THE CLUSTERING CHARACTERISTICS OF H I-SELECTED GALAXIES FROM THE 40% ALFALFA SURVEY

The 40% Arecibo Legacy Fast ALFA survey catalog (alpha.40) of similar to 10,150 H I-selected galaxies is used to analyze the clustering properties of gas-rich galaxies. By employing the Landy-Szalay estimator and a full covariance analysis for the two-point galaxy-galaxy correlation function, we obtain the real-space correlation function and model it as a power law, xi(r) = (r/r(0))(-gamma), on scales <10 h(-1) Mpc. As the largest sample of blindly H I-selected galaxies to date, alpha.40 provides detailed understanding of the clustering of this population. We find gamma = 1.51 +/- 0.09 and r(0) = 3.3 + 0.3, -0.2 h(-1) Mpc, reinforcing the understanding that gas-rich galaxies represent the most weakly clustered galaxy population known; we also observe a departure from a pure power-law shape at intermediate scales, as predicted in Lambda CDM halo occupation distribution models. Furthermore, we measure the bias parameter for the alpha.40 galaxy sample and find that H I galaxies are severely antibiased on small scales, but only weakly antibiased on large scales. The robust measurement of the correlation function for gas-rich galaxies obtained via the alpha.40 sample constrains models of the distribution of H I in simulated galaxies, and will be employed to better understand the role of gas in environmentally dependent galaxy evolution.