Recombination dynamics of primordial hydrogen and helium (He I) in the universe

Дубрович, В. К.; Грачев, С. И.

doi:10.1134/1.1940107

Cited by 87 publications

(190 citation statements)

References 7 publications

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“…Detecting DM annihilation by its effect on the recombination history requires that we understand the fiducial recombination physics to better than 1%. The current recombination calculation is accurate to ∼ 1% [42], although there recently have been claims of corrections due to two photon processes [43]. Although the current calculation may not be accurate enough, we do not know of any theoretical limit that would prevent reaching the required accuracy.…”

Section: Discussionmentioning

confidence: 94%

Detecting dark matter annihilation with CMB polarization: Signatures and experimental prospects

2005

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Dark matter (DM) annihilation during hydrogen recombination (z ∼ 1000) will alter the recombination history of the Universe, and affect the observed CMB temperature and polarization fluctuations. Unlike other astrophysical probes of DM, this is free of the significant uncertainties in modelling galactic physics, and provides a method to detect and constrain the cosmological abundances of these particles. We parametrize the effect of DM annihilation as an injection of ionizing energy at a rate ǫ dm , and argue that this simple "on the spot" modification is a good approximation to the complicated interaction of the annihilation products with the photon-electron plasma. Generic models of DM do not change the redshift of recombination, but change the residual ionization after recombination. This broadens the surface of last scattering, suppressing the temperature fluctuations and enhancing the polarization fluctuations. We use the temperature and polarization angular power spectra to measure these deviations from the standard recombination history, and therefore, indirectly probe DM annihilation. The modifications to the temperature power spectrum are nearly degenerate with the primordial scalar spectral index and amplitude; current CMB data are therefore unable to put any constraints on the annihilation power. This degeneracy is broken by polarization; Planck will have the sensitivity to measure annihilation power ǫ dm (z = 1000) > 10 −15 eV/s/proton, while high sensitivity experiments (eg. NASA's CMBPOL) could improve that constraint to ǫ dm (z = 1000) > 4 × 10 −16 eV/s/proton, assuming a fractional detector sensitivity of ∆T /T ∼ 1µK and a beam of 3 ′ . These limits translate into a lower bound on the mass of the DM particle, M dm > 10 − 100 GeV, assuming a single species with a cross section of σAv ∼ 2 × 10 −26 cm 3 /s, and a fraction f ∼ 0.1 − 1 of the rest mass energy used for ionization. The bounds for the WMAP 4y data are significantly lower, because of its lack of high S/N polarization measurements, but it can strongly constrain O( MeV) particles such as those proposed by .

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Section: Discussionmentioning

confidence: 94%

Detecting dark matter annihilation with CMB polarization: Signatures and experimental prospects

2005

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“…Among all the additional physical mechanisms during cosmological recombination that have been addressed so far, the problems connected with the radiative transfer of out by Dubrovich & Grachev (2005). They predicted a ∼5% decrease in the free electron fraction at z ∼ 1200.…”

Section: Introductionmentioning

confidence: 99%

“…After the seminal works of Zeldovich et al (1968) and Peebles (1968) on cosmological recombination, and the later improvements to the theoretical modeling of this epoch (e.g., Jones & Wyse 1985;Seager et al 2000), leading to the widely used standard recombination code Recfast (Seager et al 1999), over the past few years the detailed physics of cosmological recombination has again been reconsidered by several independent groups (e.g., Dubrovich & Grachev 2005;Chluba & Sunyaev 2006b;Kholupenko & Ivanchik 2006;Rubiño-Martín et al 2006;Switzer & Hirata 2008;Wong & Scott 2007). It is clear that understanding the cosmological ionization history at the level of ∼0.1% (e.g., see Fendt et al 2009, for a more detailed overview of the different previously neglected physical processes that are important at this level of accuracy) will be very important to accurate theoretical predictions of the cosmic microwave background (CMB) temperature and polarization angular fluctuations (e.g., see Hu et al 1995;Seljak et al 2003) to be measured by the Planck Surveyor 1 , which will be launched later this year.…”

Section: Introductionmentioning

confidence: 99%

“…Using rate coefficients for the vacuum two-photon decays of the 3s and 3d-levels in hydrogen, as computed by Cresser et al (1986), Wong & Scott (2007) concluded that Dubrovich & Grachev (2005) overestimated the impact of two-photon transitions on the ionization history by about one order of magnitude. However, the calculation of Cresser et al (1986) was incomplete, since in their attempt to separate the "1 + 1" photon contributions to the two-photon formula 2 from the "pure" twophoton decay terms, without clear justification they neglected the first non-resonant term .…”

Section: Introductionmentioning

confidence: 99%

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Lyαescape during cosmological hydrogen recombination: the 3d-1s and 3s-1s two-photon processes

Chluba

Sunyaev

2010

A&A

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We give a formulation of the radiative transfer equation for Lyman α photons, which allows us to include the two-photon corrections for the 3s-1s and 3d-1s decay channels during cosmological hydrogen recombination. We use this equation to compute the corrections to the Sobolev escape probability for Lyman α photons during hydrogen recombination, which then allow us to calculate the changes in the free electron fraction and CMB temperature and polarization power spectra. We show that the effective escape probability changes by ΔP/P ∼ +11% at z ∼ 1400 in comparison with the one obtained using the Sobolev approximation. This accelerates hydrogen recombination by ΔN e /N e ∼ −1.6% at z ∼ 1190, implying that |ΔC l /C l | ∼ 1−3% at l > ∼ 1500 with shifts in the positions of the maxima and minima in the CMB power spectra. These corrections will be important to the analysis of future CMB data. The total correction is the result of the superposition of three independent processes, related to (i) time-dependent aspects of the problem; (ii) corrections due to quantum mechanical deviations in the shape of the emission and absorption profiles in the vicinity of the Lyman α line, from the normal Lorentzian; and (iii) a thermodynamic correction factor, which is found to be very important. All of these corrections are neglected in the Sobolev-approximation, but they are important in the context of future CMB observations. All three can be naturally obtained in the two-photon formulation of the Lyman α absorption process. However, the corrections (i) and (iii) can also be deduced in the normal "1 + 1" photon language, without necessarily going to the two-photon picture. Therefore, only (ii) is really related to the quantum mechanical aspects of the two-photon process. We show here that (i) and (iii) represent the largest individual contributions to the result, although they partially cancel each other close to z ∼ 1100. At z ∼ 1100, the modification due to the shape of the line profile contributes about ΔN e /N e ∼ −0.4%, while the sum of the other two contributions gives ΔN e /N e ∼ −0.9%.

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“…19 and Chluba & RS (2008b)). However, the estimates of Dubrovich & Grachev (2005) only included the contribution to the two-photon decay rate coming from the two-photon continuum, which is due to virtual transitions, and as for example shown in Chluba & RS (2008b) in particular the interference between resonant and non-resonant contributions plays an important role in addition. This results in deviations of the line emission profiles from the normal Lorentzian shape, which are caused by quantum mechanical aspects of the problem and are most strong in the distant damping wings (e.g.…”

Section: Two-photon Transitions From Higher Levelsmentioning

confidence: 99%

Signals From the Epoch of Cosmological Recombination

Sunyaev

Chluba

2009

Reviews in Modern Astronomy

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The physical ingredients to describe the epoch of cosmological recombination are amazingly simple and well-understood. This fact allows us to take into account a very large variety of physical processes, still finding potentially measurable consequences for the energy spectrum and temperature anisotropies of the Cosmic Microwave Background (CMB). In this contribution we provide a short historical overview in connection with the cosmological recombination epoch and its connection to the CMB. Also we highlight some of the detailed physics that were studied over the past few years in the context of the cosmological recombination of hydrogen and helium.The impact of these considerations is two-fold: (i) the associated release of photons during this epoch leads to interesting and unique deviations of the Cosmic Microwave Background (CMB) energy spectrum from a perfect blackbody, which, in particular at decimeter wavelength and the Wien part of the CMB spectrum, may become observable in the near future. Despite the fact that the abundance of helium is rather small, it still contributes a sizeable amount of photons to the full recombination spectrum, leading to additional distinct spectral features. Observing the spectral distortions from the epochs of hydrogen and helium recombination, in principle would provide an additional way to determine some of the key parameters of the Universe (e.g. the specific entropy, the CMB monopole temperature and the pre-stellar abundance of helium). Also it permits us to confront our detailed understanding of the recombination process with direct observational evidence. In this contribution we illustrate how the theoretical spectral template of the cosmological recombination spectrum may be utilized for this purpose. We also show that because hydrogen and helium recombine at very different epochs it is possible to address questions related to the thermal history of our Universe. In particular the cosmological recombination radiation may allow us to distinguish between Compton y-distortions that were created by energy release before or after the recombination of the Universe finished. 1(ii) with the advent of high precision CMB data, e.g. as will be available using the Planck Surveyor or CMBpol, a very accurate theoretical understanding of the ionization history of the Universe becomes necessary for the interpretation of the CMB temperature and polarization anisotropies. Here we show that the uncertainty in the ionization history due to several processes, which until now were not taken in to account in the standard recombination code Recfast, reaches the percent level. In particular He ii → He i-recombination occurs significantly faster because of the presence of a tiny fraction of neutral hydrogen at z 2400. Also recently it was demonstrated that in the case of H i Lyman α photons the timedependence of the emission process and the asymmetry between the emission and absorption profile cannot be ignored. However, it is indeed surprising how inert the cosmological recombination hi...

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Recombination dynamics of primordial hydrogen and helium (He I) in the universe

Cited by 87 publications

References 7 publications

Detecting dark matter annihilation with CMB polarization: Signatures and experimental prospects

Detecting dark matter annihilation with CMB polarization: Signatures and experimental prospects

Lyαescape during cosmological hydrogen recombination: the 3d-1s and 3s-1s two-photon processes

Signals From the Epoch of Cosmological Recombination

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