The 2dF Galaxy Redshift Survey: the nature of the relative bias between galaxies of different spectral type |
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| Authors: | 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 Efstathiou Richard 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 |
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| Affiliation: | School of Physics &Astronomy, University of Nottingham, Nottingham NG7 2RD;Department of Physics, University of Durham, South Road, Durham DH1 3LE;Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA;Hubble Fellow, Lawrence Berkeley National Laboratory, MS50R-5032, Berkeley, CA 94720, USA;Institut für Astronomie, ETH Hönggerberg, CH-8093 Zürich, Switzerland;Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ;Department of Physics &Astronomy, Johns Hopkins University, Baltimore, MD 21218-2686, USA;Anglo-Australian Observatory, PO Box 296, Epping, NSW 2121, Australia;Research School of Astronomy &Astrophysics, The Australian National University, Weston Creek, ACT 2611, Australia;Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Birkenhead, L14 1LD;Department of Astrophysics, University of New South Wales, Sydney, NSW 2052, Australia;Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH;Space Science and Technology Division, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX;Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA;Department of Physics, University of Leeds, Woodhouse Lane, Leeds LS2 9JT;Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT;Astrophysics Group, Department of Physics, Bristol University, Tyndall Avenue, Bristol BS8 1TL |
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| 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 b 1≈ 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 . |
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| Keywords: | surveys galaxies: distances and redshifts galaxies: statistics large-scale structure of Universe |
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