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We present some first results on the variability, polarization and general properties of radio sources selected at 20 GHz, the highest frequency at which a sensitive radio survey has been carried out over a large area of sky. Sources with flux densities above 100 mJy in the Australia Telescope Compact Array 20 GHz pilot survey at declination −60° to −70° were observed at up to three epochs during 2002–04, including near-simultaneous measurements at 5, 8 and 18 GHz in 2003. Of the 173 sources detected, 65 per cent are candidate QSOs or BL Lac objects, 20 per cent galaxies and 15 per cent faint optical objects or blank fields. On a 1–2 yr time-scale, the general level of variability at 20 GHz appears to be low. For the 108 sources with good-quality measurements in both 2003 and 2004, the median variability index at 20 GHz was 6.9 per cent and only five sources varied by more than 30 per cent in flux density. Most sources in our sample show low levels of linear polarization (typically 1–5 per cent), with a median fractional polarization of 2.3 per cent at 20 GHz. There is a trend for fainter 20 GHz sources to have higher fractional polarization. At least 40 per cent of sources selected at 20 GHz have strong spectral curvature over the frequency range 1–20 GHz. We use a radio ‘two-colour diagram’ to characterize the radio spectra of our sample, and confirm that the flux densities of radio sources at 20 GHz (which are also the foreground point-source population for cosmic microwave background anisotropy experiments like Wilkinson Microwave Anisotropy Probe and Planck) cannot be reliably predicted by extrapolating from surveys at lower frequencies. As a result, direct selection at 20 GHz appears to be a more efficient way of identifying 90 GHz phase calibrators for Atacama Large Millimeter Array (ALMA) than the currently proposed technique of extrapolation from radio surveys at 1–5 GHz. [ABSTRACT FROM AUTHOR]

The ROSAT-European Southern Observatory (ESO) flux-limited X-ray (REFLEX) galaxy cluster survey and the Two-degree Field Galaxy Redshift Survey (2dFGRS), respectively, comprise the largest, homogeneous X-ray selected cluster catalogue and completed galaxy redshift survey. In this work, we combine these two outstanding data sets in order to study the effect of the large-scale cluster environment, as traced by X-ray luminosity, on the properties of the cluster member galaxies. We measure the relation from the correlated data set and find it to be consistent with recent results found in the literature. Using a sample of 19 clusters with in the 0.1–2.4 keV band, and 49 clusters with lower X-ray luminosity, we find that the fraction of early spectral type , passively evolving galaxies is significantly higher in the high- LX sample within R200. We extend the investigation to include composite bJ cluster luminosity functions, and find that the characteristic magnitude of the Schechter-function fit to the early-type luminosity function is fainter for the high- LX sample compared to the low- LX sample . This seems to be driven by a deficit of such galaxies with M bJ∼−21. In contrast, we find no significant differences between the luminosity functions of star-forming, late-type galaxies. We believe these results are consistent with a scenario in which the high- LX clusters are more dynamically evolved systems than the low- LX clusters. [ABSTRACT FROM AUTHOR]

ABSTRACT The Two-degree Field Galaxy Redshift Survey (2dFGRS) Percolation-Inferred Galaxy Group (2PIGG) catalogue of ∼29 000 objects is used to study the luminous content of galaxy systems of various sizes. Mock galaxy catalogues constructed from cosmological simulations are used to gauge the accuracy with which intrinsic group properties can be recovered. It is found that a Schechter function is a reasonable fit to the galaxy luminosity functions in groups of different mass in the real data, and that the characteristic luminosity L⋆ is slightly larger for more massive groups. However, the mock data show that the shape of the recovered luminosity function is expected to differ from the true shape, and this must be allowed for when interpreting the data. Luminosity function results are presented in both the bJ and rF wavebands. The variation of the halo mass-to-light ratio, ϒ, with group size is studied in both of these wavebands. A robust trend of increasing ϒ with increasing group luminosity is found in the 2PIGG data. Going from groups with bJ luminosities equal to 1010 h−2 L⊙ to those 100 times more luminous, the typical bJ-band mass-to-light ratio increases by a factor of 5, whereas the rF-band mass-to-light ratio grows by a factor of 3.5. These trends agree well with the predictions of the simulations which also predict a minimum in the mass-to-light ratio on a scale roughly corresponding to the Local Group. The data indicate that if such a minimum exists, then it must occur at L≲ 1010 h−2 L⊙, below the range accurately probed by the 2PIGG catalogue. According to the mock data, the bJ mass-to-light ratios of the largest groups are expected to be approximately 1.1 times the global value. Assuming that this correction applies to the real data, the mean bJ luminosity density of the Universe yields an estimate of Ωm= 0.26 ± 0.03 (statistical error only). Various possible sources of systematic error are considered, with the conclusion that these could affect the estimate of Ωm by a few tens of per cent. [ABSTRACT FROM AUTHOR]

The clustering properties of local, , radio sources are investigated for a sample of 820 objects drawn from the joint use of the Faint Images of the Radio Sky at 20 cm (FIRST) and 2dF Galaxy Redshift surveys. To this aim, we present 271 new spectroscopic counterparts of FIRST radio sources to be added to those already introduced in our previous paper. The two-point correlation function for the local radio population is found to be entirely consistent with estimates obtained for the whole sample of 2dFGRS galaxies. From measurements of the redshift-space correlation function ξ( s) we derive a redshift-space clustering length , while from the projected correlation function Ξ( rT) we estimate the parameters of the real-space correlation function and , where is assumed. Different results are instead obtained if we only consider sources that present signatures of active galactic nucleus (AGN) activity in their spectra. These objects are shown to be very strongly correlated, with and , a steeper slope than has been claimed in other recent works. No difference is found in the clustering properties of radio-AGNs of different radio luminosity. Comparisons with models for ξ( r) show that AGN-fuelled sources reside in dark matter haloes more massive than , higher than the corresponding figure for radio-quiet quasi-stellar objects. This value can be converted into a minimum black hole mass associated with radio-loud, AGN-fuelled objects of . The above results then suggest – at least for relatively faint radio objects – the existence of a threshold black hole mass associated with the onset of significant radio activity such as that of radio-loud AGNs; however, once the activity is triggered, there appears to be no evidence for a connection between black hole mass and level of radio output. [ABSTRACT FROM AUTHOR]

We constrain fiat cosmological models with a joint likelihood analysis of a new compilation of data from the cosmic microwave background (CMB) and from the 2dF Galaxy Redshift Survey (2dFGRS). Fitting the CMB alone yields a known degeneracy between the Hubble constant h and the matter density Ωm, which arises mainly from preserving the location of the peaks in the angular power spectrum. This 'horizon-angle degeneracy' is considered in some detail and is shown to follow the simple relation &Omega[sub m] h[sup 3.4] = constant. Adding the 2dF-GRS power spectrum constrains Ω[sub m] h and breaks the degeneracy. If tensor anisotropies are assumed to be negligible, we obtain values for the Hubble constant of h = 0.665 ± 0.047, the matter density Ω[sub m] = 0.313 ± 0.055, and the physical cold dark matter and baryon densities Ω[sub c] h² = 0.115 ± 0.009, Ω[sub b] h² = 0.022 ± 0.002 (standard rms errors). Including a possible tensor component causes very little change to these figures; we set an upper limit to the tensorto-scalar ratio of r < 0.7 at a 95 per cent confidence level. We then show how these data can be used to constrain the equation of state of the vacuum, and find w < -0.52 at 95 per cent confidence. The preferred cosmological model is thus very well specified, and we discuss the precision with which future CMB data can be predicted, given the model assumptions. The 2dFGRS power-spectrum data and covariance matrix, and the CMB data compilation used here, are available from http://www.roe.ac.uk/∼wjp/. [ABSTRACT FROM AUTHOR]

We use more than 110 500 galaxies from the 2dF Galaxy Redshift Survey (2dFGRS) to estimate the b[sub J]-band galaxy luminosity function at redshift z = 0, taking account of evolution, the distribution of magnitude measurement errors and small corrections for incompleteness in the galaxy catalogue. Throughout the interval -16.5 > Mb[sub J] - 5 log[sub 10] h >-22, the luminosity function is accurately described by a Schechter function with M[sup *][sub b][sub J] - 5 log[sub 10] h = -19.66 ± 0.07, α = -1.21 ± 0.03 and Φ[sup *] = (1.61 ± 0.08) × 10[sup -2] h³ Mpc[sup -3], giving an integrated luminosity density of ρ[sub L] = (1.82 ± 0.17) × 10[sup 8] h L[sub ...] Mpc[sup -3] (assuming an Ω[sub 0] = 0.3, Λ[sub 0] = 0.7 cosmology). The quoted errors have contributions from the accuracy of the photometric zero-point, from large-scale structure in the galaxy distribution and, importantly, from the uncertainty in the appropriate evolutionary corrections. Our luminosity function is in excellent agreement with, but has much smaller statistical errors than, an estimate from the Sloan Digital Sky Survey (SDSS) data when the SDSS data are accurately translated to the b[sub J] band and the luminosity functions are normalized in the same way. We use the luminosity function, along with maps describing the redshift completeness of the current 2dFGRS catalogue, and its weak dependence on apparent magnitude, to define a complete description of the 2dFGRS selection function. Details and tests of the calibration of the 2dFGRS photometric parent catalogue are also presented. [ABSTRACT FROM AUTHOR]

We perform a joint likelihood analysis of the power spectra of the 2dF Galaxy Redshift Survey (2dFGRS) and the cosmic microwave background (CMB) anisotropies under the assumptions that the initial fluctuations were adiabatic, Gaussian and well described by power laws with scalar and tensor indices of ns and nt. On its own, the 2dFGRS sets tight limits on the parameter combination ω[sub m]h, but relatively weak limits on the fraction of the cosmic matter density in baryons ω[sub b]/ω[sub m]. (Here h is Hubble's constant H[sub 0] in units of 100 km s-[sup -1] Mpc[sup 1]. The cosmic densities in baryons, cold dark matter and vacuum energy are denoted by ω[sub b], ω[sub c] and ωλ, respectively. The total matter density is ω[sub m] = &omega[sub b] + &omega[sub c] and the curvature is fixed by ω[sub k] = 1 - ω[sub m] - ωλ.) The CMB anisotropy data alone set poor constraints on the cosmological constant and Hubble constant because of a 'geometrical degeneracyrsquo; among parameters. Furthermore, if tensor modes are allowed, the CMB data allow a wide range of values for the physical densities in baryons and cold dark matter (ω[sub b] = ω[sub b]h ² and ω[sub c] = &omega[sub c]h²). Combining the CMB and 2dFGRS data sets helps to break both the geometrical and tensor mode degeneracies. The values of the parameters derived here are consistent with the predictions of the simplest models of inflation, with the baryon density derived from primordial nucleosynthesis and with direct measurements of the Hubble parameter. In particular, we find strong evidence for a positive cosmological constant with a ± 2σ range of 0.65 < ω&λ < 0.85, independently of constraints on ωA derived from Type Ia supernovae. [ABSTRACT FROM AUTHOR]

The 2dF Galaxy Redshift Survey (2dFGRS) is designed to measure redshifts for approximately 250 000 galaxies. This paper describes the survey design, the spectroscopic observations, the redshift measurements and the survey data base. The 2dFGRS uses the 2dF multifibre spectrograph on the Anglo-Australian Telescope, which is capable of observing 400 objects simultaneously over a 2° diameter field. The source catalogue for the survey is a revised and extended version of the APM galaxy catalogue, and the targets are galaxies with extinction-corrected magnitudes brighter than . The main survey regions are two declination strips, one in the southern Galactic hemisphere spanning around the SGP, and the other in the northern Galactic hemisphere spanning along the celestial equator; in addition, there are 99 fields spread over the southern Galactic cap. The survey covers 2000 deg[sup 2] and has a median depth of . Adaptive tiling is used to give a highly uniform sampling rate of 93 per cent over the whole survey region. Redshifts are measured from spectra covering at a two-pixel resolution of 9.0 Å and a median S/N of 13 pixel[sup -1]. All redshift identifications are visually checked and assigned a quality parameter Q in the range redshifts are 98.4 per cent reliable and have an rms uncertainty of 85 km s[sup -1]. The overall redshift completeness for redshifts is 91.8 per cent, but this varies with magnitude from 99 per cent for the brightest galaxies to 90 per cent for objects at the survey limit. The 2dFGRS data base is available on the World Wide Web at http://www.mso.anu.edu.au/2dFGRS. [ABSTRACT FROM AUTHOR]

The 2dF Galaxy Redshift Survey has now measured in excess of 160 000 galaxy redshifts. This paper presents the power spectrum of the galaxy distribution, calculated using a direct Fourier transform based technique. We argue that, within the k-space region , the shape of this spectrum should be close to that of the linear density perturbations convolved with the window function of the survey. This window function and its convolving effect on the power spectrum estimate are analysed in detail. By convolving model spectra, we are able to fit the power-spectrum data and provide a measure of the matter content of the Universe. Our results show that models containing baryon oscillations are mildly preferred over featureless power spectra. Analysis of the data yields 68 per cent confidence limits on the total matter density times the Hubble parameter , and the baryon fraction , assuming scale-invariant primordial fluctuations. [ABSTRACT FROM AUTHOR]

We combine the Two Micron All Sky Survey (2MASS) Extended Source Catalogue and the 2dF Galaxy Redshift Survey to produce an infrared selected galaxy catalogue with 17 173 measured redshifts. We use this extensive data set to estimate the galaxy luminosity functions in the J- and K[sub S]-bands. The luminosity functions are fairly well fitted by Schechter functions with parameters M[sub J][sup *]-5 log h=-22.36±0.02, α[sub J]=-0.93±0.04, Φ[sub J][sup *]=0.0104±0.0016 h[sup 3] Mpc[sup -3] in the J-band and M[sub K[sub S]][sup *]-5 log h=-23.44±0.03, α[sub K[sub S]]=-0.96±0.05, Φ[sub K[sub S]][sup *]=0.0108±0.0016 h[sup 3] Mpc[sup -3] in the K[sub S]-band (2MASS Kron magnitudes). These parameters are derived assuming a cosmological model with Ω[sub 0]=0.3 and Λ[sub 0]=0.7. With data sets of this size, systematic rather than random errors are the dominant source of uncertainty in the determination of the luminosity function. We carry out a careful investigation of possible systematic effects in our data. The surface brightness distribution of the sample shows no evidence that significant numbers of low surface brightness or compact galaxies are missed by the survey. We estimate the present-day distributions of b[sub J]-K[sub S] and J-K[sub S] colours as a function of the absolute magnitude and use models of the galaxy stellar populations, constrained by the observed optical and infrared colours, to infer the galaxy stellar mass function. Integrated over all galaxy masses, this yields a total mass fraction in stars (in units of the critical mass density) of Ω[sub stars]h =(1.6±0.24)×10[sup -3] for a Kennicutt initial mass function (IMF) and Ω[sub stars]h =(2.9±0.43)×10[sup -3] for a Salpeter IMF. These values are consistent with those inferred from observational estimates of the total star formation history of the Universe provided that dust extinction corrections are modest. [ABSTRACT FROM AUTHOR]