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The 2dF Galaxy Redshift Survey: stochastic relative biasing between galaxy populations

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

In: Monthly Notices of the Royal Astronomical Society, 2005, vol. 356, no. 1, p. 247-269

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    Title
    • The 2dF Galaxy Redshift Survey: stochastic relative biasing between galaxy populations
    Author
    • Wild, Vivienne. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA
    • Peacock, John A.. Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ
    • Lahav, Ofer. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA
    • Conway, Edward. School of Physics & Astronomy, University of Nottingham, Nottingham NG7 2RD
    • Maddox, Steve. School of Physics & Astronomy, University of Nottingham, Nottingham NG7 2RD
    • Baldry, Ivan K.. Department of Physics & Astronomy, Johns Hopkins University, Baltimore, MD 21118-2686, USA
    • Baugh, Carlton M.. Department of Physics, University of Durham, South Road, Durham DH1 3LE
    • Bland-Hawthorn, Joss. Anglo-Australian Observatory, PO Box 296, Epping, NSW 2111, Australia
    • Bridges, Terry. Anglo-Australian Observatory, PO Box 296, Epping, NSW 2111, Australia
    • Cannon, Russell. Anglo-Australian Observatory, PO Box 296, Epping, NSW 2111, Australia
    • Cole, Shaun. Department of Physics, University of Durham, South Road, Durham DH1 3LE
    • Colless, Matthew. Anglo-Australian Observatory, PO Box 296, Epping, NSW 2111, Australia
    • Collins, Chris. Astrophysics Research Institute, Liverpool John Moores University, 12 Quays House, Birkenhead L14 1LD
    • Couch, Warrick. Department of Astrophysics, University of New South Wales, Sydney, NSW 2052, Australia
    • Dalton, Gavin. Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH
    • De Propris, Roberto. Anglo-Australian Observatory, PO Box 296, Epping, NSW 2111, Australia
    • Driver, Simon P.. Research School of Astronomy & Astrophysics, The Australian National University, Weston Creek, ACT 2611, Australia
    • Efstathiou, George. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA
    • Ellis, Richard S.. Department of Astronomy, California Institute of Technology, Pasadena, CA 91025, USA
    • Frenk, Carlos S.. Department of Physics, University of Durham, South Road, Durham DH1 3LE
    • Glazebrook, Karl. Department of Physics & Astronomy, Johns Hopkins University, Baltimore, MD 21118-2686, USA
    • Jackson, Carole. Research School of Astronomy & Astrophysics, The Australian National University, Weston Creek, ACT 2611, Australia
    • Lewis, Ian. Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH
    • Lumsden, Stuart. Department of Physics, University of Leeds, Woodhouse Lane, Leeds LS2 9JT
    • Madgwick, Darren. Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
    • Norberg, Peder. ETHZ Institut für Astronomie, HPF G3.1, ETH Hönggerberg, CH-8093 Zürich, Switzerland
    • Peterson, Bruce A.. Research School of Astronomy & Astrophysics, The Australian National University, Weston Creek, ACT 2611, Australia
    • Sutherland, Will. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA
    • Taylor, Keith. Department of Astronomy, California Institute of Technology, Pasadena, CA 91025, USA
    Document Type
    • Postprint
    OAI-PMH Identifier
    • oai:doc.rero.ch:297414
    Summary
    It is well known that the clustering of galaxies depends on galaxy type. Such relative bias complicates the inference of cosmological parameters from galaxy redshift surveys, and is a challenge to theories of galaxy formation and evolution. In this paper we perform a joint counts-in-cells analysis on galaxies in the 2dF Galaxy Redshift Survey, classified by both colour and spectral type, η, as early- or late-type galaxies. We fit three different models of relative bias to the joint probability distribution of the cell counts, assuming Poisson sampling of the galaxy density field. We investigate the non-linearity and stochasticity of the relative bias, with cubic cells of side 10 =L = 45 Mpc (h = 0.7). Exact linear bias is ruled out with high significance on all scales. Power-law bias gives a better fit, but likelihood ratios prefer a bivariate lognormal distribution, with a non-zero ‘stochasticity', i.e. scatter that may result from physical effects on galaxy formation other than those from the local density field. Using this model, we measure a correlation coefficient in log-density space (rLN) of 0.958 for cells of length L = 10 Mpc, increasing to 0.970 by L = 45 Mpc. This corresponds to a stochasticity of 0.44 ± 0.02 and 0.27 ± 0.05, respectively. For smaller cells, the Poisson-sampled lognormal distribution presents an increasingly poor fit to the data, especially with regard to the fraction of completely empty cells. We compare these trends with the predictions of semi-analytic galaxy formation models: these match the data well in terms of the overall level of stochasticity, variation with scale and the fraction of empty cells