THE NONLINEAR BIASING OF THE zCOSMOS GALAXIES UP TO z {approx} 1 FROM THE 10k SAMPLE

Journal Article · Wed Apr 20 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/731/2/102· OSTI ID:21574700

Kovac, K; Porciani, C; Lilly, S J; Oesch, P; Peng, Y; Carollo, C M ^[1]; Marinoni, C ^[2]; Guzzo, L; Iovino, A ^[3]; Cucciati, O; Kneib, J -P; Le Fevre, O ^[4]; Zamorani, G; Bolzonella, M; Zucca, E; Bardelli, S ^[5]; Meneux, B ^[6]; Contini, T ^[7]; Mainieri, V ^[8]; Renzini, A ^[9]

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1. Institute of Astronomy, ETH Zurich, 8093 Zurich (Switzerland)
2. Centre de Physique Theorique, Marseille (France)
3. INAF Osservatorio Astronomico di Brera, Milan (Italy)
4. Laboratoire d'Astrophysique de Marseille, Marseille (France)
5. INAF Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy)
6. Max-Planck-Institut fuer extraterrestrische Physik, D-84571 Garching (Germany)
7. Laboratoire d'Astrophysique de Toulouse-Tarbes, Universite de Toulouse, CNRS, 14 avenue Edouard Belin, F-31400 Toulouse (France)
8. European Southern Observatory, Karl-Schwarzschild- Strasse 2, Garching, D-85748 (Germany)
9. INAF-Osservatorio Astronomico di Padova, Padova (Italy)

We use the zCOSMOS galaxy overdensity field to study the biasing of galaxies in the COSMOS field. By comparing the probability distribution function of the galaxy density contrast {delta}{sub g} to the lognormal approximation of the mass density contrast {delta}, we obtain the mean biasing function b({delta}, z, R) between the galaxy and matter overdensity fields and its second moments b-hat and b-tilde. Over the redshift interval 0.4 < z < 1 the conditional mean function ({delta}{sub g}|{delta}) = b({delta}, z, R){delta} is of a characteristic shape, requiring nonlinear biasing in the most overdense and underdense regions. Taking into account the uncertainties due to cosmic variance, we do not detect any significant evolution in the ({delta}{sub g}|{delta}) function, but we do detect a significant redshift evolution in the linear biasing parameter b-hat from 1.23 {+-} 0.11 at z {approx} 0.55 to 1.62 {+-} 0.14 at z {approx} 0.75, for a luminosity-complete sample of M{sub B} < -20 - z galaxies. The b-hat parameter does not change significantly with smoothing scale between 8 and 12 h{sup -1} Mpc, but increases systematically with luminosity (at 2{sigma}-3{sigma} significance between the M{sub B} < -20.5 - z and M{sub B} < -20 - z samples). The nonlinearity parameter b-tilde/b-hat is offset from unity by at most 2%, with an uncertainty of the same order. The b-tilde / b-hat parameter does not show any significant redshift evolution, dependence on the smoothing scale or on the luminosity. By matching the linear bias of galaxies to the halo bias, we infer that the M{sub B} < -20 - z galaxies reside in dark matter halos with a characteristic mass of about (2.6 - 5.6) x 10{sup 12} M{sub sun} with a small dependence on the adopted bias-mass relation. Our detailed error analysis and comparison with previous studies lead us to conclude that cosmic variance is the main contributor to the differences in the linear bias measured from different surveys. While our results support the general picture of biased galaxy formation up to z {approx} 1, the fine-tuning of the galaxy formation models is still limited by the restrictions of the current spectroscopic surveys at these redshifts.

• OSTI ID: 21574700
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 731; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COSMOLOGY
DENSITY
DISTRIBUTION FUNCTIONS
EVOLUTION
FUNCTIONS
GALACTIC EVOLUTION
GALAXIES
LUMINOSITY
MASS
NONLINEAR PROBLEMS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
PROBABILITY