Study Guide- Ch13

Chapter 13- Galaxies: Normal & Active

Study Guide

Answer is slashed threw its not the right one if in red it might be the answer.

Question 1
A ____ generally contains well over 1000 galaxies and is quite dense. They often contain many giant elliptical galaxies.
local group
poor cluster
rich cluster
tidal tail
quasar

Question 2
Centaurus A is a radio galaxy that has a visible galaxy at the center. This central elliptical galaxy of Centaurus A is encircled by a ring of gas and dust, different from most elliptical galaxies. The dust ring orbits about an axis that is perpendicular to the axis of rotation of the elliptical galaxy. What does this suggest about this central elliptical galaxy of Centaurus A?
Centaurus A is probably the result of a merger of an elliptical galaxy and a spiral galaxy.

Question 3
matter flowing into a supermassive black hole.

Question 4
We should expect galaxies to collide fairly often because
a and c {they are large with respect to their separation distances./galaxies occur in clusters.}

Question 5
The letters AGN stand for _____.
an active galaxy nucleus


Question 6
What is the Hubble constant essentially a measure of?
The expansion of the universe

Question 7
Most of the mass of a galaxy is contained in the
dark matter of the galaxy.

Question 8
Why do astronomers believe supermassive black holes are the source of an AGN's energy?
Such black holes have been found at the center of most galaxies both active and inactive.
Radio jets are seen from low mass black holes plus accretion disks inside our galaxy.
Jets and accretion disks have been observed in active galaxies.
Black holes can produce so much energy in such a small place.
all of the above

Question 9
_____ galaxies contain a supermassive black hole at their centers while active nuclei are present in _____of galaxies
Most; a few percent
Most; the majority
A small minority; a few percent
A small minority.; the majority

Question 10
The cluster method (motions of galaxies in a cluster of galaxies) can be used to determine the cluster’s mass
mass.

Question 11 
Based on the galaxies found in the Local Group of galaxies, the most common type of galaxy in the universe is expected to be
the dwarf elliptical galaxies.

Question 12
Soon after discovery, it was observed that quasars had a starlike appearance which was blurred by Earth’s atmospheric “seeing.” Despite the blurring,  it was realized that the intense energy emitting regions of quasars must be small because they
have high radial velocities.
are very luminous.
are surrounded by quasar fuzz.
radiate huge amounts of energy.
fluctuate rapidly on time scales as short as a few hours.

Question 13
We suspect that quasars are the active centers of galaxies because
“fuzz” around the central luminous regions produces spectra like a collection of normal stars.
a few quasars have large red shifts.
the central regions of some quasars fluctuate rapidly.
all of the above
none of the above

Question 14
Poor clusters
contain fewer than 1000 galaxies and tend to be irregularly shaped.


Question 15
Which of the following is the largest object?
The Local Group

Question 16
Gravitational lensing
occurs when light passes near a massive object and is deflected by the object's gravitational field.

Question 17
What type of galaxies do astronomers believe to be the most common?
Elliptical

Question 18
The look-back time is
a and b{the time it takes for the light from an object to reach Earth/numerically equal to the distance in light-years.}

Question 19
Galaxies may contain a supermassive black hole at their center but  _____ an active nucleus because of _______ into the black hole.
show; mass inflow

Question 20
The mass of a single galaxy might be found by
the rotation curve method.

An irregular galaxy contains mostly
upper and lower main sequence stars and gas and dust.

The rotation curve of a galaxy can be used to determine
the mass of the galaxy.

Mathematical models indicate that ____ galaxies are produced by high speed collisions in which a smaller galaxy passes through another galaxy almost perpendicular to the disk of the galaxy.
ring

The Milky Way is part of
I. a poor cluster.
II. a rich cluster.
III. the Virgo Cluster.
IV. the Local Group.
I and IV

The energy from an AGN is produced by
matter flowing into a supermassive black hole.

The Milky Way galaxy is part of
the Local Group.


Galactic cannibalism refers to
the merging of galaxies.

The total mass of galaxies in a cluster of galaxies dvided by the number of galaxies in the cluster can be used to determine a typical galaxy’s
luminosity.
distance.
mass.
diameter.
age.
the mass of the galaxy.

__ have elongated nuclei with spiral structure extending from the ends of the elongations. The Milky Way is a member of this class of galaxy.
Barred spiral galaxies

All ____ galaxies are spiral galaxies that have small luminous nuclei.
Seyfert

The Hubble Law is a relation between a galaxy's
distance and its recession velocity.

_ is an irregular galaxy that is passing close to the Milky Way and is expected to merge with the Milky Way in the future.
The Small Magellanic Cloud


An elliptical (E) galaxy contains
mostly lower-main sequence stars and giants.

An irregular galaxy contains mostly
upper and lower main sequence stars and gas and dust.

___ galaxies contain large clouds of gas and dust, both young and old stars, but have no obvious spiral arms or nucleus.
Irregular


Astronomers now speculate that a galaxy's shape depends on all of the following except
All of these may be important in determining a galaxy’s shape.

___ can be used to determine the galaxy's mass if the galaxy is reasonably close, so that the Doppler shift of the galaxy disk material can be measured at several distances from the galaxy's center relative to the center.
A galaxy's rotation curve

Supermassive black holes are believed to be located at the center of many galaxies because
the orbital motion of material near the center is very fast and indicates a very massive core.