Dark Ages of Astronomy Dark to Light Dark

Dark Ages of Astronomy (Dark to Light) Dark Ages z=1000 z=5. 8 z=0 2

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

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

Cosmic Reionization Razoumov et al. 2002 5

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

GRB 050904 at z=6. 295 • Observed damping wing of Lyalpha (Miralda-Escudé 1998) • Host and IGM absorption have different profiles ( -1 vs. -2) • GRB 050904 dominated by host absorption - DLA with log NHI = 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 x. HI Totani et al. 2006

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

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

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

Investment into Reionization SDSS JWST 2005 2010 2015 Wavelength JANUS ELTs 2020 WMAP ALMA LOFAR+MWA SKA 11

JANUS Objectives 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 3 D positions of high-z star-forming galaxies & SMBHs to next-generation observatories 12

JANUS Mission Concept Survey Mode Discovery Mode Via TDRSS

JANUS Observatory Near-IR Telescope (NIRT): 50 cm, 0. 71. 7 μm, J = 19. 6, 1296 arcmin 2 Fo. V Low-resolution spectroscopy of high-z GRBs & quasars X-Ray Flash Monitor (XRFM): Coded Mask, 120 ke. V, 4 sr Fo. V Detects & localizes high-z GRBs HE Monitoring Instrument (HEMI): non-imaging , 0. 021. 5 Me. V, 6 sr Fo. V γ-ray spectroscopy 14

JANUS GRB Science 15

GRB Detections w/ JANUS Swift Observed Swift Model JANUS GRB # (z>5) 5 24 47 GRB # (z>6) 1 13 26 Bromm & Loeb (2006) GRB # (z>7) 0 7 14 GRB # (z>8) 0 3 7 16

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

JANUS Quasar Science 18

Quasar Detections w/ JANUS Survey CFHTQS SDSS VHS UKIDSS LAS Pan. STARSS-1 JANUS Longest λ (μm) 0. 95 2. 4 Sky Area 900 10000 20000 z Limit 6. 5 7. 5 Quasar # (z>6. 5) 0 0 50 2. 4 4000 7. 0 5 1. 05 3000 7. 0 20 1. 7 20000 11. 0 170 19

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

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

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. 22