What do broad and strong emission lines mean and what are the main types of AGN?

[chickensagan]

Cosmic greetings,

I am reading up on active galaxies, and 'strong' and 'broad' emission lines are mentioned everywhere, yet no definitions given. Do they mean that the object is emitting energy across a large part of the spectrum, or that it's emitting a lot of energy?

Also, I am confused by the different types of active galaxies. I'm trying to work out the main ones though (I'm writing an essay and don't want to go into too much detail). Are they Seyfert, radio, blazars and quasars?

Thank you for your time!

 

[goldsax]

i found that i grasped the different AGN much better when i understood the UNIFIED MODEL of AGN.
its a model based on the energy(mass) of the ANG and the postion that it is oberved in.

the narrow and broad lines will also become evident when you see how the unified model works..
(sorry i don't know how to post images)

 

[chickensagan]

Thanks for the reply goldsax.

I can't seem to find a definitive explanation of the unified model. This is my understanding so far:

The unified model is the theory that all AGN have a black hole at their centre which is fuelled by its surrounding accretion disk, and that differences between AGN only arise because of their orientation with respect to the observer, due to obstruction by the molecular taurus.

Is that correct?

 

[goldsax]

cannot post any pics i have due to copyright ..

have a look at this link..good illustrations for the anatomy of AGN and different models
http://astronomyonline.org/Cosmology/Galaxies.asp

you will notice that the broad line region comes from close to the black hole where there is lots of energy( both thermal and velocity, up to 10000km/s!) the narrow lines are produced some distance away from the black hole where energies are lower.

 

[pmacias]

Broad and strong emission lines in active galaxies refer to the presence of intense and wide spectral lines that are emitted from the central region of the galaxy. These lines are produced by the hot gas and dust surrounding the supermassive black hole at the center of the galaxy. The broadness of the lines indicates that the gas is moving at high speeds, and the strength of the lines suggests that there is a large amount of energy being emitted from this region.

There are several types of active galaxies, including Seyfert galaxies, radio galaxies, blazars, and quasars. Seyfert galaxies are characterized by their strong emission lines and a bright, compact nucleus. Radio galaxies emit strong radio waves and have a large, extended region of radio emission. Blazars are a type of active galaxy with a jet of material pointing directly towards Earth, causing them to appear very bright and highly variable. Quasars are the most luminous and energetic type of active galaxy, often emitting high-energy radiation and displaying strong emission lines. These different types of active galaxies can also be classified based on their optical and radio properties, such as broad line radio galaxies and narrow line radio galaxies.