Galaxy Zoo Talk

No Bulge

  • elenapells by elenapells

    I don't know if my source is truthful, but I thought that in every galaxy's centre there was a black hole, which gave off a very bright gamma ray (???). What's in the centre of galaxies that have no bulge?

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  • zoob1172 by zoob1172

    Simulated galaxy from Illustris

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  • elenapells by elenapells

    I'm sorry for my late reply. What does that mean?

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  • zoob1172 by zoob1172

    Simulated galaxy from Illustris http://www.illustris-project.org/ it means you will have to go to the Illustris site and ask someone about your questions.

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  • Budgieye by Budgieye moderator in response to elenapells's comment.

    You are correct. Most galaxies have a black hole, but it may not be active ie. feeding on stars.

    I don't know how bulges and black holes are correlated, but I would think that bulgeless galaxies still have black holes.

    A study would be difficult, because it is impossible to detect a black hole that is inactive.

    Here is some info anyway.

    Talk: No Black Hole? reply by Dr Simmons https://talk.galaxyzoo.org/#/boards/BGZ0000004/discussions/DGZ0002f4x?page=1&comment_id=58ba39857d25c7008d0002f4 However, deciding a galaxy has no black hole takes a lot of work and many follow-up observations. It's impossible to rule out the presence of a black hole just by looking at a GZ image. Black holes, even very massive ones, don't take up much space, so when we observe a galaxy in our surveys even a supermassive black hole in that galaxy takes up much, much less space than a single pixel - and there would be plenty of room in that pixel for stars and other bright things to mask the presence of a black hole in our observations.

    Blog: How to find black holes? February 6, 2010 by The Zooniverse http://blog.galaxyzoo.org/2010/02/06/how-to-find-black-holes/ "The first step in trying to understand the connection between black holes and galaxies is finding them. But black holes are, well, black. In fact, you might say their blackness is their most defining feature. So, how do you find them? It turns out that when they’re feeding on infalling gas and dust, a massive black hole can turn into the brightest object known in the whole universe – a quasar! As the gas and dust falls towards the black hole, it settles into a disk around it, and as it moves in, friction in the disk heats up all the matter in it to such temperatures that it stats shining. In this way, black holes can be very bright, or quite dim, depending in part on how much matter they are munching on. There are many ways to find feeding black holes and for the Galaxy Zoo paper on black hole growth, we used the emission lines that AGN (active galactic nuclei, or feeding black holes) cause when the light coming from the accretion disk shines on some other gas floating around in the host galaxy and makes that light in turn emit light with a very particular signature that we can detect by carefully analysing the spectra.

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  • Budgieye by Budgieye moderator

    Here are some references.

    Correlation of black hole Mass and bulge mass/brightness https://www.spacetelescope.org/images/opo0022b/

    The black hole - bulge mass relation of Active Galactic Nuclei in the Extended Chandra Deep Field - South Survey https://arxiv.org/abs/1212.2999

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