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Population 3 and Cosmic Infrared Background A. Kashlinsky (GSFC). Direct CIB excess measurements CIB excess and Population 3 CIB excess and γ -ray absorption CIB fluctuations – results from Spitzer data Interpretation of the Spitzer data and Pop 3 Resolving the sources - prospects w. JWST. - PowerPoint PPT Presentation
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Population 3 and Cosmic Infrared Background
A. Kashlinsky (GSFC)
• Direct CIB excess measurements
• CIB excess and Population 3
• CIB excess and γ-ray absorption
• CIB fluctuations – results from Spitzer data
• Interpretation of the Spitzer data and Pop 3
• Resolving the sources - prospects w. JWST
From Kashlinsky (2005, Phys Rep., 409, 361)
CIB measurements - summary
CIB due to J, H, K galaxy counts
IRAC deep galaxy counts (Fazio et al 2004)
From Kashlinsky (2005, Phys. Rep., 409, 361)
Claimed mean CIB excess
Diffuse background from Pop 3 (Santos et al 2003, Salvaterra & Ferrara 2003, Cooray et al 2003, Kashlinsky et al 2004)
)1(4
)(
2z
dt
dV
d
dMMLn
dt
dF
L
∫ M n(M) dM = Ωbaryon 3H02/8πG f* f* fraction in Pop 3
dV = 4 π cdL2(1+z)-1 dt ; L ≈ LEdd ∞ M ; tL = ε Mc2/L << t(z=20)
srm
nWfhf
G
c
RI
baryonbaryon
H2*
24*
5
2 007.0044.0102.1
4
1
8
3
CIB data give:
FNIRBE = 29+/-13 nW/m2/sr F(λ>:10μm) < 10 nW/m2/sr
This can be reproduced with
f* = 4 +/- 2 % for ε=0.007
γ - ray absorption and CIB
• γ γ → e+ e-
• σ ~ σT
• X-section peaks at 0.4 σT
at EγECIB=2 (mec2)2
Dwek et al (2006)
z ~ 0.13
Aharonian et al (2006)
z ~ 0.18
From Aharonian et al (2006)
Pop 3 live at z > 10; hence any photons from them were produced then so that nγ ∞ (1+z)3 or
4π/c Iν/hPlanck(1+z)3 per dlnE = 0.6 Iν(MJy/sr) (1+z)3cm-3
Sharp cutoff at ε = 260 (1+zGRB)-2 GeV
(Kashlinsky 2005, ApJL)
dz
d
Reasons why Pop 3 should produce significant CIB fluctuations
• If massive, each unit of mass emits L/M~105 as normal stars (~L๏/M๏)
• Pop 3 era contains a smaller volume (~k2ct*), hence larger relative fluctuations
• Pop 3 systems form out of rare peaks on the underlying density field, hence their correlations are amplified
Population 3 would leave a unique imprint in the CIB structure And measuring it would offer evidence of and a glimpse into the Pop 3 era (Cooray et al 2004, Kashlinsky et al 2004)
CIB fluctuations from Population III
z Have to integrate along l.o.s.
(Limber equation)
dtzqddt
dI
cqF A
Pq ))(()(1
)/2~( 122'2
22
This can be rewritten as
)(( 1 zqdFF ACIBCIB
*
32
22 )(
2
1)(
ct
kPkk
Fractional CIB fluctuation on scale ~π/q is given by average value of rms fluctuation from Pop 3 spatial clustering over a cylinder of length ct* and diameter ~k-1.
θPop 3?
with
Cosmic infrared background fluctuations from deep Spitzer images and Population III
(A. Kashlinsky, R. Arendt, J. Mather & H. Moseley
Nature, 2005, 438, 45
+ more coming up shortly)
Pop 3 templates from Santos et al (2002)
• Used 3 fields: one main (deepest – IOC or QSO 1700), 2 auxiliary
• The deepest field is ~ 6’ by 12 ‘ and exposed for ~ 10 hrs
• The test/auxiliary field have shallower exposures.
Image processing:
• Data were assembled using a least-squares self-calibration methods from Fixsen, Moseley & Arendt (2000).
• Selected a field of 1152x512 pixels (0.6”) w. homogeneous coverage.
• Individual sources have been clipped out at >Ncutσ w Nmask =3-7
• Residual extended parts were removed by subtracting a “Model” by identifying individual sources w. SExtractor and convolving them with a full array PSF
• Finally, the Model was further refined with CLEAN-type procedure
• Clipped image minus Model had its linear gradient subtracted, FFT’d, muxbleed removed in Fourier space and P(q) computed.
• In order to reliably compute FFT, the clipping fraction was kept at >75% (Ncut=4)
• Noise was evaluated from difference (A-B) maps
• Control fields (HZF, EGS) were processed similarly
Datasets in Spitzer analysis(Kashlinsky, Arendt, Mather & Moseley 2005)
Region lGal bGal lecl becl <tobs> mVega,lim
QSO 1700
(or IOC)
94.4 36.1 194.3 83.5 Ch 1-3: 7.8 hrs
Ch 4: 9.2 hrs
> 22.5 (Ch 1)
> 20.5 (Ch 2)
> 18.25 (Ch 3)
> 17.5 (Ch 4)
HZF (Ch 1-3) 217.5 34.6 135.0 -4.9 ~ 0.5 hrs > 21.5 (Ch 1)
> 19.5 (Ch 2)
> 17.0 (Ch 3)
HZF (Ch 4) 18.4 -10.4 285.0 5.0 ~0.7 hrs > 14.5
EGSF 96.5 58.9 179.9 60.9 ~ 1.5 hrs
← Image (3.6 mic)
Exposure →
5.8 mic 8 mic
3.6 mic 4.5 mic
Ncut=4
Pmap – Pnoise:
Possible sources of fluctuations
• Instrument noise (too low and different pattern and x-correlation between the channels for the overlap region)
• Residual wings of removed sources (unlikely and have done extensive analysis and results are the same for various clipping parameters, etc)
• Zodiacal light fluctuations (too small: at 8 mic <0.1 nW/m2/sr and assuming normal zodi spectrum would be totally negligible at shorter wavelengths)
• G. cirrus: channel 4 (8 mic) may contain a non-negligible component of cirrus (~0.2 nW/m2/sr), but given the energy spectrum of cirrus emission the other channels should have negligible cirrus. Also similar excess in control fields.
• Extragalactic sources: 1) Ordinary galaxies (shot noise contributes to small scales, but
clustering component small)
2) Population 3: M/L << (M/L)Sun
5.8 mic Ncut=2 8 mic
3.6 mic 4.5 mic
Correlation function
Signal comes from mAB > 26.1 at 3.6 micron
Extragalactic component of the CIB fluctuations: Pop 3 or not Pop 3?
• Fluctuations arise from mAB > 26 (correlation function does not change to Ncut < 2)
• The clustering component measured (δF ~ 0.1 nW/m2/sr at θ > 1 arcmin)
• The shot-noise component of fluctuations
(PSN < ~ 10-11 nW2/m4/sr)
Take 3.6 micron data as an example.
Any model must explain the following:
1. Magnitude constraint:
mAB > 26.1 (mVega~ 23.5) at 3.6 mic or sources with flux < 130 nJy
Even at z =5 these sources would have 6x108 h-2LSun emitted at 6000 A
Extrapolated flux from remaining ordinary galaxies gives little CIB (~0.1-0.2 nW/m2/sr)
mVega
2. Clustering component
1. At 3.6 mic the fluctuation is δF~ 0.1 nW/m2/sr at θ≥ 1 arcmin
2. At 20>z>5 angle θ=1` subtends between 2.2 and 3 Mpc
3. Limber equation requires:
)(( 1 zqdFF ACIBCIB w. *
32
22 )(
2
1)(
ct
kPkk
4. Concordance CDM cosmology with reasonable biasing then requires Δ of at most 5-10 % on arcmin scales
5. Hence, the sources producing these CIB fluctuations should haveFCIB >1-2 nW/m2/sr
3. Shot noise clues to where does the signal come from.
PSN= ∫ f(m) dFCIB(m) = f(<m>) FCIB(m>mlim)
where f(m)=f010-0.4m and dF=f(m)dN(m).
At 3.6 mic PSN=6x10-12 nW2/m4/sr
For FCIB ~ 2 nW/m2/sr, the SN amplitude indicates the sources contributing to fluctuation must have mAB>30.
Resolving sources of CIBConfusion allows for individual detection when there are < 1/40-1/25sources per beam
For the parameters above one expects the sources to have abundance of
<n> ~ F2CIB/Psn > 8 arcsec-2
To beat the confusion at 5-σ level at 3.6 micron one needs beam of
ωbeam < 1/25 <n> ~ 5x10-3 (FCIB/2 nw/m2/sr)-2 arcsec-2
or radius
Θbeam < 0.04 (FCIB/2 nW/m2/sr) arcsec
This is (just about) reachable with JWST
Conclusions
• Mean near-IR CIB excess may be smaller than what IRTS and COBE measurements indicated
• Its level can be probed with future GLAST measurements of high z GRB spectra
• Measurements of CIB anisotropies after removal of high-z galaxies give direct probe of emissions from the putative Population III era
• CIB anisotorpies from Spitzer data indicate a presence of significant populations around mAB ~ 30 or a few nJy producing at least ~ 2 nW/m2/sr at 3.6 micron
• Such populations may just about be resolved individually with JWST