DAZLE Dark Ages Z Lyman Explorer visiting a
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DAZLE: Dark Ages “Z” Lyman Explorer (visiting a Time when Galaxies are Young) Mc. Mahon, Parry, Horton, Trentham, Bunker, Clarke, King, Mackay (Institute of Astronomy, Cambridge, UK) Bland-Hawthorn (AAO, Australia) Sackler DSI Trustees: 2001, Aug, 01 Richard Mc. Mahon (www. ast. cam. ac. uk) 1
Experimental design issues • How faint to go? • How large a volume to search? • How many galaxies or galactic sub-unit do we expect? • The large uncertainties make this an important experiment Sackler DSI Trustees: 2001, Aug, 01 Richard Mc. Mahon (www. ast. cam. ac. uk) 2
Astrophysical principles Minimum Flux limit • Previous surveys(e. g. Pritchett, Djorgovski) in the early 1990’s were based on the simple paradigm of a monolithic collapse(Eggen, Lynden. Bell and Sandage, 1962) – expected star formation rates of 50 -500 Msol yr-1 • Assume SFR detection limits more appropriate to a slowly disc or subgalactic units in a halo – i. e. 1 -3 Msol yr-1 Þ 0. 5 - 1. 0 10 -17 erg s-1 cm-2 Minimum Volume • search a comoving volume within which you expect to find the progenitors of around 10 L* galaxies. – Local density 1. 4± 0. 2 10 -2 h 50 Mpc-3 (e. g. Loveday etal, 1992) Þ minimum is 1000 Mpc 3 [c. f. 10 Mpc cube] Sackler DSI Trustees: 2001, Aug, 01 Richard Mc. Mahon (www. ast. cam. ac. uk) 3
Basic observational principles • Target spectral regions where night sky is dark – between the intense OH line emission • For z>5; i. e. >7295 angstroms – Optical; – – 7600 -7700 8100 -8250 9050 -9300 z=5. 25 - 5. 33 z=5. 66 - 5. 79 z=6. 44 - 6. 65 • Sky background is 0. 5 -1. 0 10 -17 erg cm-2 s-1 ang-1 Sackler DSI Trustees: 2001, Aug, 01 Richard Mc. Mahon (www. ast. cam. ac. uk) 4
Sackler DSI Trustees: 2001, Aug, 01 Richard Mc. Mahon (www. ast. cam. ac. uk) 5
An extremely luminous galaxy at z=5. 74 90” x 90” 500 x 500 h-1 kpc Hu, Mc. Mahon, Cowie, 1999, Ap. J, 522, L 9 Sackler DSI Trustees: 2001, Aug, 01 Richard Mc. Mahon (www. ast. cam. ac. uk) 6
Technical/Observational Issues • The sky is blue • IR sky is bright • 1 -8 micron IR sky brightness is dominated by intense, narrow OH airglow lines Sackler DSI Trustees: 2001, Aug, 01 Richard Mc. Mahon (www. ast. cam. ac. uk) 7
DAZLE Baseline Design • Rockwell Hawaii-II 20482 Hg. Cd. Te detector • Tunable Fabry-Perot filter from Queensgate Instruments – R=2000; 150 km/sec – cooled to -20 C • Target telescope: Gemini South – f/16 collimator; 0. 18”/pixel – 6. 2’x 6. 2’ • Sensitivity: 10 -18 erg s-1 cm-2; 5 s in 15, 000 secs Sackler DSI Trustees: 2001, Aug, 01 Richard Mc. Mahon (www. ast. cam. ac. uk) 8
Conclusions • In the last 5 years, the systematic detection of “normal” high redshift galaxies has gone from z=1 to z=6 (mainly due to increased aperture of 10 m Keck’s) • we have already reached the silicon/optical limit • future is the IR • future is emission line based searches • may require 1 -5 nights to find a single z>7 galaxy • 10 -50 to detect 10 i. e. • Terrestrial aperture is now available to allow such an experimental Sackler DSI Trustees: 2001, Aug, 01 Richard Mc. Mahon (www. ast. cam. ac. uk) 9
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