The power spectrum of <italic>IRAS</italic> galaxies

We estimate the three-dimensional power spectrum of IRAS galaxies from theQDOT and $1.2$Jy redshift surveys. We use identical estimators for both surveysand show how the results depend on the weights assigned to the galaxies. Thepower spectrum for the QDOT survey is steeper and has a higher amplitude atwavenumbers $k \sim 0.05\; h {\rm Mpc}^{-1}$ (where $h$ is Hubble's constant inunits of $100 \kmsmpc$) than the power spectrum derived from the $1.2$Jysample. However, the QDOT power spectrum is sensitive to a small number ofgalaxies in the Hercules supercluster, in agreement with a recent analysis ofgalaxy counts in cells in these surveys. We argue that the QDOT results are anupward fluctuation. We combine the two surveys to derive our best estimate ofthe power spectrum of IRAS galaxies. This is shallower and has a loweramplitude on scales $\simlt 0.1 h {\rm Mpc}^{-1}$ than the power spectrumderived by Feldman \et (1994) from the QDOT survey alone. The power spectrum ofthe combined surveys is well described by the linear theory power spectrum of ascale-invariant cold dark matter model with $\Omega h = 0.2$.Comment: 5 pages, uuencoded compressed PostScript, 3 figures included. Accepted for publication in MNRAS pink page