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Astronomers find most distant galaxy ever
Interesting development
Astronomers find most distant galaxy ever http://arxiv.org/abs/1502.05399 at z=7.730 only 650 Myr after the Big Bang Richard D Saam |
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Astronomers find most distant galaxy ever
On Friday, May 8, 2015 at 9:54:11 PM UTC-4, Richard D. Saam wrote:
Interesting development=20 Astronomers find most distant galaxy ever=20 http://arxiv.org/abs/1502.05399=20 at z=3D7.730 only 650 Myr after the Big Bang Richard D Saam IMO this is easily explained by revising the current cosmological model whereby black holes grow with galaxies. If we remember that the first stars were massive and that matter was unevenly distributed in the early Universe; then we can accept that, in addition to massive first generation stars there must also have been large agglomerations of matter that spontaneously collapsed into massive black holes. That means the seeds of galaxies can come first! The gravitational energy from spinning black holes in the midst the remaining un-collapsed matter would then cause star birth and galactic structure. This doesn't mean black holes don't grow, only that galactic nuclei can come earlier than the present model predicts [[Mod. note -- The problem with this scenario is in the details: * Large agglomerations of matter" at early-universe densities won't actually collapse to form black holes: the matter's random motions imply that it has some (small) amount of angular momentum, and this blocks collapse. * Precisely how does the "gravitational energy from spinning black holes" cause star formation? -- jt]] Brad J. |
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Astronomers find most distant galaxy ever
In article ,
"Richard D. Saam" writes: Astronomers find most distant galaxy ever http://arxiv.org/abs/1502.05399 at z=7.730 This is the most distant _spectroscopic confirmation_, based on a line observed at 1062 nm and likely to be Lyman alpha. There are _candidate galaxies_ at redshifts up to about 11. (I'm not sure what the record is at the moment.) Spectroscopic confirmations are difficult at high redshift not only because the candidate galaxies are faint but also because the neutral intergalactic medium is a strong absorber of Lyman alpha. There may soon be more confirmations from ALMA based on the 158 micron [C II] line or eventually from JWST based on [O II] or other UV or visible lines. Probably most of the candidates will turn out to be at the expected redshifts, but a few might be low-redshift objects with peculiar (very red) spectral energy distributions. -- Help keep our newsgroup healthy; please don't feed the trolls. Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA |
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Astronomers find most distant galaxy ever
[[Mod. note -- Please limit your text to fit within 80 columns,
preferably around 70, so that readers don't have to scroll horizontally to read each line. I have manually reformatted this article. -- jt]] On Sunday, May 10, 2015 at 9:40:43 PM UTC-4, brad wrote: =20 [[Mod. note -- The problem with this scenario is in the details: * Large agglomerations of matter" at early-universe densities won't actually collapse to form black holes: the matter's random motions imply that it has some (small) amount of angular momentum, and this blocks collapse. So there is the formation of only stars? That same random motion doesn't block collapse and star formation. It seems unreasonable to not expect a range of objects; from molecular clouds right through stars and black holes. * Precisely how does the "gravitational energy from spinning black holes" cause star formation? -- jt]] In the present Universe star formation is associated with cold molecular clouds and the shock waves from novae. Another way to look at this is as an energy difference before and after the passing shock wave. If massive black holes formed in the early Universe then there would be an energy differencebetween their gravitational fields and the surrounding medium. The comparison is an inverse relationship to be sure but the significance lies in the energy differences. Brad J. |
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Astronomers find most distant galaxy ever
On Sunday, May 10, 2015 at 9:40:43 PM UTC-4, brad wrote:
=20 IMO this is easily explained by revising the current cosmological model whereby black holes grow with galaxies. If we remember that the first stars were massive and that matter was unevenly distributed in the early Universe; then we can accept that, in addition to massive first generation stars there must also have been large agglomerations of matter that spontaneously collapsed into massive black holes. =20 Let me flesh this out a little. For gravitational collapse to proceed to the formation of some object the combined angular momentum of infalling material cannot exceed a value that prohibits collapse. This can be accomplished if there is material available to carry away angular momentum. In the early Universe there was essentially an unlimited amount of matter available to carry away angular momentum allowing much more massive objects to result before the developing object could clear a volume around itself. [[Mod. note -- As well as low angular momentum, collapse also needs low internal pressure. It's instructive to consider the question of why the Sun *today* doesn't collapse to form a black hole? The Sun currently has a radius of about 700,000 km. To form a black hole, it (or a 1-solar-mass gas cloud of the same size) would have to be compressed to a radius of around 3 km, i.e., a compression by around a factor of 10,000,000,000,000,000 in volume. That would take HUGE compressive forces... which don't seem to be available in star-forming regions. By working out the collapse physics in detail, you can model a protostar's collapse and estimate roughly the radius/temperature/luminosity at which it will halt. See http://en.wikipedia.org/wiki/Hayashi_track for a nice introduction. -- jt]] That means the seeds of galaxies can come first! The gravitational energy from spinning black holes in the midst the remaining un-collapsed matter would then cause star birth and galactic structure. This doesn't mean black holes don't grow, only that galactic nuclei can come earlier than the present model predicts =20 [[Mod. note -- The problem with this scenario is in the details: * Large agglomerations of matter" at early-universe densities won't actually collapse to form black holes: the matter's random motions imply that it has some (small) amount of angular momentum, and this blocks collapse. * Precisely how does the "gravitational energy from spinning black holes" cause star formation? -- jt]] =20 Brad J. |
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Astronomers find most distant galaxy ever
In article , Steve Willner
writes: This is the most distant _spectroscopic confirmation_, based on a line observed at 1062 nm and likely to be Lyman alpha. There are _candidate galaxies_ at redshifts up to about 11. (I'm not sure what the record is at the moment.) Note that the difference between a redshift of 7 and one of 11 is, in most respects, less than between a redshift of 0 and one of 1. In particular, in almost all cosmological models (and certainly in the one which describes our universe), it corresponds to a much shorter difference in time. |
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Astronomers find most distant galaxy ever
On 5/14/15 7:53 AM, brad wrote:
In the early Universe there was essentially an unlimited amount of matter available to carry away angular momentum allowing much more massive objects to result before the developing object could clear a volume around itself. [[Mod. note -- As well as low angular momentum, collapse also needs low internal pressure. In these formation studies, does vacuum viscosity come into play? Ref1: http://arxiv.org/abs/0806.3165 Hydrodynamics of spacetime and vacuum viscosity viscosity*entropy density = hbar/4pi Richard D Saam |
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