The PSCz Dipole Revisited

Abstract

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 Catalogue redshift survey (PSCz). 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 $\sim 185$ $h^{-1}$ Mpc and possible contribution even from $\sim 210$ $h^{-1}$ 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: (a) the large-scale dipole contributions and (b) an increase of the overall dipole amplitude due to the important contribution of the local volume ($\mincir 4 h^{-1}$Mpc), which we now take into account. This results in a lower value of the $\beta (\equiv {\Omega }_{\mathrm{m}}^{0.6}/b)$ parameter, which we find to be ${\beta }_{\mathrm{IRAS}}\simeq 0.49$ in real space. Therefore, for the concordance cosmological model (${\Omega }_{\mathrm{m}}=1-{\Omega }_{\Lambda }=0.3$) the IRAS galaxies bias factor is $b_{\mathrm{IRAS}}\simeq 1$ which means that IRAS galaxies are good traces of the underlying matter distribution.

7 pages, 3 figures, MNRAS in press

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• Large scale structure in the HI Parkes All-Sky Survey: Filling the Voids with HI galaxies?
• The growth rate of cosmic structures in the local Universe with the ALFALFA survey
• A dipole anisotropy of galaxy distribution: Does the CMB rest-frame exist in the local universe?
• Dynamical Constraints on the Local Group from the CMB and 2MRS Dipoles
• Is there evidence for anomalous dipole anisotropy in the large-scale structure?
• On the recovery of Local Group motion from galaxy redshift surveys
• The Linearity of the Cosmic Expansion Field from 300 to 30,000 km/s and the Bulk Motion of the Local Supercluster with Respect to the CMB
• Exploring cosmic origins with CORE: effects of observer peculiar motion
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• Towards the optimal window for the 2MASS dipole
• Influence of the Local Void on measurements of the clustering dipole