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Population 3 and Cosmic Infrared Background A. Kashlinsky (GSFC)

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.

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Population 3 and Cosmic Infrared Background A. Kashlinsky (GSFC)

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  1. Population 3 and Cosmic Infrared BackgroundA. 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

  2. CIB measurements - summary From Kashlinsky (2005, Phys Rep., 409, 361)

  3. CIB due to J, H, K galaxy counts

  4. IRAC deep galaxy counts (Fazio et al 2004)

  5. Claimed mean CIB excess From Kashlinsky (2005, Phys. Rep., 409, 361)

  6. Diffuse background from Pop 3 (Santos et al 2003, Salvaterra & Ferrara 2003, Cooray et al 2003, Kashlinsky et al 2004) ∫ 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) 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

  7. γ - ray absorption and CIB • γγ → e+ e- • σ ~ σT • X-section peaks at 0.4 σT at EγECIB=2 (mec2)2

  8. Dwek et al (2006) z ~ 0.13 Aharonian et al (2006) z ~ 0.18

  9. From Aharonian et al (2006)

  10. 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

  11. Sharp cutoff at ε = 260 (1+zGRB)-2 GeV (Kashlinsky 2005, ApJL)

  12. CIB fluctuations from Population III 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)

  13. z Have to integrate along l.o.s. (Limber equation) Pop 3? θ with This can be rewritten as 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.

  14. 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)

  15. Pop 3 templates from Santos et al (2002)

  16. 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.

  17. 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

  18. Datasets in Spitzer analysis(Kashlinsky, Arendt, Mather & Moseley 2005)

  19. ← Image (3.6 mic) Exposure →

  20. 3.6 mic 4.5 mic Ncut=4 5.8 mic 8 mic

  21. Pmap – Pnoise:

  22. 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

  23. 3.6 mic 4.5 mic 5.8 mic Ncut=2 8 mic

  24. Correlation function Signal comes from mAB > 26.1 at 3.6 micron

  25. Extragalactic component of the CIB fluctuations: Pop 3 or not Pop 3? Take 3.6 micron data as an example. Any model must explain the following: • 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)

  26. 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 mVega Extrapolated flux from remaining ordinary galaxies gives little CIB (~0.1-0.2 nW/m2/sr)

  27. 2. Clustering component • At 3.6 mic the fluctuation is δF~ 0.1 nW/m2/sr at θ≥ 1 arcmin • At 20>z>5 angle θ=1` subtends between 2.2 and 3 Mpc • Limber equation requires: w. 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 have FCIB >1-2 nW/m2/sr

  28. 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.

  29. Resolving sources of CIB Confusion allows for individual detection when there are < 1/40-1/25 sources 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

  30. 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

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