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Gaseous Evolution in Galaxies: The Arecibo Ultra-Deep Survey (AUDS)
W. Freudling1,L. Staveley-Smith2, M. Calabretta2, B. Catinella3, W. van Driel4, S. Linder5, R. Minchin5, E. Momjian3, M. Zwaan1 & the AUDS team.
1E

SO, Karl Schwarzschild Strasse 2 , D-85748, Germany; 2 A TNF-CSIRO, PO Box 76, Epping, NSW 1710, Australia; 3 Arecibo Observatory, HC03 Box 53995, A recibo, Puerto Rico 00612, 4 O bservatoire de Paris, GEPI, CNRS UMR 8111, France; 5D epartment of Physics and Astronomy, Cardiff University, PO Box 913, Cardiff CF24 3YB, UK.

Motivation
! the global co-moving star-formation rate increases by about a
factor of five between z~0 and z~1 (e.g. Hopkins 2004). should correspond to increase in the density of cool gas, which is the fuel for star formation, HI (1+z)2-3 (Pei et al. 1999, Cole et al. 2000, Baugh et al. 2004).

The density evolution of cool gas in the Universe as modelled by Cole et al. (2000) and Baugh et al. (2004). These, and other, models predict an increase in comoving gas density between z =0 and 1 of a factor of 2-4. Even at z=0. 2, an increase of 30-70% is predicted. This makes it feasible to use accurate Arecibo H I measurements to assess evolution models at low r edshift (from Baugh et al 2004).

Discussion of Precursor Results
For each galaxy, the maximum accessible volume was calculated and a binned HI mass function was computed using the 1/ V(max) method. Preliminary results suggest a galaxy detection rate which is a factor of 2-3 times higher than expected from the local HI mass function derived from HIPASS (Z waan et al. 2003).

! number density of Damped Lyman- Absorbers (DLA) as
function of z increases only mildly, dn/dz (1+z)1.1, (e.g. Peroux et al. 2003, Zwaan et al. 2005).

?
? Do DLAs trace bulk of gas available for star formation? ? Does star-formation rate trace available cool HI?
deep HI observations with the Arecibo t elescope to measure HI as a function of r edshift.

number density per redshift b in of DLAs. The around z~0 are from local 21cm HI surveys. The solid line is the no-evolution i n the number of systems per comoving u sit o f length. Also shown are results from local 2 1cm HI surveys converted to compared to local HI density measurements (adopted from Z waan 2005).

From top to bottom: (a) the number of detections as a function of HI mass; (b) the volume sampled; (c) the HI mass function. The green line is the HIPASS mass function of Zwaan e t al. (2003). Galaxies in the two populated HI mass bins above 5x109 solar masses (approximately M* at z=0) have densities a few times the local density in the volume surveyed.

Arecibo Ultra-Deep Survey (AUDS)
· New ALFA feed array allows 21cm HI surveys up to z~0.16 · AUDS aims to survey 0.36 square degrees · precursor observations demonstrated feasibility of deep observations

Precursor Observation
· part of the commissioning phase of the A recibo L-Band Feed Array (ALFA) · target field about 20 square arcmin centered at RA 00:00:14.9, Decl. +15:43:42.5 (J2000) · total of 53 hrs observing was acquired in `drift-and-chase' mode · maximum integration time per beam of 16 hrs per beam · data reduction with AIPS++ LiveData and Gridzilla modified for radio-frequency interference mitigation. If such a high normalization of the HI mass function were representative f or the sampled redshift of z~0.1, it would imply strong evolution in the volume averaged density of cool Hi between z =0 and z~0.1.

Future Observations
beamwidth of the A recibo telescope (3 a rcmin) and the lack of complete redshift i nformation in the field make it impossible to unambiguously identify optical counterparts. High-resolution HI maps to identify galaxies will be obtained at GMRT in February 2006. full AUDS plans survey larger field of view (0.36 deg2), longer integration times (40 hrs per pointing), giving lower noise levels (50 µ Jy) over the full redshift range 0
Results
· rms of the spectra in the most sensitive part of the precursor data is 80 µJy which was close to theoretical expectation. · 14 well-detected HI lines and nine candidate detections between r edshift 0.07 to 0.15. · there are nine well-detected HI lines and six candidates with z>0.1. · this is a larger sample than all previously published HI detections at these redshifts. · first blind 21 HI survey which overlaps in z with DLA surveys

The 7-beam A recibo L-Band Feed Array (ALFA) used in the A recibo Ultra Deep Survey (AUDS). The array is situated at the Gregorian focus of the telescope and was installed in May 2004. The frequency range extends down to 1225 MHz, allowing HI observations to a redshift of 0.16.

The HI profile of a galaxy convincingly detected at a redshift o f 0.11. Peak flux density is 0.7 m Jy

The AUDS Team
The AUDS team consists of members of the Arecibo EGAL who are interested in deep HI observations. Current memebers a re:
Elias Brinks, Noah B rosch, Barbara C atinella, Christopher C onselice, Jonathan Davies, Erwin de Blok, Wolfram Freudling, Virginia Kilborn, Suzanne Linder, Karen Masters, Martin Meyer, Robert Minchin, Emmanuel M omjian, Karen O'Neil, Daniel Pisano, Jessica Rosenberg, Kristine Spekkens, Lister Staveley-Smith, Wim van Driel, Martin Z waan

References
Baugh C.M. et al. 2004, NewAR, 48, 1239 Cole S., L acey C.G., Baugh C.M., Frenk C.S. 2000, MNRAS 319, 168 Hopkins A.M. 2004, ApJ, 615, 209 Pei Y.C., Fall S.M., Hauser M.G. 1999, ApJ, 522, 604 Peroux C., McMahon R.G., Storrie-Lombardi L. J., Irwin M.J. 2003, MNRAS, 346, 1103 Zwaan M.A. et al. 2003, AJ, 125, 2842 Zwaan M.A. et al. 2006, astro-ph 05101270

The 305-m A recibo telescope in Puerto Rico, the largest and most sensitive instrument of its kind.

HI mass against r edshift for all galaxies detected in the AUDS precursor observations. Solid squares are the best detections, crosses are mid-quality detections, and empty squares are detections that remain to be confirmed.