Third-Order Perturbation Theory With Nonlinear Pressure

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dc.contributor.utaustinauthorShoji, Masatoshien_US
dc.contributor.utaustinauthorKomatsu, Eiichiroen_US
dc.creatorShoji, Masatoshien_US
dc.creatorKomatsu, Eiichiroen_US
dc.date.accessioned2016-04-28T19:41:16Z
dc.date.available2016-04-28T19:41:16Z
dc.date.issued2009-07en
dc.description.abstractWe calculate the nonlinear matter power spectrum using the third-order perturbation theory without ignoring the pressure gradient term. We consider a semirealistic system consisting of two matter components with and without pressure, and both are expanded into the third order in perturbations in a self-consistent manner, for the first time. While the pressured component may be identified with baryons or neutrinos, in this paper we mainly explore the physics of the nonlinear pressure effect using a toy model in which the Jeans length does not depend on time, i.e., the sound speed decreases as a(-1/2), where a is the scale factor. The linear analysis shows that the power spectrum below the so-called filtering scale is suppressed relative to the power spectrum of the cold dark matter. Our nonlinear calculation shows that the actual filtering scale for a given sound speed is smaller than the linear filtering scale by a factor depending on the redshift and the Jeans length. A similar to 40% change is common, and our results suggest that, when applied to baryons, the temperature of the intergalactic medium inferred from the filtering scale observed in the flux power spectrum of Ly alpha forests would be underestimated by a factor of 2, if one used the linear filtering scale to interpret the data. The filtering mass, which is proportional to the filtering scale cubed, can also be significantly smaller than the linear theory prediction especially at low redshift, where the actual filtering mass can be smaller than the linear prediction by a factor of 3. Finally, when applied to neutrinos, we find that neutrino perturbations deviate significantly from linear perturbations even below the free-streaming scales, and thus neutrinos cannot be treated as linear perturbations.en_US
dc.description.departmentAstronomyen_US
dc.description.sponsorshipTexas Advanced Research Program 003658-0005-2006en_US
dc.description.sponsorshipNASA NNX08AM29G, NNX08AL43Gen_US
dc.description.sponsorshipNSF AST-0807649en_US
dc.description.sponsorshipAlfred P. Sloan Research Fellowshipen_US
dc.identifierdoi:10.15781/T24V66
dc.identifier.Filename2009_07_thirdorder.pdfen_US
dc.identifier.citationShoji, Masatoshi, and Eiichiro Komatsu. "Third-Order Perturbation Theory with Nonlinear Pressure." The Astrophysical Journal, Vol. 700, No. 1 (Jul., 2009): 705.en_US
dc.identifier.doi10.1088/0004-637x/700/1/705en_US
dc.identifier.issn0004-637Xen_US
dc.identifier.urihttp://hdl.handle.net/2152/35104
dc.language.isoEnglishen_US
dc.relation.ispartofen_US
dc.relation.ispartofserialAstrophysical Journalen_US
dc.rightsAdministrative deposit of works to Texas ScholarWorks: This works author(s) is or was a University faculty member, student or staff member; this article is already available through open access or the publisher allows a PDF version of the article to be freely posted online. The library makes the deposit as a matter of fair use (for scholarly, educational, and research purposes), and to preserve the work and further secure public access to the works of the University.en_US
dc.rights.restrictionOpenen_US
dc.subjectcosmology: theoryen_US
dc.subjectlarge-scale structure of universeen_US
dc.subjectly-alpha foresten_US
dc.subjectlinear perturbationsen_US
dc.subjectpower spectrumen_US
dc.subjectuniverseen_US
dc.subjectgalaxiesen_US
dc.subjectdensityen_US
dc.subjectastronomy & astrophysicsen_US
dc.titleThird-Order Perturbation Theory With Nonlinear Pressureen_US
dc.typeArticleen_US

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