SIMBAD references

The Arecibo Ultra-Deep Survey (AUDS) combines the unique sensitivity of the telescope with the wide field of the Arecibo L-band Feed Array (ALFA) to directly detect 21 cm H i emission from galaxies at distances beyond the local Universe bounded by the lower frequency limit of ALFA (z = 0.16). AUDS has collected 700 h of integration time in two fields with a combined area of 1.35 deg2. In this paper, we present data from 60 percent of the total survey, corresponding to a sensitivity level of 80µJy. We discuss the data reduction, the search for galaxies, parametrization, optical identification and completeness. We detect 102 galaxies in the mass range of log(M_H I/M)-2logh=5.6-10.3. We compute the H i mass function (HIMF) at the highest redshifts so far measured. A fit of a Schechter function results in α = - 1.37±0.03, Φ* = (7.72±1.4)x 10^–3h3Mpc-3 and log (M_H i^*/M_☉)=(9.75±0.041)+2logh. Using the measured HIMF, we find a cosmic H i density of Ω_H i=(2.33±0.07)×10^-4  h^-1 for the sample (z = 0.065). We discuss further uncertainties arising from cosmic variance. Because of its depth, AUDS is the first survey that can determine parameters for the HIMF in independent redshift bins from a single homogeneous data set. The results indicate little evolution of the comoving mass function and Ω_H i within this redshift range. We calculate a weighted average for Ω_H i in the range 0 < z < 0.2, combining the results from AUDS as well as results from other 21 cm surveys and stacking, finding a best combined estimate of Ω_H i=( 2.63±0.10)×10^-4  h^-1.