1. Sackler DSI Trustees: 2001, Aug, 01Richard McMahon (www.ast.cam.ac.uk) 1 DAZLE: Dark Ages “Z” Lyman Explorer (visiting a Time when Galaxies are Young) McMahon, Parry, Horton,Trentham, Bunker, Clarke, King, Mackay (Institute of Astronomy, Cambridge, UK) Bland-Hawthorn (AAO, Australia)

2. Sackler DSI Trustees: 2001, Aug, 01Richard McMahon (www.ast.cam.ac.uk) 2 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

3. Sackler DSI Trustees: 2001, Aug, 01Richard McMahon (www.ast.cam.ac.uk) 3 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 M sol yr -1 Assume SFR detection limits more appropriate to a slowly disc or sub- galactic units in a halo –i.e. 1-3 M sol yr -1  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)  minimum is 1000 Mpc 3 [c.f. 10Mpc cube]

4. Sackler DSI Trustees: 2001, Aug, 01Richard McMahon (www.ast.cam.ac.uk) 4 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 z=5.25 - 5.33 – 8100-8250z=5.66 - 5.79 – 9050-9300z=6.44 - 6.65 Sky background is 0.5-1.0  10 -17 erg cm -2 s -1 ang -1

5. Sackler DSI Trustees: 2001, Aug, 01Richard McMahon (www.ast.cam.ac.uk) 5

6. Sackler DSI Trustees: 2001, Aug, 01Richard McMahon (www.ast.cam.ac.uk) 6 An extremely luminous galaxy at z=5.74 Hu, McMahon, Cowie, 1999, ApJ, 522, L9 90” x 90” 500 x 500 h -1 kpc

7. Sackler DSI Trustees: 2001, Aug, 01Richard McMahon (www.ast.cam.ac.uk) 7 Technical/Observational Issues The sky is blue IR sky is bright 1-8micron IR sky brightness is dominated by intense, narrow OH airglow lines

8. Sackler DSI Trustees: 2001, Aug, 01Richard McMahon (www.ast.cam.ac.uk) 8 DAZLE Baseline Design Rockwell Hawaii-II 2048 2 HgCdTe detector Tunable Fabry-Perot filter from Queensgate Instruments –R=2000; 150km/sec –cooled to -20C Target telescope: Gemini South –f/16 collimator; 0.18”/pixel –6.2’x6.2’ Sensitivity: 10 -18 erg s -1 cm -2 ; 5  in 15,000secs

9. Sackler DSI Trustees: 2001, Aug, 01Richard McMahon (www.ast.cam.ac.uk) 9 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 10m 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>7galaxy 10-50 to detect 10 i.e. Terrestrial aperture is now available to allow such an experimental

10. Sackler DSI Trustees: 2001, Aug, 01Richard McMahon (www.ast.cam.ac.uk) 10 THE END

11. Sackler DSI Trustees: 2001, Aug, 01Richard McMahon (www.ast.cam.ac.uk) 11 Lyman-alpha galaxies at high redshift: Proof of concept Narrow band image z=4.55 Off-band continuum image From Hu, McMahon, 1996, Nature, 382, 231

12. Sackler DSI Trustees: 2001, Aug, 01Richard McMahon (www.ast.cam.ac.uk) 12 8150/105ZI R VB