much of the emission from the nucleus of the milky way galaxy and AGN's comes from
A stars.
B gas and dust clouds.
C high-speed electrons in magnetic fields.
D supernovas.
a seyfert galaxy is brightest in the
A ultraviolet
B visible
C infrared
D radio
a collision between galaxies
A would be a catastrophic event
B is the likely explanation of quasars
C is tremendously unlikely
D except for the unusual shape would be hardly noticeable
synchrotron radiation is produced when
A electrons move very rapidly
B stars exist in a highly magnetic region
C electrons move in a magnetic field
D radio waves move through a gas cloud
the source of intense radio emission from radio galaxies is probably
A explosive events in the nucleus
B a massive central black hole
C extremely rapid rotation of the galactic nucleus
D thermonuclear burning in the nucleus (e.g. proton-proton chain)
radio observations with the VLA of Centaurus A, the nearest active galaxy, show that the
A nuclear jet lines up with outer radio lobes.
B nuclear jet has a structure made of smaller blobs.
C emission from the nuclear jet is nonthermal.
D all of the above.
E none of the above.
the central galaxy in a double-lobed radio source is usually
A an irregular galaxy.
B a spiral galaxy.
C a dwarf elliptical galaxy.
D a giant elliptical galaxy.
a congressman comes to visit a major observatory and wants to see the biggest objects in the universe. he specifies that he does not want to see group or clusters of objects, but the objects that are the biggest single, connected structures. what would you show him?
A giant elliptical galaxies
B double-lobed radio galaxies
C quasars
D irregular galaxies
in general, the radio jets seen extending from the nuclei of active galaxies have
A lengths of no more than a few light years.
B a thermal (black body) spectrum.
C a nonthermal (synchrotron) spectrum.
D visible corkscrew motions in space.
E rigid, straight-line paths in space.
which of the following appears to be the energy source at the center of a spiral galaxy?
A a number of quasars.
B one large quasar.
C a cepheid variable.
D a pulsar.
E a black hole.
which region of the spectrum contains the most energy emitted by seyfert galaxies
A infrared
B radio
C visible
D x-ray
the emission from jets is thought to be synchrotron in origin. this requires that
A magnetic fields are in the jets.
B high-speed electrons are there.
C the material in the jets emits like a black body.
D (a) and (b).
E (b) and (c).
in order to produce synchrotron emission, you need
A a source of high-speed electrons.
B fairly strong magnetic fields.
C extremely hot and dense (opaque) gasses.
D (a) and (b).
E (b) and (c).
compared with the milky way galaxy, a typical AGN
A produces more energy each second.
B is larger in size and mass.
C produces more energy by nonthermal processes.
D (a) and (b).
E (a) and (c).
the radio lobes that flank some radio galaxies produce mainly
A 21-cm radiation
B synchrotron radiation.
C black body radiation.
D none of these.
collisions between galaxies are expected to be more common than collisions between stars because
A galaxies are much larger
B in clusters, galaxies are much closer together relative to their size
C galaxies move much faster
D there are more galaxies visible
the large double-lobed radio galaxies are
A remnants of the big bang.
B clusters of quasi-stellar objects.
C regions of charged, radiating particles, ejected from a galaxy.
D the faint material around bl lacertae objects.
seyfert galaxies are
A giant elliptical galaxies
B spiral galaxies
C barred spiral galaxies
D divided equally among a through c
which of the following is closest in appearance to a normal galaxy
A seyfert galaxies
B quasars
C radio galaxies
D none of the above
exploding galaxies are
A not observed
B caused by supernovae explosions
C observed but not understood
D dying quasars
in comparing the milky way with AGN's in general, which of the following is a characteristic both have in common?
A at least part of the nuclear emission is nonthermal.
B large radio lobes on both sides of the galaxy.
C a spectrum that looks like a bunch of stars.
D a concentration of x-rays from a single nuclear source.
E none of the above.
if an object is observed to be emitting synchrotron radiation, we may conclude that
A it has a very low temperature
B the object is moving near the speed of light
C the object has a magnetic field
D the object has no magnetic field
radio galaxies often show evidence of
A violent activity in the center
B jets of matter
C radio emitting lobes on either side of the galaxy
D all of the above
except for their nucleus, seyfert galaxies appear to be normal
A radio galaxies
B elliptical galaxies
C spiral galaxies
D stars
the radio waves emitted by double-lobed radio sources are produced by the process called
A synchrotron radiation
B spin-flip radiation
C recombination radiation
D thermal emission
synchrotron radiation is produced by
A hot bodies
B cool bodies
C electrons traveling with a velocity determined by the temperature of the g in which they are found
D electrons moving rapidly in a magnetic field
which is a characteristic of a seyfert galaxy
A no spiral arms
B nucleus bright with respect to rest of galaxy
C faint nucleus
D narrow absorption lines
which type of galaxy has radio emitting regions on either side of the visible galaxy
A seyfert
B radio
C colliding
D exploding
synchrotron radiation is produced whenever
A electrons jump from level to level in an atom
B atoms in a molecule vibrate back and forth
C electrons move in spirals in a magnetic field
D light passes into a transparent medium, such as glass
the radio image of a radio galaxy is usually
A exactly coincident with the visual image
B a double image with the visual image in between
C between a double optical image
D not associated with a visual image
the variability of seyfert galaxies tells us that their nuclei must be
A violent
B small
C a black hole
D composed of cepheid variable stars
most radio galaxies, when identified with an optical source, turn out to b _____ galaxies
A normal spiral
B barred spiral
C elliptical
D irregular
electrons, when moving through a magnetic field in space (in spiral patterns) will emit
A synchrotron radiation, usually radio waves
B nothing, since such electrons are in equilibrium
C a beam of protons
D sound waves
the radio emission in a typical radio galaxy is produced by _____ emission
A thermal
B synchrotron
C black hole
D thermonuclear
seyfert galaxies are
A irregular galaxies seen from the southern hemisphere
B very small elliptical galaxies
C active galaxies, with bright, starlike visible nuclei
D the largest galaxies in the universe
the nucleus of a seyfert galaxy is
A a hundred times brighter than a normal galaxy
B as big as a normal galaxy
C flat in appearance
D composed mostly of old stars
quasars, radio galaxies, and seyfert galaxies
A typically emit large amounts of radio radiation
B all exhibit evidence of extreme violence in relatively small (for galaxies) regions
C all produce at least as much energy per second as the largest normal galaxies
D all of the above
which of the following is not usually a feature of a radio galaxy?
A jets of rapidly moving matter ejected from the galaxy
B two radio lobes on either side of the visible galaxy
C less actual energy/sec emitted than a typical spiral
D explosive activity in the center
the lobes of radio galaxies
A are much smaller than the optical part of the galaxy
B are much larger than the optical galaxy
C match up fairly well with the optical features
D are never associated with galaxies which can be seen optically
a seyfert galaxy is likely to look like which of the following?
A a spiral galaxy
B an elliptical galaxy
C an irregular galaxy
D any of the above
which of the following galaxies is variable in brightness
A exploding galaxies
B colliding galaxies
C spiral galaxies
D seyfert galaxies
seyfert galaxies produce extraordinary amounts of infrared and radio radiation in their
A nuclei
B halos
C disks
D all of the above
radio galaxies are so named because
A they can only be detected in the radio region
B they were first discovered by radio astronomers
C their radio emission is very strong compared to that of normal galaxies
D all of the above
seyfert galaxy nuclei are known to be unusually small because of
A their small apparent size
B their large red shift
C their variability
D their association with normal galaxies
the energy source for a radio galaxy with jets and lobes is probably a ______ located in the ______ of that galaxy.
A supermassive neutron star, halo
B supermassive white dwarf, disk
C supermassive supernova, spiral arms
D supermassive black hole, nucleus
which of the following must be present for synchrotron radiation to be emitted
A hydrogen
B uranium
C an electric field
D a magnetic field
what observed feature of double-lobed radio galaxies indicates that the nucleus is the source of the particles that power the radio emission from the lobes?
A thin jets connecting the nucleus to the lobes.
B short-term variations in the emission from the lobes.
C quasars that appear close to the lobes and nucleus.
D strong magnetic fields associated with the lobes.
which of the following galactic types are sometimes observed to varying brightness
A spiral
B seyfert
C giant elliptical
D colliding?
radio galaxies frequently possess
A twin lobes of radio emitting matter
B jets of radio emitting matter reaching out from the center
C intense sources of radio waves in their centers
D all of the above
which type of galaxy has two large emitting regions on either side of the visible image
A exploding
B radio
C seyfert
D colliding?
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