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Don J
2012-Apr-25, 05:25 AM
Galactic Rotation Described with Bulge+Disk Gravitational Models
C. F. Gallo, James Q. Feng
(Submitted on 20 Apr 2008)
http://search.arxiv.org:8081/details.jsp?qid=1335330734365mix_nCnN_1197605809&r=pdf/0804.3203v1


(1) Balancing Newtonian gravitational and centrifugal forces at every point within the disk yields computed radial mass distributions that describe the measured rotation velocity profiles of mature spiral galaxies successfully. (2) There is no need for gravity deviations or ``massive peripheral spherical halos of mysterious Dark Matter''.


GBT Multiwavelength Survey of the Galactic Center Region
(Submitted on 28 Jan 2008)
http://search.arxiv.org:8081/paper.jsp?r=0801.4294&qid=1335329817540mix_nCnN_1197605809&qs=the+GBT+survey


We describe the results of a radio continuum survey of the central 4x1deg with the 100 m Green Bank Telescope (GBT) at wavelengths of 3.5, 6, 20, and 90 cm. The 3.5 and 6 cm surveys are the most sensitive and highest resolution single dish surveys made of the central degrees of our Galaxy. We present catalogs of compact and extended sources in the central four degrees of our Galaxy, including detailed spectral index studies of all sources. The analysis covers star-forming regions such as Sgr B and Sgr C where we find evidence of a mixture of thermal and nonthermal emission

Swift
2012-Apr-25, 12:39 PM
So?

What is your point?

Shaula
2012-Apr-25, 01:33 PM
The first paper is basically just a cold, baryonic dark matter model. They assume that star density is not as well correlated with overall mass distribution as current models, work back to a mass distribution that does fit observed rotational curves and say "if our assumptions are true then this must be the mass distribution of the galaxy". They then assign this extra mass to clouds of molecular hydrogen, assume that current estimates of its density are way too low and voila - a solution. So they replace DM (because it has such odd properties - it is invisible, we are not sure what it is, we only know it is there by its gravity) with molecular hydrogen (which has the preferable properties that it is invisible, we do not know how it behaves in their models as it doesn't quite seem to behave like we'd expect and we only know it is there by its gravity)... Umm...

kzb
2012-Apr-25, 05:46 PM
Don J we don't get what point you are making with the second paper. Are you saying they have detected a lot of hitherto undetected gas ?

Don J
2012-Apr-26, 03:58 AM
The first paper is basically just a cold, baryonic dark matter model. They assume that star density is not as well correlated with overall mass distribution as current models, work back to a mass distribution that does fit observed rotational curves and say "if our assumptions are true then this must be the mass distribution of the galaxy". They then assign this extra mass to clouds of molecular hydrogen, assume that current estimates of its density are way too low and voila - a solution. So they replace DM (because it has such odd properties - it is invisible, we are not sure what it is, we only know it is there by its gravity) with molecular hydrogen (which has the preferable properties that it is invisible, we do not know how it behaves in their models as it doesn't quite seem to behave like we'd expect and we only know it is there by its gravity)... Umm...
Based on what is described in 1.2 i was thinking that it was the the orbital velocity law applied to rotating galactic disk they were challenging for the reason they are giving .So it seem that they are doing more than just replacing dark matter molecular hydrogen.

http://search.arxiv.org:8081/details.jsp?qid=1335330734365mix_nCnN_1197605809&r=pdf/0804.3203v1



1.2 Thin-Disk Gravitational Models with Bulge Added

For a thin rotating galactic disk, we impose a balance between the Newtonian gravitational forces and centrifugal forces at each and every point. Because the gravitational field of a thin disk is not spherically symmetric, the orbital velocity law is not applicable. As illustrated by Feng & Gallo [8] [9], an axisymmetric thin disk gravitational model successfully describes the basic rotational dynamics of mature spiral galaxies with a mass density decreasing from the center to periphery. And the calculated total galactic masses are in good agreement with star count data.


Notice
For reply and discussion about
Galactic Rotation Described with Bulge+Disk Gravitational Models

Go to the thread
Galactic Rotation... no need for dark matter.
http://www.bautforum.com/showthread....07#post2011607

Don J
2012-Apr-26, 04:01 AM
Don J we don't get what point you are making with the second paper. Are you saying they have detected a lot of hitherto undetected gas ?

The second paper was included here because it is an old paper and not because it relate with the first paper.But it is cool notheless.

Originally posted by mistake in Fun Papers In Arxiv thread.

Don J
2012-Apr-26, 04:49 AM
Notice
For reply and discussion about
Galactic Rotation Described with Bulge+Disk Gravitational Models

Go to the thread
Galactic Rotation... no need for dark matter.
http://www.bautforum.com/showthread.php/131406-Galactic-Rotation...-no-need-for-dark-matter.?p=2011607#post2011607

Don J
2012-Apr-26, 04:57 AM
Moderators

It may be preferable to close this thread to avoid any confusion.

Swift
2012-Apr-26, 01:14 PM
Moderators

It may be preferable to close this thread to avoid any confusion.
Done

tusenfem
2012-Apr-26, 01:18 PM
Good idea, closed