Radio Galaxy Zoo Talk

PROOF

  • leonie_van_vliet by leonie_van_vliet

    Thanks to some great tutoring, able to see at first hand when to go to discussion & search further albeit in my own way in NED, SIMBAD,
    Also looking at the FIRST images at NVSS & even in WISE to make a comment. Being limited in recognizing what might or might not be a #candidate.

    Wondering if anyone ever did find definite PROOF of an BH here in RGZ...

    Knowing they do exist even in our own Galaxy. Proven by scientist trough the behavior of stars, speeding up near to the center.
    To be a volunteer for me on RGZ is being curious & attracted by GRAVITY...

    ~Leonie

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  • JeanTate by JeanTate in response to leonie_van_vliet's comment.

    Great post, leonie! 😃

    I'm going to respond with two separate posts; the first on "PROOF" and the second on what we've found here in RGZ ...

    So, proof (personal views only; feel free to disagree!).

    "Proof" is possible in mathematics only; there are no proofs in science. Instead there is something like "consistent with all relevant experimental and observational results within the domain of applicability". So, until ~late 1800s, everything was consistent with Newton's Universal Law of Gravitation (or is it Law of Universal Gravity?), when the orbit of Mercury seemed to be "off" by a tiny bit, but far bigger than any "errors". Einstein's General Relativity (GR) fit all that data, and a great deal more, over the ensuing century+. Yet we know that GR cannot be truly universal; it is fundamentally inconsistent with quantum mechanics ... yet all the inconsistencies are far, far beyond anything we could test, either in our labs or via astronomical observations.

    In extra-galactic astronomy, everything we know comes from detecting electromagnetic radiation and interpreting what we "see" (well, it did until 1987, when a handful of neutrinos were detected from a supernova; then again this year, when a short GRB coincided with a detection of gravitational wave radiation). We cannot travel to SDSS J140415.67+090612.6, say, and do controlled experiments on what we might find there. And it's likely that we never will ... so extra-galactic astronomy does not have even the possibility of "ground truth" that the study of Mars, say, has (we can put mobile labs onto the surface, and maybe one day drill deep into the bedrock; etc).

    (next: what we've found here in RGZ ...)

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  • JeanTate by JeanTate

    part 2: what we've found, here in RGZ ...

    Aside from some rare objects, such as "radio stars", the radio sources we classify here in RGZ come from two sources: star-forming regions, and super-massive black holes (SMBHs). For star-forming regions, the association is pretty direct: if you superpose radio contours onto optical (or IR) images, you'll see a very close match. And the (astro)physics is fairly straight-forward.

    However, for SMBHs it's not so simple.

    Our own galaxy, the Milky Way, has a SMBH at its center, a place on the sky called SgrA*. Rather a lot of independent evidence points to something very massive, very small, and very dark being there; personally, I like the motions of a handful of stars near SgrA* (on the sky) ... interpreted as orbits (Newtonian or Einsteinian), there's definitely something very massive, very small, and very dark that they're all orbiting. The biggest leap is, I think, that it's a SMBH; why? because we can't think of anything else that would be that massive, that small, and that dark.

    However, SgrA* does not seem to be associated with anything like the jets, hotspots, lobes, etc that we see so often in RGZ fields. So how do we know that it's SMBHs which, indirectly, create these? (OK, I've slipped into a common mode, using "know"; no worries, it's not too hard to change all such statements into ones containing something like "consistent with all relevant experimental and observational results within the domain of applicability" ... makes sentences rather long, and somewhat boring, don't you think?).

    Hmm ... I said two posts, but I've run out of time here, so I'll have to return later to finish. Stay tuned for the "M87 story"! 😃

    PS: some radio sources are likely both star-forming regions and created by SMBHs; for example, if there's rather a lot of star-formation happening near the nucleus of a galaxy, and if the SMBH there is busy making radio waves, you often can't tell which dominates, or even if there's both. Especially if there's a lot of dust in the way, or the galaxy is far, far away (has a redshift > ~0.2, say). These sorts of radio sources are often found in galaxy mergers.

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  • leonie_van_vliet by leonie_van_vliet

    Thanks Jean,

    For your elaborate answer to my question about "proof" knowing the basics by reading & having a clever friend who does know
    what I'm talking about so I can converse about quantum mechanics. So much is still disputed there are no set rules yet... Being the only one who doesn't "faze out" if asked or randomly talking about my voluntary work here in RGZ.
    Your way of explaining is understandable. ( Although I do find acronyms a bit tricky every now & than. ) But hey I'll always ask!

    No worries when you slipped into the language; 😃 "consistent with all relevant experimental and observational results within the domain of applicability" ... makes sentences rather long, and somewhat boring, don't you think?" I agree here and get it!

    This, by the way is no boring stuff so I am glad you satisfied my usual curiosity.
    Already made a screenshot so I can keep it in my Q & A book.

    Staying tuned for M87 story...

    ~Leonie 

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  • JeanTate by JeanTate

    Thanks leonie! 😃

    But hey I'll always ask!

    And I hope you will always continue to ask! While I may not always be able - time, knowledge, etc limitations - I think these sorts of questions are very good, and well worth the effort to try to answer. Here's a plus: I know several of the RGZ Science Team members do drop by every now and then, and I'm pretty sure many will read Discussion threads like this. So if I've made a mistake, or left out something really important, I'm confident they'll write a post with a better description/answer. So far, by the lack of such posts, it seems I'm doing OK. 😃

    Staying tuned for M87 story...

    Yeah, as you probably noticed, I've been absent for a while ... sorry about that.

    M87 is a giant elliptical galaxy, near the center of the closest galaxy cluster to us, the Virgo cluster (named after the constellation it's mostly in). It has an obvious radio jet coming from its nucleus, the sort of thing we often come across while classifying, here in RGZ (it's one-sided, which is also common). When observed with telescopes like the one used to produce all the SDSS data, you can see an optical jet; it's a lot more obvious in Hubble images. And a jet can also be "seen" in x-ray "images". Best of all, the three jets - radio, optical, and x-ray - coincide.

    Because M87 is so close to us - cosmologically speaking! - high resolution radio "images" can be made of the nucleus. These show that the radio jet does not extend to the location of the nucleus; however, it's all consistent with the jet being "launched" from a pole (position) of an accretion disk which has at its center a SMBH. And this is the standard astrophysics description of what's going! 😄 And also consistent with the apparent absence of a "counter-jet" ("bijets" are fairly common in ARG images, as I'm sure you know) ... there is another jet, but it's pointing (mostly) away from us, and because it's powered by a stream of relativistic particles (kinda like a straight-line version of the Large Hadron Collider, but vastly vastly more powerful), the electromagnetic emission - radio, light, x-rays, etc - from these particles is "beamed" away from us.

    I've saved the best until last: what would be really really convincing evidence of the existence of a SMBH powering the M87 jets etc would be an "image" revealing the "event horizon" of that SMBH. Event horizons are predicted by General Relativity, and should be found around all black holes. A really massive one - such as the SMBH in the nucleus of M87 (it makes our own galaxy's SMBH look really puny) - will have a relatively large event horizon, one large enough that a radio telescope with sufficient resolution should be able to "see" some of the effects (a relatively recent sci-fi movie had a good depiction of these (I can't recall its name just now), even if other parts of the movie were just ridiculous, scientifically speaking). May I present the Event Horizon Telescope? 😃

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  • leonie_van_vliet by leonie_van_vliet

    Hi Jean,

    Haven't been reading the latest answer due to circumstances. It is a clear explanation from your part & understandable for me.

    Because M87 is so close to us - cosmologically speaking! - high resolution radio "images" can be made of the nucleus. These show that the radio jet does not extend to the location of the nucleus; however, it's all consistent with the jet being "launched" from a pole (position) of an accretion disk which has at its center a SMBH. And this is the standard astrophysics description of what's going! 😄 And also consistent with the apparent absence of a "counter-jet" ("bijets" are fairly common in ARG images, as I'm sure you know) ... there is another jet, but it's pointing (mostly) away from us, and because it's powered by a stream of relativistic particles (kinda like a straight-line version of the Large Hadron Collider, but vastly vastly more powerful), the electromagnetic emission - radio, light, x-rays, etc - from these particles is "beamed" away from us.

    Saving the best for last;

    Thanks for presenting the Event Horizon Telescope. Have seen the movie EVENT HORIZON and agree here with you but thought it was most entertaining! So using my "huge imagination helps" 😃 Switching every now & than to other projects looking for Muons, Quarks, Bosons etc. trying to keep up with weird stuff which is intriguing on the LHC. I am not able to acces; "discuss" anymore!!!

    Ah, will we ever see the day it all make sense? Don't think so but hey, you never know these days... Evidence is just another question answered & solved for the moment puny, massive or otherwise! Keeps us on the lookout continuing the search on RGZ...

    Leonie

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  • Dolorous_Edd by Dolorous_Edd in response to JeanTate's comment.

    a relatively recent sci-fi movie had a good depiction of these

    Interstellar ?

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  • JeanTate by JeanTate in response to Dolorous_Edd's comment.

    Yes, that's it!

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  • JeanTate by JeanTate in response to leonie_van_vliet's comment.

    Glad you found what I wrote interesting and informative, Leonie, and also glad to hear you continue to be curious and inquisitive and keen on adding to the world's knowledge base by all your clicks! 😃

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  • leonie_van_vliet by leonie_van_vliet

    To @Dolorous_Edd, Hi Ivan, & Jean!

    Haven't check this thread for month's & had to react!
    Have INTERSTELLAR in my 'blue -ray' collection & watched it again last sunday. Not bad at all, since imagination is necessary...

    Greetings to both of you!
    Leonie... 

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