Density and Velocity Fields from the 2MASS Redshift Survey

1
Density and Velocity Fields from the 2MASS
Redshift Survey

• Pirin Erdogdu
• Nottingham University
• MNRAS, 373, 45 (2006)

2
The 2MRS Team

• Pirin Erdogdu
• Ofer Lahav
• John Huchra
• Matthew Colless
• Roc Cutri
• Emilio Falco
• Teddy George
• Thomas Jarrett

• Heath Jones
• Lucas Macri
• Jeff Mader
• Nathalie Martimbeau
• Michael Pahre
• Quentin Parker
• Anaïs Rassat
• Will Saunders

3
2MASS Redshift Survey

• Multiple telescopes to get all-sky coverage.
• Data from ZCAT, SDSS (although a lot of our gals
  are too bright), FLWO, McDonald, Arecibo, Nancay
  and from CTIO, 6dF, Parkes, South Africa
• 2MASS XSC is the primary sample for 6dF
• Started 1998 as 2MASS produced objects

4
2MASS Redshift Survey

• K_s lt11.25 24,832 galaxies all sky ,
  currently 22,750 of 22,966 b gt 5 degrees
• 11.25 is now essentially complete.
  
• IR galaxy colors have incredibly small
  dispersion, lt 0.08 mag J-H, 0.09 mag H-K
• 40 Early types in a K selected sample
• versus 30 Early types in a B selected sample
• K_s lt11.50 28,957 bgt10 28,671 w/zs 99
• K_s lt11.75 39,980 37,578 w/zs 94

5
The 2MASS Redshift Survey
z 0.01 0.01 lt z 0.025
0.025 lt z lt 0.05 0.05 z
6
Motivation

• Statistical Uncertainties due to Shot Noise
• Incomplete Galaxy Sampling
• Incomplete Sky Coverage
• Recovering one field from another (real-space
  mass and velocity fields from galaxies in
  redshift-space)

7
The 2MRS Redshift Distribution
8
Notice the Zone of Avodiance
z 0.01 0.01 lt z 0.025 0.025 lt z lt 0.05
0.05 z
9
Expansion of the Density Field in
Spherical Coordinates
10
Boundary Conditions

11
Resolution
(Peebles, 1980)
12
Wiener Filter
(For details see Zaroubi et al 1995, ApJ, 449,
446)
13
where the matrix WF is chosen such that the
residual
is minimised.
Hence
signal/(signal noise)
14
Fisher, Lahav, Hoffman, Lynden-Bell, Zaroubi,
1995, MNRAS, 272885
Wiener Filter
15
(No Transcript)
16
(No Transcript)
17
Poissons equation
is the eigenfunction of Laplacian operator
In linear theory
where
18
(No Transcript)
19
Acceleration on the Local
Group
Linear theory
Linear theory
From CMB vLG 627 km/sec towards l273o and
b29o
From galaxy cat.
20
(No Transcript)
21
Summary

• Recovered density and velocity fields from the
  2MRS survey using WF technique
• Expanded the observed density field into
  spherical harmonics and spherical Bessel
  Functions
• The redshift distortions were corrected for using
  a coupling matrix, Z
• The real-space density field was estimated using
  WF.
• Velocity field is reconstructed from the WFed
  density field
• The reconstructed density field resolves most of
  the known structures as well as new clusters and
  voids
• There is a backside infall towards the GA
• There is a strong outflow towards Shapley.
  Shapley plays an inportant role in the local
  dynamics.
• The reconstructed LG dipole suggests most of the
  acceleration is generated within 50 Mpc/h