Pushing the Redshi- Fron1er towards the First- Star Forma1on Epoch with Subaru 2010 (830: 5hr) 2011 (600: 4hr) 2011 (830: 2hr) z Lya =7.213 z Lya =7.308 MO et al. in prep. Ono, MO et al. (2011) Masami Ouchi (University of Tokyo)
Outline Review the recent results of large area Subaru surveys for Lya emigers and dropouts at z~7 unique large spectroscopic samples at the redshi- fron1er History of Reioniza1on Sources of Reioniza1on Introduce our next genera1on 30 deg 2 (1Gpc x 1 Gpc at z~7) survey for z=6-7 galaxies.
Open Ques1ons Reioniza1on History and Sources of Reioniza1on WMAP7 Choudhury+08 models Mh(lim)~10 9 Mo Mh(lim)~10 8 Mo Mh(lim)~10 6 Mo Cen 2003 model QSO GP Ouchi et al. (2010) QSO GP test (z~6) and CMB TS τ (z~10) sharp reioniza1on (e.g. Fukugita+94) or extended reioniza1on (Dunkley+09)? Recent ksz study of CMB probing ionized bubbles at EoR indicates Δz<=4.4 (Zhan et al. 2011) Reioniza1on history depends on sources of reioniza1on (see models) Probing z~7 w/ spec. (near heart of EoR) to constrain reioniza1on models. very high- z. Not easy!
1. SUBARU SURVEYS FOR GALAXIES AT THE REDSHIFT FRONTIER
Basic Idea behind the Subaru Survey c: UCO Lick Keck/DEIMOS c: M. Ouchi Subaru/Suprime-Cam Subaru/FOCAS c: J. Graham Keck/NIRSPEC Magellan/IMACS Probing the heart of reioniza1on epoch (z~7 +beyond) with SPECTRA (complimentary to HST photometric studies; Bouwens & Tren1 s talks) The present instruments touch the sensi1vity limit of spectroscopy. Subaru imaging (large area): Searching for RARE BRIGHT galaxies at z~7 by the largest area imager whose sensi1vity is good enough for detec1ng z~7. Keck/Subaru+ spectrogscopy (deep): Taking VERY DEEP SPECTRA OF the rare bright galaxies w/ their superb sensi1vity. (cf. Schenker s talk on HST+Keck program)
Subaru Surveys for Galaxies at z~7 SDF and GOODS-N (0.2deg2 each) SXDS (1.0 deg2) At z~7 ~200 Mpc (comoving) The largest- area survey for galaxies at z~7 COSMOS (central 1.0 deg2) (Kashikawa+06) (Furusawa+08) Sizes of HUDF and ERS for HST/WFC3 galaxies at z>6 (Capak+04) (Scoville+07/Taniguchi+07)
Subaru Lyα EmiGers and z- dropouts at z=6.5-7.3 For z~7 LAEs w/ new CCDs (Narrow- band excess color for emission) NB387 NB503 NB570 NB711 NB816 NB921 NB973 NB101 (Con1nuum color for Lya trough) For z~7 dropouts interlopers z=7 Bright Lya Emitters (LAE) with L Lyα L* Lya z=6.6: 265(72) z=7.0-7.2: 7(2) z=7.3: 5(1) Bright z-dropouts with L>L* z~7: 22(3)
Spectroscopic Iden1fica1on (1) Galaxies at z=6.5-6.6 Ouchi+10 Kashikawa+11 72 out of 265 LAEs are confirmed at z~6.6.
Spectroscopic Iden1fica1on (2) Galaxies at z=6.8-7.0 Ono, MO et al. (2011)
Spectroscopic Iden1fica1on (3) Galaxies at z=7.2-7.3 2010 (830: 5hr) 2011 (600: 4hr) 2011 (830: 2hr) z Lya =7.213 z Lya =7.308 Ono, MO et al. (2012) MO et al. in prep. z=7.213 z- dropout: Defini1ve iden1fica1on. Most distant z- dropout among 11 confirmed z- dropouts (cf. y- dropout of Lehnert+10) See Ono s talk (tomorrow) z=7.215 LAE: Asymmetric line? (Shibuya et al. 2012) z=7.308 LAE: Asymmetric line? LRIS spectroscopy for R~4000 spec.
Intense (SFR~100 Mo/yr) Starbursts at z~7 Ono+11 GN- 108036 (GN) at z=7.2 (Brightest dropout) F140W SFR=100Mo/yr M*=10 9 Mo, age~10 Myr, E(B- V)=0-0.1 (size=0.4) Ouchi+09 Himiko at z=6.6 (Brightest LAE) SFR=100Mo/yr M*=10 10 Mo, age~200-400 Myr, E(B- V)=0.15 (size=2 ) SED fivng w and w/o nebular emission models Comparison with the brightest LAE, Himiko, found at z=6.6. Both galaxies have SFR~100 Mo/yr. But, GN is less massive than Himiko younger than Himiko in stellar age less dust- ex1nc1on than Himiko in E(B- V). more compact than Himiko in UV con1nuum. The diversity of starbursts already appears at z~7. (cf. SMG vs LBG/LAE at z~3, ULIRG vs spiral at z~0.)
2. REIONIZATION PROBED BY THE SUBARU SURVEY
Lya emission for a Probe of Reioniza1on Lya emission lines from galaxies Lya damping wing absorption of IGM ) just in front of the object (GRB, QSO, and galaxies) can constrain hydrogen neutral fraction at the X HI =<n HI /n H >~0.1-1.0 level z~7-15 Exponen1al profile by thermal mo1on Intrinsic Lyα Observed (absorbed) Powerlaw (σ Δλ - 2 ) tail by natural broadening <f HII > Dijkstra et al. (2007)
Lya LF Evolution from z=5.7 to z=6.6: Lya Luminosity Func1on (Lya LF) Large Subaru data +cosmic variance errors z=5.7 Schechter parameters UV Luminosity Func1on z=6.5 Pure num. evolu1on Pure lum. evolu1on 30% Ouchi et al. (2010) The large Subaru data in independent cosmic volumes show the decrease of LF from z=5.7-6.6 at >90% CL. S1ll there are discussions of Lya LF evolu1on (e.g. Hu+10, Tilvi +10,Hibon+11 etc.)
Field Variance? Ouchi et al. (2008) Nagamine, Ouchi, Springel, Hernquist(2010) 1 deg 2 data 0.2 deg 2 (=2x10 5 Mpc 3 ) Lya LF Observa1on Lya LF simula1on SPH Even 0.2- deg 2 area (=4xGOODS- S) data show a large number- density variance by a factor of 2-5 (Poisson error+field variance; see also Shimasaku+04, Hu +05/06, Nakamura+11 etc.). It is reasonable because the survey volume defined by a narrow- band selec1on is not large (thin slice: Δz~0.1).
Contamina1on? 80% complete spectroscopy samples Ouchi+11 Kashikawa+11 Hu et al. (2010) claim that the Subaru samples are largely contaminated. But Subaru team finds no such a large contamina1on rate based on the 80%- complete spectroscopy sample. Hu et al. s results may be incomplete or would miss completeness correc1ons??
Lya LF Evolution from z=5.7 to z=6.6: Lya Luminosity Func1on (Lya LF) Large Subaru data +cosmic variance errors z=5.7 Schechter parameters UV Luminosity Func1on z=6.5 Pure num. evolu1on Pure lum. evolu1on 30% Ouchi et al. (2010) The large Subaru data in independent cosmic volumes show the decrease of LF from z=5.7-6.6 at >90% CL. Decrease of 30% in luminosity.
To Redshi- 7.3 Ouchi et al. in prep. Shibuya et al. (2012) A further decrease of LF from z=6.6 to 7.3 is found (over the uncertainty). Decrease of Lya LF from z=5.7 to 6.6 and 7.3 Signature of reioniza1on? and/or galaxy evolu1on?? (UV- con1nuum LF & EW dist do not have an accuracy of ~30% level; cf. Kashikawa+11)
Galaxy Evolu1on or Reioniza1on? Cosmic SF History w/ IGM absorp1on (Lya forest+ damping wing) w/o IGM abs. 1216 A Ouchi et al. (2009) Decrease of star- forming ac1vi1es (+possible dust ex1nc1on change etc?)
Lya Emivng Dropout Galaxy Frac1on Based on Spectra of 43 z~7 dropouts Bright sample (Muv~- 21) Faint sample (Muv~- 19.5) Ono, MO et al. (2011) The frac1on of Lya emivng galaxies is low, ~20% (Schenker s and Ono s talks for more details) Signature of reioniza1on? The amplitude of drop is larger in faint galaxies than in bright galaxies. Why? sugges1ve of inside- out reioniza1on? (Ono, MO et al. 2012).
Clustering of LAEs at z~7 Models Observa1ons Neutral IGM Ionized IGM Intrinsic LAE dist. 90 Mpc Observed LAE dist. McQuinn et al. (2007) z=5.7 z=6.6 LAEs in ionized bubbles can be observed Clustering of observed LAEs is boosted. Detec1on of clustering signal at z=6.6: b=3-5 We see no significant increase of clustering from z=5.7 to 6.6 No clear enhancement of clustering amplitude by reioniza1on at z=6.6. Upper limits: x HI 0.5 (McQuinn+07); x HI 0.5 (FurlaneGo+06) Constraints from clustering: x HI 0.5 Ouchi et al. 2010
Lyα Line Profile Ouchi et al. (2010) Damping wing absorp1on Broadening of Lya No significant Lya line broadening over the error level of >14% (see also Hu et al. 2010, Kashikawa et al. 2011) No signature of an1- correla1on in Lya Velocity- luminosity rela1on No signature of x HI ~1 at z=6.6 (cf. Haiman & Cen 2005)
Comparisons of Recent Results Dropout(X Lya ) LAE WMAP7 Choudhury+08 models Mh(lim)~10 9 Mo Mh(lim)~10 8 Mo Mh(lim)~10 6 Mo QSO QSO(DW) Linear Plot Log Plot Ouchi et al. (2010) +latest results The results are consistent within the 1-2 sigma errors of the LAE tests, but largely scagered. X Lya corresponds to x HI ~0.4-0.6 based on RT and MC simula1ons (Schenker+12,Ono+12,Pentericci+11). Such a very late reioniza1on cannot explain τ of Thomson scagering(τ=0.09±0.02; WMAP7). Large uncertain1es that cannot dis1nguish the sharp and extended reioniza1on. Next genera`on large area survey w HSC
3. SOURCES OF REIONIZATION (IONIZING PHOTON BUDGET)
UV Luminosity Func1on (LF) Ouchi et al. (2009) Bouwens et al. 2011 Decrease of UV LF from z=4 to 7 (see Bouwens s talk). Role of Subaru: Bright- end LF determina1on (e.g. Ouchi+04, Yoshida+06, Ouchi+09) Subaru data: key for determining LFslope, α es1mates for luminosity density of faint galaxies
Dropping Cosmic SFR towards high- z Cosmic SFR density Ionizing photon emission density Bouwens+10 fesc=0.05 Ouchi+09 Cosmic SFR density (from UV luminosity) drops from the peak at z = 2-3 to z~ 7 by a factor of ~100 (Ouchi+09, Bunker+10). Less star- forma1on rates towards high- z Less ionizing photons Assuming the SF proper1es similar to low- z (stellar pop. and fesc=0.05), ionizing photons are only <30% of those required for reioniza1on at z~7 (Ouchi+09) Too few!?
Missing Ionizing Photons? Robertson+10
Open Ques1on Missing Ionizing Photons (from Galaxies)? Other sources of reioniza1on? Not QSOs. But faint AGN? Maybe no? (WilloG+11, Fiore+11, Cowie+11 cf. Treister+11) What else? Primordial black hole?? Dark mager annihila1on?? (Ricov & Ostriker+04) Ionizing photon emission rate (dn ion /dt/dv) es1mates dn ion /dt/dv C x f esc x SFRD (as a func1on of redshi-) SFRD: SFR density f esc :Escape frac1on of ionizing photons from galaxies. F(esc)/F(int)at~900A(fesc=0.05) C : Ionizing photon emissivity in a given SFR, F 900 /F 1500. (depending on stellar pop) Changing proper1es of star- forming galaxies; Increase of fesc? (fesc>~0.2; Ouchi+09b, see also Inoue+06, Yajima+11) IMF/metallicity evolu1on? (S1avelli+04, Bouwens+10) Steep faint- end slope α~- 2? Excess of faint galaxies? (below obs. limits) boos1ng SFRD (Stark+07,Bouwens+11) 1. Constraints on f esc and C (see Ono, MO et al. 2010 for fesc upper limits from nebular lines.) 2. Less uncertain1es on α as well as more accurate x HI es1mates (from LAEs) at this redshi-
4. NEXT GENERATION SUBARU SURVEYS
Next Genera1on Survey with Hyper Suprime- Cam (HSC) Suprime- Cam Hyper Suprime- Cam(HSC; 2012- ) PFU N=207 Present largest obs. (Ouchi+10) 1/30 140 Mpc ~6 deg: ~0.9 comoving Gpc at z~7 Current model (Mesinger+09) Reducing the errors of IGM x HI down to ~10% (model variance limit) w 10k LAEs at z~6-7 Inves1ga1ng reioniza1on process that cannot be addressed by the previous studies (topology of ionized bubbles etc.).
Reioniza1on Processes from Bubble Topology Predicted ionized epoch HSC survey? Finlator+09 Physical processes (inside- out, outside- in, filament- last?) Clustering of Lya emigers: imprints of neutral frac1on and ionized bubble topology McQuinn et al. 2007)
Next Genera1on Survey with Hyper Suprime- Cam (HSC) Suprime- Cam Hyper Suprime- Cam(HSC; 2012- ) PFU N=207 Present largest obs. (Ouchi+10) 1/30 140 Mpc ~6 deg: ~0.9 comoving Gpc at z~7 Current model (Mesinger+09) Reducing the errors of IGM ionized frac1on down to ~10% (model variance limit) w 10k LAEs at z~6-7 Inves1ga1ng reioniza1on process that cannot be addressed by the previous studies (topology of ionized bubbles etc.). HSC survey is star1ng in 2013 (plan). Large numerical simula1ons for HSC survey (Umemura, Mori; see Hasegawa s talk)
Summary Subaru survey for the epoch of reioniza1on based on the large samples of LAEs and dropouts at z~7 Survey Idea and Data ~300 z~7 galaxy candidates Spectroscopic iden1fica1on w/ Lya : ~70 galaxies at z=6.5-6.6 and 6 galaxies at z=6.84-7.31 Diversity of intense (SFR=100Mo/yr) starbursts at z~7 History of reioniza1on probed with Lya Lya LF decrease (~30% in L*) from z=5.7 to 6.6, and more decrease towards z=7.3. Reioniza1on or Galaxy forma1on? Lya emivng galaxy frac1on decreases from z~6 to 7. Signature of neutral IGM increase. ~50% of neutral hydrogen frac1on?? Large uncertainty of models for comparison? Fainter sources have a less chance of Lya emission. Inside- out reioniza1on is preferred? Ionizing Sources UV LF decreases towards high- z rapid decrease of ionizing photon produc1on by galaxies Tension with the Thomson scagering op1cal depth? Emergence of faint galaxy popula1on Change of fesc Evolu1on of stellar popula1on (IMF, metallicity)? Forthcoming HSC 30 deg 2 (1Gpc x 1 Gpc) survey for z~7 galaxies. Ionized bubble topology and the reduc1on of the sta1s1cal uncertain1es. (first light of HSC planned this August)