2008.09.神戸研究会Lya輝絵銀河から探る宇宙再電離と初代天体柏川伸成(国立天文台)
The study of the highest-z (z>6) galaxies probes: ■ The epoch of first generation of galaxies ■ Early star formation history ■ Initial structure formation ■■ History of cosmic reionization ■ When did the reionization take place ? ■ What ionized the universe ? ■ How was the reionization process ? ■ Complement to QSO / WMAP / GRB / 21cm...
Yoshida+ 07
Dickinson+ 03

■実際分光してみると確かにz>3の銀河■すべてｍ ~25と非常に暗い→10m望遠鏡でなければ分光できない。 ■ LBGの発見→10m望遠鏡の金字塔的観測の1つ。 Steidel+ 96 APJ 462, L17いくつかのものについてはずれいLyman α連続Lyman α emitter (LAE)の日市民主人
■ライマンα線:水素のn=1(基底準位)とn=2の間の遷移に伴う共鳴縁(resonance line) ■銀河内部の中性水素･ダストに吸収･散乱されやすい(実際は複雑) ■ダストをまだ大量に持たない若い銀河からの光。 © Kobayashi
◾ Stellar mass LBG: > 1010Mo (Shapley+ 01), LAE: 5 x 10 8 Mo (z=3.1 Gawiser+ 06), a few x 10 8 Mo (z=4.1: Overzier+ 06), 5-10 x 108Mo (z=7: Egami+ 05) ■ Age LBG: > 109vr (Shapley+ 01) LAE: ～108yr (Gawiser+ 06) ■ Av LBG: <1 LAE: <0.1 (but see Finkelstein+ 07) ⇒ LBGに比べてLAEは星もダストも少なくて若い。 ◾ Dark halo mass LBG: 1011-12Mo (NK+ 06, Ouchi+ 04) LAE: 1011-12Mo??? (Hamana+ 05),ただし不定性大きい。
Partridge & Peebles (1966) "Are young galaxies visible?" "...most of the radiation from young galaxies would arrive at wavelengths of 1-3μ where detection is difficult. However, it seems possible that the Lyman-α line might be detected if it is a strong feature of the spectra of young galaxies."
■ Lyman α emitters (LAEs) ■ High-z star-forming galaxies, and would dominant at the faint end of LF of ionizing sources in reionization era ■ Easy to detect w/ narrow-band filter ■ Neutral IGM would change its line property
Lya emission line profile Optical depth distribution Haiman+ 02 Lya photon UV-cont. photon
■ Significant decline of LAE-LF suggests IGM attenuation (Haiman & Spaans 99, Malhotra & Rhoads 04) ■ Advantages ■ Disadvantages ■ Sensitive at x H <10 3 ( ⇔ GP test) ■ Hard to distinguish w/ LAE evolution ■ Statistical estimate(⇒GRB) ■ Hard to distinguish internal attenuation
■ Lyα LF at 3<z<5.7 No evolution ■ Systematic LAE survey at z=3.1/3.7/5.7 ■ 1sqdeg survey ■ Contrary to LBG evolution ■ See also Dawson+ 07 Gronwall+ 07 van Breukelen+ 05 logL(Lya) [ergs s¯¹]
Ouchi+ 07

■ Model predictions on Lyα LF ■ Bright LAE → easy to observe, Faint LAE → difficult to observe ■ The amplitude of LF decreases according to x HI , irrespective of L (or mass). ■ See also Haiman & Cen 05, Le Delliou+ 05, Dijkstra+ 06, Mesinger & Furlanetto 07
Subaru Deep Field (SDF) RA 13:24:21.38  DEC +27:29:23:04 Subaru/Prime focus camera has 10 2kx4k CCDs 34'x27' wide FOV '876 arcmin' — 5 x GOODS public data … http://soaps naoi.org/sdf/ see NK+ 04 _SDFamage GOODS:FOV size ,
■ Cosmological HII region ～  0.45pMpc ～1.3'@ z=6.5 (Haiman 02) ■ Overlapped HII region ～8.6pMpc ～24'@z=6 (Wyithe & Loeb 04) lliev+ 06 Green: H I Orange: H II Black: ionizing source Furlanetto+ 04 lonized bubble~10pMpc @EoR
B V R i’ NB816 _ z' _ NB921 11 16 18 30
■ Apparent deficit compared w/ z=5.7 ■ Based on large volume, homogeneous sample in a general field ■ Almost all of bright LAEs have been spec. identified. ■ L(LyA) of z=6.5LAEs in other fields w/o grav.L -Kurk 04  1.1x1043 erg/s -Rhoads 04  1.1x1043 -Stern 05  1.04x1043 →  consistent w/ our bright end NK+ 06 updated
■ Apparent deficit compared w/ z=5.7 ■ Reionization has not completed at z=6.5 ■  L*=0.75 mag difference →XH|<0.45 at z=6.5 (Santos 04) →×µµ=0.30 at z=6.5 (Kobayashi+ 07) →xH|<0.50 (Dijkstra+ 07) → xH |<0.38 (McQuinn+ 07) ■ Faint end slope cannot be determined L(Lyα) ergs s-l NK+ 06 updated → photon budget for reionization
■ 2007: 3nights: Subaru/FOCAS --- cloudy/TOO 17 new data ■ 2008: 2nights: Keck/DEIMOS --- cloudy No new data ■ 2009?
■ Error contours of Schechter parameters (φ*,L*) ■ The LF difference is 3-sigma significance ■ The cosmic variance (Somerville+ 04) ~30% reduces the significance to 2-sigma Inner contour=1-sigma log φ* [Mpc-³]
■  LyA LF difference is caused by IGM attenuation ? VS. galaxy evolution ? ■ The rest UV (1255A) flux is not sensitive to neutral IGM ■ The rest-UV LF of LAE at z=6.5 agrees w/ LAEs at z=5.7    & i-dropouts at z~6 (Bouwens+ 06)
■ 3 independent tests ■ ACF ■ VPF ■ 2d-KS test ■ LAE at z=6.5 has a homogeneous distribution ~40Mpc ■ Spatial homogeneous also in LyA luminosity/ EW ■ In general, low-z LAEs are sensitive to LSS (Shimasaku+03, Ouchi+ 05, Malhotra+ 05) ■ Cosmic variance ? see Hu+ in prep.
父

■ composite spectrum has an apparent red wing ■ Reionization model ■ red damping wing ■ R H ll =0.45Mpc ■ Galactic wind model ■ double gaussian comp. ■ wind=200km/s 9200 Obs.  λ[å] ■ Lyα-LFの変化は銀河進化で説明できるのでは？(Dijkstra+, McQuinn+) ■ z=3-6で無進化。z>6で急に進化？ ■ UV-LFはz=5.7と6.5で変わらない。 ■ ●hotra & Rhoads, ●u et al.とは結果が違うじゃん。 ■データクオリティが全然違う。 ■ LF導出の方法は極めていい加減。 ■ Cosmic varianceじゃないの？ ■そうかも。 ■標準的なCDMではcosmic varianceは30%→Lyα LFの違いは説明できない。 ■そもそも空間的に非一様な再電離プロセスでcosmic varianceができているのかも。 ■もっと広い観測、low-zの観測が必要。
■ The only one galaxy at z=7 hardly constrain the LyA-LF, but… ■ The LAE number density at high-L end decreases: 1.00 → 0.24 → 0.04 (z=5.7 z=6.5 z=7.0) ■ The LyA luminosity density (L>1x1043erg/s) of LAEs gradually decreases from z=5.7 to 7.0 Redshift The history of neutral fractio High-z galaxy5c Neutral fraction Clumpiness
7=6 LAË LAE Ota+ 07 Yg Votra+ 06 Structure formation 5 10 Cabs
■ Intrinsic properties of LAEs ■ Does LAE really have no LF evolution ? ■ Does LAE trace large-scale structure ? ■ Is L(LyA) of LAE proportional to its mass ? ■ How large the effect of dust is ? ■ What is the escape mechanism of LyA photons ? ■ Internal structure of LAE ■ How internal density profile of HI does LAE have ? ■ Does LAE have galactic wind ? ■ IGM physics ■ How large the typical density of IGM ? ■ How large the clumping factor of IGM ? ■ Does LAE really have cosmological HII region ? ■ cosmic variance

■ LF
■ Higher-z →  Lyα-LF is sensitive in early reionization w/ on-going NIR survey, JWST, TMT ■ Spatial distribution ■ Correlation function w/ HSC, JWST ■ Counts-in-cell (Mesinger&Furlanetto 07) w/ JWST ◾ Line profile ■ w/ TMT (Haiman+ 02, Dijkstra+ 07) ■ Correlation w/ 21-cm HI emission ■ w/ MWA-LFD, LOFAR (Wyithe&Loeb 07) ■ Pop-III candidates ■ LAEs w/ large EW → Hellλ1640A detection (Shaerer+ 03)
■ Low-metal Z<10 5Zo High effective temperature, hard SED ■ Large EW of Lyα+ Hellλ1640A emission ■ Feedback from popIII will have strong impact on initial galaxy formation and the subsequent SFH+ IGM evolution (Ciardi+ 07)
BンR " NB816 ´Z NB921 ■ SDF-poplll-1 ■ z=6.545 LAE ■ Continuum flux is detected (28mag) ■ EW=406+58-61A (rest) ■ Intrinsic EW~800A ■ Need NIR spec. to detect Hell emission ■ See also; Nagao+ 08 100 200 300 400 500
■ HSCAM ■ 2.0degφ ■ 120~180 CCDs (1.0~1.4 Gpixels) ■ 0″.16 / pixel ■ Red-sensitive CCDs ～1.1µm ◾ Powerful tool for ■ Larger sample of high-z LAEs ■ Spatial distribution ■ Patchy reionization TMT 30m telescope Thirty Meter relescope (TMT)
The LyA-LF at z=6.5 has an apparent deficit compared w/5.7 The LyA luminosity density gradually decreases from z=5.7 to 7.0 ■ Reionization has not completed at z=7.0-6.5 ■ x H l=0.52 at z=7.0, x H l=0.30 at z=6.5 (exc. galactic evolution) ■ Galaxy evolution? ■ Abrupt Lyα-LF evolution at z~6 ?? ■ The UV-LF has almost unchanged: LAEs might have little intrinsic evolution from z=7.0 to 5.7 ■ Cosmic variance? ■ Larger cosmic variance in LAEs than general population ? ■ Inhomogeneous reionization / High clumping factor of IGM ? Looking at the final stage of the reionization by LAEs