2. Dark Ages of Astronomy (Dark to Light) 2 Dark Ages z=1000 z=5.8 z=0

3. SDSS Reionization Studies 3 End of Reionization - SDSS Quasars - Fan et al. 2006 SDSS telescope at Apache Point

4. 4 Possible Causes of Reionization Dark Matter-Driven Gravitational Collapse Hydrodynamic Interactions Atomic and Molecular Cooling Star Formation Stellar Death Synthesis and Dispersal of Metallic Elements Birth & Feeding of the 1 st Supermassive BHs {

5. Cosmic Reionization Razoumov et al. 2002 5

6. Movie of a Typical Reionization Model Time in movie is linear in physical time. 100 Mpc Overdense to Underdense: yellow, green, light blue, dark blue Black regions are neutral.

7. GRB 050904 at z=6.295 Observed damping wing of Ly- alpha (Miralda-Escudé 1998) Host and IGM absorption have different profiles ( -1 vs. -2 ) GRB 050904 dominated by host absorption - DLA with log N HI = 21.6 Upper limit on IGM neutral fraction: x HI < 0.6 (90% c.l.) First cosmological constraint from a GRB observation Taken 3.4 days after the burst Totani et al. 2006 x HI

8. Damping Wing Lyα Absorption Miralda-Escude (1998) Lyα Cross Section:Absorption profile:

9. GRB Cosmology GRBs only require a single massive star Theoretical expectations of a maximum redshift z>10 Afterglows bright enough, for a brief time, to enable cosmological measurements (GRB 050904) Possibility to harvest more such bursts than Swift does by pursuing a targeted strategy: –Softer band for prompt emission –Infrared telescope for follow-up, with low resolution spectroscopy –Aiming to provide a redshifts in real time

10. Reionization Questions How does the cosmic SFR evolve beyond z=5? Did high-mass stars play a dominant role in reionization? How did the metal enrichment of star-forming regions progress? What was the contribution of quasars to reionization? When were the first quasars born? How fast did quasars grow? How did reionization proceed over 6<z<10? 10

11. Investment into Reionization 11 SDSS WMAP JWST ALMA LOFAR+MWA SKA ELTs 2005 20102015 2020 Wavelength JANUS

12. JANUS Objectives 12 Science Objectives: (1) Measure SFR 5<z<12 by discovering high-z GRBs & afterglows; (2) Enumerate brightest quasars over 6<z<10 & measure reionization contribution; (3) Enable detailed studies of the reionization history & metal enrichment in the early Universe; (4) Provide 3D positions of high-z star-forming galaxies & SMBHs to next-generation observatories

13. JANUS Mission Concept Survey Mode Discovery Mode

14. JANUS Observatory 14 X-Ray Flash Monitor (XRFM): Coded Mask, 1- 20 keV, 4 sr FoV Near-IR Telescope (NIRT): 50 cm, 0.7- 1.7 μm, J = 19.6, 1296 arcmin 2 FoV HE Monitoring Instrument (HEMI): non-imaging, 0.02- 1.5 MeV, 6 sr FoV Detects & localizes high-z GRBs Low-resolution spectroscopy of high-z GRBs & quasars γ-ray spectroscopy

15. JANUS GRB Science 15

16. GRB Detections w/ JANUS 16 GRB # (z>5) GRB # (z>6) GRB # (z>7) GRB # (z>8) Swift Observed5100 Swift Model241373 JANUS4726147 Bromm & Loeb (2006)

17. JANUS Survey Science Measure the ionizing flux of quasars over 6 < z < 10 by discovering and observing the brightest high-redshift quasars 20,000 deg 2 survey 300 z > 6 quasars Maximum z≈10 Ionizing flux of each quasar measured directly from continuum

18. JANUS Quasar Science 18

19. Quasar Detections w/ JANUS 19 Survey Longest λ (μm) Sky Area z Limit Quasar # (z>6.5) CFHTQS0.959006.50 SDSS0.95100006.50 VHS2.4200007.550 UKIDSS LAS 2.440007.05 Pan- STARSS-1 1.0530007.020 JANUS1.72000011.0170

20. JANUS Science for “Free” Brown Dwarf studies GRB-SNe connection –3-11/year X-ray All-Sky Monitor –Super-flares from solar-type stars –Supergiant fast X-ray transients –Tidal Disruption Events 20

21. JANUS Status One of six missions selected for a Phase A Concept Study (May-2008) Concept Study Report due (Dec-2008) Two of six missions selected by NASA for build phase (May-2009) Phase B begins (Jun-2009) Launch (~2013) 21

22. 22 Janus was the god of gates, doors, doorways, beginnings, and endings. Janus was frequently used to symbolize change and transitions such as the progression of future to past, of one condition to another, of one vision to another, and of one universe to another. He was also known as the figure representing time because he could see into the past with one face and into the future with the other. Janus is also know as “custodian of the universe” and was a deity of beginnings.