Quasars and Other Active Galaxies Flashcards
what were some sources or radio emission?
- gas heated and ionized by young stars
- supernovae remnants
what causes non-thermal emission in astronomical sources?
synchrotron emission
what is synchrotron emission?
acceleration of relativistic moving electrons by a magnetic field
what regions use thermal emission?
HII regions
what uses synchrotron emission?
SNR
quasars
radio synchrotron emitting object that had an appearance similar to a star but were producing very strong radio emission
who was first to deal with quasars using spectra?
Maarten Schmidt
what was unique about Schmidt’s spectra?
enormous redshifts
how to determine luminosity of quasars?
observed brightness
-large luminosities
are quasars bright?
yes, very
what do quasars vary rapidly in?
light output
how big is the size of where quasar’s energy comes from?
small region
elliptical galaxies
also can be radio producers
where does radio emission often come from?
two large lobes located beyond visible galaxies
how can we produce so much energy in a small region of space?
supermassive black hole (100 million solar masses)
how do supermassive black holes power?
AGNs
what happens as gas falls inward?
gravitational potential energy is converted to heat energy
what produces the large luminosities of these objects?
hot gas
what are the “jets”
composed of high speed material funneled by a twisted magnetic field
can the accretion of matter onto a supermassive black hole produce sufficient energy to power AGNs?
yes…luminosity of over 1 trillion solar luminosities due to large grave potential energy
what gives a measure of the mass of the central black hole?
the Doppler shift of gas orbiting in the accretion disk
1.5 x 10^9 solar masses
what does quasars being highly redshifted tell us?
it tells us when quasars were active, and since we are seeing them from great distances we are seeing them in the past
when did the massive black holes gain their mass?
about 9 billion yrs ago
-peak of quasar activity
center of MWG?
very active region
what is at the very center of our galaxy?
a compact radio source called Sgr A*
how do we know there is a very massive object at center?
motions of stars in the cluster
what do rapid variations in the infrared indicate?
that the emission originates close to the Schwarzschild radius of massive black hole
what is the accretion rate like?
very low
supermassive black holes
often found at center of galaxies, however are vert dim
