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Thread: Light is no basis to infer stellar mass of galaxies?

  1. #31
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    Quote Originally Posted by Nereid View Post
    Other than molecular hydrogen*, it's quite difficult to come up with hypotheses for such large masses of undetected H and He (hypotheses which are consistent with all relevant observational results); it's even more difficult to come up with hypotheses for their formation and evolution (consistent with ...).

    * and, perhaps, ~km to 10^3 km balls of solid hydrogen

    Thanks for the constructive comment.

    Let's see if i understand this.

    If a significant amount of dark matter is normal matter that is hidden below detection threshold, then it must be H and He because that's what would be there unless it has been through at least one cycle of star formation, which is not very likely to be the case.

    And also it must be cold and in at most fairly small condensed formations, otherwise it would already have been detected.

  2. #32
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    Quote Originally Posted by noncryptic View Post
    ... And also it must be cold and in at most fairly small condensed formations, otherwise it would already have been detected.
    Right. If it is a gas, we'd detect it. If it is too massive, we'd detect it. If it is solid lumps of Hydrogen under the mass of Pluto (as a rough estimate of the limit), it might be very hard to explain how these things could have formed before the ambient temperature of the universe was above the freezing point of Hydrogen, but it would be undetectable in our local area.
    Forming opinions as we speak

  3. #33
    Quote Originally Posted by TooMany View Post
    To quote from the paper:
    It has long been thought that elliptical galaxies were the result of mergers of spirals. So the merger rate of spirals was assumed to be high enough to be consistent with that hypothesis. Hence, our assumptions about merger rates were based (in part) on that hypothesis. However, if that hypothesis has now been shown to be false, then any merger rate assumptions based on that hypothesis must be discounted.
    As someone who has written papers addressing the merger rate of galaxies, let me rephrase that to more exactly match my reading of the last 20+ years of work on galaxy history:

    "It has long been noted that some elliptical galaxies are almost certainly the result of spiral-spiral mergers, since stages in the process are evident even among nearby galaxies. Estimates of the merger rate based on the incidence and properties of such mergers, and on the change in the fraction of paired galaxies with redshift expected as some pair members merge, are broadly consistent with a large fraction of ellipticals having such an origin. The overall role of a merger origin for ellipticals depends critically on what happened at such high redshifts that extrapolations back from the present galaxy population will not be helpful and in particular mergers making the most luminous galaxies must have taken place between ellipticals because luminous-enough spirals are at best very rare."

  4. #34
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    Quote Originally Posted by ngc3314 View Post
    As someone who has written papers addressing the merger rate of galaxies, let me rephrase that to more exactly match my reading of the last 20+ years of work on galaxy history:

    "It has long been noted that some elliptical galaxies are almost certainly the result of spiral-spiral mergers, since stages in the process are evident even among nearby galaxies. Estimates of the merger rate based on the incidence and properties of such mergers, and on the change in the fraction of paired galaxies with redshift expected as some pair members merge, are broadly consistent with a large fraction of ellipticals having such an origin.
    OK, if they are the result of spiral-spiral mergers, then are the recent findings of a large population of low mass stars (in ellipticals) consistent with that? Is it possible that the merger conditions (collision induced starbursts) result in this bottom heavy distribution while the original populations of the spirals account for a small part of the resulting stars?

    Quote Originally Posted by ngc3314 View Post
    The overall role of a merger origin for ellipticals depends critically on what happened at such high redshifts that extrapolations back from the present galaxy population will not be helpful and in particular mergers making the most luminous galaxies must have taken place between ellipticals because luminous-enough spirals are at best very rare."
    You mean that perhaps most of the mergers occurred far enough away that we cannot observe them?

    I'm trying to make sense of this from the paper:
    Quote Originally Posted by ngc3314 View Post
    ...there is growing evidence that present-day massive early-type galaxies formed most of their stars in more intense starbursts and at higher redshift than spiral galaxies.
    Are they perhaps saying that the spirals merged to form ellipticals before most spiral's stars had formed?

    I'd like to read your papers about mergers so I can better understand what's going on.

  5. #35
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    Quote Originally Posted by antoniseb View Post
    Right. If it is a gas, we'd detect it. If it is too massive, we'd detect it. If it is solid lumps of Hydrogen under the mass of Pluto (as a rough estimate of the limit), it might be very hard to explain how these things could have formed before the ambient temperature of the universe was above the freezing point of Hydrogen, but it would be undetectable in our local area.
    Has anyone used or proposed to use microlensing to detect the cold bodies that exist in the Oort cloud. Perhaps they are too close to us for the technique to work?

  6. #36
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    Quote Originally Posted by TooMany View Post
    I'd like to read your papers about mergers so I can better understand what's going on.

    Go to ADS

    http://adsabs.harvard.edu/abstract_service.html

    and look it up. I just did, and was given
    this list of papers

    Many of them have preprint versions which you can read freely.

    Have fun!

  7. #37
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    Quote Originally Posted by TooMany View Post
    Has anyone used or proposed to use microlensing to detect the cold bodies that exist in the Oort cloud. Perhaps they are too close to us for the technique to work?
    Proposed it? Probably not. I've done some back-of-the-envelope calculations for several ways to attempt to detect them, including occultation, and lensing, and radar or light echo... and all are way outside our ability to detect at the moment. Occultation is the closest one to feasible. In it you'd need to watch millions of background stars trying to observe drops in brightness lasting tens to hundreds of milliseconds. This would require a huge collecting surface to get enough light for the photon count per star to be fast enough to register the event... and also a different kind of detector that doesn't just bin data over long collection cycles... essentially taking 100 frames per second.

    On the plus side such an observation effort would probably also turn up lots of other new science as well... details on varying stellar brightness, and what it implies. On the down side, at the rate we're increasing telescope size and detector efficiency, we're probably a century away from being able to do this.
    Forming opinions as we speak

  8. #38
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    Quote Originally Posted by TooMany View Post
    Has anyone used or proposed to use microlensing to detect the cold bodies that exist in the Oort cloud. Perhaps they are too close to us for the technique to work?
    As antoniseb said, such a project would have essentially zero chance of success with today's technology (unless the budget - both time and money - were truly astronomical ).

    However, there is an occultation project already underway, for KBOs: TAOS.

  9. #39
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    Quote Originally Posted by Nereid View Post
    As antoniseb said, such a project would have essentially zero chance of success with today's technology (unless the budget - both time and money - were truly astronomical ).

    However, there is an occultation project already underway, for KBOs: TAOS.
    Too bad. I suppose objects on the order of 1km in the Oort cloud are too small in angular size for such detection?

    Apparently they found nothing so far and have concluded some upper limit for objects >~1km. Interesting that the HST happened to spot a 1km KBO and at an ecliptic altitude of 14 degrees which is higher than the 5 degrees of the TAOS search (90% of the search).

    It wasn't really clear to me whether these finding are in conflict with theories about KBO's as a source of some comets.

  10. #40
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    Quote Originally Posted by Nereid View Post
    Let's have a show of hands: who, among the BAUTians who have posted in this thread, have read "this paper by Cappellari et al." (not just the popsci pieces)?
    I have.

    Quote Originally Posted by Nereid View Post
    And among those who read it, who would claim to understand it?
    I don´t. Not all of it, anyway. I understand (I think) they use simulations to determine the IMF for different sized elliptical galaxies, and conclude that not all galaxies form the exact same way. What I do not understand is the work they do with the IMF. Heck, I can barely understand what sort of beast something like an `IMF´ must be. I sort of understand (I think) what the different types of IMF are like. And I think I understand broadly what the conclusions of the paper are (and I don't see it saying or suggesting that no elliptical can have spirals merging).

    It's not an easy paper to read, and I did not try to follow up on the references.
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  11. #41
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    Quote Originally Posted by slang View Post
    ..and I don't see it saying or suggesting that no elliptical can have spirals merging.
    You're right, it doesn't say that but I think it suggests that most mergers would have to occur prior to the formation of most stars in the spirals.

    Would anyone care to take a shot at interpreting the meaning of these statements in their conclusions?
    The results presented pose an interesting challenge to galaxy formation models, which will have to explain how stars ‘know’ what kind of galaxy they will end up inside.
    ...
    Although galaxies merge hierarchically, there is growing evidence that present-day massive early-type galaxies formed most of their stars in more intense starbursts and at higher redshift than spiral galaxies.
    As I understand it, their main conclusion is the star populations of these galaxies are quite bottom heavy (more small starts than in spirals) and that their masses have been underestimated. They seem to have concluded that this is true regardless of assumptions about the form of dark matter halo.

    I was hoping that ngc3314 would shed some light on the relationship to mergers.

  12. #42
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    Quote Originally Posted by TooMany View Post
    You're right, it doesn't say that but I think it suggests that most mergers would have to occur prior to the formation of most stars in the spirals.

    Would anyone care to take a shot at interpreting the meaning of these statements in their conclusions?
    I will try.. but as my background is computer stuff, not astronomy, I welcome any corrections and/or additions from the pros! This is almost rocket science!

    The results presented pose an interesting challenge to galaxy formation models,
    I don't know enough about galaxy formation models to comment on this. Generally I see people who know about this say that galaxy formation is generally not well understood. This paper concludes that there can´t be one simple start situation to explain the evolution of the different types (or sizes) of early-type galaxies. As, AFAIK, there is no consensus on such a simple model anyway, there is no huge impact on this branch of astronomy.

    which will have to explain how stars ‘know’ what kind of galaxy they will end up inside.
    I think the "how stars ‘know’ [...]" remark is awkward, and don't quite understand it.

    Although galaxies merge hierarchically, there is growing evidence that present-day massive early-type galaxies formed most of their stars in more intense starbursts and at higher redshift than spiral galaxies.
    So most stars in massive early-type galaxies are older than (most?) current spirals we see... which might mean that this star formation happened in ellipticals as they intrinsically formed, and/or most spirals that could contribute to the ellipticals have already done so.
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  13. #43
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    Nereid wrote (back in post #24)

    Other than molecular hydrogen*, it's quite difficult to come up with hypotheses for such large masses of undetected H and He (hypotheses which are consistent with all relevant observational results); <EDIT>

    * and, perhaps, ~km to 10^3 km balls of solid hydrogen

    You are a secret GHD supporter

  14. #44
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    Quote Originally Posted by kzb View Post
    Nereid wrote (back in post #24)

    Other than molecular hydrogen*, it's quite difficult to come up with hypotheses for such large masses of undetected H and He (hypotheses which are consistent with all relevant observational results); <EDIT>

    * and, perhaps, ~km to 10^3 km balls of solid hydrogen

    You are a secret GHD supporter
    GHD? Do you mean GHD (Garzo, Hrenya, and Dufty) granular kinetic theory?

    What is striking to me is that we assume that only the things we can detect exist. We know about stars because they emit light. We know about gas from absorption and emission lines. We know about dust because the particles are small enough and numerous enough to absorb UV and visible and emit significant IR. Perhaps we know or think we know from MACHO surveys that there is nothing between Jupiter size hunks of matter and brown dwarfs. That leaves a range of sizes from 10^-5m to 10^7m (12 orders of magnitude in size) that are invisible objects, if they exist. Moreover cold molecular hydrogen gas is itself close to invisible.

    Time will tell I guess, but I don't know how we can detect such things. Non-baryonic matter has the same problem, it just that we don't even know whether there is such a thing.

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    TooMany wote:
    GHD? Do you mean GHD (Garzo, Hrenya, and Dufty) granular kinetic theory?

    I PM'd you a little while back. Please check if it got through OK. All will become clear if you read that.

    What is striking to me is that we assume that only the things we can detect exist.

    The whole thing IS a bit of a headache. As we were discussing on another thread, the mass budget of our galaxy disk appears to be pretty complete, at least in our locality. There does not seem to be room for much more matter, whether baryonic or not.

    You probably WILL find 4% more matter, you MAY find 40%, but we need 400%. To achieve this, you have to think of some pretty unlikely hiding places.

  16. #46
    Quote Originally Posted by TooMany View Post
    What is striking to me is that we assume that only the things we can detect exist. We know about stars because they emit light. We know about gas from absorption and emission lines. We know about dust because the particles are small enough and numerous enough to absorb UV and visible and emit significant IR. Perhaps we know or think we know from MACHO surveys that there is nothing between Jupiter size hunks of matter and brown dwarfs. That leaves a range of sizes from 10^-5m to 10^7m (12 orders of magnitude in size) that are invisible objects, if they exist. Moreover cold molecular hydrogen gas is itself close to invisible.
    And we come back to Nereid's attempt on another thread to get you to calculate the required metallicities of the gas that such objects would have formed from, and how that squares with our understanding of the metallicity and radiation history of the Galaxy. I think you'll find that proposing enough such objects to fill in the "missing mass" results in many more problems than it might solve.

    Plus, there's the Baryon Acoustic Peak in the matter distribution, the precise temperature and polarization of the CMB and the shape of its power spectrum, the history of structure formation from z~10 to z~0, etc. All of which are, independently and together, inconsistent with a baryon dominated universe.

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    Quote Originally Posted by parejkoj View Post
    Plus, there's the Baryon Acoustic Peak in the matter distribution, the precise temperature and polarization of the CMB and the shape of its power spectrum, the history of structure formation from z~10 to z~0, etc. All of which are, independently and together, inconsistent with a baryon dominated universe.
    Why do we always have to deduce what's out there from some theory about the creation of the Universe? Forget that for a while and let's ask what can we know directly about baryonic matter without these highly theoretical conclusions. I might point out that LCDM is running into serious problems explaining what's right close by to study. Given that, why should we be so compelled by LCDM arguments?

  18. #48
    Quote Originally Posted by TooMany View Post
    Why do we always have to deduce what's out there from some theory about the creation of the Universe? Forget that for a while and let's ask what can we know directly about baryonic matter without these highly theoretical conclusions.
    We don't "have to", but any alternate explanation is going to have to deal with all of the above (and more). And the list I gave was not a theoretical list, but rather a list of observations that, at present, only LCDM can coherently explain.

    Quote Originally Posted by TooMany View Post
    I might point out that LCDM is running into serious problems explaining what's right close by to study.
    e.g.?

  19. #49
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    Quote Originally Posted by parejkoj View Post
    TooMany: "I might point out that LCDM is running into serious problems explaining what's right close by to study."

    e.g.?
    Nearby:

    Baryonic Tully-Fisher relation. Disk/halo conspiracy.
    Lack of large numbers of dwarf galaxies.
    Lack of cuspy halos predicted by the collisionless DM particles.
    Dwarf galaxies with ultra-high percentages of DM, but following BTF.
    Galaxies with no CDM.
    Supposed stripping of CDM in dwarf galaxy mergers with MW.
    Hierarchical formation of plentiful perfect-looking spiral galaxies.
    Absolutely no detection of putative CDM particles.
    Absence of expected CDM in our neighborhood of the Galaxy.
    Lithium abundance problem.

    And at broader scales:

    Very large scale structures.
    Cold spot in the CMB.
    Incredibly massive, bright and compact galaxies at high z.
    Train Wreck cluster.
    Galaxy size evolution proportional to 1/(1+z).
    Intercluster speeds ~1% c.
    Vast flows.
    Axis of evil.
    Galaxies found at z~10.
    Clusters at z~8.
    Re-ionization epoch, where?
    Evidence of little change in metallicity with z.
    LCDM requires multiple assumptions of new physics - CDM, inflation, dark energy.

    There are plenty of papers out there pointing out that some of the more local observations rule out the LCDM scenario anywhere from sigma 2 to 4.

    Never mind that, it's the best theory we have and we're sticking with it! We really need to think outside of this box and fortunately a lot of people are.

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    Cold spot in the CMB.
    You know that was a processing artefact, right? Pointed that out in one of the other threads on this topic.

  21. #51
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    Quote Originally Posted by Shaula View Post
    You know that was a processing artefact, right? Pointed that out in one of the other threads on this topic.
    No I didn't. Do you mind citing something. Last I heard was 1.8% chance of being a random coincidence.

    Thanks.

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    This paper shows how the spot is only found using a small class of window functions. When you use other, equally valid, windows it becomes statistically insignificant. It is a common issue in image processing - usually it is a sensor or data cleaning artefact being brought out by a basis function related to it. I am not sure they have traced its provenance, but it is still not a significant feature.

  23. #53
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    Quote Originally Posted by Shaula View Post
    This paper shows how the spot is only found using a small class of window functions. When you use other, equally valid, windows it becomes statistically insignificant. It is a common issue in image processing - usually it is a sensor or data cleaning artefact being brought out by a basis function related to it. I am not sure they have traced its provenance, but it is still not a significant feature.
    I can't give you a citation off hand (maybe this), but I have read some papers that specifically acknowledge that it does not show up in certain types of analysis, but it does in wavelet analysis including Spherical Mexican Hat Wavelets and those papers argued that this analysis is significant and capable of detecting features not apparently in others.

    Apparently one man's evidence is another's coincidence.

    I'll give you this, it needs more study, but it should not be swept under the rug. There are many who take it seriously. Including those in the LCDM camp who have come up with a new thing called "cosmic texture" to explain it. A lot of what you see in papers can reflect human nature more than reality. People committed to LCDM want to make any problem go away and write papers trying to do that and vice versa.

    It will be interesting to see if the Planck data can resolve the issue (or maybe just continue the controversy).
    Last edited by TooMany; 2012-May-10 at 09:48 PM. Reason: Add citation

  24. #54
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    Quote Originally Posted by TooMany View Post
    ...
    Never mind that, it's the best theory we have and we're sticking with it! We really need to think outside of this box and fortunately a lot of people are.
    That is correct - it is the best theory we have and we're sticking with it until a better one comes around!
    Lots of people are thinking outside the box but unfortunately not coming up with models that can explain as much as the LCDM model.

    LCDM includes multiple observations of actual physics - dark matter and dark energy. Inflation is backed up by observations but of course is not possible to observe.

    Much of your list is not about LCDM issues, e.g. lack of large numbers of dwarf galaxies == galaxy formation models, lithium abundance problem is more to do with stellar nucleosynthesis models, etc.

  25. #55
    Quote Originally Posted by TooMany View Post
    Baryonic Tully-Fisher relation. Disk/halo conspiracy.
    I'm not sure this is much of a problem anymore, once more complete models of the physics of ionized and neutral gas are included in the galaxy simulations.

    Quote Originally Posted by TooMany View Post
    Lack of large numbers of dwarf galaxies.
    Mostly solved. LSST is predicted to find a large number of dwarfs that are as-yet undetectable, and more detailed simulations suggest that the number of dwarfs is fewer than initially thought. Also see the possible solution to the cuspy-cores problem.

    Quote Originally Posted by TooMany View Post
    Lack of cuspy halos predicted by the collisionless DM particles.
    See above.

    Quote Originally Posted by TooMany View Post
    Dwarf galaxies with ultra-high percentages of DM, but following BTF.
    citation needed?

    Quote Originally Posted by TooMany View Post
    Galaxies with no CDM.
    citation needed?

    Quote Originally Posted by TooMany View Post
    Supposed stripping of CDM in dwarf galaxy mergers with MW.
    I'm not sure what the problem is here. Tidal stripping of CDM is expected in any gravitational interaction with a more massive system. What am I missing?

    Quote Originally Posted by TooMany View Post
    Hierarchical formation of plentiful perfect-looking spiral galaxies.
    citation needed?

    Quote Originally Posted by TooMany View Post
    Absolutely no detection of putative CDM particles.
    It took about 25 years from Pauli's proposal of the neutrino to their initial direct detection. The possible search space for CDM particles is much larger than the search space for the electron neutrino. It'll be several years before this one starts to worry me.

    Quote Originally Posted by TooMany View Post
    Absence of expected CDM in our neighborhood of the Galaxy.
    citation needed?

    Quote Originally Posted by TooMany View Post
    Lithium abundance problem.
    This one seems to be more a problem of "which of these possible explanations is the correct one." Type lithium abundance into ADS for a wild ride of speculation. Having too many feasible solutions to chose from is not a bad place to be. Especially if you're a theorist.

    As for your other list, I'm going to have to say [citation needed] for pretty much all of them. And when I say that I mean "citation for how this is a serious problem for LCDM", please.

    Quote Originally Posted by TooMany View Post
    Never mind that, it's the best theory we have and we're sticking with it! We really need to think outside of this box and fortunately a lot of people are.
    Well, let me know when someone proposes something that explains just as much as the current concordance cosmology, and we'll all jump aboard. At present, there are no such models. Maybe one of the things on your list really is a serious problem, but so far most such problems have disappeared with either better data, better simulations, or both. If we've exhausted most of the search space for CDM particles in a decade or two, then I'll seriously start to worry. But that still requires an alternate proposal that handles all the same observations.

    As others have said, you really don't seem to know astronomers very well. We're all kinda hoping for something to really crack here, because the repeated confirmations of LCDM are getting rather boring. If the best we can come up with is ~1-sigma deviations in our most precise surveys (e.g. Figure 20 from Anderson et al. 2012), there's not a lot of room left...

  26. #56
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    Quote Originally Posted by TooMany View Post
    People committed to LCDM want to make any problem go away and write papers trying to do that and vice versa.
    And people who dislike LCDM will grasp at any hint of deviation and trumpet it as the end of the theory.

    Having read both papers I think it is safe to say I agree it needs more work. I am highly wary about only being able to use wavelets and needlets on this though. As the paper you gave rightly points out these act similarly to matched filters for gaussian signals embedded in other data. And Matched Filters are notoriously tricky things. Even attempting to assign a significance to the results of one is a bit of an art sometimes. The trouble is that the most common significance tests used have some inbuilt issues relating to data dimensionality that can lead to non-comparable results between two versions of the analysis. Essentially the effective dimensionality of the data, if reduced, can artificially increase the significance of the event. Performing multiscale wavelet analysis builds that problem right into the algorithm used and is not a problem I have ever seen cracked. Or even all that often acknowledged.

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    Quote Originally Posted by Shaula View Post
    And people who dislike LCDM will grasp at any hint of deviation and trumpet it as the end of the theory.
    Perhaps a bit of an exaggeration, but certainly true that they will highlight the contradictions.

    Quote Originally Posted by Shaula View Post
    Having read both papers I think it is safe to say I agree it needs more work. I am highly wary about only being able to use wavelets and needlets on this though. As the paper you gave rightly points out these act similarly to matched filters for gaussian signals embedded in other data. And Matched Filters are notoriously tricky things. Even attempting to assign a significance to the results of one is a bit of an art sometimes. The trouble is that the most common significance tests used have some inbuilt issues relating to data dimensionality that can lead to non-comparable results between two versions of the analysis. Essentially the effective dimensionality of the data, if reduced, can artificially increase the significance of the event. Performing multiscale wavelet analysis builds that problem right into the algorithm used and is not a problem I have ever seen cracked. Or even all that often acknowledged.
    OK, I'm no expert on these methods of analysis, but it is what was chosen and what you see in almost every graphic presentation of the WMAP results. So if it's wrong (an illusion), doesn't throw a lot into question? We see the ubiquitous graphs showing the exact match of the data with baryonic acoustic predictions (neglecting the largest angular scales). Doesn't that data come from the same analysis?

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    Quote Originally Posted by parejkoj View Post
    I'm not sure this is much of a problem anymore, once more complete models of the physics of ionized and neutral gas are included in the galaxy simulations...
    It is true that the mainstream theorists are working hard to find ways to explain away the contradictions. Whether these explanations are sound is a matter of considerable difference of opinion. For every one of these counters, such as above, I can probably find you a paper that tends to discredit it. Take the above one that blames the lack of a cusp on SN's that clear out the center. Well maybe but I wonder how many SN's it takes. I have in fact read another paper that cast serious doubt on the viability of that proposed explanation. And how does such a proposal square with the idea that SN's are a primary creator of stars? Can you really have it both ways? One way to explain one thing and another way to explain another?

    Quote Originally Posted by parejkoj View Post
    Well, let me know when someone proposes something that explains just as much as the current concordance cosmology, and we'll all jump aboard.
    The point is no matter how many things some theory explains, if it is contradiction with observations it may be wrong. My point is more that we should not be jumping aboard theoretic band wagons. Theories are nice things but observations are even better. Because this theory is taken as proven by much of the community, there is some stubbornness about consideration of alternatives explanations of just about any observation.

    Quote Originally Posted by parejkoj View Post
    At present, there are no such models. Maybe one of the things on your list really is a serious problem, but so far most such problems have disappeared with either better data, better simulations, or both. If we've exhausted most of the search space for CDM particles in a decade or two, then I'll seriously start to worry. But that still requires an alternate proposal that handles all the same observations.
    Not everyone feels that the problems will disappear or have already been explained away.

    We've already been looking for CDM for about 30 years. Recent sensitive experiments have been done with null results. Nothing too encouraging has come from LHC yet. There are people with alternative ideas that seem reasonable but they get next to no attention at all. Can't we make some progress in understanding what's around us without having to start with some grand theory of how the cosmos was created? You know, get a little humble and try to work bottom up toward an understanding rather than driving all investigation from a theory of creation.

    Quote Originally Posted by parejkoj View Post
    As others have said, you really don't seem to know astronomers very well. We're all kinda hoping for something to really crack here, because the repeated confirmations of LCDM are getting rather boring. If the best we can come up with is ~1-sigma deviations in our most precise surveys (e.g. Figure 20 from Anderson et al. 2012), there's not a lot of room left...
    Well, I see it differently. I see that the theory is running into problems and people are scrambling to explain them away.

    Tell me something, besides a rough match with nucleosynthesis theory, what has the theory literally predicted that has been found to be true? I would claim that it has not really been predictive, it has simply been continually changed to adjust it to new findings. So is it really a theory in the sense of GR for example? I don't think it's anything like that. It's a mass of parameters and new physics (unbound by specific properties and behaviors) that is endlessly tweaked to match observations. Those matches are then announced as further evidence that the theory is correct and even called predictions. Indeed that does get boring.

  29. #59
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    Quote Originally Posted by TooMany View Post
    Perhaps a bit of an exaggeration, but certainly true that they will highlight the contradictions.
    And "People committed to LCDM want to make any problem go away and write papers trying to do that and vice versa." is not? Give me a break.

    Quote Originally Posted by TooMany View Post
    OK, I'm no expert on these methods of analysis, but it is what was chosen and what you see in almost every graphic presentation of the WMAP results. So if it's wrong (an illusion), doesn't throw a lot into question? We see the ubiquitous graphs showing the exact match of the data with baryonic acoustic predictions (neglecting the largest angular scales). Doesn't that data come from the same analysis?
    No, it does not. The BAO work relies on analysis of the Fourier transforms of the data, something which requires a windowing function in order to avoid the dreaded Gibbs wiggles but which is far more analytically tractable than matched filter and similar approaches. I have been involved in doing and writing algorithms to do this kind of analysis for more than ten years - I know you dismiss me as a hopelessly close minded LCDM fanatic but ignoring the context I can safely and impartially say that these are not the same techniques at all.

  30. #60
    I may respond to your other comments later, but I just wanted to take this one on right now.

    Quote Originally Posted by TooMany View Post
    Tell me something, besides a rough match with nucleosynthesis theory, what has the theory literally predicted that has been found to be true?
    The baryon acoustic feature in the matter correlation function/power spectrum. Not only was this a direct prediction of LCDM before its first detection by SDSS in 2005, but there are no other cosmological theories that produce this feature. MOND doesn't do it. TeVeS doesn't do it. Actually, neither of those is even close.

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