In this paper we calculate the radio burst signals from three kinds of structures of superconducting cosmic strings. By taking into account the observational factors including scattering and relativistic effects, we derive the event rate of radio bursts as a function of redshift with the theoretical parameters Gμ and I of superconducting strings. Our analyses show that cusps and kinks may have noticeable contributions to the event rate and in most cases cusps would dominate the contribution, while the kink-kink collisions tend to have secondary effects. By fitting theoretical predictions with the normalized data of fast radio bursts, we for the first time constrain the parameter space of superconducting strings and report that the parameter space of Gμ ∼ [10 −14 , 10 −12 ] and I ∼ [10 −1 , 10 2 ] GeV fit the observation well although the statistic significance is low due to the lack of observational data. Moreover, we derive two types of best fittings, with one being dominated by cusps with a redshift z = 1.3, and the other dominated by kinks at the range of the maximal event rate.
The anisotropies of the B-mode polarization in the cosmic microwave background radiation play a crucial role for the study of the very early Universe. However, in the real observation, the mixture of the E-mode and B-mode can be caused by the partial sky surveys, which must be separated before applied to the cosmological explanation. The separation method developed by Smith (Smith 2006) has been widely adopted, where the edge of the top-hat mask should be smoothed to avoid the numerical errors. In this paper, we compare three different smoothing methods, and investigate the leakage residuals of the E-B mixture.We find that, if the less information loss is needed and the smaller region is smoothed in the analysis, the sin-and cos-smoothing methods are better. However, if we need a clean constructed B-mode map, the larger region around the mask edge should be smoothed. In this case, the Gaussian-smoothing method becomes much better. In addition, we find that the leakage caused by the numerical errors in the Gaussian-smoothing method mostly concentrates on two bands, which is quite easy to be reduced for the further E-B separations.
The detection of the magnetic type B-mode polarization is the main goal of future cosmic microwave background (CMB) experiments. In the standard model, the B-mode map is a strong non-gaussian field due to the CMB lensing component. Besides the two-point correlation function, the other statistics are also very important to dig the information of the polarization map. In this paper, we employ the Minkowski functionals to study the morphological properties of the lensed B-mode maps. We find that the deviations from Gaussianity are very significant for both full and partial-sky surveys. As an application of the analysis, we investigate the morphological imprints of the foreground residuals in the B-mode map. We find that even for very tiny foreground residuals, the effects on the map can be detected by the Minkowski functional analysis. Therefore, it provides a complementary way to investigate the foreground contaminations in the CMB studies. PACS numbers: 95.85.Sz, 98.70.Vc, 98.80.Cq I. INTRODUCTIONThe temperature and polarization anisotropies of the cosmic microwave background (CMB) radiation contain useful cosmological information (see for instance, [1-3]), playing a crucial role in constraining the cosmological parameters and testing the cosmological principle in modern cosmology [4,5]. In the standard model, the CMB is a linearly polarized photon field, which is completely described by the stocks parameters T (γ), Q(γ) and U (γ). T is a two-dimensional random scalar field, which describes the CMB temperature anisotropy. Q and U , which are not scalar fields in mathematics, describe the linear polarization. It is then convenient to define the electric-type (i.e. E-mode) and magnetic-type (i.e. B-mode) polarization from the observables Q and U [6,7]. So, equivalently, T , E and B maps compose all the CMB information.Nowadays, due to very precise observations from WMAP and Planck satellites, the detection of T map is close to the cosmic variance limit [4,5]. For E-mode polarization, the recent released Planck data have also shown very precise observations, and quite close to the cosmic variance limit for low multipoles ℓ 1000 [8]. Therefore, the detection of B-mode polarization becomes the main goal of future CMB experiments [9]. In the standard model, the B-mode polarization is generated by two sources: The primordial gravitational waves (i.e. tensor perturbations) [10,11], which are important in the low-multipole range [6,7,12], and the cosmic weak lensing [13][14][15], which is dominant at high multipoles. The B-mode observable is a combination of these two components. In the past two years, several ground-based experiments, including SPTPol [16], POLARBEAR [17], ACTPol [18], BICEP2 and Keck Array [19][20][21][22], as well as Planck satellite [23] have detected the definite lensed B-mode signal in the high-multipole range. It is also expected that Planck detects the B-mode signal in the low multipoles for the first time in the forthcoming year [24]. For the potential observations in the near future, various ...
Identifying galaxy groups from redshift surveys of galaxies plays an important role in connecting galaxies with the underlying dark matter distribution. Current and future high-z spectroscopic surveys, usually incomplete in redshift sampling, present both opportunities and challenges to identifying groups in the high-z Universe. We develop a group finder that is based on incomplete redshift samples combined with photometric data, using a machine learning method to assign halo masses to identified groups. Test using realistic mock catalogs shows that $\gtrsim 90\%$ of true groups with halo masses $\rm M_h \gtrsim 10^{12} M_{\odot }/h$ are successfully identified, and that the fraction of contaminants is smaller than $10\%$. The standard deviation in the halo mass estimation is smaller than 0.25 dex at all masses. We apply our group finder to zCOSMOS-bright and describe basic properties of the group catalog obtained.
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