Fermi and dark matter

[Michael Mozina]

You're still sidestepping the key issue Ben. There is a "known source" of high energy gamma rays, and it has nothing whatsoever to do with exotic or hypothetical forms of matter.

To explain gamma rays only requires "electricity' and "normal matter". Supernovas are also known to produce high energy shock waves. Any theory that relies upon multiple "leaps of faith" cannot be considered to be "on par" with a theory that is based upon pure empirical physics and occurs "naturally" right here on Earth and inside our solar system.

The claim "electricity did it" is empirically justified. The statement 'dark matter did it" is not. Even if we simply make qualification as important as quantification, your theory about how DM did it isn't going to survive a simple Occum's razor argument.

 

[ben m]

You're still sidestepping the key issue Ben. There is a "known source" of high energy gamma rays, and it has nothing whatsoever to do with exotic or hypothetical forms of matter.

Your argument is not "there is no dark matter", nor "dark matter cannot emit gamma rays". Your argument is "there are so many other gamma rays out there that Fermi cannot possibly isolate the dark matter ones, if any".

It's a question of backgrounds, then. Yes: the Fermi team knows that there are backgrounds. They are not morons. High-resolution gamma ray astronomy is nearly 20 years old and we know darn well to expect gamma rays from supernova remnants, compact stars, pulsars, quasars, CR bombardment of the Moon, and other sources including the Sun. The Fermi team is NOT, as you would know if you read their papers, saying, "Hey, gamma rays---must be dark matter!". Rather, they are trying to separate known sources from unknown sources, point sources from diffuse sources, and to understand the energy spectrum (curiously absent from your vocabulary, MM) of each such source.

To illustrate how this is done right: before Fermi was launched many people speculated that the best place to look for dark matter gammas would be the Galactic center. Later, it was determined that the Galactic center was the source of a huge number of GeV gammas from mundane sources (like cosmic rays) which made some WIMP searches lose sensitivity. Nobody misinterpreted those GeV gamma rays as dark matter, MM. Why not? Because we are not morons.

Now, your claim seems to be that "if Fermi sees any excess gammas at all, they are probably explained by the Electric Sun hypothesis" or whatever you call it these days. Two comments:

a) Wow, that's some hypothesis. Could the electric sun hypothesis explain a 300 GeV monoenergetic gamma line? A broad energy peak between 100 and 150 GeV coming from subdwarf satellite galaxies, but not from nearby stars? If it can explain any observations whatsoever, MM, it's not a science hypothesis, it's a magic leprechaun.

b) Your electric sun hypothesis has failed many, many times over already. Were you hoping no one will notice? "Hmm, this Mozina person is talking about the Sun as though he's a recognized expert on solar electromagnetism! If he says there's a previously-unrecognized gamma ray background he must be right!" No, MM. There are a great many people who are qualified to discuss Fermi's normal-astrophysics backgrounds, sources, and uncertainties therein. You are not one of them, and mentioning Electric Sun (or whatever you call it) crackpottery just reminds me of that.

Imagine getting a press release about, say, General Relativity. "The Gravity Probe B experiment has misinterpreted its data; rather than seeing frame dragging they have seen the Steorn Free Energy Effect." Or about, I dunno, nutrition. "Omega-3 fatty acids, contrary to mainstream science, are not good for you. See our web site for details. Therefore we insist that Omega-3s be removed from vaccines immediately to stem the autism epidemic."

 

[ben m]

To explain gamma rays only requires "electricity' and "normal matter".

You could, similarly inaccurately, say the same thing about radio waves, optical photons, and x-rays. "Why are astronomers talking about quasars, quasar jets, accretion disks, supernovae, neutron star crusts, synchrotron radiation, type-II Fermi acceleration, and so on? It's all just electricity and normal matter."

Different sources have different spectra. That's it in a nutshell. The SUSY gamma ray spectrum is expected not look like synchrotron radiation, nor like pulsars, nor like proton-proton collisions, etc.

 

[Reality Check]

You're still sidestepping the key issue Ben. There is a "known source" of high energy gamma rays, and it has nothing whatsoever to do with exotic or hypothetical forms of matter.

You are still ignnorant of the key issue Michael. There are known sources of high energy gamma rays detectable by Fermi and they have nothing whatsoever to do with exotic or hypothetical forms of matter. They are subtracted from the raw Fermi data to give the unknown sources of gamma rays. These unknown sources include dark matter candidates that produce gamma rays.

To explain gamma rays only requires "electricity' and "normal matter".

To explain the known gamma rays only requires electromagnetism and normal matter.

The claim "electricity did it" is empirically justified. The statement 'dark matter did it" is not. Even if we simply make qualification as important as quantification, your theory about how DM did it isn't going to survive a simple Occum's razor argument.

The claim that electromagnetism produced the excess gamma rays is empirically justified.
The claim that dark matter produced the excess gamma rays is empirically justified.

Occam's razor could actually be in faviour of DM, e.g
Hypothesis 1: An previously unknown astrophysical mechanism produces the gamma rays excess using black holes and electromagnetic fields (2 entities).
Hypothesis 2: Dark matter of a specific type produces the gamma ray excess (one entity)
The hypothesis postulating the fewer entities and more likely to be correct is DM.

 

[ben m]

The other bit of Occam's Razor here: remember, MM is supposed to be allowing for the sake of argument that the general hypothesis "New-physics particles make up the gravitationally-known missing matter".

MM seems to be claiming based on no knowledge whatsoever that it is inconcievable for those new particles to have a gamma ray annihilation channel. This is strange: the entire rest of the Particle Zoo has a gamma ray annihilation channel. Quark-antiquark and lepton-antilepton can all annihilate to gammas. Neutrino-antineutrino can annihilate to gammas via, for example, vv->WW and W final states containing pions. Heck, gluon-gluon can annihilate to gammas via any number of channels, as can WW and ZZ and Higgs Higgs (as much as it pains me to draw that diagram).

Within the hypothesis that WIMPs exist, the existence of an annihilation channel containing gammas is the default in general. If the WIMP hypothesis is specifically SUSY or KK, it's unavoidable.

But Michael Mozina, with his nonexistent training in particle-physics phenomenology, has declared this to be an extra assumption. Sorry, MM, you are incorrect. It is you who are making an extra assumption---you are going out of your way to turn off the obvious photon annihilation channels, and you are doing so based on mistaken and ill-informed intuition.

Of course there's nothing wrong with such extra assumptions; it just generates a different hypothesis. Some hidden-sector dark matter hypotheses, for example, have this no-photons property.

Under the MM "WIMPs exist but don't annihilate to any photon final state" hypothesis, we can predict that Fermi will see normal astrophysical sources and no WIMP-like excess. See how easy that was? That's how science works.

 

[DSo]

Nobody misinterpreted those GeV gamma rays as dark matter, MM. Why not? Because we are not morons.

Well said.

Ben/RC- I bet you are unable to get the last word in on the subject.

 

[ben m]

Apropos of nothing: of course all particle decay-gamma radiation is simply "electricity", if you want to view it that way. All photon-creating processes, including exotic-sounding ones like the Primakoff Process, particle-antiparticle annihilation, SUSY decays and annihilations, etc., come from the standard QED coupling of photons to charge. That coupling is basically the quantized version of Maxwell's Equations. Hence: yes, gamma rays "come from electricity".

I doubt this changes MM's mind on anything.

 

[DazzaD]

Apropos of nothing: of course all particle decay-gamma radiation is simply "electricity", if you want to view it that way. All photon-creating processes, including exotic-sounding ones like the Primakoff Process, particle-antiparticle annihilation, SUSY decays and annihilations, etc., come from the standard QED coupling of photons to charge. That coupling is basically the quantized version of Maxwell's Equations. Hence: yes, gamma rays "come from electricity".

I doubt this changes MM's mind on anything.

I dont wish to do MM a disservice but I wonder if he is even aware of this?

 

[ben m]

I dont wish to do MM a disservice but I wonder if he is even aware of this?

If it's not a component of his electric-sun idea, I'm going to guess "no". Pointing out its derivation from Maxwell's Equations did not change his mind about magnetic reconnection, IIRC.

 

[Reality Check]

Another bit of astronomy that I did not know know about.
Found on the Resonances blog: Fermi says "nothing"...like sure sure?

Astronomers have observed a couple of dozen low intensity satellite galaxies ("subhalos") of the Milky Way. These subhalos have a large mass to light ratio (over 1000 for the darkest) implying a large concentration of dark matter.

Although the resulting gamma-ray flux is expected to be smaller than that from the galactic center, the subhalos with its small visible matter content offer a much cleaner environment to search for a signal.

The Fermi collaboration presented a poster at the Fermi Symposium with four candidates but could not match the observed spectrum with 3 randomly selected dark matter models. They thus conclude that their candidates are not dark matter subhalos. The poster has this interesting section:

Overview of Galactic Dwarfs
• Currently only 25 galactic dwarfs are known, and they have been discovered by optical telescopes. 14 of these are ultra faint [SDSS, 2005, 2007] . There should be many more according to CDM simulations [e.g., Via Lactea II, 2009]. Current theoretical models predict we could observe a factor of ~10 more [Tollerud, et al., 2008].
• The most recently discovered galactic dwarfs have very few stars, e.g., Segue 1 might have 65 stars associated with it [Geha, 2009]. They also have M/L ratios ~>1000 (compared with ~10 for the Milky Way galaxy). Thus they appear to contain dark matter and little else.
• Such dwarf galaxies are good dark matter source candidates for Fermi LAT as any γ-ray emission in the Fermi range would likely come from dark matter annihilation or decay. (Interesting limits from the known dwarfs for some dark matter models are reported at this conference [Farnier, C., et. al., 2009].)
• In this work we are searching for galactic dwarfs that have no counterparts at this time. We are trying to discover new galactic dwarfs via a γ-ray signal that would be a distinctive signature for the nature of dark matter distinguishable from a purely astrophysical source.

 

[Michael Mozina]

Apropos of nothing: of course all particle decay-gamma radiation is simply "electricity", if you want to view it that way. All photon-creating processes, including exotic-sounding ones like the Primakoff Process, particle-antiparticle annihilation, SUSY decays and annihilations, etc., come from the standard QED coupling of photons to charge. That coupling is basically the quantized version of Maxwell's Equations. Hence: yes, gamma rays "come from electricity".

I doubt this changes MM's mind on anything.

The fact that the emission of moving positrons and electrons is a form of "current flow", turning your DM into a regular source of "electricity", is probably the only "attractive" thing about that theory from the perspective of EU theory. The fact this process never shows up in a controlled experiment is what keeps it from "changing my mind", or the mind of any EU theorist that places a high emphasis on empirical physics.

In all of these "dark theories" there must be a point where actual empirical physics supposedly takes over. It's the fact you can't demonstrate that this process does occur "naturally" in any controlled experiment or any event on Earth that makes your theory "weak".

FYI, it's been a crazy week at work, and a really busy (and great) week as a parent, but I will see about catching up with the conversation over the weekend.

http://www.mtshastanews.com/enterta...ar-crossed-lovers-at-Mount-Shasta-High-School

 

[ben m]

In all of these "dark theories" there must be a point where actual empirical physics supposedly takes over. It's the fact you can't demonstrate that this process does occur "naturally" in any controlled experiment or any event on Earth that makes your theory "weak".

Repeating that over and over does not make it more true.

Anyway, the dark matter hypothesis is indeed based on perfectly empirical physics: measurements of velocities of stars and galaxies, which translate straightforwardly to measurements of gravity, which translate straightforwardly to measurements of mass. Measurements of light bending which translate ditto to mass measurements and orbit measurements. That's all as empirical as anything else in astronomy. Are you suggesting that astronomers have the gravity measurements wrong?

Then there's "figuring out what this mass is", which is a matter of plasmas and atomic absorption spectra and whatnot. Are you suggesting that astronomers have star-counting, the Lyman-Alpha forest, and hot hydrogen spectroscopy wrong? Are you suggesting that "UV light above 10 eV is absorbed by hydrogen" is not empirical? Are you suggesting that microlensing (basically a long-distance version of Eddington's 1918 observation) is not empirical?

 

[DazzaD]

The fact that the emission of moving positrons and electrons is a form of "current flow", turning your DM into a regular source of "electricity", is probably the only "attractive" thing about that theory from the perspective of EU theory. The fact this process never shows up in a controlled experiment is what keeps it from "changing my mind", or the mind of any EU theorist that places a high emphasis on empirical physics.

In all of these "dark theories" there must be a point where actual empirical physics supposedly takes over. It's the fact you can't demonstrate that this process does occur "naturally" in any controlled experiment or any event on Earth that makes your theory "weak".

This constant statement about having to be able to repeat the experiment on Earth is a misnomer.

Please explain to me, that for my version of how fusion works in say the Sun, you are going to demonstrate that physics, directly, in an experiment, here on Earth.

Because you cannot.

 

[Michael Mozina]

This constant statement about having to be able to repeat the experiment on Earth is a misnomer.

It may be a "misnomer" from your perspective perhaps, but there in fact a distinct difference between a process that shows up in a controlled experiment, and one that does not.

Please explain to me, that for my version of how fusion works in say the Sun, you are going to demonstrate that physics, directly, in an experiment, here on Earth.

Because you cannot.

You're right, I cannot do that. What I can do is verify that fusion actually occurs here on Earth and I can isolate the physical conditions where it can occur. I can verify the fusion process to be an 'energy source" under specific conditions.

Whether fusion is the primary power source of a sun is a completely separate question, but the fact that fusion "could be" a power source of a sun is easily confirmed. It's therefore completely rational of you to point at a distant object and claim "fusion did it". Right or wrong, your belief and your claim is based upon an empirically demonstrated process that is known to occur here on Earth.

Like the "fusion releases energy" claim, if you decide to point at the sky and claim "invisible stuff did it", I will also expect you to demonstrate that 'invisible stuff' exists and has the effect you claim it has. In this scenario of linking gamma rays to DM, there are at least three claims that cannot be empirically verified. I cannot verify that any exotic forms of matter exist in an experiment, including but not limited to theoretical SUSY particles. I cannot verify that said particle is "long lived" enough to remain stable for billion of years. I cannot verify that it emits "gamma rays" during annihilation. There are at least three separate claims in relationship to that Fermi data that lack empirical support.

That is quite different in the case of fusion. I can't verify the conditions in the core or a hydrogen sun are capable of producing the fusion process, but I can verify that the fusion process is a known power source. In the case of fusion, you're simply "scaling" a known process to something larger than can be created here in a lab, and the only unverified claim is that the core produces the conditions necessary to drive this process on an ongoing basis. Things like neutrino measurements can/should be used to validate such a claim.

All theories will eventually need to be "scaled to size" to include conditions that cannot be duplicated on Earth. That's not my complaint. I don't mind you scaling a known and demonstrated process like fusion to size. I don't mind you claiming that the conditions of the core of sun are capable of sustaining the process. I may eventually take exception to that concept due to some other observation, but the basic concept of fusion as an energy source can and has been verified. Compare and contrast that with the utter lack of empirical support that "dark matter" emits gamma rays. In that case it's not just a "scaling problem". You can't even demonstrate that DM exists at all, let alone that it lasts more than a millisecond or that it emits anything.

 

[Tubbythin]

It may be a "misnomer" from your perspective perhaps, but there in fact a distinct difference between a process that shows up in a controlled experiment, and one that does not.

No there isn't! The laws of physics are completely independent of whether you or I or anyone else think an experiment is controlled or not. Our ability to isolate a specific phenomenon may depend on how well we understand the observations which may depend on the level of control we have over what we choose to observe. But that does not mean lab based experiments are always inherently better than non-lab based experiments. You only need to look at Kepler's laws to see that.

 

[Michael Mozina]

You are still ignnorant of the key issue Michael.

No, I am not ignorant of the fact that you cannot demonstrate the claim that "dark matter emits gamma rays". That's the key issue.

There are known sources of high energy gamma rays detectable by Fermi and they have nothing whatsoever to do with exotic or hypothetical forms of matter. They are subtracted from the raw Fermi data to give the unknown sources of gamma rays.

Okey, Dokey.

These unknown sources include dark matter candidates that produce gamma rays.

Those "unknown sources" have nothing to do with DM because you never showed an empirical link between DM and gamma rays. Hoy.

Occam's razor could actually be in faviour of DM,

Oh that's rich. I gotta see you justify that statement.....

e.g
Hypothesis 1: An previously unknown astrophysical mechanism produces the gamma rays excess using black holes and electromagnetic fields (2 entities).
Hypothesis 2: Dark matter of a specific type produces the gamma ray excess (one entity)
The hypothesis postulating the fewer entities and more likely to be correct is DM.

Er, stars and EM fields are "known and demonstrated" entities RC. They are known to be directly involved with Fermi observations as well.

So let me get this straight.....

It's all one big coincidence in your opinion that the binary star population of the core just so happens to match this excess gamma ray distribution?

Whereas binary star populations can be verified, and suns and discharges can be directly linked to Fermi data, your DM thingy doesn't do squat here inside this solar system.

In any "DM caused gamma rays" claim, you're necessarily adding a variable that is utterly unnecessary and that is completely and utterly unrelated to the evidence. Whereas stars do exist, and discharges do emit gamma rays, and binary star formations are common, DM doesn't do squat. In any Occum's razor argument you loose. You invented an unnecessary entity, and stuffed it into the discussion in a purely ad hoc manner. There isn't even an empirical link between gamma rays and DM to begin with. Even if you just introduced a known source that was "unnecessary", you might lose an Occum's razor argument, but when you stuff the argument with a "pure act of faith" it's not even a contest.

 

[Michael Mozina]

No there isn't! The laws of physics are completely independent of whether you or I or anyone else think an experiment is controlled or not.

An "experiment' without any control mechanism is called an "observation". Observations do not allow us to easily distinguish cause/effect relationships, where as real "experiments" with actual control mechanisms make it easy to isolate cause/effect relationships.

Our ability to isolate a specific phenomenon may depend on how well we understand the observations which may depend on the level of control we have over what we choose to observe. But that does not mean lab based experiments are always inherently better than non-lab based experiments. You only need to look at Kepler's laws to see that.

Could you define the "better" as it relates to determining "cause/effect" relationships? How can you tell from a distant observation of gamma rays, what that source of gamma rays might be?

 

[Tubbythin]

An "experiment' without any control mechanism is called an "observation".

You can call it a hippopotamus if you want. It doesn't stop the fact that the laws of physics are independent of how good we think we're doing things.

Observations do not allow us to easily distinguish cause/effect relationships, where as real "experiments" with actual control mechanisms make it easy to isolate cause/effect relationships.

Of course they do. We observe a white dwarf accreting matter from its binary companion. Subsequently we observe the supernova explosion of the white dwarf. Now, what do we conclude from our observations?
a) That the matter being accreted on to to the WD surface was the cause of the supernova explosion.
or
b) That the supernova explosion caused a message to be sent back in time to the white dwarf and told it to start accreting matter from its companion?

Could you define the "better" as it relates to determining "cause/effect" relationships? How can you tell from a distant observation of gamma rays, what that source of gamma rays might be?

By "better" I just mean more likely to give you the correct results. I thinks its obvious that in most cases for astrophysical phenomena its "better" to look at astrophysical entities than stuff that you think might vaguely approximate an astrophysical entity in a lab.

 

[Michael Mozina]

You could, similarly inaccurately, say the same thing about radio waves, optical photons, and x-rays. "Why are astronomers talking about quasars, quasar jets, accretion disks, supernovae, neutron star crusts, synchrotron radiation, type-II Fermi acceleration, and so on? It's all just electricity and normal matter."

Well, for one thing, your industry refuses to acknowledge the role of electricity in space, so you require a host of exotic terms. Is it really my fault that you call a stream of fast moving charged particles (aka "current flow") a "quasar jet"?

Why do you folks make up terms like "magnetic reconnection"? The only reason you do any of that stuff is to avoid EU theory at all costs. The moment you let electricity into astronomy classroom, a lot of your naming conventions will go bye-bye, starting with the term "magnetic reconnection".

Different sources have different spectra.

Different discharge processes produce different spectra too.

That's it in a nutshell. The SUSY gamma ray spectrum is expected not look like synchrotron radiation, nor like pulsars, nor like proton-proton collisions, etc.

How would you even know what these processes should "look like"? You haven't even included the EM field into the astronomy discussion or classroom so you really don't even have a clue what these things "should" do in the first place IMO.

SUSY theory is just *ONE* of several different *NON STANDARD* particle physics theories that all lack empirical support. That's why it is still a "non standard" theory in fact. If and when LHC finds something "exotic" let me know. The first thing I'll ask you is "how long did it last", followed by "did it emit anything"? Do you really think they'll find something, and do you really think it's going to support your argument? Even if it emitted gamma rays and disappeared immediately, the longevity issue would still remain. Even if it could be shown that some exotic form of matter did form, but we couldn't "see it", you'd have the gamma ray claim/issue still hanging over your head. About the only way that LHC could help you case is to show them being created in massive quantities and only emitting gamma rays very infrequently. What are the odds that's going to happen in your lifetime in your opinion?

The problem here is simple Ben. You've never provided an empirical connection between the observation in question (gamma rays) and the entity and the process that you claim is responsible for them. You skipped a huge empirical step in there and you simply expect me to "have faith" in these things with you. You expect me to accept on faith that that WIMPS exist, they live more than millisecond, and accept on faith that they create gamma rays too. It's a faith based "trilogy" of unsupported claims.

"Electricity did it" is a legitimate empirical scientific "explanation" (right or wrong) for an "observation" of gamma rays. "Invisible stuff did it" is not. There is no empirical connection between DM and gamma rays. That's a pure ad hoc assertion based on your "faith" in SUSY theory evidently.

 

[Michael Mozina]

You can call it a hippopotamus if you want. It doesn't stop the fact that the laws of physics are independent of how good we think we're doing things.

You're still intentionally blurring the distinction between a true "experiment" (with real control mechanisms) and an "observation" IMO. That is dangerous IMO.

Of course they do.

Well, sometimes the cause can be obvious. If I see a bolt of lightning in the distance and hear the sound of thunder a few seconds later, I might conclude they are related.

Sometime it's not so obvious, like the "cause" of those gamma rays.

By "better" I just mean more likely to give you the correct results.

I would/could agree to that concept if you were not also including a series of "hypothetical" arguments in the discussion. The binary star explanation seems "more than adequate" to explain these excess gamma rays. Why would any theory that requires hypothetical entities be "better than" such a simple explanation?

I thinks its obvious that in most cases for astrophysical phenomena its "better" to look at astrophysical entities than stuff that you think might vaguely approximate an astrophysical entity in a lab.

IMO what the industry is doing is intentionally avoiding including any EU oriented idea into the discussion, and emphasizing any solution based upon "dark" stuff. There's no empirical link between gamma rays and DM. There is no empirical link between DM and anything. How then could such a theory be "better than" the one I provided you with earlier? I can see our own sun emits gamma rays that Fermi is able to observe. I can see it traverse the Fermi images in fact. Fermi also observes these gamma rays from Earth. I see absolutely no need to invent additional variables to explain gamma rays in whatever quantities we might need. Since there is no link between "invisible Michaels" and gamma rays, no "theory" based upon mythical Michael particles can be "better than" an empirically oriented explanation, even if my math happens to work out better.