New model lends support to Lambda CDM.

Trippy

Trippy

ALEA IACTA EST
Staff member
Eris is a recently completed high resolution model of the milkyway.

A comparison of the simulation results to 2MASS.
comparison-350.jpg


After nine months of number-crunching on a powerful supercomputer, a beautiful spiral galaxy matching our own Milky Way emerged from a computer simulation of the physics involved in galaxy formation and evolution. The simulation by researchers at the University of California, Santa Cruz, and the Institute for Theoretical Physics in Zurich solves a longstanding problem that had led some to question the prevailing cosmological model of the universe.
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more...
more on arxiv...
 
not all galaxies are spiral and flat, some are globular.
the question i have is whether the same physical laws modeled by the software can produce both types.

there is also this:
To perform the Eris simulation, the researchers began with a low-resolution simulation of dark matter evolving to form the haloes that host present-day galaxies. Then they chose a halo with an appropriate mass and merger history to host a galaxy like the Milky Way and "rewound the tape" back to the initial conditions.
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is "rewinding the tape" a valid premise?
 
Anyone have an idea how that new discovery of a star that shouldn't be around (the almost pure hydrogen and helium one) would affect this, since they mention taking stellar formation into account? My guess would be either that it's seen so far as an outlier, or that chemical breakdown wouldn't be a factor in this study, but was curious.
 
leopold99 said:
not all galaxies are spiral and flat, some are globular.
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So? We have a good handle on how elliptical galaxies form under the Λ-CDM model.

leopold99 said:
the question i have is whether the same physical laws modeled by the software can produce both types.
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Yes.

leopold99 said:
there is also this:
To perform the Eris simulation, the researchers began with a low-resolution simulation of dark matter evolving to form the haloes that host present-day galaxies. Then they chose a halo with an appropriate mass and merger history to host a galaxy like the Milky Way and "rewound the tape" back to the initial conditions.
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is "rewinding the tape" a valid premise?
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Yes, in fact it's the best test - derive a set of starting conditions from an observation, apply your model to your derived starting conditions and see how closely your predictions match your observations.
 
Rhaedas said:
Anyone have an idea how that new discovery of a star that shouldn't be around (the almost pure hydrogen and helium one) would affect this, since they mention taking stellar formation into account? My guess would be either that it's seen so far as an outlier, or that chemical breakdown wouldn't be a factor in this study, but was curious.
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The computer model does not go down to that fine of detail. Unless that star type was discovered to be abundant it most likely would be of no statistical value any way.

We are always finding things that stretch and challenge what we think we know. That fact that we find we don't know as much as we thought we did, as often as we do, only encourages further exploration and research, with the objective to learn, more than we thought we knew.., to begin with.
 
It is obvious that the pictures of spiral galaxies cannot be our Milky Way, isn't it?
 
Were those just simulations? They looked like Hubble photographs of other spiral galaxies.
 
AlexG said:
Were those just simulations? They looked like Hubble photographs of other spiral galaxies.
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This picture:
comparison-350.jpg

The top image is the Eris simulation in an edge on view, the bottom image is our view of the milkyway, as mapped by 2MASS.

These:
eris-stars-350.jpg

Are edge on and face on views of the Eris simulation.

As far as any images in the Arxiv article go, I haven't looked at it yet, and I won't looka t it until I get home from work.
 
the bottom image is our view of the milkyway, as mapped by 2MASS
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How did the 2MASS get outside the plane of the galaxy to photograph it?
 
AlexG said:
How did the 2MASS get outside the plane of the galaxy to photograph it?
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It didn't.
2MASS was a survey of the stars within our own milkyway galaxy.

2MASS = 2 Micron All Sky Survey.

They've catalogued something like 300 million point sources, and 1 million extended sources.

2MASS @ IPAC.

The 2MASS image simply represents our view of the milkyway from within it.
 
Addendum:
I believe that this image (large JPG linked) is the source of the 2MASS image being discussed (or one related to it), and it's worth noting that this is an Aitoff projection, which might be expected to give the apperance of an external view.
 
Last I heard, there was some speculation that the Milky Way may actually be a barred spiral galaxy.

Has that theory been debunked?
 
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