dark ages of astronomy (dark to light) 2 dark ages z=1000 z=5.8 z=0

Dark Ages of Astronomy(Dark to Light)

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DarkAges

z=1000 z=5.8 z=0

SDSS Reionization Studies

3End of Reionization - SDSS Quasars - Fan et al. 2006

SDSS telescope at Apache Point

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Possible Causes of Reionization

Dark Matter-Driven Gravitational CollapseHydrodynamic InteractionsAtomic and Molecular CoolingStar FormationStellar DeathSynthesis and Dispersal of Metallic ElementsBirth & Feeding of the 1st Supermassive BHs{

Cosmic Reionization

Razoumov et al. 2002

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Movie of a Typical Reionization Model

Time in movie is linear in physical time.

100 Mpc

Overdense to Underdense: yellow, green, light blue, dark blueBlack regions are neutral.

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 burstTotani et al. 2006

xHI

Damping Wing Lyα Absorption

Miralda-Escude (1998)

Lyα Cross Section: Absorption profile:

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?

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Investment into Reionization

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SDSS

WMAP

JWST

ALMA

LOFAR+MWA SKA

ELTs

2005 2010 2015 2020

Wa

vele

ng

th

JANUS

JANUS Objectives

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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

Survey Mode

Discovery Mode

Via TDRSS

JANUS Observatory

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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

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

Detects & localizeshigh-z GRBsLow-resolution spectroscopy

of high-z GRBs & quasars

γ-ray spectroscopy

JANUS GRB Science

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GRB Detections w/ JANUS

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GRB # (z>5)

GRB # (z>6)

GRB # (z>7)

GRB # (z>8)

Swift Observed 5 1 0 0Swift Model 24 13 7 3JANUS 47 26 14 7

Bromm & Loeb (2006)

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 Quasar Science

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Quasar Detections w/ JANUS

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Survey Longestλ (μm)

Sky Area

zLimit

Quasar# (z>6.5)

CFHTQS 0.95 900 6.5 0SDSS 0.95 10000 6.5 0VHS 2.4 20000 7.5 50UKIDSS LAS 2.4 4000 7.0 5

Pan-STARSS-1 1.05 3000 7.0 20

JANUS 1.7 20000 11.0 170

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

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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)

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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.