A. VELOCITY DISPERSIONS OF COMPACT ETGs at z · PDF fileETGs in the redshift range 1.2
Peculiar velocity decomposition, redshift distortion and velocity reconstruction in redshift surveys...
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Transcript of Peculiar velocity decomposition, redshift distortion and velocity reconstruction in redshift surveys...
Peculiar velocity decomposition, redshift distortion and velocity reconstruction in redshift
surveys
Zheng, Yi 郑逸Shanghai Astronomical Observatory
P. Zhang, J. Pan, and Y. Zheng, 1207.2722.Y. Zheng, P. Zhang et al. (2012), in preparation.
Outline
• I. Introduction. (Why RSD interesting?) • II. Velocity decomposition. (What do
decomposed velocity components look like?)• III. RSD modeling and velocity reconstruction. • IV. Discussions and conclusions
Introduction
A. J. S. Hamilton, astro-ph/9708102
Observationally:
Euclid, BigBOSS et all:
O(1%)
5-10%
Theoretically:1. Nonlinear mapping 2. Nonlinear evolution 3. Bias modelling
Torre & Guzzo, 1202.5559
The redshift position s:
𝒔=𝒙+𝑣 𝑧/ (𝑎𝐻) �̂�
Reid et al. 2012
RSD modeling I
The redshift position s: 𝒔=𝒙+𝑣 𝑧/ (𝑎𝐻) �̂�
From mass conservation: (1+𝛿𝑠 (𝒔 ) )𝑑3 𝑠=(1+𝛿(𝒙 ))𝑑3 𝑥
The redshift space power spectrum:
Dark matter and LCDM cosmology
Velocity decomposition
Background from Wang et al. 2012
𝑽 (𝒙)rotational component
𝑽 𝑩=𝑽 (𝒌 )−𝑽 𝑬
irrotational component
𝑽 𝑬=[𝑽 (𝒌 ) ∙ �̂�]�̂�
𝜃 (𝒌 )=𝑖𝒌∙𝑽 𝑬 (𝒌)/𝑎𝐻
correlated with
𝜃𝛿(𝑘)=𝛿 (𝑘 )𝑊 (𝑘)
uncorrelated with
𝜃𝑆 (𝑘 )=𝜃 (𝑘 )−𝜃𝛿
Velocity power spectrum
Definition:
𝑽 𝛿
𝑽 𝑆
Simulation: 1200 Mpc/h & 100 Mpc/h, 1024^3Nearest Particle method
𝑽 𝐵
Velocity correlation function
Definition:
O(1 Mpc/h) O(10 Mpc/h)
𝑽 𝛿 𝑽 𝑆𝑽 𝐵
2.Determined by W(k)!
A new RSD formulae 1.Underestimation of by
3. Physical FOG:CL, dispersion, NG
Window function I
𝜃= 𝑓 𝛿
underestimation
~𝑊 (𝑘 )=𝑃𝛿𝜃
𝑓 𝑃𝛿𝛿
= 11+𝛼 𝑓 𝛽 Δ𝛿𝛿
2 (𝑘)
𝛼=0.48 , 𝛽=0.5125% 𝑎𝑡 𝑘≳ 0.7h/𝑀𝑝𝑐
Window function II
Do fitting using region Δ𝛿𝛿2 =𝑘3 Δ𝛿𝛿
2 /2𝜋
3D velocity reconstruction
1. The 1st Method:
2. The 2nd Method:
By tuning such that is isotropic at large scales, we could obtain the correct and hence the correct field.
k-SZ effect
Application example: k-SZ tomography (Ho et al. 0903.2845, Shao et al. 1004.1301)
Velocity field Momentum field
CMBMissing baryons
Conclusions and discussions
• Conclusions:– a velocity decomposition method a new RSD model lower systematic error.
– a simple fitting formula for – 2 new methods for 3D velocity reconstruction in light of
RSD information.
• Future work:– More simulation calculations to impove RSD model and
test its accuracy, halo, galaxy....– Velocity reconstruction methods need more theoretical and
numerical considerations.