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A Galaxies without SMBH's?

  1. Mar 23, 2016 #1
    I'm wondering about large, regular galaxies that lack SMBH's. Here are some possible examples I found. The general question is, what large galaxies have no central SMBH?


    A2261-BCG: From the Astrophysical Journal, 756:159, 2012 September 10, "A BRIGHTEST CLUSTER GALAXY WITH AN EXTREMELY LARGE FLAT CORE":

    One possibility for the puffy [i.e., large with flat luminosity profile] core may be two central black holes orbiting each other. ... In this scenario, ... each gravitational slingshot [ejecting stars] robbed the black holes of momentum, moving the pair ever closer together, until finally they merged, forming one supermassive black hole that still resides in the galaxy's center.

    Another related possibility is that the black-hole merger created gravity waves, ... The imbalance of forces would have ejected the merged black hole from the center at speeds of millions of miles an hour, resulting in the rarity of a galaxy without a central black hole.

    QUESTION: What is the latest on A2261-BCG? have they decided whether it has a SMBH or not?


    Similar uncertainty exists concerning CID-42, where a BH is leaving. The headline is "Giant Black Hole Kicked Out of Home Galaxy". Popular accounts say galaxies merged, the 2 SMBH's (now one) were kicked by gravitational waves, and it's leaving at "several million miles per hour". But the 2010 paper says:

    "This black hole kickback was caused either by a slingshot effect produced in a triple black hole system, or from the effects of gravitational waves produced after two supermassive black holes merged a few million years earlier."

    QUESTION: The popular headline is unambiguous, but NASA doesn't know whether a SMBH is still there. Have they decided whether there is, in fact, a 3rd SMBH remaining behind in CID-42?


    Spirals without bulges:

    wikipedia: "Until recently it was thought that one could not have a supermassive black hole without a bulge around it, but galaxies hosting supermassive black holes without accompanying bulges have now been observed."

    Ok, I find that in 2008 Hubble saw a spiral galaxy with no bulge, but jets emerging, probably due to SMBH. NASA concludes that perhaps such spirals often do have SMBH's.

    But at solstation.com it says: in 2011, The astronomers found, however, that galaxies without a bulge -- even if they are embedded in massive dark matter halos -- contain very low mass black holes, if any.

    It's hard to reconcile these reports since the 2011 report doesn't explain or mention the 2008 report. I suspect wikipedia is right.

    QUESTION: What's the latest thinking? Do spirals without bulges contain SMBH's, or not?


    QUESTION: Can you give me examples of large galaxies with no SMBH? Or a link - but don't just send me to NASA
  2. jcsd
  3. Mar 28, 2016 #2
    According to PF rules I'm allowed one bump after 24 hours if no responses. So let me re-phrase my question:

    Where can I go to get answers to questions about galactic composition and dynamics? Can you recommend any good sites?
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