TCHoU Seminor

What is the origin of the Cosmic
Near-Infrared Background ?
~ from recent result of the CIBER experiment ~Shuji Matsuura(Kwansei Gakuin University)

Tsukuba University TCHoU seminor 2018126

Cosmic Background Radiation• Cosmic Background Radiation – the total integrated lightemitted and absorbed along the line of sight.
• Measurement of the cosmic background gives constraints on
the cosmic evolution history as global mean.

The Extragalactic Background Light
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Cosmic Microwave
Background (CMB)

400 thousand yr
初期元素合成陽子・ニュートリノ
素粒子標準理論
物質が生き残った
インフレーション・大統一理論
物質・反物質の生成
宇宙のはじまりImage
www.eso.org
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University TCHoUseminor 2018126

Cosmic background radiation
Photon energy

Ressell & Turner, 1989

Infrared ~microwave

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wavelengthUniverse was re-ionized

IonizedNeutralRe-ionizedz ~ 10Fully ionized
The re-ionization may be caused by strong UV radiationfrom the first-generation stars and galaxies.

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Result of the CMB-pol measurement• Thomson scattering optical depth in ionized IGM in LoS (te)is derived from the CMB polarization measurements (EE-mode)• te ~ 0.09/0.06 from WMAP/Planck• Re-ionization redshift zre ~ 8 - 10
te ~ 0.06

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CMB-pol power spectrum

Planck 2016

IGM neutrality from galaxy observations• Neutrality of IGM can be estimated from star formation ratedensity from redshift distribution of distant galaxies.
• Planck result does NOT require additional re-ionization sources.
NeutralSFRD

IonizedTsukuba University TCHoU seminor 2018126

Robertson et al. ApJL 2015First-generation Stars••••

First stars are thought to be extremely massive.
They emit strong UV light, that may ionize intergalactic medium.
The UV radiation is redshifted into the near-infrared.
Radiation spectrum indicates sharp edge due to IGM absorption.

Intensity

First Star’s spectrum (model)

Neutral H
absorption

0.1

1

10

100

wavelength [μm]Cooray&Yoshida 2004 (MNRAS, 351, L71), Santos et al. 2002 (MNRAS, 336, 1082)

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Observations of the infrared background• Precise measurements of the near-infrared backgroundwere carried out by space infrared telescopes.

COBE (NASA) 1989

IRTS/SFU
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seminor (ISAS)
201811995
26

Spitzer (NASA) 2004

AKARI (ISAS) 2006

Observed near-infrared background• Clear discrepancy between the measured background andthe expected levels of the integrated galaxy light.

Excess~ 40 nWm-2sr-1

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Deep galaxy counts

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Keenan et al., ApJ, 2010
MOIRCS / SUBARU

Observed near-infrared background• Clear discrepancy between the measured background andthe expected levels of the integrated galaxy light.

Excess~ 40 nWm-2sr-1
Re-ionization?

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Foreground subtraction• To measure the background radiation, subtraction of theforeground radiation from the observed total brightness
is necessary.
Total sky = Zodiacal light (interplanetary dust) ~80%
+ Galactic light (starlight and dust) ~10%
+ Integrated light of external galaxies ~5% (?)+ additional isotropic background ?
• Underestimate of ZL is most plausible
Tsukuba University TCHoU seminor 2018126Zodiacal light is strong
 COBE IRTS Pioneer

CIBER

0.3
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0.5

0.7
12
Wavelength [µm]35Rocket experiment CIBER• We have already flown CIBER four times.
(Feb 2009, Jul 2010, Mar 2012, and June 2013)
Four-stage Black Brant XII for 4 flight• All flights were successful.
2013.6.5 23:05 EDT• NASA team awardth

NASA Sounding Rocket
Two-stage Terrier-Black Brant IX

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Launch vehicle & orbit
0.45m

Payload1.2m

apogee: 330km

CIBERObservation >200km

15m

Black Brant
VC MK1

Observing time: ~400s

Telemetry: 30Mbps
Attitude control:arcsec
recovery
Terrier MK70

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CIBER payload

From Zemcov et al. (2012)

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Observed sky brightness
Sky brightness levels are similar to previous observations
SWIRE
NEP
Elat10
Elat30
BootesA
IRTS/NIRS
COBE/DIRBE

CIBER
1000

Foregrounds- zodiacal light (ZL)
- integrated star light (ISL)- diffuse galactic light (DGL)

λ-2-1

Sky brightness λI [nW m sr ]Extragalactic background= Sky - foregrounds

ZL100

ISL

10DGL
10.60.8

1234

Wavelength [µm]
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Matsuura et al. 2017, ApJ acceptedZodiacal light – major foreground• Zodi dust cloud has complex
structure, not easy to model• COBE team constructed complex
but reliable model of ZL• But, we still need better
understanding of the ZL spectrum

COBE all-sky observation
Total skyAfter subtraction of Zodiacal light

After subtraction of Galactic light

Image courtesy May (2007)

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Courtesy of NASA

Zodiacal light spectrum• Slightly redderthan the solar,but similar.
• This is the firstmeasurement ofZL spectrum inthis region.
• Subtracted ZL
using the COBE
model of ZL
distribution.
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ZL template spectrum normalized at 1.25 µm• ZL spectrum – difference of sky spectra (Sky-ISL-DGL) at different
ecliptic latitudes, cancelling out any isotropic offset.
Matsuura et al. 2017

22nd flight
3rd flight
4th flight
All flights meanSolar spectrum

1.5

10.5

0.8

11.2

1.4

Wavelength [µm]

1.6

1.8

IRTS (Matsumoto 15)
DIRBE (Levenson 07)
DIRBE (Sano 15)
AKARI (Tsumura 13)
Pioneer10/11 (Matsuoka 11)
Dark cloud (Mattila 11)
HST (Bernstein 07)

CIBER nominal EBL(Kelsall ZL model)-2-1

Surface brightness λI [nW m sr ]CIBER background result

λ100

Gamma-ray limit
100.4
Tsukuba University TCHoU seminor 2018126

0.6

0.8

1

Wavelength [µm]234Matsuura et al. 2017

IGM absorption of TeV γ-rays by NIR EBLTsukuba University TCHoU seminor 2018126

Model-independent minimum CIB• Subtraction of “Quasi-isotropic” ZL component• 5% more subtraction than nominal case (Kelsall et al. ZL model)

Nominal(before)
ZL spectrumaftergalaxies
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-1

CIBER minimum EBL
IGL in 0.8-1.0 µm

100IRTS (Matsumoto 15)
DIRBE (Levenson 07)
DIRBE (Sano 15)
AKARI (Tsumura 13)
Pioneer10/11 (Matsuoka 11)
Dark cloud (Mattila 11)
HST (Bernstein 07)

λSurface brightness λI [nW m sr ]CIBER nominal EBL(Kelsall ZL model)-2

CIBER background result

Gamma-ray limit

100.4
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0.60.8

1

Wavelength [µm]234Matsuura et al. 2017

CIBER – AKARI combined result• Minimum CIB result – Integrated galaxy light

Tsukuba University TCHoU seminor 2018126

First stars ?
• Comparison of the CIBER
minimum CIB with models ofearly stars at z>8• A maximum model can
explain the observed level.
• assumes a Top-heavy IMF,
extremely high starformation efficiency, anddeep obscuration within
neutral gas, to be consistent
with the electron opticaldepth from WMAP/Planck.
(f* >> 0.1, fesc ~ 0)
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Helgason et al. (2016)

Early black holes ?
• Direct Collapse Black Hole(DCBH) may solve theproblem• Intermediate mass (< 10^6)
BH formed by direct gas
collapseYue et al. (2013)• Radiation efficiency is highenough to account for largepart of the background excess• highly obscured as Comptonthick AGN not to be in conflictwith CXB
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Helgason et al. (2016)

DCBH density & SED• Cumulative mass density of Direct Collapse Black Holes (DCBH)
and the accreting one.
• The accretion is necessary for contributing to CIB.

Tsukuba University TCHoU seminor 2018126

ZL is still suspect• It might be ZL with isotropic distribution, though
the spectrum should be extraordinary, i.e., ZL
should have similar spectral shape to the nominal.

Nominal(before)
ZL spectrum

after
Gamma-raylimit

galaxies
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CIB Fluctuation measurements
Spitzer 3.6μm

AKARI 2.4μm

10 arcmin

Matsumoto et al. 2011

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Kashlinsky et al. 2005, 2007

Helgason et al. 2016

CIBER observed fluctuation power
1.1μm

B 1.1μm
R 1.6μm
P crossgalaxies

0.1 degstars (J > 18)
1.6μm
DGL

large
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small

First stars ?
• Comparison of the lower limit from CIBER with a modelof early stars at z>8
Helgason et al. (2016)

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Early black holes ?
• CIB-CXB cross-power spectra showthat small-scale CIB fluctuations areassociated with AGNs.
• Large-scale clustering of CXB may
contribute to CIB fluctuations.

Helgason et al. (2014, 2016)
Tsukuba University TCHoU seminor 2018126

Early black holes ?
• DCBH model can explain both
CIB and CXB fluctuations.
• constrained by CXB intensity• NH > 10^25 cm-2 is required

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Yue et al. (2013)

SED of CIB fluctuations
Intrahalo light(IHL) of nearby galaxies rather than high-z objects ?

CIBER Imager FoV 2 degrees

Zemcov et al. Science (2014)

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IHL model fits mean intensity ?

IHL model

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Matsuura et al. 2017

CIBER-2 experiment• >10 times better sensitivity than CIBER• Measuring the optical background for accurate ZL sub• Measuring the spatial fluctuation in 6 wave-bands• Plan to launch in 2018 !

Tsukuba University TCHoU seminor 2018126

CIBER-2 payload modelHardware work on CB2 in progress• Optics fabrication and testing100
Z方向測定値

振動伝達率 [G/G]

Z方向シミュレーション値

1010.10.01

Tsukuba University TCHoU seminor 2018126110周波数 [Hz]1001000

ZL decreases with heliocentric distance• Best solution to mitigate ZL is interplanetary mission• If the model is true, we have chance to see naked
extragalactic background with no ZL contamination.
1. 0AU (Earth orbit)

COBE model based calculation

1. 5AU (Mars orbit)

5. 2AU (Jupiter orbit)

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OKEANOS - Solar Power Sail
OKEANOS (The Oversized Kite-craft for Exploration and Astronautics in the Outer Solar System)• Mission to explore Jupiter-Trojan asteroid• Proposed as a candidate of ISAS M-class and on the way
to be real project• We plan to measure
CIB in cruising phasewith a science
instrument (EXZIT:
Exo-Zodiacal Infrared
Telescope).
– Passively cooled
10cm telescope
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DESTINY-Z• ISAS小型衛星計画 DESTINY+ 小惑星Phaeton探査機• 同探査機システムを黄道面外へ (DESTINY-Z !)Ø ダスト密度が指数的に低下
Ø 地球スイングバイによる傾斜角増大
Ø 黄道面外~1AU軌道
高軌道傾斜角 黄道面脱出
深宇宙観測衛星

太陽
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地球

黄道光の位置変化
惑星間ダスト分布モデルからの予測• 小惑星帯(3AU)や黄道面外(0.7AU)では10分の１以下に

DESTINY-ZSPS

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EXZIT ‒ 惑星間ダスト雲からの脱出
EXZITでは地球軌道と比べて，黄道光差引きによる系統誤差の著しい低減が期待される．

DESTINY-ZSPS

Matsuuraet al.
ApJ,839,20187, 2017
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Interplanetary Space Telescope (IPST)

ご清聴ありがとうございました。
Tsukuba University TCHoU seminor 2018126

Summary• CIBER measured CIB mean intensity after
foreground subtraction based on the COBE ZL
model is consistent with previous satellite results.
• We derived a ZL model-independent CIB lower limit
from CIBER data, and it is marginally consistent
with the gamma-ray limit.
• First star and DCBH models may explain thederived CIB lower limit and observed CIB
fluctuations, but extreme condition has to be
assumed to avoid conflict with Planck electron
scattering optical depth.
• Need more observations to test varieties of theory.
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END

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