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The Dipole Anisotropy of the 2MASS Redshift Survey

The Dipole Anisotropy of the 2MASS Redshift Survey. Pirin Erdo ğ du (University of Nottingham) and the 2MRS Team MNRAS, in press. OUTLINE. What is the 2MASS Redshift Survey? What is the acceleration on our Local Group of galaxies? Why do I think I am right?. Main Assumptions.

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The Dipole Anisotropy of the 2MASS Redshift Survey

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  1. The Dipole Anisotropy of the 2MASS Redshift Survey Pirin Erdoğdu (University of Nottingham) and the 2MRS Team MNRAS, in press

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

  3. 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.

  4. The 2MASS Redshift Survey z ≤ 0.01 0.01 < z ≤ 0.025 0.025 < z < 0.050.05 ≤ z

  5. 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 l=273o and b=29o From galaxy cat.

  6. The 2MRS Redshift Distribution

  7. LG Gal 1 with d=100 km/sec v pec = 20 km/sec Thus calculated distance=120 km/sec Thus calculated dipole= 44% less than the real dipole Gal 2 with d = 100 km/sec v pec= -20 km/sec Thus calculated distance=80 km/sec Thus calculated dipole = 64 % more than the Real dipole The Rocket Effect(Kaiser, 1987) cz=H0r + (vpec- v(0)).(r/r) Net effect: A spurious contribution to the LG dipole from All the galaxies.

  8. Flux Weighting Technique If we have a perfect 2-dimensional galaxy catalogue with no selection effects, constant mass-to-light ratio and with linear biasing then since

  9. Luminosity Weighting Function

  10. Notice the Zone of Avodiance

  11. 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

  12. 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 β2mrs = 0.4±0.1 • 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!

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