CONSTRAINTS ON COSMOLOGICAL MODELS FROM THE IRAS QDOT SURVEY RESULTS

Constraints on the nature of the galaxy density field are explored using the results of the recent IRAS QDOT survey. Analytic modeling of the power spectrum gives a best fit to observed density variances when P(k) approximately k(n) with n = -1.26(-0.35)+0.39 (68% confidence limits) or P(k) approximately P(CDM)(OMEGA-h) with (OMEGA-h) = 0.17(-0.09)+0.17 over the scales covered by the survey (lambda approximately 100h-1 Mpc). Realistic simulations of the survey made from N-body simulations of the n = -1 power-law power spectrum and the OMEGA = 1 CDM models show that the power-law model is basically consistent with all QDOT variance results, while the CDM model has a smaller variance than the observation at the 20h-1 Mpc Gaussian smoothing scale (2-sigma-effect). We conclude that the QDOT results are best explained if the power spectrum of the galaxy density field has a slope of approximately -1 near lambda approximately 100h-1 Mpc, while the CDM model has a slope of approximately 0 at that scale. Possibility of the marginal non-Gaussian behavior at the 20h-1 Mpc scale reported by Saunders et al. (1.5-sigma-effect) is examined for gravitational instability models with Gaussian initial conditions. It is argued that the observed <delta-3> versus <delta-2> in redshift space is not what these models would predict.