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 < 0.05 0.05 ≤ 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 Linear theory: From CMB: v LG = 627 km/sec towards l=273 o and b=29 o From galaxy cat. Number Weighting Technique

6. The 2MRS Redshift Distribution

7. The Rocket Effect (Kaiser, 1987) cz=H 0 r + (v pec - v(0)).(r/r) cz=H 0 r + (v pec - v(0)).(r/r) 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 Net effect: A spurious contribution to the LG dipole from All the galaxies.

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

9. Luminosity Weighting Function

10. Notice the Zone of Avodiance Notice the Zone of Avodiance

13. Shapley Centaurus Hydra 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)

14. 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 β 2mrs = 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!