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Thread: Hubble Discovers Vast New Reservoir of Gas Near the Milky Way

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    Hubble Discovers Vast New Reservoir of Gas Near the Milky Way

    Hubble Finds Vast New Reservoir of Gas Near the Milky Way

    by Ken Croswell

    The Milky Way may have found a solution to its gas shortage. Astronomers had calculated that our home galaxy possesses only enough fuel to forge new stars for just a few billion more years. But scientists have now discovered that a long stream of gas falling into the Milky Way is four times as massive as previously thought and could power our galaxy's starmaking career for a long time to come.

    Link: ScienceNOW

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    Quote Originally Posted by Fox
    To their surprise, Fox and his colleagues detected so much absorption of the background ultraviolet light that they concluded the Magellanic Stream must contain far more ionized gas than neutral gas. In The Astrophysical Journal, the team quadruples the estimated amount of gas the Magellanic Clouds have lost.
    It is a little surprising to me that this is such a surprise. We know space is an environment with great ionizing potentials. It is interesting that the search for baryonic matter keeps turning up stuff where we do not expect it; and searches for dark, nonbayronic has erased most of the parameter-space it could occupy.

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    Quote Originally Posted by Jerry View Post
    It is a little surprising to me that this is such a surprise. We know space is an environment with great ionizing potentials. It is interesting that the search for baryonic matter keeps turning up stuff where we do not expect it; and searches for dark, nonbayronic has erased most of the parameter-space it could occupy.
    There is plenty of parameter space left for dark matter. Eliminating possibilities is generally though of a as a good thing in science, rather than as you keep implying a cause for concern with the models. Worth noting that the parameter space left for this baryonic matter to explain things is pretty much zero. It just doesn't work. Something you keep ignoring.

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    Quote Originally Posted by Shaula View Post
    There is plenty of parameter space left for dark matter. Eliminating possibilities is generally though of a as a good thing in science, rather than as you keep implying a cause for concern with the models. Worth noting that the parameter space left for this baryonic matter to explain things is pretty much zero. It just doesn't work. Something you keep ignoring.
    It is ironic that existing physical matter (baryonic dark matter) has been replaced with new physics (non-baryonic dark matter) as the preferred solution to what is now an eighty-year-old problem with gravity. I agree, there does not seem to be enough well understood matter to explain our observations.

    The 'surprising' five-fold increase in the amount of total hydrogen has other implications. Radiation transfer within an ionized gas is complex. Each ionized atom is a minute electric dipole; and every photon passing within a critical radius of an ionized atom will experience radiation transfer effects; polarizing the light and increasing the kinetic energy of the gas. The energy budget for these transfers requires a drop in the transferred photons energy level. Think about this, when you determine the redshift distance of highly-reddened objects-like submm galaxies.

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    Tired light is old hat and not supported by the evidence. Five times more gas in a galactic merger filament is not evidence of five times more gas everywhere.

    Jerry, if you think you have a strong case take it to ATM. Otherwise stop rehashing this stuff at every opportunity you can. It is boring having the same arguments with you over and over.

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    Quote Originally Posted by Jerry View Post
    It is ironic that existing physical matter (baryonic dark matter) has been replaced with new physics (non-baryonic dark matter) as the preferred solution to what is now an eighty-year-old problem with gravity. I agree, there does not seem to be enough well understood matter to explain our observations.
    Actually physical matter still exists, Jerry !
    As you know, dark matter is the observation that there is not enough visible matter in the universe to explain many observations and the best explanation for this is old physics (non-baryonic dark matter) like neutrinos. Changes to gravity (MOND, etc.) just do not work except for galaxies.

    Eighty years ago there was an argument that the observations could be explained by normal visible matter for the simple reason that astronomers did not have instruments that could detect all of the visible matter. Now the problem is that other way around - astronomers have instruments that cover enough of the spectrum that they should detect all of the visible matter but they do not detect enough! The last time I checked it was abut half of the 4% of the universe that should be visible matter has been accounted for.

    Think about what the measured redshifts of galaxies actually are, Jerry, and you will see that there is no effect from this "five-fold increase in the amount of total hydrogen".
    Think about the scattering of photons caused by the interaction with this "five-fold increase in the amount of total hydrogen" and the consequences for highly-reddened objects-like submm galaxies (hint: look at the reasons why tired light theories are considered invalid).

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    I will also point out that there is no "five-fold increase in the amount of total hydrogen", Jerry.
    The title of Hubble finds vast reservoir of gas near the Milky Way is deceptive.
    What Hubble found was that an existing stream of gas from the Large and Small Magellanic Clouds into the Milky Way was 4 times more massive than previously thought (because ionized gas was not detected). It is not applicable to galaxies in general.

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    Quote Originally Posted by Shaula View Post
    Tired light is old hat and not supported by the evidence. Five times more gas in a galactic merger filament is not evidence of five times more gas everywhere.

    Jerry, if you think you have a strong case take it to ATM. Otherwise stop rehashing this stuff at every opportunity you can. It is boring having the same arguments with you over and over.
    Radiation transfer is not voodoo. It is the natural process by which radiant light moves through any transparent medium, regardless of density. Garden variety radiation transfer is ruled-out in many examples of redshift, because the transfer process also leads to scattering of light; especially at the high end of the spectrum. It is the scattering of the light in the high energy spectrum that is the identifying feature of submillimeter galaxies; and radiation transfer equations are used in the modeling of this population. There is a large degree of degeneracy in trying to separate dust scattering from atmospheric-like processes; but the fact that spectral bandwidth features are preserved in submillimeter galaxies indicates that not all of the energy is thermalized - (otherwise, they would be red blobs, not galaxies). At the present time, we do not have enough spectral information on the submillimeter sample to separate dust extinction from Rayleigh scattering.

    See Blain, Submillimeter Galaxies; astro-ph/0202228v2

    Submillimeter galaxies are as a family, the most luminous galaxies ever found (based upon extrapolations of their dusky red emissions); and there is evidence that only 10-15% of this luminosity can be accounted for by star formation activity; and even less to active galactic nuclei. (http://arxiv.org/pdf/0910.2464v1.pdf) So why, (if there is not intense activity traceable to star formation), are they - regardless of morphology - so damn luminous?


    Herschel ⋆-ATLAS: correlations between dust and gas in local submm-selected galaxies http://arxiv.org/pdf/1308.4406v1.pdf

    Probing the Dust Properties of Galaxies at Submillimetre Wavelengths II. Dust-to-gas mass ratio trends with metallicity and the submm excess in dwarf
    galaxies http://arxiv.org/pdf/1104.0827v1.pdf

    The AGN fraction of submm-selected galaxies and contributions to the submm/mm-wave extragalactic background light http://arxiv.org/abs/1002.3618

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    Quote Originally Posted by Reality Check View Post
    I will also point out that there is no "five-fold increase in the amount of total hydrogen", Jerry.
    The title of Hubble finds vast reservoir of gas near the Milky Way is deceptive.
    What Hubble found was that an existing stream of gas from the Large and Small Magellanic Clouds into the Milky Way was 4 times more massive than previously thought (because ionized gas was not detected). It is not applicable to galaxies in general.
    That means that this nearby stream is four to five times more massive; and the jury is out on every other stream detected as molecular Hydrogen. No, it does not mean the total mass of hydrogen is 5x greater; but that was not implied either.

    Ionized gas is not a total game-changer, but there are implications. See http://arxiv.org/pdf/0907.2308.pdf On the abundance of gravitational arcs produced by
    submillimeter galaxies at radio and submm wavelengths
    Last edited by Jerry; 2014-Jul-23 at 11:09 PM.

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    Quote Originally Posted by Jerry View Post
    That means that this nearby stream is four to five times more massive;
    Yes - that is what I wrote: "What Hubble found was that an existing stream of gas from the Large and Small Magellanic Clouds into the Milky Way was 4 times more massive than previously thought"
    This has implications for other gas streams, i.e. there should be more mass in them.
    It could have other implications but not for things that are not gas streams like galaxies and definitely not for gravitational lensing itself. In gravitational lensing you use the lensing to estimate the mass of the gravitational lens (the foreground galaxy). That includes all mass including that of ionized gas.

    On the abundance of gravitational arcs produced by submillimeter galaxies at radio and submm wavelengths ihas
    The adopted typical size of the radio and submm emitting regions of SMGs is based on current radio/CO observations and the FIR-radio correlation
    But we do not know whether discovery of a gas stream outside of a galaxy is more massive than previously expected means that these emission regions in galaxies are affected.

    ETA: I would expect this to be irrelevant as far as the paper is concerned. This is a correlation between the observations of radio and submm emitting regions of SMGs which the discovery has not changed even if there was a gas stream between us and one of these regions. The additional observation is in the UV.
    Last edited by Reality Check; 2014-Jul-24 at 01:50 AM.

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    This is why it becomes relevant:

    Colour matters: the effects of lensing on the positional offsets between optical and submillimetre galaxies in Herschel-ATLAS http://arxiv.org/abs/1407.5994

    Quote Originally Posted by Bourne et al
    We report an unexpected variation in the positional offset distributions between Herschel-ATLAS sub-millimetre (submm) sources and their optical associations, depending on both 250-{\mu}m signal-to-noise ratio and 250/350-{\mu}m colour. We show that redder and brighter submm sources have optical associations with a broader distribution of positional offsets than would be expected if these offsets were due to random positional errors in the source extraction.
    Gravitational lensing would not produce the deep reddening we observe in submm galaxies, but puffballs of undetected ionized gas would; and they would also displace the spectrum. The correlation between redder and brighter optical offsets is an insane juxiposition; unless the distance estimate is skewed by the process.

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    Quote Originally Posted by Jerry View Post
    This is why it becomes relevant:.
    I do not see any relevance, Jerry. This is about positional offsets and has two possible effects:
    The observation can be explained by two possible effects: either red submm sources trace a more clustered population than blue ones, and their positional errors are increased by confusion; or red submm sources are generally at high redshifts and are frequently associated with low-redshift lensing structures which are identified as false counterparts.
    Are you saying that the submm emissions from gas streams somehow shift the positions of submm sources?

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    Quote Originally Posted by Reality Check View Post
    Are you saying that the submm emissions from gas streams somehow shift the positions of submm sources?
    No. The authors state: "we conclude that the effects are most likely to be explained by widespread weak lensing of Herschel-SPIRE sources by foreground structures."

    I think I can make a good argument that the foreground structure causing the weak lensing in many cases may be gas clouds with cold and mostly diffused centers - Maxwellan rather than gravitational lenses. Maxwellian lenses reddened objects and blur spectral lines; and require many times less mass than gravitational lenses. It takes a pretty tricky alignment for a very dense foreground object to lens an object gravitationally without obliterating the object.

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    Quote Originally Posted by Jerry View Post
    No. The authors state: "we conclude that the effects are most likely to be explained by widespread weak lensing of Herschel-SPIRE sources by foreground structures."
    I could make a good argument that gas streams that are a tiny fraction of the mass of a galaxy would have no measurable weak lensing. Mass of the Milky Was gas stream ~ 2 billion solar masses. Mass of the Milky Way, Jerry ?
    The "foreground structures" in the abstract are galaxies, groups or clusters.
    It can also be compounded by gravitational lensing, which magnifies background sources when a foreground galaxy, group or cluster is close to the line of sight...
    This paper is about positional offsets and that weak lensing conclusion is about:
    An alternative hypothesis is that gravitational lensing can also affect the offset distribution. Differential k–corrections in the optical and submm mean that an apparent optical counterpart is likely to be a foreground lens, while the submm survey detects only the lensed image of the background source, which is offset from the lens itself.
    This "tricky alignment" is seen lots of times, Jerry! Herschel-ATLAS was to survey over 250,000 galaxies - not sure what the current status is.
    A link to some literature on "Maxwellian lenses" and how they cause positional offsets (as in weak lensing) would be appreciated.

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    Quote Originally Posted by Reality Check View Post
    I could make a good argument that gas streams that are a tiny fraction of the mass of a galaxy would have no measurable weak lensing. Mass of the Milky Was gas stream ~ 2 billion solar masses. Mass of the Milky Way, Jerry ?
    The "foreground structures" in the abstract are galaxies, groups or clusters.

    This paper is about positional offsets and that weak lensing conclusions...:


    A link to some literature on "Maxwellian lenses" and how they cause positional offsets (as in weak lensing) would be appreciated.
    Weak refractive lensing will clearly create positional offsets when 1) The bandwidths are broadly separated. 2) The lens is not perfect. In the weak lensing caused by a nebulous cloud, one should anticipate positional offsets from Xray or UV wavelengths relative to the longer wavelengths gathered by infrared or visible detectors. Differential wavelength dispersion is only 'unexpected' when the lensing is gravitational.

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    Quote Originally Posted by Jerry View Post
    ...
    I wrote: A link to some literature on "Maxwellian lenses" and how they cause positional offsets (as in weak lensing) would be appreciated.
    And now: A link to some literature on "weak refractive lensing" and how that creates positional offsets would be appreciated.
    It sounds like you are proposing giant imperfect glass lenses in the universe to focus different wavelengths at different positions, Jerry !

    P.S. Gravitational lensing is wavelength independent as far as I know, e.g. What is Gravitational Lensing?
    Last edited by Reality Check; Yesterday at 03:51 AM.

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