The%20Dipole%20Anisotropy%20of%20the%202MASS%20Redshift%20Survey

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The Dipole Anisotropy of the 2MASS Redshift
Survey

• Pirin Erdogdu
• (University of Nottingham)
• and the 2MRS Team
• MNRAS, in press

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OUTLINE

• What is the 2MASS Redshift Survey?
• What is the acceleration on our Local Group of
  galaxies?
• Why do I think I am right?

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Main Assumptions

• CMB dipole is due to the motion of the Sun.
• Linear theory of density perturbations is
  acceptable.
• The 2MASS has constant mass-to-light ratio and
  linear bias.

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The 2MASS Redshift Survey
z 0.01 0.01 lt z
0.025 0.025 lt z lt 0.05 0.05 z
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If we have a perfect 3-dimensional galaxy
catalogue with same mass, with no selection
effects, no z-distortions and with linear biasing
then
Number Weighting Technique
Linear theory
Linear theory
From CMB vLG 627 km/sec towards l273o and
b29o
From galaxy cat.
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The 2MRS Redshift Distribution
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The Rocket Effect(Kaiser, 1987)

• czH0r (vpec- v(0)).(r/r)

Net effect A spurious contribution to the LG
dipole from All the galaxies.
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If we have a perfect 2-dimensional galaxy
catalogue with no selection effects, constant
mass-to-light ratio and with linear biasing then
Flux Weighting Technique
since
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Luminosity Weighting Function
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Notice the Zone of Avodiance
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Star CMB Triangle 2MRS Lum Weighted Triangle
2MRS-Num Weighted Circle 2MASS by Maller etal
2003 Upside down Triangle IRAS PSCz
Dipole Upside down Triangle 2MASS dipole of
PSCz galaxies Triangle 2MRS Lum Weighted
without Maffei 1, 2, Dwingeloo 1, IC342, M87 Blue
square Dipole from X-Ray Clusters (Kocevski
Ebeling 2005)
Hydra
Centaurus
Shapley
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To summarise

• The flux weighted galaxy dipoles are better.
• Most of the LG dipole is caused by the tug-of-war
  between the GA and Per-Pis. The dipole converges
  by 60 Mpc/h.
• If dipole converged ß2mrs 0.40.1
• Small discrepancy between LG and CMB dipoles are
  due to ZoA, 2nd and 3rd assumptions mentioned in
  the earlier slide and structure beyond. But no
  big deal!