High-order 2MASS galaxy correlation functions: Probing the primordial density field and the linearity of galaxy bias

Abstract

We use the 2MASS extended source catalogue to determine angular correlation functions, w_p, to high orders (p<=9). The main sample contains 650,745 galaxies and represents an order of magnitude increase in solid angle over previous samples used in such analysis. The high-order correlation functions are used to determine the projected and real space hierarchical amplitudes, s_p and S_p. In contrast to recent results, for p<=6 these parameters are found to be quite constant over a wide range of scales to r=40 Mpc, consistent with a Gaussian form to the primordial distribution of density fluctuations which has evolved under the action of gravitational instability. We test the sensitivity of our results to the presence of rare fluctuations in the local galaxy distribution by cutting various regions of over-density from the main sample; unlike previous analyses, we find that our results are relatively robust to the removal of the largest superclusters. We use our constraints on the K-band S_p parameters in two ways. First, we examine their consistency with non-Gaussian initial conditions; we are able to rule out strong non-Gaussianity in the primordial density field, as might be seeded by topological defects such as cosmic strings or global textures at the 2.5 sigma confidence level. Second, we investigate the way in which galaxies trace the underlying mass distribution. We find evidence for a non-zero quadratic contribution to the galaxy bias, parameterised by c_2=0.57+/-0.33. This positive result represents a significant difference from the negative values found previously; we examine a possible explanation in the light of recent observations which universally provide negative values for c_2.

13 pages, 5 figures, submitted to MNRAS

References in corpus (12)

• The 2dF Galaxy Redshift Survey: Power-spectrum analysis of the final dataset and cosmological implications
• The 6dF Galaxy Survey: Samples, Observational Techniques and the First Data Release
• Ghost Inflation
• Large Scale Structure in the Local Universe: The 2MASS Galaxy Catalog
• Statistical Analysis of Galaxy Surveys-II. The 3-point galaxy correlation function measured from the 2dFGRS
• The 2dF Galaxy Redshift Survey: higher order galaxy correlation functions
• The 2dF Galaxy Redshift Survey: voids and hierarchical scaling models
• The 2dF Galaxy Redshift Survey: Hierarchical galaxy clustering
• 2MASS Constraints on the Local Large-Scale Structure: A Challenge to LCDM?
• The 2MASS galaxy angular power spectrum: Probing the galaxy distribution to Gigaparsec scales
• Hydrogen Clouds before Reionization: a Lognormal Model Approach
• The Growth of the Local Void and the Origin of the Local Velocity Anomaly

Cited by in corpus (5)

• The assembly bias of dark matter haloes to higher orders
• Primordial non-Gaussianity in the large scale structure of the Universe
• Statistical analysis of galaxy surveys - III: The non-linear clustering of red and blue galaxies in the 2dFGRS
• Higher-Order Angular Galaxy Correlations in the SDSS: Redshift and Color Dependence of non-Linear Bias
• The galaxy luminosity function and the Local Hole