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We have used the Australia Telescope Compact Array (ATCA) at 95 GHz to carry out continuum observations of 130 extragalactic radio sources selected from the Australia Telescope 20 GHz (AT20G) survey. We use a triple-correlation method to measure simultaneous 20- and 95-GHz flux densities for these objects, and over 90 per cent of our target sources are detected at 95 GHz. We demonstrate that the ATCA can robustly measure 95-GHz flux densities with an accuracy of ∼10 per cent in a few minutes for sources stronger than about 50 mJy. We measure the distribution of radio spectral indices in a flux-limited sample of extragalactic sources, and show that the median 20–95 GHz spectral index does not vary significantly with flux density for . This finding allows us to estimate the extragalactic radio source counts at 95 GHz by combining our observed 20–95 GHz spectral-index distribution with the accurate 20-GHz source counts measured in the AT20G survey. Our derived 95-GHz source counts at flux densities above 80 mJy are significantly lower than those found by several previous studies. The main reason is that most radio sources with flat or rising spectra in the frequency range 5–20 GHz show a spectral turnover between 20 and 95 GHz. As a result, there are fewer 95-GHz sources (by almost a factor of 2 at 0.1 Jy) than would be predicted on the basis of extrapolation from the source populations seen in lower-frequency surveys. We also derive the predicted confusion noise in cosmic microwave background surveys at 95 GHz and find a value 20–30 per cent lower than previous estimates. The 95-GHz source population at the flux levels probed by this study is dominated by quasi-stellar objects with a median redshift . We find a correlation between optical magnitude and 95-GHz flux density which suggests that many of the brightest 95-GHz sources may be relativistically beamed, with both the optical and millimetre continuum significantly brightened by Doppler boosting. [ABSTRACT FROM AUTHOR]

The Australia Telescope 20-GHz (AT20G) Survey is a blind survey of the whole southern sky at 20 GHz (with follow-up observations at 4.8 and 8.6 GHz) carried out with the Australia Telescope Compact Array from 2004 to 2007. The Bright Source Sample (BSS) is a complete flux-limited subsample of the AT20G Survey catalogue comprising 320 extragalactic ) radio sources south of with Jy. Of these, 218 have near simultaneous observations at 8 and 5 GHz. In this paper we present an analysis of radio spectral properties in total intensity and polarization, size, optical identifications and redshift distribution of the BSS sources. The analysis of the spectral behaviour shows spectral curvature in most sources with spectral steepening that increases at higher frequencies (the median spectral index α, assuming , decreases from between 4.8 and 8.6 GHz to between 8.6 and 20 GHz), even if the sample is dominated by flat spectra sources (85 per cent of the sample has . The almost simultaneous spectra in total intensity and polarization allowed us a comparison of the polarized and total intensity spectra: polarized fraction slightly increases with frequency, but the shapes of the spectra have little correlation. Optical identifications provided an estimation of redshift for 186 sources with a median value of 1.20 and 0.13, respectively, for QSO and galaxies. [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]

ABSTRACT We have determined the composite luminosity function (LF) for galaxies in 60 clusters from the 2dF Galaxy Redshift Survey. The LF spans the range -22.5 < M[sub b[sub J]] < -15 , and is well fitted by a Schechter function with M*[sub b[sub J]]=-20.07 ± 0.07 and α=-1.28 ± 0.03 (H[sub 0]= 100 km s[sup -1] Mpc[sup -1], Ω[sub M]= 0.3, Ω[sub Λ]= 0.7) . It differs significantly from the field LF, having a characteristic magnitude that is approximately 0.3 mag brighter and a faint-end slope that is approximately 0.1 steeper. There is no evidence for variations in the LF across a wide range of cluster properties: the LF is similar for clusters with high and low velocity dispersions, for rich and poor clusters, for clusters with different Bautz–Morgan types, and for clusters with and without substructure. The core regions of clusters differ from the outer parts, however, in having an excess of very bright galaxies. We also construct the LFs for early (quiescent), intermediate and late (star-forming) spectral types. We find that, as in the field, the LFs of earlier-type galaxies have brighter characteristic magnitudes and shallower faint-end slopes. However, the LF of early-type galaxies in clusters is both brighter and steeper than its field counterpart, although the LF of late-type galaxies is very similar. The trend of faint-end slope with spectral type is therefore much less pronounced in clusters than in the field, explaining why variations in the mixture of types do not lead to significant differences in the cluster LFs. The differences between the field and cluster LFs for the various spectral types can be qualitatively explained by the suppression of star formation in the dense cluster environment, together with mergers to produce the brightest early-type galaxies. [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 use redshift determinations and spectral analysis of galaxies in the 2dF Galaxy Redshift Survey to study the properties of local radio sources with S≥1 mJy . 557 objects (hereafter called the spectroscopic sample) drawn from the FIRST survey, corresponding to 2.3 per cent of the total radio sample, are found in the 2dFGRS catalogue within the area 9[sup h]48[sup m]&lsim;RA(2000)&lsim;14[sup h]32[sup m] and -2°.77&lsim;Dec.(2000)&lsim;2°.25 , down to a magnitude limit b[sub J]=19.45 . The excellent quality of 2dF spectra allows us to divide these sources into classes, according to their optical spectra. Absorption-line systems make up 63 per cent of the spectroscopic sample. These may or may not show emission lines due to AGN activity, and correspond to ‘classical’ radio galaxies belonging mainly to the FRI class. They are characterized by relatively high radio-to-optical ratios, red colours, and high radio luminosities (10[sup 21]&lsim;P[sub 1.4 GHz]/W Hz[sup -1] sr[sup -1]&lsim;10[sup 24]) . Actively star-forming galaxies contribute about 32 per cent of the sample. These objects are mainly found at low redshifts (z&lsim;0.1) and show low radio-to-optical ratios, blue colours and low radio luminosities. We also found 18 Seyfert 2 galaxies (3 per cent) and four Seyfert 1s (1 per cent). Analysis of the local radio luminosity function (LF) shows that radio galaxies are well described by models that assume pure luminosity evolution, at least down to radio powers P[sub 1.4 GHz]&lsim;10[sup 20.5] W Hz[sup -1] sr[sup -1] . Late-type galaxies, whose relative contribution to the radio LF is found to be lower than was predicted by previous works, present an LF which is comparable with the IRAS galaxy LF. This class of sources therefore plausibly constitutes the radio counterpart of the dusty spirals and starbursts that dominate the counts at 60 μm. [ABSTRACT FROM AUTHOR]

We calculate the optical b[sub J] luminosity function (LF) of the 2dF Galaxy Redshift Survey (2dFGRS) for different subsets defined by their spectral properties. These spectrally selected subsets are defined using a new parameter, η, which is a linear combination of the first two projections derived from a Principal Component Analysis. This parameter η identifies the average emission- and absorption-line strength in the galaxy rest frame spectrum, and hence is a useful indicator of the present star formation. We use a total of 75 000 galaxies in our calculations, chosen from a sample of high signal-to-noise ratio, low-redshift galaxies observed before 2001 January. We find that there is a systematic steepening of the faint-end slope (α) as one moves from passive (α=-0.54) to active (α=-1.50) star-forming galaxies, and that there is also a corresponding faintening of the rest frame characteristic magnitude M*-5 log[sub 10](h) (from -19.6 to -19.2). We also show that the Schechter function provides a poor fit to the quiescent (Type 1) LF for very faint galaxies [M[sub b[sub J]]-5 log[sub 10](h) fainter than -16.0], perhaps suggesting the presence of a significant dwarf population. The LFs presented here give a precise confirmation of the trends seen previously in a much smaller preliminary 2dFGRS sample, and in other surveys. We also present a new procedure for determining self-consistent k-corrections, and investigate possible fibre-aperture biases. [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]

Analyzes galaxy clustering in the two-degree-field Galaxy Redshift Survey (2dFGRS), which supports the simplest picture of cosmological structure formation in which the primary mechanism is gravitational instability in a sea of collisionless dark matter. Extrapolation of the fluctuations in the cosmic microwave background (CMB) to predict the peculiar velocities that distort redshift-space clustering; Results favoring a low-density Universe with OMEGA approximately equal to 0.3.