galaxies are always round or elliptical.
C) Spiral galaxy disks contain lots of cold gas and dust whereas elliptical galaxies do not.
D) Spiral galaxies tend to have bluish areas whereas elliptical galaxies tend to be all reddish.
E) Spiral galaxies have dark matter halos whereas elliptical galaxies do not.

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A) " $\nu$ $\infty$ r ^{- 2}"
B) " $\nu$ $\infty$ r ^{- 1}"
C) " $\nu$ $\infty$ "
D) " $\nu$ $\infty$ r"
E) " $\nu$ $\infty$ r²"

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A) everywhere inside galaxies
B) only in the outer regions of galaxies
C) only in star clusters
D) near the centers of galaxies
E) only around an AGN

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A) The black holes powering them collapse even further.
B) They simply become normal galaxies.
C) They slowly dissipate into clouds of gas and dust.
D) They eventually pull in material from farther out, starting the AGN process all over again.
E) They explode as gamma-ray bursts.

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True

A) a central supermassive black hole
B) dark matter
C) massive O- and B-type stars
D) cold molecular gas clouds
E) low-mass G-, K-, and M-type stars

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A) Emitted by neutral hydrogen, it traces the location of high concentrations of gas.
B) Emitted by O and B stars, it traces the location of newly formed stars.
C) Emitted by ionized hydrogen, it traces the location of H II regions.
D) Emitted by molecular hydrogen, it traces the location of clouds in the process of collapsing into stars.
E) Emitted by red supergiants, it traces the presence of massive stars that are experiencing high rates of mass loss.

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A

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More distant galaxies are seen at an ear...

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A) Quasars are extremely luminous.
B) Quasars are rare in our local vicinity.
C) Quasars have high brightnesses.
D) Quasars are extremely massive.
E) Quasars are located at the centers of some active galaxies.

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Individual galaxies are oriented at a variety of angles to our line of sight. Sometimes we see that spirals look round on the sky; this means we are looking at the disk face-on. Sometimes spirals look quite thin, which means we are seeing these edge-on. The fraction of galaxies that look thin are what we expect to see if all spiral galaxies have thin disks. Elliptical galaxies, on the other hand, never look thin, so they must be roundish (elongated but not flat) in three dimensions.

A) 20 AU
B) 30 AU
C) 50 AU
D) 70 AU
E) 120 AU

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A) 960 km/s
B) 1,200 km/s
C) 2,300 km/s
D) 3,800 km/s
E) 4,400 km/s

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A) distributed in roughly the same way as
B) much more extended in radius than
C) much more centrally concentrated than
D) much less uniform in density than
E) much clumpier than

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