Open AccessLocal Group velocity versus gravity: the coherence function
Author(s) -
Chodorowski Michał J.,
Cieciela¸g Paweł
Publication year - 2002
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2002.05161.x
Subject(s) - physics , normalization (sociology) , spectral density , quantum decoherence , coherence (philosophical gambling strategy) , perturbation (astronomy) , acceleration , perturbation theory (quantum mechanics) , classical mechanics , statistical physics , quantum mechanics , statistics , mathematics , sociology , anthropology , quantum
In maximum‐likelihood analyses of the Local Group (LG) acceleration, the object describing non‐linear effects is the coherence function (CF), i.e. the cross‐correlation coefficient of the Fourier modes of the velocity and gravity fields. We study the CF both analytically, using perturbation theory, and numerically, using a hydrodynamic code. The dependence of the function on Ω m and the shape of the power spectrum is very weak. The only cosmological parameter that the CF is strongly sensitive to is the normalization σ 8 of the underlying density field. A perturbative approximation for the function turns out to be accurate as long as σ 8 is smaller than about 0.3. For higher normalizations we provide an analytical fit for the CF as a function of σ 8 and the wavevector. The characteristic decoherence scale which our formula predicts is an order of magnitude smaller than that determined by Strauss et al. This implies that present likelihood constraints on cosmological parameters from analyses of the LG acceleration are significantly tighter than hitherto reported.