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Galaxy cluster at 1100 million years after BB
NASA publishes the discovery of a galaxy cluster at 12.6 billion light
years: http://www.jpl.nasa.gov/news/news.cf...y&auid=7616512 It has a central black hole of approx 30 million suns. Our own galaxy has a central BH with only 2.6 million sun masses. (from http://www.eso.org/public/news/eso0226/) Now, 1.1 billion years is a VERY short time for a cluster. Our own galaxy does 4 revolutions in that time only, imagine building a CLUSTER of galaxies in that time. Bsides, supposing that the black hole started growing immediately after the big bang, it should have been eating 0.2727 sun masses a year to achieve that mass... without interruption. I remember when people told everyone that no cluster of galaxies would be discovered beyond 7 billion years. Then it was 9, later was 10. Now we are at 12.6. |
#2
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Galaxy cluster at 1100 million years after BB
Le 12/01/11 23:39, jacob navia a écrit :
Bsides, supposing that the black hole started growing immediately after the big bang, it should have been eating 0.2727 sun masses a year to achieve that mass... without interruption. I forgot that this figure is the effective mass incorporated into the black hole. Since the accretion efficiency is around 10%, the black hole would need 2.7 stars like the sun each year to arrive at that gargantuan mass only 1100 million years after the supposed Big Bang. A continuous line of stars, falling into the BH each 5 months would be needed. Since the efficency is 10%, 90% of the mass of those stars would be re-radiated, i.e. around 2.5 Mo would be left at the accretion disk. That enormous mass being "left over" would disturb the falling of the following stars into the BH. I do not see how such a growth rate can be sustained for 1100 million years. [Mod. note: I think you may have your efficiency factors the wrong way round. Accretion efficiency factors of 10% -- which are an order of magnitude estimate, not a number fixed by physics -- usually mean that 10% of the mass-energy is radiated, not that only 10% of the mass makes it in. There are real problems in understanding black hole growth, but it's not necessary to exaggerate the problem by an order of magnitude -- mjh] |
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Galaxy cluster at 1100 million years after BB
In article , "Robert L.
Oldershaw" writes: Don't you just love those "adjustable" theories that never take a scientific stand, as in a definitive prediction, but rather stretch to fit the new data in a most plastic manner. Very postmodern. Like those which predicted one-solar-mass objects as the dark matter, then stopped predicting them when observations said otherwise? It reminds me of the endless search for the "transition to rigorous (as opposed to statistical) cosmological homogeneity" which has undergone a similar sequence of multiple crossings of "lines drawn in the sand", followed each time by new "lines drawn in the sand". Did fundamentally inhomogeneous models ever get the attention and respect they have always deserved? Yes they did. It was not much attention since they didn't deserve much. Not a chance. They are still sent to the back of the bus. One can publish papers on this subject, but one can also expect flak and ignore-ance. Just ask Pietronero and Labini Same as it ever was. Indeed---a good summary of their numerous papers, which have been saying the same thing for decades despite tremendous observational advances during that time. |
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Galaxy cluster at 1100 million years after BB
Le 13/01/11 19:18, jacob navia a écrit :
Le 12/01/11 23:39, jacob navia a écrit : [Mod. note: I think you may have your efficiency factors the wrong way round. Accretion efficiency factors of 10% -- which are an order of magnitude estimate, not a number fixed by physics -- usually mean that 10% of the mass-energy is radiated, not that only 10% of the mass makes it in. There are real problems in understanding black hole growth, but it's not necessary to exaggerate the problem by an order of magnitude -- mjh] You are right. I misunderstood Accretion, black holes, AGN and all that..... Andrew King Theoretical Astrophysics Group, University of Leicester, UK http://www.exp-astro.phys.ethz.ch/se...tures_King.pdf I was mislead by page 62 of that document where he speaks about 10% efficiency. Question then: What is the maximal black hole accretion rate? There is a super massive black hole already at 13 billion years, i.e. only 700 million years after that "bang"... |
#5
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Galaxy cluster at 1100 million years after BB
In article ,
jacob navia wrote: Question then: What is the maximal black hole accretion rate? Answer: it depends. For example, suppose I collect a bunch of stars, extract all their angular momentum, and drop them one by one on radial trajectories into a non-rotating black hole which already has a mass large enough that the event horizon is the typical stellar radius. The accretion rate is very high (limited only by how fast I can shove the stars in without them colliding), the radiation generated is zero -- all the kinetic energy generated as the star falls in is carried in with it over the event horizon (advected). Obviously nobody is out there doing this, but it illustrates that you have to understand what sort of material is accreting and in what way before you can answer questions about black hole growth rate. Standard calculations such as the Eddington limit implicitly assume radiatively efficient flows with an efficiency ~ 10%. They also assume quasi-spherical symmetry. It is certainly possible (& observed) for systems to exceed the Eddington 'limit'. If you go to ADS and search abstracts for 'black hole growth early universe' or something along those lines you will find a bunch of people discussing different scenarios for black hole growth, including some where the black holes do indeed grow rapidly without producing much radiation in the early universe. Everybody working in this area is aware (and has been for some time given the existence of high-z quasars) that this needs to be understood. Martin -- Martin Hardcastle School of Physics, Astronomy and Mathematics, University of Hertfordshire, UK Please replace the xxx.xxx.xxx in the header with herts.ac.uk to mail me |
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Galaxy cluster at 1100 million years after BB
On Jan 12, 10:39 pm, jacob navia wrote:
Bsides, supposing that the black hole started growing immediately after the big bang, it should have been eating 0.2727 sun masses a year to achieve that mass... without interruption. What leads you to assume that the central black hole has acquired its mass by means of accretion? In the process of the formation of our solar system about 99.9% of the total mass have directly collapsed into the central object (our sun). So it is not a big deal if 0.03% of the mass of a typical galaxy (10^11 solar masses) have directly collapsed into the central object. Besides, black hole or not, such an object would anyway only be visible in the X-ray region of the electromagnetic spectrum due to the high temperature associated with its gravitational energy. I remember when people told everyone that no cluster of galaxies would be discovered beyond 7 billion years. Then it was 9, later was 10. Now we are at 12.6. It hardly matters. Big-Bang cosmologists can practically accommodate any observations by adjusting the free parameters in their equations accordingly. Thomas |
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Galaxy cluster at 1100 million years after BB
Le 18/01/11 06:26, Thomas Smid a ?crit :
On Jan 12, 10:39 pm, jacob wrote: Bsides, supposing that the black hole started growing immediately after the big bang, it should have been eating 0.2727 sun masses a year to achieve that mass... without interruption. What leads you to assume that the central black hole has acquired its mass by means of accretion? Nothing. If you read what I wrote I just said that it must have increased its mass by 0.27 solar masses per year. Then I tried to figure out how much REAL mass would be needed to inject 0.27 M0 into the black hole since the injection process is not 100% efficient. THERE I made a mistake. It is more than 10% of the mass of a star that can be accretted, but probably not more than 50%. Even at 50%, we would need a star of the mass of the sun each 2 years. Assuming: (1) At the start of the big bang there were no atoms, just some "particle soup" (2) 1100 million years later we find a blackhole that has 30 million solar masses, made by atoms falling down into it. This means that somehow that black hole went from 2 solar masses (a stellar black hole) to 30 million in that time, i.e. 0.27 M0 per year in average. In the same period, a CLUSTER of galaxies is created. Not only galaxies but a CLUSTER. Now, coming back to our huge hole, it could grow by swallowing whole galaxies of course. The only problem is that the process is quite long and takes MUCH more than a billion years for a single galaxy. How then? In the process of the formation of our solar system about 99.9% of the total mass have directly collapsed into the central object (our sun). So it is not a big deal if 0.03% of the mass of a typical galaxy (10^11 solar masses) have directly collapsed into the central object. Yes, it is surely not a big deal, as you say, but that is not the point. The point is that it is a BIG deal to do it in 1100 million years only! To collapse that mass directly in the form of gas, etc, the ring around the BH gets very hot, and keeps further infalling gas AWAY. Then, the ring must cool, lose angular momentum and get incorporated into the BH. That takes TIME. Besides, black hole or not, such an object would anyway only be visible in the X-ray region of the electromagnetic spectrum due to the high temperature associated with its gravitational energy. Yes, but since light gets red shifted, we should be able to see it now since the X rays are no longer X rays. [[Mod. note -- That does depend on the redshift. For example, a soft X-ray source at a redshift z=10 could well wind up in the millimeter-wave range, where (alas) not many astronomical observations have yet been made. -- jt]] I remember when people told everyone that no cluster of galaxies would be discovered beyond 7 billion years. Then it was 9, later was 10. Now we are at 12.6. It hardly matters. Big-Bang cosmologists can practically accommodate any observations by adjusting the free parameters in their equations accordingly. Thomas But that is precisely the point. We have a theory that can always be "shifted" to please any new observations. |
#9
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Galaxy cluster at 1100 million years after BB
In article
, "Robert L. Oldershaw" writes: False. There is ongoing debate over what % of the dark matter is observed to be in the form of stellar-mass black holes. First, no one has OBSERVED any sort of black hole in observations designed to detect dark matter; at best, black holes are inferred. A microlensing signature has been observed by several microlensing groups. No one denies that microlensing has been observed. The question is how much microlensing would one expect if an appreciable fraction of the dark matter were in compact objects, and the answer is that one would expect much more than is observed. The interpretation of what they have observed and the statistics of the population are not decided scientifically. Then how are they decided? |
#10
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Galaxy cluster at 1100 million years after BB
In sci.astro.research message ,
Tue, 18 Jan 2011 00:27:42, Dan Birchall posted: (jacob navia) wrote: NASA publishes the discovery of a galaxy cluster at 12.6 billion light years: http://www.jpl.nasa.gov/news/news.cfm?release=2011-013 &cid=release_2011-013&msource=11013&tr=y&auid=7616512 Anybody got a link to the paper(s)? Ask Whitney Clavin. -- (c) John Stockton, nr London, UK. Turnpike v6.05 MIME. Web http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms and links; Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc. No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News. |
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