arXiv subjects

Alexander A. Kaurov

Publications and source records attributed to Alexander A. Kaurov.

22 records · Page 2Linked to original sources

arXiv2014

Cosmic Reionization On Computers II. Reionization History and Its Back Reaction on Early Galaxies

We compare the results from several sets of cosmological simulations of cosmic reionization, produced under Cosmic Reionization On Computers (CROC) project, with existing observational data on the high-redshift Ly-alpha forest and the abundance of Ly-alpha emitters. We find good consistency with the observational measurements and the previous simulation work. By virtue of having several independent realizations for each set of numerical parameters, we are able to explore the effect of cosmic variance on observable quantities. One unexpected conclusion we are forced into is that cosmic variance is unusually large at z>6, with both our simulations and, most likely, observational measurements are still not fully converged for even such basic quantities as the average Gunn-Peterson optical depth or the volume-weighted neutral fraction. We also find that reionization has little effect on the early galaxies or on global cosmic star formation history, because galaxies whose gas content is affected by photoionization contain no molecular (i.e. star-forming) gas in the first place. In particular, measurements of the faint end of the galaxy luminosity function by JWST are unlikely to provide a useful constraint on reionization.

astro-ph.CO↗

arXiv2014

Recombination clumping factor during cosmic reionization

We discuss the role of recombinations in the IGM, and the related concept of the clumping factor, during cosmic reionization. The clumping factor is, in general, a local quantity that depends on the local over-density and the scale below which the baryon density field can be assumed smooth. That scale, called the filtering scale, is itself depended on over-density and local thermal history. We present a method for building a self-consistent analytical model of inhomogeneous reionization assuming the linear growth rate of the density fluctuation, which accounts for these effects simultaneously. We show that taking into account the local clumping factor introduces significant corrections to the total recombination rate, comparing to the model with a globally uniform clumping factor.

astro-ph.CO↗

arXiv2012

Quasi-periodical features in the distribution of Luminous Red Galaxies

A statistical analysis of radial distributions of Luminous Red Galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS DR7) catalogue within an interval $0.16 \leq z \leq 0.47$ is carried out. We found that the radial distribution of $\sim$ 106,000 LRGs incorporates a few quasi-periodical components relatively to a variable $η$, dimensionless line-of-sight comoving distance calculated for the $Λ$CDM cosmological model. The most significant peaks of the power spectra are obtained for two close periodicities corresponding to the spatial comoving scales $(135 \pm 12) h^{-1}$ Mpc and $(101 \pm 6)h^{-1}$ Mpc. The latter one is dominant and consistent with the characteristic scale of the baryon acoustic oscillations. We analyse also the radial distributions of two other selected LRG samples: $\sim$ 33,400 bright LRGs ($-23.2 < M \leq -21.8$) and $\sim$ 60,300 all LRGs within a rectangle region on the sky, and show differences of the quasi-periodical features characteristic for different samples. Being confirmed the results would allow to give preference of the spatial against temporal models which could explain the quasi-periodicities discussed here. As a caveat we show that estimations of the significance levels of the peaks strongly depend on a smoothed radial function (trend) as well as characteristics of random fluctuations.

astro-ph.CO↗

arXiv2012

Effect of halo bias and Lyman Limit Systems on the history of cosmic reionization

We extend the existing analytical model of reionization by Furlanetto et al. (2004) to include the biasing of reionization sources and additional absorption by Lyman Limit systems. Our model is, by construction, consistent with the observed evolution of the galaxy luminosity function at z<8 and with the observed evolution of Ly-α forest at z<6. We also find that, for a wide range of values for the relative escape fraction that we consider reasonable, and which are consistent with the observational constraints on the relative escape fraction from lower redshifts, our reionization model is consistent with the WMAP constraint on the Thompson optical depth and with the SPT and EDGES constraints on the duration of reionization. We, therefore, conclude that it is possible to develop physically realistic models of reionization that are consistent with all existing observational constraints.

astro-ph.CO↗