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) ∫ M n(M) dM = Ω baryon 3H 0 2 /8πG f * f * fraction in Pop 3 dV = 4 π cd L 2 (1+z) -1 dt ; L ≈ L Edd ∞ M ;t L = ε Mc 2 /L << t(z=20) CIB data give: F NIRBE = 29+/-13 nW/m 2 /sr F( λ>:10 μm) < 10 nW/m 2 /sr This can be reproduced with f * = 4 +/- 2 % for ε=0.007

γ - ray absorption and CIB γ γ → e + e - σ ~ σ T X-section peaks at 0.4 σ T at E γ E CIB =2 (m e c 2 ) 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 n γ ∞ (1+z) 3 or 4π/c I ν /h Planck (1+z) 3 per dlnE = 0.6 I ν (MJy/sr) (1+z) 3 cm -3

Sharp cutoff at ε = 260 (1+z GRB ) -2 GeV (Kashlinsky 2005, ApJL)

Reasons why Pop 3 should produce significant CIB fluctuations If massive, each unit of mass emits L/M~10 5 as normal stars (~L ๏ /M ๏ ) Pop 3 era contains a smaller volume (~k 2 ct * ), 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) 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. θ Pop 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 >N cut σ w N mask =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% (N cut =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) Regionl Gal b Gal l ecl b ecl m Vega,lim QSO 1700 (or IOC) Ch 1-3: 7.8 hrs Ch 4: 9.2 hrs > 22.5 (Ch 1) > 20.5 (Ch 2) > (Ch 3) > 17.5 (Ch 4) HZF (Ch 1-3) ~ 0.5 hrs > 21.5 (Ch 1) > 19.5 (Ch 2) > 17.0 (Ch 3) HZF (Ch 4) ~0.7 hrs > 14.5 EGSF ~ 1.5 hrs

← Image (3.6 mic) Exposure →

5.8 mic 8 mic 3.6 mic4.5 mic N cut =4

P map – P noise :

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/m 2 /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/m 2 /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 N cut =2 8 mic 3.6 mic 4.5 mic

Correlation function Signal comes from m AB > 26.1 at 3.6 micron

Extragalactic component of the CIB fluctuations: Pop 3 or not Pop 3? Fluctuations arise from m AB > 26 (correlation function does not change to N cut < 2) The clustering component measured (δF ~ 0.1 nW/m 2 /sr at θ > 1 arcmin) The shot-noise component of fluctuations (P SN < ~ nW 2 /m 4 /sr) Take 3.6 micron data as an example. Any model must explain the following:

1. Magnitude constraint: m AB > 26.1 (m Vega ~ 23.5) at 3.6 mic or sources with flux < 130 nJy Even at z =5 these sources would have 6 x 10 8 h -2 L Sun emitted at 6000 A Extrapolated flux from remaining ordinary galaxies gives little CIB (~ nW/m 2 /sr) m Vega

2. Clustering component 1.At 3.6 mic the fluctuation is δF~ 0.1 nW/m 2 /sr at θ≥ 1 arcmin 2. At 20>z>5 angle θ=1` subtends between 2.2 and 3 Mpc 3. 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 F CIB >1-2 nW/m 2 /sr

3. Shot noise clues to where does the signal come from. P SN = ∫ f(m) dF CIB (m) = f( ) F CIB (m>m lim ) where f(m)=f m and dF=f(m)dN(m). At 3.6 mic P SN =6 x nW 2 /m 4 /sr For F CIB ~ 2 nW/m 2 /sr, the SN amplitude indicates the sources contributing to fluctuation must have m AB >30.

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 ~ F 2 CIB /P sn > 8 arcsec -2 To beat the confusion at 5-σ level at 3.6 micron one needs beam of ω beam ~ 5x10 -3 (F CIB /2 nw/m 2 /sr) -2 arcsec -2 or radius Θ beam < 0.04 (F CIB /2 nW/m 2 /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 m AB ~ 30 or a few nJy producing at least ~ 2 nW/m 2 /sr at 3.6 micron Such populations may just about be resolved individually with JWST