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Thread: What kinds of galaxy has a jet (or pair of jets) coming from its nucleus?

  1. #1
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    What kinds of galaxy has a jet (or pair of jets) coming from its nucleus?

    In more detail: "What sort of galaxies are found with jets then? Are AGNs and quasars thought to be the same phenomenon, the result of central SMBHs in galaxies?"

    These questions come from here, and were posed by TooMany. I think they are excellent questions, of general interest (so I started a separate thread on them).

  2. #2
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    Quote Originally Posted by Nereid View Post
    In more detail: "What sort of galaxies are found with jets then?
    All types, aside from dwarf galaxies. This is a gross generalization.


    Are AGNs and quasars thought to be the same phenomenon, the result of central SMBHs in galaxies?
    "
    Yes. The name generally describes the ratio of nuclear light to light from the rest of the galaxy. When the nuclear light dominates, it's a quasar; when it doesn't, it's an AGN. And, yes, this is a gross generalization.
    Last edited by pzkpfw; 2012-May-01 at 11:59 PM. Reason: Fix quote tags

  3. #3
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    In the other thread, when I saw it stated that spiral galaxies don't
    usually have jets, I was surprised, but it has been too long since
    I read about the subject for me to say anything myself.

    Some years ago I saw an article which included several diagrams
    of the same galaxy with polar jets at different angles to the viewer,
    ranging from head-on to perpendicular to the line of sight. IIRC,
    the author was asserting that all different types of AGN from
    quasars on down could be accounted for by the different angles.
    I don't recall whether I saw it on the Internet or Scientific American
    magazine, but the diagrams were in the same style as SciAm
    diagrams always have.

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    Something like the diagram here?

    The viewing angle AGN unification model was what we were taught in uni. Seems to be the standard model for them all now.

  5. #5
    Spiral galaxies practically never have large, luminous radio jets - when they have radio jets, they are usually short (<kpc or so) and often distorted. The clear exceptions I know of are 0313-192 and SDSS J140948.85−030232.5. The other thousands shown in VLA surveys (when at low enough redshift to tell) are ellipticals, S0 galaxies (which are still interesting as being disk-dominated, unlike ellipticals), or disturbed galaxies that likely included ellipticals beforehand. There has naturally been speculation as to why - black-hole mass, angular momentum, surrounding dense ISM disrupting relativistivc but low-mass jets, and on and on.

  6. #6
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    Here's another Galaxy with a jet coming from its center. But maybe it doesn't count because this Galaxy essentially is a jet.
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  7. #7
    Quote Originally Posted by slang View Post
    Here's another Galaxy with a jet coming from its center. But maybe it doesn't count because this Galaxy essentially is a jet.
    Ba-doom CHING! Suckered me right in.

  8. #8
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    I'm sure most galaxies have jets eminating perpendicularly from the plane where most of their mass inhabits. That is what galaxies are--hyperstars with too much mass. It compiles itself into a disc because of gravity, and the only way to expel it is perpendicularly. That is to say perpendicularly is the path of least resistance so if such a system were capable of expelling mass from outward forces it would be in those two perpendicular directions in dual jets.

  9. #9
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    That seems to be a very unusual definition of a galaxy - any references for what you mean by that?

  10. #10
    Quote Originally Posted by CaptainToonces View Post
    I'm sure most galaxies have jets eminating perpendicularly from the plane where most of their mass inhabits. That is what galaxies are--hyperstars with too much mass. It compiles itself into a disc because of gravity, and the only way to expel it is perpendicularly. That is to say perpendicularly is the path of least resistance so if such a system were capable of expelling mass from outward forces it would be in those two perpendicular directions in dual jets.
    Sort of. In elliptical galaxies, the jets are generally perpendicular to any disk of gas and dust we see on 100-light-year scales, which don't necessarily align with the galaxy's overall shape. For small-scale jets from Seyfert-galaxy nuclei, there is surprisingly little correlation between their direction and the galaxy disk, which has been used by some folks to infer that very local processes determine the angular momentum direction of the accretion disk (and if the disk is massive enough, eventually the black hole as well). In spirals, it has been suggested that the few powerful jets that do emerge are more likely to escape the dense interstellar medium if they start out more or less pointed out of the disk.

    Galaxies are hyperstars with too much mass?

  11. #11
    Nicely played, slang. Got me too.

    To the second question, quasars are luminous AGN, and AGN are accreting supermassive black holes. I'd quibble with StupendousMan's statement about it being due to the ratio of AGN light to galaxy stellar light (it's usually a strict luminosity cut these days). But that's only a quibble, and he already said it was a gross generalization.

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