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More Conclusive Evidence that DM does exist:

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Dark matter is a mysterious, invisible substance that typically dominates the makeup of galaxies; finding an object that's missing dark matter is unprecedented, and came as a complete surprise.

"If there's one object, you always have a little voice in the back of your mind saying, 'but what if you're wrong?' Even though we did all the checks we could think of, we were worried that nature had thrown us for a loop and had conspired to make something look really special whereas it was really something more mundane," said team leader Pieter van Dokkum, Sol Goldman Family Professor of Astronomy at Yale University.



Read more at: https://phys.org/news/2019-03-unusual-galaxies-defy-dark-theory.html#jCp

 

the paper:

https://iopscience.iop.org/article/10.3847/2041-8213/ab0e8c/meta

Still Missing Dark Matter: KCWI High-resolution Stellar Kinematics of NGC1052-DF2

Abstract:

The velocity dispersion of the ultra diffuse galaxy NGC1052-DF2 was found to be  km s−1, much lower than expected from the stellar mass–halo mass relation and nearly identical to the expected value from the stellar mass alone. This result was based on the radial velocities of 10 luminous globular clusters that were assumed to be associated with the galaxy. A more precise measurement is possible from high-resolution spectroscopy of the diffuse stellar light. Here we present an integrated spectrum of the diffuse light of NGC1052-DF2 obtained with the Keck Cosmic Web Imager (KCWI), with an instrumental resolution of σ instr ≈ 12 km s−1. The systemic velocity of the galaxy is v sys = 1805 ± 1.1 km s−1, in very good agreement with the average velocity of the globular clusters ( km s−1). There is no evidence for rotation within the KCWI field of view. We find a stellar velocity dispersion of  km s−1, consistent with the dispersion that was derived from the globular clusters. The implied dynamical mass within the half-light radius r 1/2 = 2.7 kpc is M dyn = (1.3 ± 0.8) × 108 M ⊙, similar to the stellar mass within that radius (M stars = (1.0 ± 0.2) × 108 M ⊙). With this confirmation of the low velocity dispersion of NGC1052-DF2, the most urgent question is whether this "missing dark matter problem" is unique to this galaxy or applies more widely.

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https://iopscience.iop.org/article/10.3847/2041-8213/ab0d92/meta

A Second Galaxy Missing Dark Matter in the NGC 1052 Group:

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I would say this is by far the strongest evidence that we have for DM, even conclusive in my opinion.

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I'lll be honest and say that I don't know much about this subject.  However, what would be conclusive is the actual measurement and characterisation of dark matter otherwise we might as speculate that leprechauns or unicorns cause the expansion of space/galaxies from each other.

So, IMHO, dark matter is a hypothesis that fits in with the current data but we cannot say more about it yet but speculate. Even the authors are being cautious. 

 

Quote

The origin of these large, faint galaxies with an excess of luminous globular clusters and an apparent lack of dark matter is, at present, not understood.

https://iopscience.iop.org/article/10.3847/2041-8213/ab0d92/meta

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36 minutes ago, jimmydasaint said:

I'lll be honest and say that I don't know much about this subject.  However, what would be conclusive is the actual measurement and characterisation of dark matter otherwise we might as speculate that leprechauns or unicorns cause the expansion of space/galaxies from each other.

Not sure why dark matter needs to be held to a higher standard than other physics - evidence for basically all subatomic particles is indirect.

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So, IMHO, dark matter is a hypothesis that fits in with the current data but we cannot say more about it yet but speculate. Even the authors are being cautious. 

 

https://iopscience.iop.org/article/10.3847/2041-8213/ab0d92/meta

"[the] apparent lack of dark matter is, at present, not understood" is not a statement of caution about the existence of dark matter. It's a statement about the lack of understanding of mechanism(s) by which dark matter might not appear in a galaxy.

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9 hours ago, jimmydasaint said:

I'lll be honest and say that I don't know much about this subject.  However, what would be conclusive is the actual measurement and characterisation of dark matter otherwise we might as speculate that leprechauns or unicorns cause the expansion of space/galaxies from each other.

So, IMHO, dark matter is a hypothesis that fits in with the current data but we cannot say more about it yet but speculate. Even the authors are being cautious. 

 

https://iopscience.iop.org/article/10.3847/2041-8213/ab0d92/meta

DM was hypothesised to explain the rotational curves and angular momentum of the majority of galaxies. As further observations were undertaken to explain this anomalous motion, other affects with gravitational lensing and the bullet cluster observation, also pointed to this unseen matter.

The other more incredible possible inference from  all of this would be that we have our model of gravity all wrong, at least over large scales. The findings of galaxies where the angular momentum and rotational curves is explained by the normal stellar and baryonic matter in them, eliminates that possibility conclusively in at least my opinion.

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As far as I recall, the evidence for subatomic particles and most molecular biological phenomena is indirect. However, at least the electromagnetic spectrum interacts with all matter and we can "see" a pellet of DNA at the bottom of an Eppendorf. How on Earth do you have conclusive proof where the whole of the electromagnetic spectrum does not allow access to it.   I could hypothesise that God has ordered the angels to push apart galaxies and expand space and I can use the same evidence that you have used.  Where there are galaxies with apparent less dark matter, there are just fewer angels.

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2 hours ago, jimmydasaint said:

However, at least the electromagnetic spectrum interacts with all matter and we can "see" a pellet of DNA at the bottom of an Eppendorf. How on Earth do you have conclusive proof where the whole of the electromagnetic spectrum does not allow access to it.

Neutrinos do not interact electromagnetically, either. But we have made detailed measurements of their properties despite that.

So far, dark matter has only been detected by its gravitational effects. But multiple lines of such evidence produce consistent results. That is about all you can expect. Conclusive proof arguably doesn't exist in any domain of science.

2 hours ago, jimmydasaint said:

I could hypothesise that God has ordered the angels to push apart galaxies and expand space and I can use the same evidence that you have used. 

Can you make quantitatively testable predictions with that hypothesis?

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8 hours ago, jimmydasaint said:

 How on Earth do you have conclusive proof where the whole of the electromagnetic spectrum does not allow access to it. 

Conclusive possibly is too strong a word, but this latest finding [or absence of finding] adds further support to the already well supported DM concept.

 

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I could hypothesise that God has ordered the angels to push apart galaxies and expand space and I can use the same evidence that you have used.  Where there are galaxies with apparent less dark matter, there are just fewer angels.

Except such nonsense is unfalsifiable.

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A follow up to the original article and paper in the OP........

https://phys.org/news/2019-06-mystery-galaxy-dark.html

Researchers solve mystery of the galaxy with no dark matter:

A group of researchers from the Instituto de Astrofísica de Canarias (IAC) has clarified a 2018 mystery in the field of extragalactic astrophysics: The supposed existence of a galaxy without dark matter.

Galaxies with no dark matter are impossible to understand in the framework of the current theory of galaxy formation, because the role of dark matter is fundamental in causing the collapse of the gas to form stars. In 2018, a study published in Nature announced the discovery of a galaxy that apparently lacked dark matter.

Now, according to an article published in the Monthly Notices of the Royal Astronomical Society (MNRAS) a group of researchers at the Instituto de Astrofísica de Canarias (IAC) has solved this mystery via a very complete set of observations of KKS2000]04 (NGC1052-DF2).

more at link.....

the paper:

A distance of 13 Mpc resolves the claimed anomalies of the galaxy lacking dark matter:

Abstract:

The claimed detection of a diffuse galaxy lacking dark matter represents a possible challenge to our understanding of the properties of these galaxies and galaxy formation in general. The galaxy, already identified in photographic plates taken in the summer of 1976 at the UK 48-in Schmidt telescope, presents normal distance-independent properties (e.g. colour, velocity dispersion of its globular clusters). However, distance-dependent quantities are at odds with those of other similar galaxies, namely the luminosity function and sizes of its globular clusters, mass-to-light ratio, and dark matter content. Here we carry out a careful analysis of all extant data and show that they consistently indicate a much shorter distance (13 Mpc) than previously indicated (20 Mpc). With this revised distance, the galaxy appears to be a rather ordinary low surface brightness galaxy (Re = 1.4 ± 0.1 kpc; M⋆ = 6.0 ± 3.6 × 107 M⊙) with plenty of room for dark matter (the fraction of dark matter inside the half-mass radius is >75 per cent and Mhalo/M⋆>20) corresponding to a minimum halo mass >109 M⊙. At 13 Mpc, the luminosity and structural properties of the globular clusters around the object are the same as those found in other galaxies.

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