Editing Galaxy rotation curve (section)

==Further investigations==
[[File:Comparison of rotating disc galaxies in the distant Universe and the present day.jpg|thumb|Comparison of rotating disc galaxies in the present day (left) and the distant Universe (right).<ref>{{cite web |title=Dark Matter Less Influential in Galaxies in Early Universe – VLT observations of distant galaxies suggest they were dominated by normal matter |url=https://www.eso.org/public/news/eso1709/ |website=www.eso.org |access-date=16 March 2017}}</ref>]]

The rotational dynamics of galaxies are well characterized by their position on the [[Tully–Fisher relation]], which shows that for spiral galaxies the rotational velocity is uniquely related to their total luminosity. A consistent way to predict the rotational velocity of a spiral galaxy is to measure its [[bolometric luminosity]] and then read its rotation rate from its location on the Tully–Fisher diagram. Conversely, knowing the rotational velocity of a spiral galaxy gives its luminosity. Thus the magnitude of the galaxy rotation is related to the galaxy's visible mass.<ref>{{cite journal |last1=Yegorova |first1=I. A. |last2=Salucci |first2=P. |year=2007 |title=The radial Tully-Fisher relation for spiral galaxies – I |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=377 |issue=2 |pages=507–515 |arxiv=astro-ph/0612434 |bibcode=2007MNRAS.377..507Y |doi=10.1111/j.1365-2966.2007.11637.x|doi-access=free |s2cid=17917374 }}</ref>

While precise fitting of the bulge, disk, and halo density profiles is a rather complicated process, it is straightforward to model the observables of rotating galaxies through this relationship.<ref>{{cite magazine |url=http://www.scientificamerican.com/article.cfm?id=dark-matter-doubts&page=2 |title=Reliance on Indirect Evidence Fuels Dark Matter Doubts |last=Dorminey |first=Bruce |date=30 Dec 2010 |magazine=Scientific American}}</ref>{{better source|date=December 2016}} So, while state-of-the-art cosmological and [[galaxy formation]] simulations of dark matter with normal [[baryonic matter]] included can be matched to galaxy observations, there is not yet any straightforward explanation as to why the observed scaling relationship exists.<ref>{{cite journal |last1=Weinberg |first1=David H. |last2=et |first2=al. |date=2008 |title=Baryon Dynamics, Dark Matter Substructure, and Galaxies |journal=The Astrophysical Journal |volume=678 |issue=1 |pages=6–21 |bibcode=2008ApJ...678....6W |doi=10.1086/524646 |arxiv=astro-ph/0604393|s2cid=14893610 }}</ref><ref>{{cite journal |last1=Duffy |first1=Alan R. | author-link1=Alan Duffy (astronomer) |last2=al. |first2=et |date=2010 |title=Impact of baryon physics on dark matter structures: a detailed simulation study of halo density profiles |journal=Monthly Notices of the Royal Astronomical Society |volume=405 |issue=4 |pages=2161–2178  |arxiv=1001.3447 |bibcode=2010MNRAS.405.2161D |doi=10.1111/j.1365-2966.2010.16613.x|doi-access=free |s2cid=118517066 }}</ref> Additionally, detailed investigations of the rotation curves of [[Low-surface-brightness galaxy|low-surface-brightness galaxies]] (LSB galaxies) in the 1990s<ref>{{cite journal |last1=de Blok |first1=W. J. G. |last2=McGaugh |first2=S. |year=1997 |title=The dark and visible matter content of low surface brightness disc galaxies |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=290 |issue=3 |pages=533–552 |arxiv=astro-ph/9704274 |bibcode=1997MNRAS.290..533D |doi=10.1093/mnras/290.3.533|doi-access=free }}</ref> and of their position on the Tully–Fisher relation<ref>{{cite journal  |last1=Zwaan |first1=M. A. |last2=van der Hulst |first2=J. M. |last3=de Blok |first3=W. J. G. |last4=McGaugh |first4=S. S. |year=1995 |title=The Tully-Fisher relation for low surface brightness galaxies: implications for galaxy evolution |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=273 |issue=2 |pages=L35–L38 |arxiv=astro-ph/9501102 |bibcode=1995MNRAS.273L..35Z |doi=10.1093/mnras/273.1.l35|doi-access=free }}</ref> showed that LSB galaxies had to have [[dark matter halo]]es that are more extended and less dense than those of galaxies with high surface brightness, and thus surface brightness is related to the halo properties. Such dark-matter-dominated [[dwarf galaxy|dwarf galaxies]] may hold the key to solving the [[dwarf galaxy problem]] of [[structure formation]].

Very importantly, the analysis of the inner parts of low and high surface brightness galaxies showed that the shape of the rotation curves in the centre of dark-matter dominated systems indicates a profile different from the [[Navarro–Frenk–White profile|NFW]] spatial mass distribution profile.<ref>{{cite journal |last1=Gentile |first1=G. |last2=Salucci |first2=P. |last3=Klein |first3=U. |last4=Vergani |first4=D. |last5=Kalberla |first5=P. |year=2004 |title=The cored distribution of dark matter in spiral galaxies |journal=Monthly Notices of the Royal Astronomical Society |volume=351 |issue=3 |pages=903–922 |arxiv=astro-ph/0403154 |bibcode=2004MNRAS.351..903G |doi=10.1111/j.1365-2966.2004.07836.x|doi-access=free |s2cid=14308775 }}</ref><ref>{{cite journal |last1=de Blok |first1=W. J. G. |last2=Bosma |first2=A. |year=2002 |title=High-resolution rotation curves of low surface brightness galaxies |url=https://www.aanda.org/articles/aa/pdf/2002/15/aah3018.pdf |journal=[[Astronomy & Astrophysics]] |volume=385 |issue=3 |pages=816–846 |arxiv=astro-ph/0201276 |bibcode=2002A&A...385..816D |doi=10.1051/0004-6361:20020080|s2cid=15880032 }}</ref> This so-called [[cuspy halo problem]] is a persistent problem for the standard cold dark matter theory. Simulations involving the feedback of stellar energy into the interstellar medium in order to alter the predicted dark matter distribution in the innermost regions of galaxies are frequently invoked in this context.<ref>{{Cite journal |arxiv=1302.2268 |last1=Salucci |first1=P. |last2= De Laurentis |first2=M. |year=2012 |title=Dark Matter in galaxies: Leads to its Nature |url=https://pos.sissa.it/archive/conferences/161/012/DSU%202012_012.pdf |journal=[[Proceedings of Science]] |issue=DSU 2012 |page=12 |bibcode = 2013arXiv1302.2268S }}</ref><ref>{{cite journal |arxiv=0910.3538 |last1=de Blok |first1=W. J. G. |year=2010 |title=The Core-Cusp Problem |journal=[[Advances in Astronomy]] |volume=2010 |pages=789293 |doi=10.1155/2010/789293 |bibcode=2010AdAst2010E...5D|doi-access=free }}</ref>