Understanding Observing Frequency and Its Significance in Radio Astronomy

[shirin]

I believe that when we say that this is radio telescope, it means that reciving frequency of it is in radio band. And also it means an observed object by that is in a particular redshift that its emission has a particular frequency that when receives us, is in radio band. Am I right?
For ex. We say cynus A is a radio galaxy. But it doesn't mean that it emits in radio freq. So it doesn't give us any info about physical activities happening in the galaxy, it just tells us about its distance from us.
Sorry for my confusing question! I'm just wondering observing fre just tells us about distance?

 

[HallsofIvy]

It is true that "it doesn't mean that its emission has a particular frequency that when receives us, is in radio band." However, the rest of what you say, in particular "it just tells us about its distance from us" seems to be assuming that what we receive as "radio band" is redshifted visible light. That is not in general true.

 

[shirin]

Are all the radio galaxies in the (approximarely) same distance from us? And is the reciveing frequency from all of them in radio band?
I am wondering whether the difference between a radio and x-ray galaxy is their redshift or their emission mechanism ?

 

[Matterwave]

Can you cite where you have seen these terms "radio galaxy" and "x-ray galaxy" and such? I am not familiar with them as standard terminology, but it could be something I haven't heard until now. Also, I think this thread belongs better in the Astronomy and Astrophysics section.

 

[shirin]

Oh, you are right! I'm sorry, I was supposed to post them in astronomy section.
Thanks though!

 

[davenn]

Can you cite where you have seen these terms "radio galaxy"

That is an extremely standard and common term in astronomy
in another thread earlier today I posted an example ... The Centaurus A radio galaxy

as can be seen, it pumps out masses of EM right across the spectrum

https://en.wikipedia.org/wiki/Cygnus_A

Cygnus A (3C 405) is a radio galaxy, and one of the strongest radio sources in the sky. It was discovered by Grote Reber in 1939. In 1951, Cygnus A, along with Cassiopeia A, and Puppis A were the first "radio stars" identified with an optical source. Of these, Cygnus A became the first radio galaxy; the other two being nebulae inside the Milky Way.[2] In 1953 Roger Jennison and M K Das Gupta showed it to be a double source.[3] Like all radio galaxies, it contains an active galactic nucleus.

Images of the galaxy in the radio portion of the electromagnetic spectrum show two jets protruding in opposite directions from the galaxy's center. These jets extend many times the width of the portion of the host galaxy which emits radiation at visible wavelengths.[4] At the ends of the jets are two lobes with "hot spots" of more intense radiation at their edges. These hot spots are formed when material from the jets collides with the surrounding intergalactic medium.[5]

cheers
Dave