「中間」 z~1-5の系外背景放射光につ Extragalactic Backgroundいて Light at “Intermediate” z~1-5 井上進 (ICRR/MPP -> MPIK) 協力：長島雅広、小林正和、井上芳幸、戸谷友則ほか what we can (may) learn: - cosmic star formation -> global evolution of cosmic gas - sub-Galactic scale star formation; non-cold dark matter? - HeII reionization, quasar formation+evolution GRB blazar diffuse extragalactic background radiation at z=0 EBL= extragalactic background light: IR-optical-UV from stars+AGN+others gamma-ray absorption: probe of diffuse radiation fields g + g → e+ + eE e threshold condition: E e (1-cos q )>2 me2c4 s peak ,, =4 me2c4 Costamante+ 03 e.g. TeV + 1eV (IR) 100 GeV + 10 eV (UV) blazar probe of local IRB from gg absorption in TeV blazars Extragalactic Background Light IACT gVHE gEBL e+ e- from M. Teshima EBL: direct vs indirect measurements direct source counts g absorption detection or upper limit lower limit detection or upper limit faint+diffuse bright sources faint+diffuse z-integrated z-dependent z-dependent constraints on local EBL (z~0) from g-ray absorption HESS observations of TeV blazars @z=0.165, 0.186 Aharonian+ 06 Nat. • disfavors strong near-IR peak no strong Pop III • close to lower limits from galaxy counts constraints on EBL at z~0.5 Albert+ 08 Sci. Eg(=1) MAGIC observation 80-500 GeV 3C279 @z=0.536 close to lower limits from galaxy counts (little missing light) if “normal” blazar spectra G>1.5 constraints on EBL at z~0.5-4.5 Abdo+ 10 highest energy photons from Fermi blazars+GRBs vs EBL models (=3) highest EBL model (Stecker+) ruled out measurement of EBL at z<0.2 Biteau+ (HESS) 75000 photons from 7 brightest blazars, 0.03<z<0.19 Gamma 2012 assume wide variety of intrinsic spectra inc. curvature EBL template Franceschini, normalization free consistent with upper limits from previous TeV lower limits from galaxy counts measurement of EBL at z<1.6 Ajello+ (Fermi) Gamma 2012 hard, nonvariable BL Lacs only 50 sources each in z=0-0.2, 0.2-0.5, 0.5-1.6 assume log-parabolic intrinsic spectra EBL template Franceschini, norm. free some models ruled out (Stecker+) or disfavored (Kneiske+) current EBL models theory -> predictions -> obs. (understanding <- deductions <- obs.) cosmic star formation rate -> l-dep. luminosity density -> gg opacity Gilmore+ 12 current EBL models: comparison z=0 z=1 z=2 Gilmore+ 12 current EBL models: comparison Gilmore+ 12 observations can discriminate among models by different groupsBut so what? Who cares?? What can we really learn about the Universe from EBL studies? Eg(=1) CTA sensitivity: for steady sources Funk & Hinton, arXiv:1205.0832 現行チェレンコフ望遠鏡より格段に感度向上 エネルギー閾値の有意な低減 -> よりhigh-zの天体、GeV-TeV間感度ギャップの改善 CTA sensitivity: for variable/transient sources Funk & Hinton, arXiv:1205.0832 有効面積 ~104 x LAT@30GeV 短時間積分では圧倒的感度 高速指向性能 ~180deg/20sec (LST; 20 GeV-1TeV) -> 高速変動天体・突発天体に対して強力 Sol, Zech, Boisson+ inc. Y. Inoue (for CTA) to appear in Astropart. Phys. high-z blazars with CTA 2FGLJ1504.3+1029 z=1.84 zmax~ 0.5 now -> ~2.5 with CTA GRB spectra with CTA: GRB 090902B at z=1.8 S. Inoue, J. Granot, P. O’Brien+ inc. Y. Inoue (for CTA) to appear in Astropart. Phys. 系外背景光 (EBL) とのgg → e+e-吸収 によるcutoff 高い光子統計 -> 詳細スペクトル -> EBL測定 -> 詳細時間変動 -> EBL吸収と内部cutoff（e.g. 内部gg吸収）の識別 GRB spectra with CTA: GRB 080916C at z=4.3 Mazin+ inc. Y. Inoue S. Inoue (for CTA) to appear in Astropart. Phys. GRBスペクトル -> high-z EBLの進化 -> 宇宙星形成史・QSO活動史 cosmic star formation rate: dispersion at low z Kobayashi+ 12 obs’d. dispersion factor ~3 at z~1-2: different assumed faint-end slope, Lmin of galaxy luminosity func. galaxy LF cosmic star formation rate: from GRB rate Robertson & Ellis 12 (guys from galaxies, not GRBs!) cosmic star formation rate: from Lya forest Faucher-Giguere+ 08 hierarchical galaxy formation from Nagashima cosmic star formation rate: interpretation growth of structure formation vs decrease of gas supply peak of CSFR “cosmic gas shortage” Nagashima+ in prep. suppression of star formation on sub-Galactic scales: “missing satellites” Wolf+ 10 Diemand+ 08 dark halos in Galaxy formation simulation critical mass scale ~107Msun ~<106 Lsun suppression of star formation on sub-Galactic scales astrophysical solutions: feedback heating/expulsion by SN? AGN? UV background? tidal disruption? dark matter solutions: warm dark matter? nontrivial power spectrum? star formation on small scales -> reflected in EBL: z-dependence environmental dependence BUT effect only a factor of a few WDM simulation Polisensky & Ricotti 11 QSO contribution to UV EBL: HeII Gunn-Peterson effect ionization energy: HeI – 24.6 eV near-simultaneous with H reionization (massive stars)? HeII – 54.4 eV quasars only! HeII reionized at z~3 quasars important for UV EBL! Worseck+ 11 UV EBL including quasars Faucher-Guigere+ 2011 characteristic energy Erest ~ 72 GeV (2mec2/54.4 eV) Eobs~ 18 GeV (1+z/4) QSOs not included in most EBL models for g rays -> too transparent (exc. Gilmore+ 09) summary - ガンマ線吸収を用いたEBL探査は近年大きく進歩 今後MAGIC、CTAでさらに CTAでblazarはz~<2、GRBはz~<4 (7?) まで - z~<5のEBLについて、個々のモデル予測は多数あり が、観測から何が本質的に理解できるのか、議論が不足 - 宇宙星形成史について、直接観測と相補的な測定 宇宙全体でのガスの熱的進化の情報 - sub-Galactic scaleでの星形成（の抑制）について示唆も？ astrophysical feedback or non-cold dark matter - z>~3-4ではquasarも重要な寄与 考慮すればよりopaqueなはず 銀河間HeIIの再電離、quasar進化・形成について重要な情報 これからより定量化します
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