Deck 17: Active Galaxies and Supermassive Black Holes

Question 1

In the unified model of active galactic nuclei,the broad line region in an active galactic nucleus is

A) composed of clouds of gas and stars moving at very high orbital velocities.
B) composed of a super massive black hole.
C) responsible for producing the bright continuous radiation observed in blazars.
D) responsible for the narrow absorption lines seen in Type 2 Seyfert galaxies.
E) located further from the core than the narrow line emission region.

Answer 1

composed of clouds of gas and stars moving at very high orbital velocities.

Question 2

The local hypothesis states that

A) active galactic nuclei are produced by the merger of galaxies.
B) blazars are produced when material is ejected along the poles of a super massive black hole.
C) quasars are produced when two galaxies merge to form a super massive black hole.
D) the center of the Milky Way and Andromeda galaxies contain super massive black holes.
E) quasars' red shifts are not due to the cosmological expansion of the universe.

Answer 2

quasars' red shifts are not due to the cosmological expansion of the universe.

Question 3

Astronomers can estimate the mass of the black hole at the center of the active galaxy M87 from the

A) orbital speed of the gas disk around it.
B) the distance of the orbiting gas from the center.
C) both a and B

Answer 3

both a and B

Question 4

Quasars must be small because they

A) have high radial velocities.
B) are very luminous.
C) are surrounded by quasar fuzz.
D) radiate huge amounts of energy.
E) fluctuate rapidly.

Question 5

The fact that many radio lobes emit more intensely from the side away from the galaxy suggests that

A) they are formed by material falling into the galaxy.
B) they are powered by magnetic fields.
C) they are excited by radiation from nearby galaxies.
D) they are powered by the rapid rotation of the galaxy.
E) they are created by jets from the galaxy.

Question 6

The unified model describes active galactic nuclei using

A) a super massive black hole at the center of a normal spiral galaxy.
B) a super massive black hole surrounded by an accretion disk and a dense disk of gas.
C) an accretion disk around a neutron star.
D) gravitational lenses to intensify the radiation coming from them.
E) different lines of sight toward a dwarf irregular galaxy.

Question 7

The tiny point sources of many quasars are surrounded by a visual "fuzz" with a(n)_____spectrum indicating the quasar is within an otherwise normal galaxy mostly of normal sun-like stars.

A) emission line
B) absorption line (on a continuous)visual spectrum
C) continuous synchrotron radio
D) both (a)and (b)
E) all of (a),(b)and (c)

Question 8

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.
E) a quasar.

Question 9

Head-tail galaxies are

A) found most often in clusters.
B) dependent on an inter-galactic medium.
C) powered by jets in the nucleus of the galaxy.
D) a and b
E) a,b,and c

Question 10

The hot spots in the double-lobed radio galaxies are

A) produced by nuclear fusion of hydrogen.
B) produced by the interaction of high speed particles from the jets with the intergalactic medium.
C) found in the portion of the lobes that are closest to the galaxy producing the lobes.
D) produced by a gravitational lens of a single quasar.
E) produced by the accretion disk around a super massive black hole.

Question 11

Recent high resolution radio observations show that some quasars have ____.

A) double lobes of radio emission
B) central jets of visual and radio emission
C) intense nuclear radio and visual emission
D) All of the above features.

Question 12

If the red shifts of quasars arise from the expansion of the universe,then

A) a quasar must be very small.
B) a quasar must be within the Local Group.
C) a quasar must be single star with an extremely large mass.
D) a quasar must be moving toward the earth at a large radial velocity.
E) a quasar must be very luminous.

Question 13

Seyfert galaxies

A) are more common in close pairs of galaxies than in isolated systems.
B) emit more energy at x-ray,ultraviolet,infrared,or radio wavelengths than normal spiral galaxies.
C) generally show red shifts greater than 1.
D) a and b
E) a,b,and c

Question 14

The hot gas of a radio lobe could be held together by

A) collision with the intergalactic medium.
B) the lobe's magnetic field.
C) the lobe's gravitational field.
D) the angular momentum of the galaxy.
E) the shock wave from a nearby quasar.

Question 15

A BL Lac object is the same as a

A) Type 1 Seyfert.
B) Type 2 Seyfert.
C) double-lobed radio galaxy.
D) blazar.
E) quasar.

Question 16

The radio lobes that flank some radio galaxies produce mainly

A) 21-cm radiation.
B) synchrotron radiation.
C) black body radiation.
D) emission lines due to hydrogen.
E) absorption lines due to hydrogen.

Question 17

We suspect that quasars are the active centers of galaxies because

A) quasar fuzz produces stellar spectra.
B) a few quasars have large red shifts.
C) some quasars fluctuate rapidly.
D) all of the above
E) none of the above

Question 18

Images of the centers of active galaxies reveal a

A) disk of gas.
B) a dim star.
C) single planet.

Question 19

A(n)____ is observed if our line of sight is parallel to the plane of the dense disk of an active galactic nucleus.

A) blazer
B) Type 1 Seyfert
C) Type 2 Seyfert
D) superluminal expansion
E) quasar

Question 20

The disks which have been observed in the centers of some active galaxies evidently have a ____ at their centers.

A) black hole
B) main sequence star
C) terrestrial planet
D) jovian planet

Question 21

When we observe quasars to have large red shifts,we are seeing them as they

A) are now
B) will be in the future
C) were in the past

Question 22

How are astronomers able to determine that quasars are so small?

A) They are variable over a short period of time.
B) They emit mainly X-rays.
C) They are only found at very large distance.
D) The structure of a quasar is completely resolved in images.

Question 23

Early in the history of the universe,assume a galaxy which had an active nucleus was near our Milky Way Galaxy.Today,that galaxy is not active.The most likely explanation is that

A) its red shift is too great.
B) its blue shift is too great.
C) its central black hole is not being fed infalling gas.
D) the central white hole is not being fed infalling gas.

Question 24

What is the most distant active galaxy type?

A) Seyfert galaxies
B) Radio galaxies
C) BL Lac objects
D) Quasars

Question 25

Recent high resolution radio observations show that quasars can be classified as_____.

A) exploding supernova stars
B) exploding planets
C) normal galaxies like our Milky Way Galaxy
D) a kind of active galaxy similar to Seyferts and radio galaxies

Question 26

Jet-shaped regions of radio and optical emission have been observed in

A) quasars.
B) radio galaxies.
C) the 3° Kelvin radiation.
D) both a and

Question 27

Astronomers who discovered quasars found that they show ________ of their spectral lines and are thus probably much ________ than nearby galaxies.

A) large red shifts,farther away
B) large blue shifts,farther away
C) no wavelength difference,nearer
D) large red shifts,nearer
E) large blue shift,nearer

Question 28

How does the study of quasars reveal information of the history of the universe?

A) Quasars are very distant so we can view how galaxy evolution occurred in the past.
B) Quasars contain of stars of all ages.
C) Quasars typically act as host galaxies for gravitational lensing.
D) Quasars have been found to exist in every stage of the universe's evolution.

Question 29

The hydrogen Balmer line H $\beta$ has a wavelength of 486.1 nm in the laboratory.It is observed in a quasar at 2430.5 nm.What is the red shift of this quasar?

A) 5
B) 0.5
C) 0.25
D) 4
E) 1944.4

Question 30

Evidence that tidal interactions and collisions of galaxies may make ordinary galaxies active is that ....

A) Many active galaxies are distorted.
B) Some active galaxies have companions.
C) Both (a)and (b)
D) Neither (a)or (b)

Question 31

Active galaxies are thought to have _______ in their centers.

A) accretion disks
B) massive black holes
C) both a and b
D) the Local Group
E) a cluster of galaxies

Question 32

If Hubble's constant is taken to be 70 km/sec/Mpc,and a quasar is found with a radial velocity of 0.95 times the speed of light,how far away is the quasar?

A) 4100 Mpc
B) 0.014 Mpc
C) 67 Mpc
D) 74 Mpc
E) 300,000 Mpc

Question 33

If a quasar has a red shift of 1,then its radial velocity is

A) 100,000 km/sec.
B) 112,000 km/sec.
C) 180,000 km/sec.
D) 300,000 km/sec.
E) 0.6 km/sec

Question 34

What is the major observational difference between a Seyfert galaxy and a normal spiral galaxy?

A) Normal spiral galaxies usually have shorter spiral arms.
B) Normal spiral galaxies never contain a supermassive black hole at their center.
C) The central region of a Seyfert galaxy is much brighter.
D) Seyfert galaxies don't contain any star formation.

Question 35

How do astronomers know that the nuclei of some galaxies are active?

A) Their nuclei are much brighter than expected.
B) The orbits of stars near the center of the galactic nuclei are faster than expected.
C) The luminosity of the nuclei varies over time.
D) The color of the nuclei is different than expected.

Question 36

A galaxy which has a close encounter with another can have

A) its shape tidally distorted.
B) an inflow of gas induced into its center.
C) activity induced in its nucleus.
D) all of the above

Question 37

Encounters between galaxies would be ____ in the past versus now.

A) the same
B) more frequent
C) less frequent

Question 38

Why do astronomers believe black holes are the source of an AGN's energy?

A) It's expected since black holes have been found at the center of most galaxies.
B) Radio jets are seen in many AGN and those only come from black holes.
C) Black holes have been observed directly there.
D) Only black holes can produce so much energy in such a small place.

Question 39

The hydrogen Balmer line H $\beta$ has a wavelength of 486.1 nm in the laboratory.It is observed in a quasar at 972.2 nm.What is the radial velocity of this quasar?

A) 2.4*10⁵ km/sec
B) 1.8*10⁵ km/sec
C) 6*10⁵ km/sec
D) 2
E) 1

Question 40

Most galaxies appear to be ...

A) composed of one star and seven planets.
B) inside our Milky Way.
C) located on the Earth.
D) moving toward us.
E) moving away from us.

Question 41

The radio radiation emitted by a radio lobe is mainly synchrotron radiation.

Question 42

Quasar red shifts are usually larger than the red shifts of visible galaxies.

Question 43

The spectrum of a(n)____________________ consists of a continuum and a few highly red shifted emission lines due to hydrogen.

Question 44

If a quasar has a red shift of 0.98,then it is receding from the earth at 98 percent the speed of light.

Question 45

The large redshift of most quasars reveals that they are relatively close to the Milky Way.

Question 46

____________________ galaxies are radio lobe galaxies that are moving rapidly through the intergalactic medium and dragging their radio lobes behind them.

Question 47

The high ____________________ of quasars reveals to astronomers that they must be very distant.

Question 48

Seyfert galaxies are spiral galaxies with active cores.

Question 49

Head-tail galaxies are pairs of galaxies interacting with each other.

Question 50

The majority of Seyfert galaxies are elliptical galaxies.

Question 51

Double-lobed radio galaxies appear to be emitting jets of gas and radiation.

Question 52

Some quasars have fuzz around them that produces spectra like that of normal galaxies.

Question 53

____________________ Seyfert galaxies are very luminous at x-ray and ultraviolet wavelengths and have broad emission lines in their spectra

Question 54

Radio lobes are held together by their magnetic fields.

Question 55

The Milky Way galaxy is not a radio galaxy; it emits no radio radiation.

Question 56

The rapid fluctuations of quasars show that the objects must be very small.

Question 57

Double-lobed radio galaxies appear to be emitting jets of gas and radiation.

Question 58

If the jet from a black hole points directly at Earth,you see a blazar.