Quasars and Other Active Galaxies

Question 1

what were some sources or radio emission?

Answer 1

• gas heated and ionized by young stars

- supernovae remnants

Question 2

what causes non-thermal emission in astronomical sources?

Answer 2

synchrotron emission

Question 3

what is synchrotron emission?

Answer 3

acceleration of relativistic moving electrons by a magnetic field

Question 4

what regions use thermal emission?

Answer 4

HII regions

Question 5

what uses synchrotron emission?

Answer 5

SNR

Question 6

quasars

Answer 6

radio synchrotron emitting object that had an appearance similar to a star but were producing very strong radio emission

Question 7

who was first to deal with quasars using spectra?

Answer 7

Maarten Schmidt

Question 8

what was unique about Schmidt’s spectra?

Answer 8

enormous redshifts

Question 9

how to determine luminosity of quasars?

Answer 9

observed brightness

-large luminosities

Question 10

are quasars bright?

Answer 10

yes, very

Question 11

what do quasars vary rapidly in?

Answer 11

light output

Question 12

how big is the size of where quasar’s energy comes from?

Answer 12

small region

Question 13

elliptical galaxies

Answer 13

also can be radio producers

Question 14

where does radio emission often come from?

Answer 14

two large lobes located beyond visible galaxies

Question 15

how can we produce so much energy in a small region of space?

Answer 15

supermassive black hole (100 million solar masses)

Question 16

how do supermassive black holes power?

Answer 16

AGNs

Question 17

what happens as gas falls inward?

Answer 17

gravitational potential energy is converted to heat energy

Question 18

what produces the large luminosities of these objects?

Answer 18

hot gas

Question 19

what are the “jets”

Answer 19

composed of high speed material funneled by a twisted magnetic field

Question 20

can the accretion of matter onto a supermassive black hole produce sufficient energy to power AGNs?

Answer 20

yes…luminosity of over 1 trillion solar luminosities due to large grave potential energy

Question 21

what gives a measure of the mass of the central black hole?

Answer 21

the Doppler shift of gas orbiting in the accretion disk

1.5 x 10^9 solar masses

Question 22

what does quasars being highly redshifted tell us?

Answer 22

it tells us when quasars were active, and since we are seeing them from great distances we are seeing them in the past

Question 23

when did the massive black holes gain their mass?

Answer 23

about 9 billion yrs ago

-peak of quasar activity

Question 24

center of MWG?

Answer 24

very active region

Question 25

what is at the very center of our galaxy?

Answer 25

a compact radio source called Sgr A*

Question 26

how do we know there is a very massive object at center?

Answer 26

motions of stars in the cluster

Question 27

what do rapid variations in the infrared indicate?

Answer 27

that the emission originates close to the Schwarzschild radius of massive black hole

Question 28

what is the accretion rate like?

Answer 28

very low

Question 29

supermassive black holes

Answer 29

often found at center of galaxies, however are vert dim