blazar 「中間」 z~1-5 の系外背景放射光につ いて grb z~30-6 井上進 (icrr/mpp ->...
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「中間」 z~1-5 の系外背景放射光について
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
GRB
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
Extragalactic Background Light at “Intermediate” z~1-5
blazar
diffuse extragalactic background radiation at z=0
EBL=extragalacticbackground light:IR-optical-UVfromstars+AGN+others
gamma-ray absorption:probe of diffuse radiation fields
+ → e+ + e-
threshold condition: E (1-cos )>2 me2c4
E
e.g. TeV + 1eV (IR) 100 GeV + 10 eV (UV)
peak ,, =4 me2c4
probe of local IRB from absorption in TeV blazars
Costamante+ 03
e+
e-
EBLVHE
IACT
Extragalactic Background Lightblazar
from M. Teshima
EBL: direct vs indirect measurements
direct source counts absorption
detection lower limit detectionor upper limit or upper limit
faint+diffuse bright sources faint+diffuse
z-integrated z-dependent z-dependent
constraints on local EBL (z~0) from -ray absorption
Aharonian+ 06 Nat.HESS observations of TeV blazars @z=0.165, 0.186
no strong Pop III• disfavors strong near-IR peak• close to lower limits from galaxy counts
E(=
1)constraints on EBL at z~0.5
Albert+ 08 Sci.
close to lower limits from galaxy counts (little missing light)if “normal” blazar spectra >1.5
MAGIC observation80-500 GeV3C279 @z=0.536
constraints on EBL at z~0.5-4.5 Abdo+ 10highest 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)Gamma 201275000 photons from 7 brightest blazars, 0.03<z<0.19
assume wide variety of intrinsic spectra inc. curvatureEBL template Franceschini, normalization free
consistent withupper limits from previous TeVlower limits from galaxy counts
measurement of EBL at z<1.6Ajello+ (Fermi) Gamma 2012
hard, nonvariable BL Lacs only50 sources each in z=0-0.2, 0.2-0.5, 0.5-1.6assume log-parabolic intrinsic spectraEBL template Franceschini, norm. free
some models ruled out (Stecker+)or disfavored (Kneiske+)
current EBL models
Gilmore+ 12
theory -> predictions -> obs.(understanding <- deductions <- obs.)
cosmic star formation rate -> -dep. luminosity density -> opacity
current EBL models: comparison Gilmore+ 12
z=0
z=1
z=2
current EBL models: comparison Gilmore+ 12
E(=1)
observations candiscriminate amongmodels by differentgroups-But so what?Who cares??
What can we reallylearn about the Universefrom EBL studies?
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
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
Funk & Hinton, arXiv:1205.0832
high-z blazars with CTA
2FGLJ1504.3+1029 z=1.84
Sol, Zech, Boisson+inc. Y. Inoue (for CTA)to appear in Astropart. Phys.
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 inAstropart.Phys.
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. 内部吸収)の識別
系外背景光 (EBL)との → e+e- 吸収による cutoff
GRB spectra with CTA: GRB 080916C at z=4.3
Mazin+inc.Y. InoueS. Inoue (for CTA)to appear inAstropart.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 zKobayashi+ 12
obs’d. dispersionfactor ~3 at z~1-2:different assumedfaint-end slope,Lmin of galaxyluminosity func.
galaxy LF
cosmic star formation rate: from GRB rate
Robertson & Ellis 12(guys from galaxies, not GRBs!)
cosmic star formation rate: from Ly forest
Faucher-Giguere+ 08
hierarchical galaxy formation from Nagashima
cosmic star formation rate: interpretation Nagashima+in prep.growth of structure formation vs decrease of gas supply
peak of CSFR “cosmic gas shortage”
suppression of star formation on sub-Galactic scales:“missing satellites”
Diemand+ 08dark halos inGalaxy formation simulation
Wolf+ 10
critical mass scale ~107Msun
~<106 Lsun
suppression of star formation on sub-Galactic scalesdark matter solutions:warm dark matter?nontrivial power spectrum?
astrophysical solutions:feedback heating/expulsion by SN? AGN? UV background?tidal disruption?
WDM simulation Polisensky & Ricotti 11
star formation on small scales ->reflected in EBL:z-dependenceenvironmental dependenceBUT effect only a factor of a few
QSO contribution to UV EBL: HeII Gunn-Peterson effectWorseck+ 11ionization energy:
HeI – 24.6 eV near-simultaneous with H reionization (massive stars)? HeII – 54.4 eV quasars only!
HeII reionized at z~3quasars important for UV EBL!
UV EBL including quasars Faucher-Guigere+ 2011
characteristic energy Erest ~ 72 GeV (2mec2/54.4 eV) Eobs~ 18 GeV (1+z/4)
QSOs not includedin most EBLmodels for 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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