Editing Galaxy formation and evolution (section)

====Interstellar medium====

Complex multi-phase structure, including relativistic particles and magnetic field, makes simulation of interstellar medium difficult. In particular, modeling the cold phase of the interstellar medium poses technical difficulties due to the short timescales associated with the dense gas. In the early simulations, the dense gas phase is frequently not modeled directly but rather characterized by an effective polytropic equation of state.<ref name="SpringelHernquist2003">{{cite journal | last1 = Springel | first1 = V. | last2 = Hernquist | first2 = L. | title = Cosmological smoothed particle hydrodynamics simulations: a hybrid multiphase model for star formation | journal = Monthly Notices of the Royal Astronomical Society | date = 21 February 2003 | volume = 339 | issue = 2 | pages = 289–311 | issn = 0035-8711 | eissn = 1365-2966 | doi = 10.1046/j.1365-8711.2003.06206.x | pmid = | url = | doi-access = free | arxiv = astro-ph/0206393 | bibcode = 2003MNRAS.339..289S }}</ref> More recent simulations use a [[multimodal distribution]]<ref name="HopkinsQuataertMurray2012">{{cite journal | last1 = Hopkins | first1 = Philip F. | last2 = Quataert | first2 = Eliot | last3 = Murray | first3 = Norman | title = The structure of the interstellar medium of star-forming galaxies | journal = Monthly Notices of the Royal Astronomical Society | date = 16 March 2012 | volume = 421 | issue = 4 | pages = 3488–3521 | issn = 0035-8711 | doi = 10.1111/j.1365-2966.2012.20578.x | doi-access = free | pmid = | url = | arxiv = 1110.4636 | bibcode = 2012MNRAS.421.3488H | s2cid = 119199512 }}</ref><ref name="AgertzKravtsovLeitner2013">{{cite journal | last1 = Agertz | first1 = Oscar | last2 = Kravtsov | first2 = Andrey V. | last3 = Leitner | first3 = Samuel N. | last4 = Gnedin | first4 = Nickolay Y. | title = Toward a Complete Accounting of Energy and Momentum from Stellar Feedback in Galaxy Formation Simulations | journal = The Astrophysical Journal | date = 21 May 2013 | volume = 770 | issue = 1 | page = 25 | issn = 0004-637X | eissn = 1538-4357 | doi = 10.1088/0004-637X/770/1/25 | pmid = | url = | arxiv = 1210.4957 | bibcode = 2013ApJ...770...25A | s2cid = 118587852 }}</ref> to describe 
the gas density and temperature distributions, which directly model the multi-phase structure. However, more detailed physics processes needed to be considered in future simulations, since the structure of the interstellar medium directly affects [[star formation]].