Dark Ages of Astronomy (Dark to Light)
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Transcript of Dark Ages of Astronomy (Dark to Light)
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. 20025
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
Wavelength
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 ConceptSurvey 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.