Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userOne percent determination of the primordial deuterium abundance
57
0
0.0
(
0
)
Authors
Ryan Cooke
Ask ChatGPT about the research
No Arabic abstract
We report a reanalysis of a near-pristine absorption system, located at a redshift z_abs=2.52564 toward the quasar Q1243+307, based on the combination of archival and new data obtained with the HIRES echelle spectrograph on the Keck telescope. This absorption system, which has an oxygen abundance [O/H]=-2.769+/-0.028 (~1/600 of the Solar abundance), is among the lowest metallicity systems currently known where a precise measurement of the deuterium abundance is afforded. Our detailed analysis of this system concludes, on the basis of eight D I absorption lines, that the deuterium abundance of this gas cloud is log_10(D/H) = -4.622+/-0.015, which is in very good agreement with the results previously reported by Kirkman et al. (2003), but with an improvement on the precision of this single measurement by a factor of ~3.5. Combining this new estimate with our previous sample of six high precision and homogeneously analyzed D/H measurements, we deduce that the primordial deuterium abundance is log_10(D/H)_P = -4.5974+/-0.0052 or, expressed as a linear quantity, (D/H)_P = (2.527+/-0.030)x10^-5; this value corresponds to a one percent determination of the primordial deuterium abundance. Combining our result with a BBN calculation that uses the latest nuclear physics input, we find that the baryon density derived from BBN agrees to within 2 sigma of the latest results from the Planck CMB data.
rate research
Read More
We report the discovery of deuterium absorption in the very metal-poor ([Fe/H] = -2.88) damped Lyman-alpha system at z_abs = 3.06726 toward the QSO SDSS J1358+6522. On the basis of 13 resolved D I absorption lines and the damping wings of the H I Lyman alpha transition, we have obtained a new, precise measure of the primordial abundance of deuterium. Furthermore, to bolster the present statistics of precision D/H measures, we have reanalyzed all of the known deuterium absorption-line systems that satisfy a set of strict criteria. We have adopted a blind analysis strategy (to remove human bias), and developed a software package that is specifically designed for precision D/H abundance measurements. For this reanalyzed sample of systems, we obtain a weighted mean of (D/H)_p = (2.53 +/- 0.04) x 10^-5, corresponding to a Universal baryon density100 Omega_b h^2 = 2.202 +/- 0.046 for the standard model of Big Bang Nucleosynthesis. By combining our measure of (D/H)_p with observations of the cosmic microwave background, we derive the effective number of light fermion species, N_eff = 3.28 +/- 0.28. We therefore rule out the existence of an additional (sterile) neutrino (i.e. N_eff = 4.046) at 99.3 percent confidence (2.7 sigma), provided that N_eff and the baryon-to-photon ratio (eta_10) did not change between BBN and recombination. We also place a strong bound on the neutrino degeneracy parameter, xi_D = +0.05 +/- 0.13 based only on the CMB+(D/H)_p observations. Combining xi_D with the current best literature measure of Y_p, we find |xi| <= +0.062. In future, improved measurements of several key reaction rates, in particular d(p,gamma)3He, and further measures of (D/H)_p with a precision comparable to those considered here, should allow even more stringent limits to be placed on new physics beyond the standard model.
The metal-poor damped Lyman alpha (DLA) system at z = 3.04984 in the QSO SDSSJ1419+0829 has near-ideal properties for an accurate determination of the primordial abundance of deuterium, (D/H)_p. We have analysed a high-quality spectrum of this object with software specifically designed to deduce the best fitting value of D/H and to assess comprehensively the random and systematic errors affecting this determination. We find (D/H)_DLA = (2.535 +/-0.05) x 10^(-5), which in turn implies Omega_b h^2 = 0.0223 +/- 0.0009, in very good agreement with Omega_b h^2 (CMB) = 0.0222 +/- 0.0004 deduced from the angular power spectrum of the cosmic microwave background. If the value in this DLA is indeed the true (D/H)_p produced by Big-Bang nucleosynthesis (BBN), there may be no need to invoke non-standard physics nor early astration of D to bring together Omega_b h^2 (BBN) and Omega_b h^2 (CMB). The scatter between most of the reported values of (D/H)_p in the literature may be due largely to unaccounted systematic errors and biases. Further progress in this area will require a homogeneous set of data comparable to those reported here and analysed in a self-consistent manner. Such an endeavour, while observationally demanding, has the potential of improving our understanding of BBN physics, including the relevant nuclear reactions, and the subsequent processing of 4He and 7Li through stars.
Deuterium abundances measured recently from QSO absorption-line systems lie in the range from 3 10^{-5} to 3 10^{-4}, which shed some questions on standard big bang theory. We show that this discordance may simply be an artifact caused by inadequate analysis ignoring spatial correlations in the velocity field in turbulent media. The generalized procedure (accounting for such correlations) is suggested to reconcile the D/H measurements. An example is presented based on two high-resolution observations of Q1009+2956 (low D/H) [1,2] and Q1718+4807 (high D/H) [8,9]. We show that both observations are compatible with D/H = 4.1 - 4.6 10^{-5}, and thus support SBBN. The estimated mean value <D/H> = 4.4 10^{-5} corresponds to the baryon-to-photon ratio during SBBN eta = 4.4 10^{-10} which yields the present-day baryon density Omega_b h^2 = 0.015.
74 -
Sergei A. Levshakov (National Astronomical Observatory
, Japan andn Ioffe Institute
, St. Petersburg
1997
The current status of extragalactic deuterium abundance is discussed using two examples of `low and `high D/H measurements. We show that the discordance of these two types of D abundances may be a consequence of the spatial correlations in the stochastic velocity field. Within the framework of the generalized procedure (accounting for such effects) one finds good agreement between different observations and the theoretical predictions for standard big bang nucleosynthesis (SBBN). In particular, we show that the deuterium absorption seen at z = 2.504 toward Q1009+2956 and the H+D Ly-alpha profile observed at z = 0.701 toward Q1718+4807 are compatible with D/H $sim 4.1 - 4.6times10^{-5}$. This result supports SBBN and, thus, no inhomogeneity is needed. The problem of precise D/H measurements is discussed.
Gravitational waves from binary black holes that are gravitationally lensed can be distorted by small microlenses along the line of sight. Microlenses with masses of a few tens of solar masses, and that are close to a critical curve in the lens plane, can introduce a time delay of a few millisecond. Such time delay would result in distinctive interference patterns in the gravitational wave that can be measured with current experiments such as LIGO/Virgo. We consider the particular case of primordial black holes with masses between 5 and 50 solar masses acting as microlenses. We study the effect of a population of primordial black holes constituting a fraction of the dark matter, and contained in a macrolens (galaxy or cluster), over gravitational waves that are being lensed by the combined effect of the macrolens plus microlenses. We find that at the typical magnifications expected for observed GW events, the fraction of dark matter in the form of compact microlenses, such as primordial black holes, can be constrained to percent level. Similarly, if a small percentage of the dark matter is in the form of microlenses with a few tens of solar masses, at sufficiently large magnification factors, all gravitational waves will show interference effects. These effects could have an impact on the inferred parameters. The effect is more important for macroimages with negative parity, which usually arrive after the macroimages with positive parity.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
