An UltraDeep ALFA survey Erwin de Blok Erwin

An Ultra-Deep ALFA survey Erwin de Blok <Erwin. de. Blok@astro. cf. ac. uk> Elias Brinks <ebrinks@inaoep. mx> Wolfram Freudling <wfreudli@eso. org> G. Lyle Hoffman <hoffmang@lafayette. edu> Suzanne Linder <Suzanne. Linder@astro. cf. ac. uk> Karen Masters <masters@astro. cornell. edu> Karen O'Neil <koneil@gb. nrao. edu> Daniel J. Pisano <DJ. Pisano@atnf. csiro. au> Lister Staveley-Smith <Lister. Staveley-Smith@csiro. au> Martin Zwaan <mzwaan@eso. org>

Starformation rate history Thompson, 2003, Ap. J 596, 748 Rowan-Robinson, 2003, MNRS 345, 819 Bouwens et al. , 2004, astroph/0403167 EALFA workshop 2 – Arecibo May 2004 2

damped Lya systems toward Q 0249 -2212 EALFA workshop 2 – Arecibo May 2004 3

STORRIELOMBARDI & WOLFE, 2000, Ap. J 543, 552 EALFA workshop 2 – Arecibo May 2004 4

PEI, FALL, & HAUSER 1999, Ap. J, 522, 604 EALFA workshop 2 – Arecibo May 2004 5

How Does the Density of Cool Gas evolve with time? Ø Models, based on multi-λ observations, (Madau plots etc), predict Ωgas∝(1+z)3. 2 at low-z (Pei et al. 1999). Ø Damped Ly-α absorption lines suggest d. NDLA /dz= 0. 05(1+z)1. 1, implying NO intrinsic evolution of >2 x 1020 cm-2 absorbers - i. e. constant co-moving gas density (Storrie. Lombardi & Wolfe 2000). EALFA workshop 2 – Arecibo May 2004 6

Ø To differentiate between evolving and nonevolving HI density, need to be able to discern a 50% change in density at z=0. 15. Ø Need ~40 galaxies with M~109. 5 M for detection at 99% CL. EALFA workshop 2 – Arecibo May 2004 7

The ALFA advantage - I Ø Speed – e. g. 7 days would complete Decl. range 25 o-38 o to HIPASS sensitivity! sensitivity #beams beam area EALFA workshop 2 – Arecibo May 2004 8

The ALFA advantage - II Ø Sensitivity – HIPASS ( =250 sec/pix) is complete for M* galaxies only for cz<4000 km s-1. – ALFA (same ) would be complete to cz<15, 000 km s-1 ! – Deep ALFA ( = days) should be able to detect M* galaxies to z=0. 1 -0. 16 (the max ALFA redshift) HI at z=0. 18 in a A 2218 spiral with WSRT (Zwaan et al. 2001) EALFA workshop 2 – Arecibo May 2004 9

The ALFA advantage - III Ø Resolution N. B. for a filled aperture, linear resolution always the same at the max survey depth dmax (A/T )1/2. Arecibo beam Parkes beam HIPASS spectrum HIPASS J 0620 -57 = ESO 161 -G 001/NGC 2222/NGC 2221 (ATCA observation) EALFA workshop 2 – Arecibo May 2004 10

Possible survey parameters Ø Need to be sensitive to MHI~109 -10 M Ø 200 km/sec linewidth 0. 2 m. Jy at z~0. 16 Ø rms~0. 05 m. Jy/beam (260 x deeper than HIPASS) Ø 0. 36 deg 2 in 1000 hrs, or 70 hrs/beam Ø Volume = 8000 Mpc 3 Ø 160 galaxies in range 109 -10 M EALFA workshop 2 – Arecibo May 2004 11

Required obs parameters Ø 200 MHz, 2 pol, 7 beams (need high-z) Ø Multi-bit (9 -levels or more) Ø 8192 channels (need 5 km/s resolution) Ø No RFI, fast dumping Ø Radar blanking, or v. fast dumping (1 ms) Ø Nightime observations (willing to test days) Ø Need calibration and beam parameters for all ZA Ø Decl. near 17. 5 deg or 19. 5 deg, |b|>30 deg Ø Could be near existing deep field EALFA workshop 2 – Arecibo May 2004 12

Will it work? Ø Interference ___ Ø σ Tint ? Ø Baselines, standing waves Ø Efficiency (time on “source”) EALFA workshop 2 – Arecibo May 2004 13

Will it work? Precursor Proposal The total integration time to reach the cosmological interesting sensitivity outlined above is 70 hour per beam. We propose precursor observations to reach half this integration time per beam using both channels of the WAPPS with 100 MHz bandwidth. We estimate that with our “drift and chase" mode, this can be achieved in a total of 70 hours of scheduled observing time. By collecting repeated observations of the same source over an extended period of time, we will be able to investigate stability and robustness of calibration of the whole system. EALFA workshop 2 – Arecibo May 2004 14