Publication Date:
2015-08-08
Description:
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 ${\rm H\,{\small i}}$ 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 deg 2 . In this paper, we present data from 60 per cent of the total survey, corresponding to a sensitivity level of 80 μJy. We discuss the data reduction, the search for galaxies, parametrization, optical identification and completeness. We detect 102 galaxies in the mass range of $\log (M_{{\rm H\,{\small {I}}}}/M)-2\log h=5.6{\rm -}10.3$ . We compute the ${\rm H\,{\small i}}$ mass function (HIMF) at the highest redshifts so far measured. A fit of a Schechter function results in α = – 1.37 ± 0.03, * = (7.72 ± 1.4) x 10 –3 h 3 Mpc –3 and $\log \,(M_{\rm H\,{\small i}}^{*}/{\rm M}_{{\odot }})=({9.75\pm 0.041})+2\log h$ . Using the measured HIMF, we find a cosmic ${\rm H\,{\small i}}$ density of $\Omega _{\rm H\,{\small i}}=({2.33\pm 0.07})\times 10^{-4}\, h^{-1}$ 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 $\Omega _{\rm H\,{\small i}}$ within this redshift range. We calculate a weighted average for $\Omega _{\rm H\,{\small i}}$ 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 $\Omega _{\rm H\,{\small i}}=( 2.63\pm 0.10)\times 10^{-4}\, h^{-1}$ .
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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