The 2dF Galaxy Redshift Survey: the nature of the relative bias between galaxies of different spectral type

E Conway, S Maddox, V Wild, J A Peacock, E Hawkins, P Norberg, D S Madgwick, I K Baldry, C M Baugh, J B Hawthorn, T Bridges, R Cannon, S Cole, M Colless, C Collins, W Couch, G Dalton, R De Propris, S P Driver, G EfstathiouR S Ellis, C S Frenk, K Glazebrook, C Jackson, B Jones, O Lahav, I Lewis, S Lumsden, W Percival, B A Peterson, W Sutherland, K Taylor, 2dFGRS Team

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18 Citations (Scopus)


We present an analysis of the relative bias between early- and late-type galaxies in the Two-degree Field Galaxy Redshift Survey(2dFGRS) - as defined by the parameter of Madgwick et al., which quantifies the spectral type of galaxies in the survey. We calculate counts in cells for flux-limited samples of early- and late-type galaxies, using approximately cubical cells with sides ranging from 7 to 42 h(-1) Mpc. We measure the variance of the counts in cells using the method of Efstathiou et al., which we find requires a correction for a finite volume effect equivalent to the integral constraint bias of the autocorrelation function. Using a maximum-likelihood technique we fit lognormal models to the one-point density distribution, and develop methods of dealing with biases in the recovered variances resulting from this technique. We then examine the joint density distribution function, f (delta(E), delta(L)), and directly fit deterministic bias models to the joint counts in cells. We measure a linear relative bias of approximate to1.3, which does not vary significantly with.Adeterministic linear bias model is, however, a poor approximation to the data, especially on small scales (l less than or equal to 28 h(-1) Mpc) where deterministic linear bias is excluded at high significance. A power-law bias model with index b(1) approximate to 0.75 is a significantly better fit to the data on all scales, although linear bias becomes consistent with the data for l greater than or similar to 40 h(-1) Mpc.

Original languageEnglish
Pages (from-to)456-474
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - 11 Jan 2005


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