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Register a new userCMB Anisotropies due to Feedback-Regulated Inhomogeneous Reionization
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We calculate the secondary anisotropies in the CMB produced by inhomogeneous reionization from simulations in which the effects of radiative and stellar feedback effects on galaxy formation have been included. This allows to self-consistently determine the beginning ($z_iapprox 30$), the duration ($ delta zapprox 20$) and the (nonlinear) evolution of the reionization process for a critical density CDM model. In addition, from the simulated spatial distribution of ionized regions, we are able to calculate the evolution of the two-point ionization correlation function, $C_chi$, and obtain the power spectrum of the anisotropies, $C_ell$, in the range $5000 < ell < 10^6$. The power spectrum has a broad maximum around $ell approx 30000$, where it reaches the value $2times 10^{-12}$. We also show that the angular correlation function $C(theta)$ is not Gaussian, but at separation angles $% theta lower.5exhbox{ltsima} 10^{-4}$ rad it can be approximated by a modified Lorentzian shape; at larger separations an anticorrelation signal is predicted. Detection of signals as above will be possible with future mm-wavelength interferometers like ALMA, which appears as an optimum instrument to search for signatures of inhomogeneous reionization.
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Recently, we have presented the first large-scale radiative transfer simulations of reionization. Here we present new simulations which extend the source halo mass range downward to 10^8M_solar, to capture the full range of halo masses thought to be primarily responsible for reionization by their star formation following atomic hydrogen radiative cooling and gravitational collapse. Haloes below about 10^9M_solar, however, are subject to Jeans-mass filtering in the ionized regions, which suppresses their baryonic content and their ability to release ionizing radiation. By including these smaller-mass haloes but accounting for their suppression, too, we find that reionization is ``self-regulating, as follows. As the mean ionized fraction rises, so does the fraction of the volume within which suppression occurs. Hence, the degree of suppression is related to the mean ionized fraction. Since low-mass haloes with high emissivity achieve a given mean ionized fraction earlier than do those with low efficiency, Jeans-mass filtering compensates for the difference in the emissivity of the suppressible haloes in these two cases. As a result, in the presence of lower-mass source haloes, reionization begins earlier, but the later stages of reionization and the time of overlap are dictated by the efficiency of the higher-mass haloes, independent of the efficiency of the suppressible, lower-mass haloes. Reionization histories consistent with current observational constraints are shown to be achievable with standard stellar sources in haloes above 10^8M_solar. Neither minihalos nor exotic sources are required, and the phenomenon of ``double reionization previously suggested does not occur. (abridged)
We present an analytical calculation of the spectra of CMB anisotropies and polarizations generated by relic gravitational waves (RGWs). As a substantial extension to the previous studies, three new ingredients are included in this work. Firstly, the analytic $C_l^{TT}$ and $C_l^{TE}$ are given; especially the latter can be useful to extract signal of RGWs from the observed data in the zero multipole method. Secondly, a fitting formula of the decaying factor on small scales is given, coming from the visibility function around the photon decoupling. Thirdly, the impacts by the neutrino free-streaming (NFS) is examined, a process that occurred in the early universe and leaves observable imprints on CMB via RGWs. It is found that the analytic $C_l^{TT}$ and $C_l^{TE}$ have profiles agreeing with the numeric ones, except that $C^{TT}_l$ in a range $l le 10$ and the $1^{st}$ trough of $C_l^{TE}$ around $l sim 75$ have some deviations. With the new damping factor, the analytic $C^{EE}_l$ and $C^{BB}_l$ match with the numeric ones with the maximum errors only $sim 3%$ up to the first three peaks for $lle 600$, improving the previous studies substantially. The correspondence of the positions of peaks of $C^{XX}_l$ and those of RGWs are also demonstrated explicitly. We also find that NFS reduces the amplitudes of $C^{XX}_l$ by $(20% sim 35%)$ for $lsimeq(100sim 600)$ and shifts slightly their peaks to smaller angles. Detailed analyses show that the zero multipoles $l_0$, where $C_l^{TE}$ crosses 0, are shifted to larger values by NFS. This shifting effect is as important as those causedby different inflation models and different baryon fractions.
Confusion noise due to extragalactic sources is a fundamental astrophysical limitation for experiments aimed at accurately determining the power spectrum of the Cosmic Microwave Background (CMB) down to arcmin angular scales and with a sensitivity $Delta T/T simeq 10^{-6}$. At frequencies $lsim 200-300$ GHz, the most relevant extragalactic foreground hampering the detection of intrinsic CMB anisotropies is constituted by radio loud Active Galactic Nuclei (AGN), including ``flat--spectrum radiogalaxies, quasars, BL-LACs and blazars. We review our present understanding of astrophysical properties, spectra, and number counts of the above classes of sources. We also study the angular power spectrum of fluctuations due both to Poisson distributed and clustered radio sources and give preliminary predictions on the power spectrum of their polarized components. Furthermore, we discuss the capabilities of future space missions (NASAs MAP, Bennett et al. 1995; ESAs Planck Surveyor, Bersanelli et al. 1996) in studying bright radio sources over an almost unexplored frequency interval where spectral signatures, essential for the understanding of the physical processes, show up.
Spatially fluctuating primordial magnetic fields (PMFs) inhomogeneously reheat the Universe when they dissipate deep inside the horizon before recombination. Such an energy injection turns into an additional photon temperature perturbation. We investigate secondary cosmic microwave background (CMB) temperature anisotropies originated from this mechanism, which we call {it inhomogeneous magnetic reheating}. We find that it can bring us information about non-linear coupling between PMFs and primordial curvature perturbations parametrized by $b_{rm NL}$, which should be important for probing the generation mechanism of PMFs. In fact, by using current CMB observations, we obtain an upper bound on the non-linear parameter as $log (b_{rm NL} (B_{lambda}/{rm nG})^2) lesssim {-36.5n_{B} - 94.0}$ with $B_{lambda}$ and $n_{rm B}$ being a magnetic field amplitude smoothed over $lambda=1; {rm Mpc}$ scale and a spectral index of the PMF power spectrum, respectively. Our constraints are far stronger than a previous forecast based on the future CMB spectral distortion anisotropy measurements because inhomogeneous magnetic reheating covers a much wider range of scales, i.e., $1; {rm Mpc}^{-1} lesssim klesssim 10^{15}; {rm Mpc}^{-1}$.
We have searched the 1st-year WMAP W-Band CMB anisotropy map for evidence of cosmic strings. We have set a limit of $delta = 8 pi G mu / c^2 < 8.2 times 10^{-6}$ at 95% CL for statistical search for a significant number of strings in the map. We also have set a limit using the uniform distribution of strings model in the WMAP data with $delta = 8 pi G mu / c^2 < 7.34 times 10^{-5}$ at 95% CL. And the pattern search technique we developed here set a limit $delta = 8 pi G mu / c^2 < 1.54 times 10^{-5}$ at 95% CL.
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