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In article ,
jacobnavia writes: http://www.eso.org/public/archives/r...5/eso1545a.pdf That article says (page 16) "Our results indicate that some very massive galaxies are present since the universe was only a billion years old." The milky way is more than 10Gy old. How a galaxy TWICE AS MASSIVE can appear in just 945My (z=6) ?? What the article actually says is that such galaxies appear in significant numbers between z = 5 and 6. At lower redshifts, more massive galaxies form faster than less massive galaxies. Why is it surprising that the same thing is found at z 5? And the authors say that many more galaxies even more massive are lurking behind, obscured by dust. If so, I missed that. The observations can't rule out such galaxies, but where does the paper say they exist? This confirms what I have reported here in a previous discussion: the sea of galaxies waiting for us behind the farthest galaxies that we can see now. Did you look at the space density plots (Figs 8 and 13)? Why do you think there are more galaxies at higher redshifts? Of course there are some (as reported in other papers), but so far the masses and space densities at z6 are much lower than at 5z6. -- 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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In article ,
"Robert L. Oldershaw" writes: The question is which scenario corresponds best to high-redshift=20 galaxies. Certainly many "surprising" claims have been made in the=20 literature, but, as I mentioned, some have been debunked. Since no-one=20 has debunked the debunking, it stands, even if those debunked don't=20 loudly admit it. Are you referring to "surprising" claims made within the context of conventional cosmology (i.e., the discovery of gravitational waves, various failed dark matter predictions, various predicted turnovers to "homogeneity" at less than 100 Mpc, etc) that have been convincingly debunked. Or are these problems not on your radar? No. A non-detection is not a surprise unless there is a REALLY FIRM prediction. That's not the case with gravitational waves. I guess you mean "non-discovery", since they haven't been directly detected and if they had been, that wouldn't have been a surprise. (That they exist is a firm prediction, but at what amplitude in what frequency range is not.) Dark matter is a firm prediction, but not the specific qualities. Homogeneity? Look at the CMB. It's pretty homogeneous, so it is obvious that there is a turnover at some scale. Apart from a handful of people who have been saying that the large-scale structure is fractal on all observable scales for the last 30 years or so, whatever the observational data, everyone is convinced that there is a turnover. [[Mod. note -- There actually are a few "really firm" predictions of gravitational waves with amplitudes and frequencies already tightly constrained from other astronomical observations, namely various binary stars. In fact, the gravitational-wave predictions for some of these are sufficiently firm that it is planned to use these as test sources to verify that the (proposed) LISA space-based gravitational-wave detector is working correctly. See Stroerr and Vecchio, "The LISA verification binaries", Classical & Quantum Gravity 23 (2006), S809 http://dx.doi.org/10.1088/0264-9381/23/19/S19 astro-ph/0605227 -- jt]] |
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Le 23/11/2015 19:37, jacobnavia a écrit :
So how do we know that 750 My isn't enough time? Dust. That needs billions of years to be a) Produced in stars b) Released and dispersed into the interstellar medium in such big quantities that make the galaxy darker. By the way, the mass of our galaxy is around 6.42*10^42 Kg. Twice that is around 1.3*10^43 Kg. 750 Million years is (3.1*10^7 seconds) in a year * 7.5*10^8 (750 My) in seconds -- 1.06*10^16 seconds. Just with an "orders of magnitude" calculations 43-16 = 27 Each second that galaxy must accrete around 10^27 Kg, around a solar mass per 20 minutes... And that rate must be sustained without stop! And the problem is not even there. The problem is that the article says that there are MORE galaxies BEHIND!!!! That is why this idea of a sea of galaxies is so fascinating... The Universe has NO beginning and NO end, there wasn't any "creation moment" 13.7 Gy ago. I remember the times when Big Bang proponents said that all far away galaxies were small... and that that observation confirmed the supposed bang. When we discover galaxies twice the milky way then... it is OK. [[Mod. note -- I'm allowing this posting, but I think in the future I'm going to be a bit stricter in requiring that postings that essentially say "such-and-such is impossible" give some argument as to *why* that's impossible. -- jt]] |
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Le 25/11/2015 00:52, Steve Willner a écrit :
In article , jacobnavia writes: http://www.eso.org/public/archives/r...5/eso1545a.pdf That article says (page 16) "Our results indicate that some very massive galaxies are present since the universe was only a billion years old." The milky way is more than 10Gy old. How a galaxy TWICE AS MASSIVE can appear in just 945My (z=6) ?? What the article actually says is that such galaxies appear in significant numbers between z = 5 and 6. Well that is the same! At lower redshifts, more massive galaxies form faster than less massive galaxies. Why is it surprising that the same thing is found at z 5? Because we have been told by big bang proponents that the early galaxies were quite small! They are not. At what z we will still accept that the theory has not been rejected by observations? I suppose that when we find old and dusty galaxies at z=7 the bang will (hopefully) go away. And the authors say that many more galaxies even more massive are lurking behind, obscured by dust. If so, I missed that. The observations can't rule out such galaxies, but where does the paper say they exist? quote The presence of very massive (Mst = 2*10^11 M0) galaxies in our sample at 5 = z 6 and the virtual absence at 6 = z 7 provide a strong constraint on the evolution of the GSMF highest-mass end, which suggests that the appearance of such massive galaxies took place in the few hundred million years of elapsed time between z ~ 6 and z ~ 5. end quote So, the authors arrive at the conclusion that in a few hundred million years the massive galaxies appear out of the blue. That is quite a bitter pîll to swallow... how can those massive galaxies appear almost instantaneously? Then, the authors offer an alternative to that: quote The only alternative to this conclusion is that, among the [4.5] 23 galaxies that remain unidentified and/or those that have no redshift determination in our current sample, there is a population of very massive galaxies at z 6 that are significantly dust obscured. One possible candidate for such galaxies was discussed by Caputi et al. (2012) in one of the CANDELS fields, but the level of dust obscuration (AV = 0.90 mag) is atypical, given our current knowledge of galaxies in the early universe (but see Oesch et al. 2015). Further studies in other fields, as well as future follow-up with JWST and ALMA, are necessary to confirm whether such sources exist at z 6. end quote You (may) know that any frontal attack of big bang theory provokes a banning of the concerned astronomer. Doubts about the theory must be voiced with extreme calm... I am surprised the authors express themselves quite clearly in the paper. quote In this paper we find only one massive galaxy candidate at z = 6 over the UltraVISTA ultradeep stripe area (∼0.8 deg2). end quote So, we have a galaxy with z=6! quote The best-fit SED indicates that this is a 0.1 Gyr old galaxy at zphot = 6.04 (the age of the universe is ∼0.9 Gyr at z = 6), with extinction AV = 0.30. This source is not detected at 24 mm, as expected for such a distant source (unless it were an AGN). The derived stellar mass is Mst approx 1.8 * 10^11 M0. end quote This confirms what I have reported here in a previous discussion: the sea of galaxies waiting for us behind the farthest galaxies that we can see now. Did you look at the space density plots (Figs 8 and 13)? Why do you think there are more galaxies at higher redshifts? Of course there are some (as reported in other papers), but so far the masses and space densities at z6 are much lower than at 5z6. So far, because of instrument problems. We are at the limits of what astronomy can yield for observers... Big bang theory is decaying slowly. There isn't now any "smoking gun". The theory holds because people (specially astronomers that have invested their whole career in expanding and honing that theory) do not want to see the trend in the observations. And that is human, I do not blame them or want their demisse! Maybe we have to wait for more powerful scopes, that is all. Plese note that a single OLD galaxy at z=8 or 9 suffices to disprove big bang theory. [[Mod. note -- Actually, a single OLD galaxy at z=8 or 9 *might* (a) disprove big bang theory, and/or (b) it might disprove whatever combination of theoretical models and observation that were used to infer that the galaxy was "old". Given our poor state of knowledge about early-universe galaxy formation/evolution, (b) doesn't seem implausible to me. -- jt]] |
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On 11/25/2015 1:11 AM, jacobnavia wrote:
Le 23/11/2015 19:37, jacobnavia a écrit : So how do we know that 750 My isn't enough time? Dust. That needs billions of years to be a) Produced in stars Why? It was produced 3 minutes after the big bang (look up nucleosysnthesis). Only after that material was used up, the need arose for more dust created by stars. ... The Universe has NO beginning and NO end, So then where does the dust come from for those quickly formed galaxies? The more of them we see, the more it shows that in fact there must have been a moment of massive dust creation in that era! Contrary to what you conclude.. there wasn't any "creation moment" 13.7 Gy ago. But if we go backwards in time we see galaxies receding towards each other, so what kind of singularity do you think there was, if it wasn't the concordance big bang? I remember the times when Big Bang proponents said that all far away galaxies were small... and that that observation confirmed the supposed bang. They definitely must have been vanishingly small at the time when nucleosynthesis just started. Non-existent, I would even dare to propose! But that was 3 minutes after the big bang. Soon afterwards there was lots of building material for free, so the galaxies may have formed must faster than currently is possible. When we discover galaxies twice the milky way then... it is OK. Well, provided it is after t = 3 minutes! -- Jos |
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In article , jacobnavia
writes: [[Mod. note -- I'm allowing this posting, but I think in the future I'm going to be a bit stricter in requiring that postings that essentially say "such-and-such is impossible" give some argument as to *why* that's impossible. -- jt]] I agree. And even if some of the wilder claims stand up, it seems more reasonable to question models of galaxy formation, rather than the idea of the big bang. |
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In article , "Phillip Helbig (undress to
reply)" writes: No. A non-detection is not a surprise unless there is a REALLY FIRM prediction. That's not the case with gravitational waves. I guess you mean "non-discovery", since they haven't been directly detected and if they had been, that wouldn't have been a surprise. (That they exist is a firm prediction, but at what amplitude in what frequency range is not.) Dark matter is a firm prediction, but not the specific qualities. Homogeneity? Look at the CMB. It's pretty homogeneous, so it is obvious that there is a turnover at some scale. Apart from a handful of people who have been saying that the large-scale structure is fractal on all observable scales for the last 30 years or so, whatever the observational data, everyone is convinced that there is a turnover. [[Mod. note -- There actually are a few "really firm" predictions of gravitational waves with amplitudes and frequencies already tightly constrained from other astronomical observations, namely various binary stars. In fact, the gravitational-wave predictions for some of these are sufficiently firm that it is planned to use these as test sources to verify that the (proposed) LISA space-based gravitational-wave detector is working correctly. Right, but it is not a surprise that they haven't YET been detected. |
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Le 23/11/2015 19:37, jacobnavia a =E9crit :=20
So how do we know that 750 My isn't enough time?=20 Dust. That needs billions of years to be=20 a) Produced in stars=20 b) Released and dispersed into the interstellar medium in such big=20 quantities that make the galaxy darker Maybe this adds a little clarification. This isn't behind a paywall.=20 ESO. "Aging star's weight loss secret revealed: Giant star caught in the ac= t of slimming down." ScienceDaily. ScienceDaily, 25 November 2015. www.sci= encedaily.com/releases/2015/11/151125083542.htm. |
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On Tuesday, November 24, 2015 at 7:09:57 PM UTC-5, Phillip Helbig (undress =
to reply) wrote: not.) Dark matter is a firm prediction, but not the specific qualities. Homogeneity? Look at the CMB. It's pretty homogeneous, so it is=20 obvious that there is a turnover at some scale. Apart from a handful of= =20 people who have been saying that the large-scale structure is fractal on= =20 all observable scales for the last 30 years or so, whatever the=20 observational data, everyone is convinced that there is a turnover. =20 ------------------------------------------------- Two corrections to this post are in order. 1.How can one say that "Dark matter is a firm prediction" if one does not have any idea of what it specifically is, far less any shred of empirical evidence for any member of the zoo of pop candidates? 2. It is quite incorrect to say that only those interested in fractal modeling have investigated inhomogeneity in the cosmological context. If you do a search at arXiv.org on "cosmological inhomogeneity" or "large-scale inhomogeneity" you will find many papers, and most are not specifically linked to fractal modeling.=20 Saying that "everyone is convinced that there is a turnover" is untrue and clearly an over the top exhortation. RLO Fractal Cosmology |
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Le 26/11/2015 09:34, Jos Bergervoet a e(C)crit :
On 11/25/2015 1:11 AM, jacobnavia wrote: Le 23/11/2015 19:37, jacobnavia a e(C)crit : So how do we know that 750 My isn't enough time? Dust. That needs billions of years to be a) Produced in stars Why? It was produced 3 minutes after the big bang (look up nucleosysnthesis). Only after that material was used up, the need arose for more dust created by stars. Well, I do not want to contradict the professionals here but this (seems to me) quite NEW. According to popular legend (wikipedia) nucleosynthesis produces: quote Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons, primarily protons and neutrons. The first nuclei were formed about three minutes after the Big Bang, through the process called Big Bang nucleosynthesis. It was then that hydrogen and helium formed to become the content of the first stars, and this primeval process is responsible for the present hydrogen/helium ratio of the cosmos. end quote No word of DUST, I am sorry. Hydrogen and Helium aren't dust! Again "wikipedia" quote The key parameter which allows one to calculate the effects of BBN is the baryon/photon number ratio, which is a small number of order 6 x 10-10. This parameter corresponds to the baryon density and controls the rate at which nucleons collide and react; from this we can derive elemental abundances. Although the baryon per photon ratio is important in determining elemental abundances, the precise value makes little difference to the overall picture. Without major changes to the Big Bang theory itself, BBN will result in mass abundances of about 75% of hydrogen-1, about 25% helium-4, about 0.01% of deuterium and helium-3, trace amounts (on the order of 10e-10) of lithium, and negligible heavier elements. end quote You see? "... and negligible heavier elements." Maybe you can point me to a reference? Thanks |
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