The PSCz dipole revisited

We re-examine the gravitational acceleration (dipole) induced on the Local Group of galaxies by the Infrared Astronomical Satellite (IRAS) galaxy distribution of the Point Source Catalog redshift (PSCz) survey. We treat the cirrus-affected low galactic latitudes by utilizing a spherical harmonic expansion of the galaxy surface density field up to the octapole order. We find strong indications for significant contributions to the Local Group motion from depths up to ∼185 h -1 Mpc and a possible contribution even from ∼210h -1 Mpc, in agreement with the recent analysis of Kocevski & Ebeling of a whole-sky X-ray cluster survey. What changes with respect to the previous PSCz dipole analyses is: (i) the large-scale dipole contributions and (ii) an increase of the overall dipole amplitude due to the important contribution of the local volume (? 4 h -1 Mpc), which we now take into account. This results in a lower value of the β (≡ Ω 0.6 m /6) parameter, which we find to be β IRAS ≃ 0.49 in real space. Therefore, for the concordance cosmological model (Ω m = 1 - Ω A = 0.3), the IRAS galaxies bias factor is b ΙRAS ≃ 1, which means that IRAS galaxies are good tracers of the underlying matter distribution.

[1]  Harald Ebeling,et al.  On the Origin of the Local Group’s Peculiar Velocity , 2005, astro-ph/0510106.

[2]  R. Scaramella,et al.  Study of the Core of the Shapley Concentration: I. the Sample † , 1993 .

[3]  M. Plionis,et al.  The X-Ray Cluster Dipole , 1998 .

[4]  P. Peebles.  The local extragalactic velocity field as a test of the explosion and gravitational instability pictures , 1988 .

[5]  J. Willick,et al.  Maximum Likelihood Comparison of Tully-Fisher and Redshift Data. II. Results from an Expanded Sample , 1998, astro-ph/9801307.

[6]  A comparison of local Type Ia supernovae with the IRAS PSCz gravity field , 2004, astro-ph/0409551.

[7]  Edward J. Wollack,et al.  First-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Preliminary Maps and Basic Results , 2003, astro-ph/0302207.

[8]  The QDOT and cluster dipoles: evidence for a low-Ω0 Universe? , 1993 .

[9]  Will Saunders,et al.  The PSCz catalogue , 1999, astro-ph/9909191.

[10]  M. Plionis.  Large-scale optical dipole anisotropy , 1988 .

[11]  J. P. Huchra,et al.  Final Results from the Hubble Space Telescope Key Project to Measure the Hubble Constant , 1998, astro-ph/9801080.

[12]  A. Banday,et al.  Dipole Anisotropy in the COBE Differential Microwave Radiometers First-Year Sky Maps , 1993 .

[13]  David Burstein,et al.  Spectroscopy and photometry of elliptical galaxies. V - Galaxy streaming toward the new supergalactic center , 1988 .

[14]  Consistent β values from density–density and velocity–velocity comparisons , 2002, astro-ph/0207356.

[15]  The Clustering Dipole of the Local Universe from the Two Micron All Sky Survey , 2003, astro-ph/0303592.

[16]  M. Rowan-Robinson,et al.  A non-parametric model for the cosmic velocity field , 1999, astro-ph/9901366.

[17]  O. Lahav,et al.  Cosmological deductions from the alignment of local gravity and motion , 1989 .

[18]  R. Scaramella,et al.  A marked concentration of galaxy clusters: is this the origin of large-scale motions? , 1989, Nature.

[19]  M. Hudson,et al.  Cosmological Parameters from the Comparison of the 2MASS Gravity Field with Peculiar Velocity Surveys , 2005, astro-ph/0511012.

[20]  O. Lahav,et al.  The dipole anisotropy of the 2 Micron All-Sky Redshift Survey , 2005, astro-ph/0507166.

[21]  M. Hudson.  Optical galaxies within 8000 km s–1 – II. The peculiar velocity of the Local Group , 1993 .

[22]  M. Plionis,et al.  Evidence for large-scale structure on scales about $\sim 300 \,h^{-1}$ Mpc , 1991 .

[23]  O. Lahav.  Optical dipole anisotropy , 1987 .

[24]  Likelihood analysis of the Local Group acceleration , 1999, astro-ph/9901087.

[25]  Helen Valentine,et al.  The IRAS PSCz dipole , 1999 .

[26]  Somak Raychaudhury.  The distribution of galaxies in the direction of the 'Great Attractor' , 1989, Nature.

[27]  M. Rowan-Robinson,et al.  Spherical Harmonic Analysis of the PSCz Galaxy Catalogue: Redshift distortions and the real-space power spectrum , 1999, astro-ph/9901351.

[28]  W. K. Huchtmeier,et al.  A Catalog of Neighboring Galaxies , 2004 .

[29]  Dennis W. Sciama,et al.  Reconstructing Positions and Peculiar Velocities of Galaxy Clusters within 25,000 Kilometers per Second: The Bulk Velocity , 1996 .

[30]  R. Scaramella,et al.  The distribution of clusters of galaxies within 300 Mpc/h and the crossover to an isotropic and homogeneous universe , 1991 .

[31]  Harald Ebeling,et al.  The Dipole Anisotropy of the First All-Sky X-Ray Cluster Sample , 2004, astro-ph/0403275.

[32]  LARGE-SCALE COHERENT DIPOLE ANISOTROPY? , 1998 .

[33]  J. Lucey,et al.  Structures in the Great Attractor region , 2006, astro-ph/0603692.

[34]  Cosmological Implications of Large-Scale Flows , 1997, astro-ph/9705033.

[35]  T. Miyaji,et al.  The X-ray flux dipole of active galactic nuclei and the peculiar motion of the local group , 1990 .

[36]  A. Nusser,et al.  Comparison of Velocity and Gravity Fields: The Mark III Tully-Fisher Catalog versus the IRAS 1.2 Jy Survey , 1996, astro-ph/9604101.

[37]  E. Branchini,et al.  Reconstructing positions and peculiar velocities of galaxy clusters within 25,000 kilometers per second: The cluster real space dipole , 1996 .

[38]  The Solar Motion Relative to the Local Group , 1999, astro-ph/9903298.

[39]  N. Kaiser.  Clustering in real space and in redshift space , 1987 .

[40]  A. Yahil,et al.  The dipole anisotropies of the IRAS galaxies and the microwave background radiation , 1986 .

[41]  Ian R. Parry,et al.  A sparse-sampled redshift survey of IRAS galaxies. I. The convergence of the IRAS dipole and the origin of our motion with respect to the microwave background. , 1990 .

[42]  Likelihood analysis of the Local Group acceleration revisited , 2004, astro-ph/0401195.

[43]  A. Kashlinsky,et al.  Large-scale structure in the Universe , 1991, Nature.

[44]  J. Huchra,et al.  A Redshift Survey of IRAS Galaxies. V. The Acceleration on the Local Group , 1992 .