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

Edward Conway*, Steve Maddox, Vivienne Wild, John A. Peacock, Ed Hawkins, Peder Norberg, Darren S. Madgwick, Ivan K. Baldry, Carlton M. Baugh, Joss Bland-Hawthorn, Terry Bridges, Russell Cannon, Shaun Cole, Matthew Colless, Chris Collins, Warrick Couch, Gavin Dalton, Roberto De Propris, Simon P. Driver, George EfstathiouRichard S. Ellis, Carlos S. Frenk, Karl Glazebrook, Carole Jackson, Bryn Jones, Ofer Lahav, Ian Lewis, Stuart Lumsden, Will Percival, Bruce A. Peterson, Will Sutherland, Keith Taylor

*Corresponding author for this work

    Research output: Contribution to journalReview articlepeer-review

    18 Citations (Scopus)

    Abstract

    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 η 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(δE, δL), and directly fit deterministic bias models to the joint counts in cells. We measure a linear relative bias of ≈1.3, which does not vary significantly with ℓ. A deterministic linear bias model is, however, a poor approximation to the data, especially on small scales (ℓ ≤ 28 h-1 Mpc) where deterministic linear bias is excluded at high significance. A power-law bias model with index b1 ≈ 0.75 is a significantly better fit to the data on all scales, although linear bias becomes consistent with the data for ℓ ≳ 40 h-1 Mpc.

    Original languageEnglish
    Pages (from-to)456-474
    Number of pages19
    JournalMonthly Notices of the Royal Astronomical Society
    Volume356
    Issue number2
    DOIs
    Publication statusPublished - 11 Jan 2005

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