Probing the Reionization Epoch in the GMT Era

Xiaohui Fan (University of Arizona)Seoul/GMT Meeting

Oct 5, 2010

Probing Reionization History

XF, Carilli & Keating 2006

Key Questions:When? - reionization redshiftHow? - uniform/patchy? topologyWhat? - galaxies, AGN, other?

Two Key Constraints:1. WMAP 7-yr: zreion~ 102. IGM transmission: zreion > 6

WMAP: early reionization?

• WMAP seventh-year: = 0.088+/- 0.014 z=10.5+/-

1.2– Larger signal comparing to

late reionization model (but marginally consistent!)

• However, no direct conflict to Gunn-Peterson result, which is sensitive only to ~1% neutral IGM

• Overlapping could still be at z~6

• IGM could have complex reionization history

direct observation of high-z sources Dunkely+ 2009, Komatsu+2010

zreion =

7

Accelerated Evolution at z>5.7

• Optical depth evolution accelerated– z<5.7: ~ (1+z)4.5

– z>5.7: ~ (1+z)>11

– End of reionization?

• Evolution of neutral fraction– fHI > 10-3 - 10-2 at z=6– Order of magnitude

increase from z~5– G-P absorption saturates;

needs more sensitive tests

(1+z)4.5

(1+z)11

XF et al. 2006

Iye et al. 2006Kashikawa et al. 2006Ota et al. 2007, 2010

Ly Galaxy LF at z>6

• Neutral IGM has extended GP damping wing attenuates Ly emission line• Detectability of Ly galaxies as markers of IGM optical depth

– Reionization not completed by z~6.5– fHI ~ 0.3 - 0.6 at z~7– Overlapping at z=6-7?

z=6.96

Ly- in high-z galaxies

• GLARE survey of high-z Ly galaxies; 36hr integration with Gemini+GMOS[Stanway et al 2006]

Ly flux > 5x10-18 erg/cm2/s

• Simulated observation of z=6 Ly galaxy; 30hr with GMT+GMACS [McCarthy 2007]

Ly flux (erg/cm

2/s)

Ground-based Ly surveys• DAZEL - The Dark Age Z(redshift) Lyman-

Explorer on VLT: – dedicated Ly narrow band survey

instrument for z=7 - 10– ~ 1 object per 10 hour field

• Keck blind spectroscopic survey along critical lines of high-z clusters

– Six promising Ly emitter candidates at z=8.7 - 10.2

– Large abundance of low-L galaxies; providing sufficient reionization photons

– Limit of current search;

• New generation of OH suppression technique and AO:

– Ground-based surveys could find Ly emitters at z<12

Stark et al.

J H K Bland-Hawthorn

Reionization Topology with Ly Emitters

• Ly emitter could provide sensitive probe to reionization history, especially during overlapping– Evolution of LF (constrain fHI)

– Clustering

Distribution of Ly emittersover 3’ FOV

McQuinn et al.

Neutral Ionized

Probing the Neutral Era with ELT Quasar/GRB

SpectroscopyQSO @ z=9.4Magellan 8hrs

GMT 8hrs

F

F

Lyman- redshift

Wavelength (m)X.Fan

• High S/N, moderate (R~5000) resolution spectroscopy of bright quasars/GRBs will allow determination of reionization, using– optical depth measurements

– distribution of dark absorption troughs

– sizes of quasar HII regions

Reionization with OI Absorption

• OI Forest (Oh 2002)– OI and H have almost

identical ionization potentials

– In charge exchange equilibrium with H but much lower abundance

– Fluctuating OI forest during neutral era to probe ionization topology and metal pollution in the IGM

OI system at z=6.26

Becker et al. 2006

Evolution of IGM Metals• Early Enrichment of the

IGM by First stars– First sign of rapid evolution

at z~6

Ryan-Weber et al.

Evolution of CIV systems

• IGM enrichment•Signature of first stars•Chemical feedback of earliest galaxies

G. Becker

Next Generation Quasar Surveys

• Optical surveys: limited to z<7

• New generations of red-sensitive CCD devices

– Improved QE at 1 micron (Y band)

– SUBARU/Princeton (2012+): a few hundred deg, Y<25;?

– Pan-Starrs (2010+): 3: Y<22.5; 1000 deg2: Y<24; 30 deg2: Y<26

– LSST (2017+): 3: Y< 25

– Discovery of large number of quasars at z<7.5

• New generation of Near-IR surveys:

– UKIDSS (2005 - 2012?): 4000 deg2: JAB<21

– VISTA/VHS (2010+): 20000 deg2: JAB<21

– Discovery of a handful of quasars at z=7-9

• Future Space Missions

– WFIRST/ECULID (2020+)

– JANUS (2015+)

– Quasars up to z~10+ (assuming they existed)

Quest to the Highest Redshift

080913

050904

090423

000131

970228

GRBs

Probing Pop III Star Formation with He II

Emission• He II 1640A– High ionization potential

– Results of metal-free star formation

• Deep HST observation of the highest redshift galaxy– Non-detections of HeII at

z~7

– Pop III star formation < 0.3 solar mass/year

Cai, XF+ 2010

Star-formation at z~10

• Lyman 1216Å

• 20% escape   fraction

Star-forming region, z~10, GMT+GLAO, R=3000 filter, 8 hours

• He II 1640Å

• Salpeter IMF      (ext. to 500M)

• Zero metals

• He II 1640Å

• Top-heavy IMF    (300-1000M)

• Zero metals

GMT For Reionization Epoch

• Highest redshift galaxies through Ly alpha– GMACS, NIRMOS

• Reionization history– Ly alpha galaxy mapping – GMACS, NIRMOS

– GRBs and quasars – NIRMOS, GMTIFS

– First metals in the IGM – NIROS, GMTIFS, GMTNIRS?

• First stars– HeII, signature of Pop.III – NIRMOS, GMTIFS

– Extremely metal poor stars in the Galaxy – GMACS, G-CLEF, GMTNIRS