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Multi-object spectroscopy (MOS) instruments, such as the Two-degree Field (2dF) facility of the Anglo-Australian Observatory (AAO), have facilitated large-scale redshift surveys. Yet despite their acclaim, instrument design has been suspected of introducing subtle selection effects into surveys. Investigation into these selection effects has been overshadowed by instrument complexity. We identify the field configuration algorithm (FCA) used to select targets for observation as mainly responsible for such effects. An FCA can imprint artificial structure on observed target distributions, which may accrue over large angular scales, potentially to the detriment of statistical analyses applied to such surveys. We present here a new FCA developed for 2dF that is based on simulated annealing (SA), a generic method commonly used to solve constrained optimization problems. We generate synthetic fields and utilize mock 2dF volumes to contrast the behaviour of previous strategies with the SA FCA. The angular two-point correlation function and other sensitive techniques reveal that the new FCA achieves unprecedented sampling uniformity and target yield with improved target priority handling and observational flexibility over current FCAs. The SA FCA is generic enough to be used by current 2dF-like and potentially next-generation MOS instruments with little modification. [ABSTRACT FROM AUTHOR]

We measure the autocorrelation function, ξ, of galaxies in the IRAS Point Source Catalogue galaxy redshift (PSCz) survey and investigate its dependence on the far-infrared colour and absolute luminosity of the galaxies. We find that the PSCz survey correlation function can be modelled out to a scale of 10 h[sup -1] Mpc as a power law of slope 1.30±0.04 and correlation length 4.77±0.20. At a scale of 75 h[sup -1] Mpc we find the value of J[sub 3] to be 1500±400. We also find that galaxies with higher 100 μm/60 μm flux ratio, corresponding to cooler dust temperatures, are more strongly clustered than warmer galaxies. Splitting the survey into three colour subsamples, we find that, between 1 and 10 h[sup -1] Mpc, the ratio of ξ is a factor of 1.5 higher for the cooler galaxies compared with the hotter galaxies. This is consistent with the suggestion that hotter galaxies have higher star formation rates, and correspond to later-type galaxies which are less clustered than earlier types. Using volume-limited subsamples, we find a weak variation of ξ as a function of absolute luminosity, in the sense that more luminous galaxies are less clustered than fainter galaxies. The trend is consistent with the colour dependence of ξ and the observed colour–luminosity correlation, but the large uncertainties mean that it has a low statistical significance. [ABSTRACT FROM AUTHOR]

We use the Least Action Principle to predict the peculiar velocities of PSCz galaxies inside cz=2000 km s[sup -1]. Linear theory is used to account for tidal effects to cz=15 000 km s[sup -1], and we iterate galaxy positions to account for redshift distortions. As the Least Action Principle is valid beyond linear theory, we can predict reliable peculiar velocities even for very nearby galaxies (i.e., cz≤500 km s[sup -1]). These predicted peculiar velocities are then compared with the observed velocities of 12 galaxies with Cepheid distances. The combination of the PSCz galaxy survey (with its large sky coverage and uniform selection) with the accurate Cepheid distances makes this comparison relatively free from systematic effects. We find that galaxies are good tracers of the mass, even at small (≤10 h[sup -1] Mpc) scales; under the assumption of no biasing, 0.25≤β≤0.75 (at 90 per cent confidence). We use the reliable predicted peculiar velocities to estimate the Hubble constant H[sub 0] from the local volume without ‘stepping up’ the distance ladder, finding a confidence range of 65–75 km s[sup -1] Mpc[sup -1] (at 90 per cent confidence). [ABSTRACT FROM AUTHOR]

The algorithm ztrace of Monaco & Efstathiou is applied to the IRAS PSCz catalogue to reconstruct the initial conditions of our local Universe with a resolution down to ~5 h[sup -1] Mpc. The one-point probability distribution function (PDF) of the reconstructed initial conditions is consistent with the assumptions that: (i) IRAS galaxies trace mass on scales of ~5 h[sup -1] Mpc and (ii) the statistics of the primordial density fluctuations are Gaussian. We use simulated PSCz catalogues, constructed from N-body simulations with Gaussian initial conditions, to show that local non-linear bias can cause the recovered initial PDF (assuming no bias) to be non-Gaussian. However, for plausible bias models, the distortions of the recovered PDF would be difficult to detect using the volume finely sampled by the PSCz catalogue. So, for Gaussian initial conditions, a range of bias models remain compatible with our PSCz reconstruction results. [ABSTRACT FROM AUTHOR]

We present the catalogue, mask, redshift data and selection function for the PSCz survey of 15 411 IRAS galaxies across 84 per cent of the sky. Most of the IRAS data are taken from the Point Source Catalog, but this has been supplemented and corrected in various ways to improve the completeness and uniformity. We quantify the known imperfections in the catalogue, and we assess the overall uniformity, completeness and data quality. We find that overall the catalogue is complete and uniform to within a few per cent at high latitudes and 10 per cent at low latitudes. Ancillary information, access details, guidelines and caveats for using the catalogue are given. [ABSTRACT FROM AUTHOR]

We use the PSCz IRAS galaxy redshift survey to analyse the cosmological galaxy dipole out to a distance of 300 h[sup -1] Mpc. The masked area is filled in three different ways, first by sampling the whole sky at random, secondly by using neighbouring areas to fill a masked region, and thirdly using a spherical harmonic analysis. The method of treatment of the mask is found to have a significant effect on the final calculated dipole. The conversion from redshift space to real space is accomplished by using an analytical model of the cluster and void distribution, based on 88 nearby groups, 854 clusters and 163 voids, with some of the clusters and all of the voids found from the PSCz data base. The dipole for the whole PSCz sample appears to have converged within a distance of 200 h[sup -1] Mpc and yields a value for β = Ω 0.6/β - 0.75[sup +0.11][sub -0.08], consistent with earlier determinations from IRAS samples by a variety of methods. For b=1, the 2σ range for Ω[sub 0] is 0.43–1.02. The direction of the dipole is within 13° of the cosmic microwave background (CMB) dipole, the main uncertainty in direction being associated with the masked area behind the Galactic plane. The improbability of further major contributions to the dipole amplitude coming from volumes larger than those surveyed here means that the question of the origin of the CMB dipole is essentially resolved. [ABSTRACT FROM AUTHOR]

We present a direct comparison of the clustering properties of two redshift surveys covering a common volume of space: the recently completed IRAS Point Source Catalogue redshift survey (PSCz) containing 14 500 galaxies with a limiting flux of 0.6 Jy at 60 μm, and the optical Stromlo–APM survey containing 1787 galaxies in a region of 4300 deg[sup 2] in the south Galactic cap. We use three methods to compare the clustering properties: the counts-in-cells comparison of Efstathiou, the two-point cross-correlation function, and the Tegmark ‘null-buster’ test. We find that the Stromlo variances are systematically higher than those of PSCz, as expected owing to the deficit of early-type galaxies in IRAS samples. However, we find that the differences between the cell counts are consistent with a linear bias between the two surveys, with a relative bias parameter b[sub rel]≡b[sub Stromlo]b[sub PSCz]≈1.3, which appears approximately scale-independent. The correlation coefficient R between optical and IRAS densities on scales ∼20 h[sup -1] Mpc is R⩾0.72 at 95 per cent confidence limit, placing limits on types of ‘stochastic bias’ that affect optical and IRAS galaxies differently. [ABSTRACT FROM AUTHOR]

We describe the construction of the QDOT survey, which is publicly available from an anonymous FTP account. The catalogue consists of infrared properties and redshifts of an all-sky sample of 2387 IRAS galaxies brighter than the IRAS PSC 60-μm completeness limit (S[sub 60]>0.6 Jy), sparsely sampled at a rate of one-in-six. At |b|>10°, after removing a small number of Galactic sources, the redshift completeness is better than 98 per cent (2086/2127). New redshifts for 1401 IRAS sources were obtained to complete the catalogue; the measurement and reduction of these are described, and the new redshifts tabulated here. We also tabulate all sources at |b|>10° with no redshift so far, and sources with conflicting alternative redshifts either from our own work, or from published velocities. A list of 95 ultraluminous galaxies (i.e. with L[sub 60 μm]>10[sup 12] L[sub ⊙]) is also provided. Of these, ∼20 per cent are AGN of some kind; the broad-line objects typically show strong Fe ii emission. Since the publication of the first QDOT papers, there have been several hundred velocity changes: some velocities are new, some QDOT velocities have been replaced by more accurate values, and some errors have been corrected. We also present a new analysis of the accuracy and linearity of IRAS 60-μm fluxes. We find that the flux uncertainties are well described by a combination of 0.05-Jy fixed size uncertainty and 8 per cent fractional uncertainty. This is not enough to cause the large Malmquist-type errors in the rate of evolution postulated by Fisher et al. We do, however, find marginal evidence for non-linearity in the PSC 60-μm flux scale, in the sense that faint sources may have fluxes overestimated by about 5 per cent compared with bright sources. We update some of the previous scientific analyses to assess the changes. The main new results are as follows. (1) The luminosity function is very well determined overall but is uncertain by a factor of several at the very highest luminosities (L[sub 60 μm]>5×10[sup 12] L[sub ⊙]), as this is where the remaining unidentified objects are almost certainly concentrated. (2) The best-fitting rate of evolution is somewhat lower than our previous estimate; expressed as pure density evolution with density varying as (1+z)[sup p], we find p=5.6±2.3. Making a rough correction for the possible (but very uncertain) non-linearity of fluxes, we find p=4.5±2.3. (3) The dipole amplitude decreases a little, and the implied value of the density parameter, assuming that IRAS galaxies trace the mass, is Ω=0.9(+0.45, -0.25). (4) Finally, the estimate of density variance on large scales changes negligibly, still indicating a significant discrepancy from the predictions of simple cold dark matter cosmogonies. [ABSTRACT FROM AUTHOR]

ABSTRACT We measure the redshift-space power spectrum P(k) for the recently completed IRAS Point Source Catalogue (PSC) redshift survey, which contains 14 500 galaxies over 84 per cent of the sky with 60-μm flux ≥0.6 Jy. Comparison with simulations shows that our estimated errors on P(k) are realistic, and that systematic errors resulting from the finite survey volume are small for wavenumbers k ≳ 0.03 h Mpc[sup -1]. At large scales our power spectrum is intermediate between those of the earlier QDOT and 1.2-Jy surveys, but with considerably smaller error bars; it falls slightly more steeply to smaller scales. We have fitted families of CDM-like models using the Peacock–Dodds formula for non-linear evolution; the results are somewhat sensitive to the assumed small-scale velocity dispersion σ[sub V]. Assuming a realistic σ[sub V] ≈ 300 km s[sup -1] yields a shape parameter Γ ∼ 0.25 and normalization bσ[sub 8] ∼ 0.75; if σ[sub V] is as high as 600 km s[sup -1] then Γ = 0.5 is only marginally excluded. There is little evidence for any ‘preferred scale’ in the power spectrum or non-Gaussian behaviour in the distribution of large-scale power. [ABSTRACT FROM AUTHOR]

ABSTRACTWe apply the formalism of spherical harmonic decomposition to the galaxy density field of the IRAS PSCz redshift survey. The PSCz redshift survey has almost all-sky coverage and includes IRAS galaxies to a flux limit of 0.6 Jy. Using maximum likelihood methods to examine (to first order) the distortion of the galaxy pattern resulting from redshift coordinates, we have measured the parameter β≡Ω{0.6}/b. We also simultaneously measure either (a) the undistorted amplitude of perturbations in the galaxy distribution when a parametrized power spectrum is assumed, or (b) the shape and amplitude of the real-space power spectrum if the band-power in a set of passbands is measured in a step-wise fashion. These methods are extensively tested on a series of CDM, Λ CDM and MDM simulations and are found to be unbiased. We obtain consistent results for the subset of the PSCz catalogue with flux above 0.75 Jy, but inclusion of galaxies to the formal flux limit of the catalogue gives variations which are larger than our internal errors. For the 0.75-Jy catalogue we find, in the case of a parametrized power spectrum, β=0.58±0.26 and the amplitude of the real-space power measured at wavenumber k=0.1h Mpc-1 is Δ0.1=0.42±0.03. Freeing the shape of the power spectrum we find that β=0.47±0.16 (conditional error) and Δ0.1=0.47±0.03. The shape of the real-space power spectrum is consistent with a Γ=0.2 CDM-like model, but does not strongly rule out a number of other models. Finally by combining our estimate of the amplitude of galaxy clustering and the distortion parameter we find the amplitude of mass fluctuations on a scale k=0.1h Mpc-1 is Δρ=0.24Ω0-0.6, with an uncertainty of 50 per cent. [ABSTRACT FROM AUTHOR]