The effect of early radiation in N-body simulations of cosmic structure formation

TY - JOUR

T1 - The effect of early radiation in N-body simulations of cosmic structure formation

AU - Adamek, Julian

AU - Brandbyge, Jacob

AU - Fidler, Christian

AU - Hannestad, Steen

AU - Rampf, Cornelius

AU - Tram, Thomas

PY - 2017/9

Y1 - 2017/9

N2 - Newtonian N-body simulations have been employed successfully over the past decades for the simulation of the cosmological large-scale structure. Such simulations usually ignore radiation perturbations (photons and massless neutrinos) and the impact of general relativity (GR) beyond the background expansion. This approximation can be relaxed and we discuss three different approaches that are accurate to leading order in GR. For simulations that start at redshift less than about 100, we find that the presence of early radiation typically leads to per cent-level effects on the numerical power spectra at large scales. Our numerical results agree across the three methods, and we conclude that all of the three methods are suitable for simulations in a standard cosmology. Two of the methods modify the N-body evolution directly, while the third method can be applied as a post-processing prescription.

AB - Newtonian N-body simulations have been employed successfully over the past decades for the simulation of the cosmological large-scale structure. Such simulations usually ignore radiation perturbations (photons and massless neutrinos) and the impact of general relativity (GR) beyond the background expansion. This approximation can be relaxed and we discuss three different approaches that are accurate to leading order in GR. For simulations that start at redshift less than about 100, we find that the presence of early radiation typically leads to per cent-level effects on the numerical power spectra at large scales. Our numerical results agree across the three methods, and we conclude that all of the three methods are suitable for simulations in a standard cosmology. Two of the methods modify the N-body evolution directly, while the third method can be applied as a post-processing prescription.

KW - Cosmology: theory

KW - Dark matter

KW - Large-scale structure of Universe

UR - http://www.scopus.com/inward/record.url?scp=85021782933&partnerID=8YFLogxK

U2 - 10.1093/mnras/stx1157

DO - 10.1093/mnras/stx1157

M3 - Journal article

AN - SCOPUS:85021782933

SN - 0035-8711

VL - 470

SP - 303

EP - 313

JO - Royal Astronomical Society. Monthly Notices

JF - Royal Astronomical Society. Monthly Notices

IS - 1

M1 - stx1157

ER -