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Dark Ages of Astronomy (Dark to Light)

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Dark Ages of Astronomy (Dark to Light). Dark Ages. z =0. z =5.8. z =1000. SDSS Reionization Studies. SDSS telescope at Apache Point. End of Reionization - SDSS Quasars - Fan et al. 2006. Possible Causes of Reionization. Dark Matter-Driven Gravitational Collapse Hydrodynamic Interactions

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sdss reionization studies
SDSS Reionization Studies

SDSS telescope at Apache Point

End of Reionization - SDSS Quasars - Fan et al. 2006


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 1st Supermassive BHs


cosmic reionization
Cosmic Reionization

Razoumov et al. 2002

movie of a typical reionization model
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
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 NHI = 21.6
  • Upper limit on IGM neutral fraction: xHI < 0.6 (90% c.l.)
  • First cosmological constraint from a GRB observation
  • Taken 3.4 days after the burst


Totani et al. 2006

damping wing ly absorption
Damping Wing Lyα Absorption

Lyα Cross Section:

Absorption profile:

Miralda-Escude (1998)

grb cosmology
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
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?
investment into reionization
Investment into Reionization














janus objectives
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 3D positions of high-z star-forming galaxies & SMBHs to next-generation observatories

janus mission concept
JANUS Mission Concept

Survey Mode

Discovery Mode


janus observatory
JANUS Observatory

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 arcmin2 FoV

Detects & localizes

high-z GRBs

Low-resolution spectroscopy of high-z GRBs & quasars

HE Monitoring Instrument (HEMI): non-imaging , 0.02-1.5 MeV, 6 sr FoV

γ-ray spectroscopy

grb detections w janus
GRB Detections w/ JANUS

Bromm & Loeb (2006)

janus survey science
JANUS Survey Science
  • Measure the ionizing flux of quasars over 6 < z < 10 by discovering and observing the brightest high-redshift quasars
  • 20,000 deg2 survey
  • 300 z> 6 quasars
  • Maximum z≈10
  • Ionizing flux of each quasar measured directly from continuum
janus science for free
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
janus status
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)

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.