New Milky Way Observations, Impact on Old and New Theories

As a result of recent multi-wave length surveys with large star counts, there is now comprehensive data for the Milky Way. I thought the new papers that discuss this data would be interesting to discuss, as any theory must explain the observations. The observations show clear evidence of structures that indicates there are fundamental mechanisms involved, to form the structures, rather than random mergers.

This thread starts with a brief outline of the formation of the galaxy using the old abrupt cloud collapse theory (see below for details) that has been discussed before in the forum along with some known observation vs theory problem for the abrupt cloud collapse model.

The galactic formation model that has been mentioned a few times in the forum is the “Collapse Model”, which is also called the ELS model, named after the model founders Eggen, Lynden-Bell, and Sandage. The ELS model was developed when there was limited data concerning the Milky Way, as noted below and subsequent papers, new data shows the ELS model, is fundamental flawed. As the ELS model is a dark matter based model the data in question also fundamentally challenges the existence of dark matter. The dark matter theory has bounds, as to how the hypothesized dark matter can affect real matter. (See Dark Matter Puzzle thread in Q&A for additional details.)

Excerpt from “An Introduction to Astrophysics” 2nd Editon, published 2007 by Bradley Carrol & Dale Ostlie, Page 1016, Ch #26 Galactic Evolution


Problems with ELS Model (Same source but paraphrased for length.)
1. Roughly half of the stars in the Milky Way’s halo have retrograde orbits, so the net angular momentum of the halo is 0 km/m^2. On the other hand stars in the inner halo appear to have a small net rotation velocity.

2. A second problem with the ELS model is an age variance between the global clusters and halos stars of approximately 2 billion years which would indicate the collapse took an order of magnitude longer the 200 million years predicted. The ELS model also does not explain the difference in age of the narrow region of the Milky Way’s galactic disk which is roughly 8 billion years old and the thick portion of the disk which is 10 billion years old.

3. A third age difficulty is that clusters near the Galactic core are generally the most metal rich and the oldest, while clusters in the outer halo exhibit a wider range in metallicity and tend to be younger.

The paper is interesting concerning the finding of ultra dense quiescent galaxies at z~2.3, in the early universe. The massive early galaxies appear to no longer be forming new stars. As noted by the authors a mechanism is required to expand these massive compact galaxies, which are roughly 40 times smaller than a similar mass nearby galaxy. As a comparison the mass of the Milky Way is 5.8 x 10^11 solar masses and the Milky Way disk has a diameter of around 45 kpc.

http://arxiv.org/abs/0802.4094v1

“Confirmation of the remarkable compactness of massive quiescent galaxies at z~2.3: early-type galaxies did not form in a simple monolithic collapse” by P. G. Van Dokkum , M. Franx, M. Kriek, & et al.



http://www.sciencedaily.com/releases...0429095054.htm

As noted in the first comment, the Milky Way’s halo is comprised of two components, an inner halo that rotates in the same direction as the Milky Way’s disk and an outer halo that rotates in the opposite direction of the Milky Way disk. The inner halo has a metallicity that is roughly 1/3 greater than the outer halo. This is the paper that provides the data to support that statement.

http://arxiv.org/abs/0706.3005
The following is a quote from the above paper which states the current standard hypothesis concerning the mechanism to explain the evolution of elements in the intergalactic/extragalactic gas clouds and in the stars and quasars that are formed from the gas clouds.


Comment:
It is suggested, to explain metallicity anomalies such as super solar metallicity in high redshift quasars, the Milky Way regional variances in metallicity and in rotation, a second non-nucleosynthesis mechanism is required to explain metallicity variance. Supporting the need for a non-nucleosynthesis explanation for metallicity variance, is the need to explain the mechanism for star burst galaxies and the paradox of youth stars in the galactic core.

I am looking at the data and analysis concerning metallicity and stellar formation. I will start a separate thread later.

For us slow learners does this mean that the galactic orbital velocities of approximately half the stars are opposite in direction to the other half, but within each half the range of velocities subtends a wide spectrum as do the orbital ellipticities? For this to be credible data (analytical conclusion), what fraction of stars' velocities have been measured?

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For those inclined to oppose human meddling with the structure of the universe or the composition and configuration of objects and groups of objects within the universe, consider:
Whether there is a limit to the magnitude of a modulation of chaos below which order remains invariant? Or, is order but a fiction invented by perspectives applied over finite, however large, time intervals?

William. I think a simpler explanation for the differences in the metallicities of the two regions is that they formed in different galaxies. A merger of a small halo galaxy with the cannabilistic tendencies of the giant Milky Way can lead to an outer halo of stars with a distinct difference in metallicities from the inner Milky Way, and a velocity distribution that is counter to the inner Milky Way too.
Postulating a completely different mechanism in the two spatially separated regions is phenomenologically unnecessary as galactic mergers are clearly transpiring...(Arp's Catalogue of Peculiar Galaxies). pete


see;http://members.aol.com/arpgalaxy/

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A third rate theory forbids
A second rate theory explains after the fact
A first rate theory predicts...A. Lomonosov

In reply to GOURDHEAD's
Yes the angular momentum of the halo is zero but it consists of two separate components with the inner halo rotating with the galaxy and the outer component of the halo rotating opposite to the galaxy's rotation.

The velocities and metallicity of 20,000 stars were measured. Which the authors note is sufficient to confirm at high degree of certainty, their conclusions.

It appears that you should have considered trinitree88's answer more carefully...

AND, "you" have to be very careful with your usage of 'Retrograde' orbits!

http://en.wikipedia.org/wiki/Retrogr..._direct_motion

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RussT
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Everything is, as it should be, otherwise, it wouldn't be!

In reply to trinitree88's comment:

The hypothesis you provide seems reasonable in terms of what happens when a small galaxy mergers with a larger galaxy.

Galaxy Morphology and Evolution
The halo is what would be expected from a dry merger. From a morphological standpoint, would not the merger of two large spiral galaxies produce a elliptical (spheroid). Would a dry major merger produce an elliptical galaxy that would as the halo does show some evidence of the merger history, but have roughly 0 angular momentum. The paper I quoted in the Why do spiral galaxies have angular momentum and elliptical galaxies have zero net angular momentum, noted that theoretically, early formed galaxies have had 4 or 5 major mergers.

The questions are 1) why do elliptical galaxies form in some cases and spiral in others? 2) Why does the percentage of elliptical galaxy (18%) to spiral (75%, there are irregular galaxies also) remain constant, rather than gradually becoming higher in favour of elliptical.

Metallicity
I agree an explanation for metallicity variance in the halo need not be more than the hypothesis that by chance one merger type had relatively higher metallicity stars (inner halo) and the outer halo by chance had relatively lower metallicity stars. That explanation is reasonable except if all spiral galaxies had the same structure, then a different mechanism would be required. For the spiral disk, the metallicity and velocity differences probably require a different mechanism.

There are other specific metallicity problems such as the G dwarf problem which it appears is a problem for all galaxies and all galaxy components or the quasar lack of metallicity evolution with redshift except at high redshift at which point some quasar's show evidence of super solar metallicity, that require an explanation.

I am looking for a possible answer to metallicity evolution and lack of evolution by looking at observations and data concerning Wolf-Rayet galaxies and star burst galaxies. The observation appears to be similar to the "Paradox of Youth" stars (a very large number of stars in a small region of space near the galaxy's in question core) found near the Milky Way's core, but on a larger scale. The Wolf-Rayet stars are outgassing, but I suspect the out gassed matter has not be created from nucleosynthesis.