Search

We present a power spectrum analysis of the final 2dF Galaxy Redshift Survey, employing a direct Fourier method. The sample used comprises 221,414 galaxies with measured redshifts. We investigate in detail the modelling of the sample selection. A new angular mask is derived, based on revisions to the photometric calibration. The redshift selection function is determined by dividing the survey according to rest-frame colour, and deducing a self-consistent treatment of k-corrections and evolution for each population. The covariance matrix for the power-spectrum estimates is determined using two different approaches to the construction of mock surveys which are used to demonstrate that the input cosmological model can be correctly recovered. We are confident that the 2dFGRS power spectrum can be used to infer the matter content of the universe. On large scales, our estimated power spectrum shows evidence for the `baryon oscillations' that are predicted in CDM models. Fitting to a CDM model, assuming a primordial $n_{s}=1$ spectrum, $h=0.72$ and negligible neutrino mass, the preferred parameters are $\Omega_{M} h = 0.168 \pm 0.016$ and a baryon fraction $\Omega_{b} /\Omega_{M} = 0.185\pm0.046$ (1$\sigma$ errors). The value of $\Omega_{M} h$ is $1\sigma$ lower than the $0.20 \pm 0.03$ in our 2001 analysis of the partially complete 2dFGRS. This shift is largely due to the signal from the newly-sampled regions of space, rather than the refinements in the treatment of observational selection. This analysis therefore implies a density significantly below the standard $\Omega_{M} =0.3$: in combination with CMB data from WMAP, we infer $\Omega_{M} =0.231\pm 0.021$. (Abridged.), Comment: Updated to match the in press MNRAS version. P(k) data and covariance matrix available at http://www.mso.anu.edu.au/2dFGRS/Public/Release/PowSpec

The clustering properties of local, S_{1.4 GHz} > 1 mJy, radio sources are investigated for a sample of 820 objects drawn from the joint use of the FIRST and 2dF Galaxy Redshift surveys. To this aim, we present 271 new bj < 19.45 spectroscopic counterparts of FIRST radio sources to be added to those already introduced in Magliocchetti et al. (2002). 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. We estimate the parameters of the real-space correlation function xi(r)=(r/r_0)^{-\gamma}, r_0=6.7^{+0.9}_{-1.1} Mpc and \gamma=1.6\pm 0.1, where h=0.7 is assumed. Different results are instead obtained if we only consider sources that present signatures of AGN activity in their spectra. These objects are shown to be very strongly correlated, with r_0=10.9^{+1.0}_{-1.2} Mpc and \gamma=2\pm 0.1, 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. These results show that AGN-fuelled sources reside in dark matter halos more massive than \sim 10^{13.4} M_{\sun}},higher the corresponding figure for radio-quiet QSOs. This value can be converted into a minimum black hole mass associated with radio-loud, AGN-fuelled objects of M_{BH}^{min}\sim 10^9 M_{\sun}. 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. (abridged), Comment: 10 pages, 8 figures, minor changes, to appear on MNRAS

Monthly Notices of the Royal Astronomical Society, 356 (2), ISSN:0035-8711, ISSN:1365-2966, ISSN:1365-8711

We have calculated the two-point correlation functions in redshift space, xi(sigma,pi), for galaxies of different spectral types in the 2dF Galaxy Redshift Survey. Using these correlation functions we are able to estimate values of the linear redshift-space distortion parameter, beta = Omega_m^0.6/b, the pairwise velocity dispersion, a, and the real-space correlation function, xi(r), for galaxies with both relatively low star-formation rates (for which the present rate of star formation is less than 10% of its past averaged value) and galaxies with higher current star-formation activity. At small separations, the real-space clustering of passive galaxies is very much stronger than that of the more actively star-forming galaxies; the correlation-function slopes are respectively 1.93 and 1.50, and the relative bias between the two classes is a declining function of radius. On scales larger than 10 h^-1 Mpc there is evidence that the relative bias tends to a constant, b(passive)/b(active) ~ 1. This result is consistent with the similar degrees of redshift-space distortions seen in the correlation functions of the two classes -- the contours of xi(sigma,pi) require beta(active)=0.49+/-0.13, and beta(passive)=0.48+/-0.14. The pairwise velocity dispersion is highly correlated with beta. However, despite this a significant difference is seen between the two classes. Over the range 8-20 h^-1 Mpc, the pairwise velocity dispersion has mean values 416+/-76 km/s and 612+/-92 km/s for the active and passive galaxy samples respectively. This is consistent with the expectation from morphological segregation, in which passively evolving galaxies preferentially inhabit the cores of high-mass virialised regions., Comment: 10 pages, 7 figures. Submitted to MNRAS

We constrain flat 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 Ωm h3.4 = constant. Adding the 2dF-GRS power spectrum constrains Ωm 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 Ωm = 0.313±0.055, and the physical cold dark matter and baryon densities Ωm h2 = 0.115±0.009, Ωm 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 tensor-to-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/.

We measure the projected cross-correlation between low-redshift (z < 0.5) far-infrared selected galaxies in the science demonstration phase (SDP) field of the Herschel-ATLAS (H-ATLAS) survey and optically selected galaxies from the Galaxy and Mass Assembly (GAMA) redshift survey. In order to obtain robust correlation functions, we restrict the analysis to a subset of 969 out of 6900 H-ATLAS galaxies, which have reliable optical counterparts with r < 19.4 mag and well-determined spectroscopic redshifts. The overlap region between the two surveys is 12.6 deg2; the matched sample has a median redshift of z≈ 0.2. The cross-correlation of GAMA and H-ATLAS galaxies within this region can be fitted by a power law, with correlation length r0≈ 4.63 ± 0.51 Mpc. Comparing with the corresponding autocorrelation function of GAMA galaxies within the SDP field yields a relative bias (averaged over 2–8 Mpc) of H-ATLAS and GAMA galaxies of bH/bG≈ 0.6. Combined with clustering measurements from previous optical studies, this indicates that most of the low-redshift H-ATLAS sources are hosted by haloes with masses comparable to that of the Milky Way. The correlation function appears to depend on the 250-μm luminosity, L250, with bright (median luminosity νL250∼ 1.6 × 1010 L⊙) objects being somewhat more strongly clustered than faint (νL250∼ 4.0 × 109 L⊙) objects. This implies that galaxies with higher dust-obscured star formation rates are hosted by more massive haloes.

Monthly Notices of the Royal Astronomical Society, 355 (3), ISSN:0035-8711, ISSN:1365-2966, ISSN:1365-8711

Monthly Notices of the Royal Astronomical Society, 352 (4), ISSN:0035-8711, ISSN:1365-2966, ISSN:1365-8711

We present a detailed analysis of the two-point correlation function, from the 2dF Galaxy Redshift Survey (2dFGRS). We estimate the redshift-space correlation function, xi(s), from which we measure the redshift-space clustering length, s_0=6.82+/-0.28 Mpc/h. We also estimate the projected correlation function, Xi(sigma), and the real-space correlation function, xi(r), which can be fit by a power-law, with r_0=5.05+/-0.26Mpc/h, gamma_r=1.67+/-0.03. For r>20Mpc/h, xi drops below a power-law as is expected in the popular LCDM model. The ratio of amplitudes of the real and redshift-space correlation functions on scales of 8-30Mpc/h gives an estimate of the redshift-space distortion parameter beta. The quadrupole moment of xi on scales 30-40Mpc/h provides another estimate of beta. We also estimate the distribution function of pairwise peculiar velocities, f(v), including rigorously the effect of infall velocities, and find that it is well fit by an exponential. The accuracy of our xi measurement is sufficient to constrain a model, which simultaneously fits the shape and amplitude of xi(r) and the two redshift-space distortion effects parameterized by beta and velocity dispersion, a. We find beta=0.49+/-0.09 and a=506+/-52km/s, though the best fit values are strongly correlated. We measure the variation of the peculiar velocity dispersion with projected separation, a(sigma), and find that the shape is consistent with models and simulations. Using the constraints on bias from recent estimates, and taking account of redshift evolution, we conclude that beta(L=L*,z=0)=0.47+/-0.08, and that the present day matter density of the Universe is 0.3, consistent with other 2dFGRS estimates and independent analyses., 19 pages, revised following referee's report, and accepted by MNRAS. Higher resolution Figures, an animated version of Figure 12 and a colour version of Figure 22 are available from http://www.nottingham.ac.uk/~ppxeh/

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 n_s and n_t. On its own, the 2dFGRS sets tight limits on the parameter combination Omega_m h, but relatively weak limits on the fraction of the cosmic matter density in baryons Omega_b/Omega_m. The CMB anisotropy data alone set poor constraints on the cosmological constant and Hubble constant because of a `geometrical degeneracy' 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. 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 pm 2sigma range of 0.65 < Omega_Lambda < 0.85, completely independently of constraints on Omega_��derived from Type Ia supernovae., 7 pages, 7 figures, mn.sty submitted to mnras

We combine the 2MASS extended source catalogue and the 2dFGRS to produce an IR selected galaxy catalogue with 17,173 measured redshifts. We use this extensive dataset to estimate the J and K-band galaxy luminosity functions. The LFs are fairly well fit by Schechter functions with J: M*-5log h= -22.36+/-0.02, alpha= -0.93+/-0.04, Phi=0.0104+/-0.0016 h^3/Mpc^3 and K: M*-5log h= -23.44+/-0.03, alpha=-0.96+/-0.05, Phi=0.0108+/-0.0016 h^3/Mpc^3 (2MASS Kron magnitudes). These parameters assume a cosmological model with Omega=0.3 and Lambda=0.7. With datasets of this size, systematic rather than random errors are the dominant source of uncertainty in the determination of the LF. 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-K and J-K colours as a function of 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 Omega_*.h= (1.6+/-0.24)/10^3 for a Kennicutt IMF and Omega_*.h= (2.9+/-0.43)/10^3 for a Salpeter IMF. These values agree with those inferred from observational estimates of the star formation history of the universe provided that dust extinction corrections are modest., Typo in Table 3 Fixed (MNRAS 326 255). Catalogue with 17,173 2dFGRS z's at http://star-www.dur.ac.uk/~cole/2dFGRS-2MASS

The 2dF Galaxy Redshift Survey (2dFGRS) is designed to measure redshifts for approximately 250000 galaxies. This paper describes the survey design, the spectroscopic observations, the redshift measurements and the survey database. The 2dFGRS uses the 2dF multi-fibre spectrograph on the Anglo-Australian Telescope, which is capable of observing 400 objects simultaneously over a 2-degree 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 b_J=19.45. The main survey regions are two declination strips, one in the southern Galactic hemisphere spanning 80deg x 15deg around the SGP, and the other in the northern Galactic hemisphere spanning 75deg x 10deg along the celestial equator; in addition, there are 99 fields spread over the southern Galactic cap. The survey covers 2000 sq.deg and has a median depth of z=0.11. Adaptive tiling is used to give a highly uniform sampling rate of 93% over the whole survey region. Redshifts are measured from spectra covering 3600A-8000A at a two-pixel resolution of 9.0A and a median S/N of 13 per pixel. All redshift identifications are visually checked and assigned a quality parameter Q in the range 1-5; Q>=3 redshifts are 98.4% reliable and have an rms uncertainty of 85 km/s. The overall redshift completeness for Q>=3 redshifts is 91.8%, but this varies with magnitude from 99% for the brightest galaxies to 90% for objects at the survey limit. The 2dFGRS database is available on the WWW at http://www.mso.anu.edu.au/2dFGRS, accepted by MNRAS; version with high-resolution figures at http://www.mso.anu.edu.au/2dFGRS/Public/Publications; accompanies the 2dFGRS 100k Release, now available at http://www.mso.anu.edu.au/2dFGRS