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Muons produced by the Bethe–Heitler process from laser wakefield accelerated electrons interacting with high
materials have velocities close to the laser wakefield. It is possible to accelerate those muons with laser wakefield directly. Therefore for the first time we propose an all-optical ‘Generator and Booster’ scheme to accelerate the produced muons by another laser wakefield to supply a prompt, compact, low cost and controllable muon source in laser laboratories. The trapping and acceleration of muons are analyzed by one-dimensional analytic model and verified by two-dimensional particle-in-cell (PIC) simulation. It is shown that muons can be trapped in a broad energy range and accelerated to higher energy than that of electrons for longer dephasing length. We further extrapolate the dependence of the maximum acceleration energy of muons with the laser wakefield relativistic factor
and the relevant initial energy
. It is shown that a maximum energy up to 15.2 GeV is promising with
on the existing short pulse laser facilities.
Huang et al have classified pulsars into two types according to the role played by the superfluid neutron vortexes in the interior of neutron stars. They have also presented the formule of P for these two types of pulsars. In this short remark, we shall compare the conclusions about the evolutions of these two types of pulsars with the observational distributions. The consequences obtained are summarized as follws.
Our calculations show that the cross section of the inverse Compton scattering in strong magnetic fields may be larger than that of Thompson scattering by sevaral orders of magnitude in the case of polar cap surface of pulsars. We can also see that when the energy of e± exceeds a certain value, their energy loss caused by the inverse Compton scattering may be larger than the energy gain from electric field in the inner gap, which implies that the e± could not be accelerated to γ = 106. Meanwhile, the electrostatic forces acting on the electrons will be balanced by the radiative pressure if temperature T > 108 K.
It is beleived that the surface temperarure for most of pulsars is less than 106 K, in that case the ions of iron can not be emitted from the surface of pulsars. However, the temperarure at the polar cap can be increased to 3×106 through the bombardment of electrons to the polar cap according to R-S model. This quasi-equilibrium state by self-regulating must make the coherent radio emission unstable on the contrary.
We have suggested a scenario of fractal turbulence which might explain the origin of galaxies and the observed large scale structure of the universe (Liu and Deng, 1987). Under the condition of the early universe, the cosmic fluid can be regarded as incompressible. If we assume that the density perturbations in the early universe are adiabatic and have the scale-free Zeldovich spectrum, we may obtain the spectrum of the velocity perturbations. Perturbations with scales less than horizon will undergo dissipative process by Thomson scattering. So, the cosmic fluid can be considered as a viscous fluid (Peebles, 1971). We can find the largest and smallest scale of the perturbations in the cosmic fluid by taking account of the Reynold's number on given scale and the scale of horizon. Using the present values of Hubble constant and the mean density of matter, we have found that on the scale of horizon the Reynold's number is just the order of 102. This result shows that perturbations with scale a little smaller than horizon may produce Karman vortices before recombination and the vortices might form fractal turbulence due to Thomson drag.
In this work, we start from the definition of fractal dimension and by the number counting of galaxies to investigate that if the large scale distribution of galaxies has really a fractal structure. A fractal dimension in a distribution of objects is defined as
where N(R) is the number of objects within scale R. To find out D from number counting we have to pay attention to that the distribution of galaxies could not be a regular fractal map. The N(R) would understand as a statistical average. To avoid the edge effect appearing in the number counting we compare it with that obtained from an average by many times Monte Carlo sampling which is a uniform distribution and would have Dr = 3. From eq. (1) we get
In the former work (Xia, Deng and Zhou, 1986), we have showed by two- point correlation analysis that more luminous galaxies cluster stronger. Now we present the result of cross-correlation analysis for galaxies with different luminosity. This analysis supplies information about the relations between the distributions of galaxies with different luminosity. The analyses are based on the data given by CfA survey and have made the same corrections as in the former work. The samples are divided into three subgroups in absolute magnitude ranges: a) −21–22, b) −20–21 and c)−19–20. We make the cross-correlation analysis for each two subgroups. Fig. 1 gives the obtained cross-correlation function ξc(r) and Fig. 2 shows the log ξc(r)-log r diagram, the straight lines in Fig. 2 are given by linear regression. These results show that the two brightest subgroups have the strongest correlation. Combining with the results of former work, it follows that the probability of two brighter galaxies being close to each other is larger than that of fainter galaxies.
Flour whiteness (FW) is an important factor in assessing flour quality and determining the end product quality. It is an integrated sensory indicator reflecting flour colour and is negatively correlated with protein content. In order to dissect the genetic relationship between FW and its five related traits at the quantitative trait locus (QTL)/gene level, a recombinant inbred line population was evaluated under three environments. Quantitative trait loci for FW were analysed by unconditional and conditional QTL mapping. Four unconditional additive QTLs and 16 conditional additive QTLs were detected across the three environments. Of these QTLs, only one major additive QTL (Qfw1D1-1) was consistently identified using both unconditional and conditional QTL analysis. This QTL was independent of flour colour a* (a function of red-green with a positive a* for redness and negative for greenness) and b* (a green-blue value with positive value for yellowness and negative for blueness) and was only slightly affected by flour protein content. A minor additive QTL (Qfw4A-4) was also detected using these two QTL mapping methods, being independent of flour colour a* and b*. Five unconditional and ten conditional epistatic minor QTLs were detected, from which only one pair (Qfw3A-10/Qfw6B-6) was identified by both unconditional and conditional QTL mapping, also independent of flour colour a* and b*. The major QTL (Qfw1D1-1) identified in the current study for the first time can be used for improving wheat FW in marker-assisted breeding.
Analyses for complete samples of galaxies and clusters of galaxies showed that the two-point correlation function of galaxy-galaxy and cluster-cluster have form of power law with power indices about −1.8 (Peebles, 1980; Bahcall and Soneira, 1983). Because the completeness of a sample means that we have observed completely the objects brighter than a given apparent magnitude in certain sky region. But, we know that a complete sample will be lack of faint objects at distant region. If we attempt to avoid the influences of any non-intrinsic properties on the analysis, we have to use the samples which are complete in certain interval of absolute magnitude.
After taking account of the selection effects in the identification of emission lines and choosing the sample within a narrow range of absolute magnitude, we can investigate the evolutionary function of quasars from their redshift distribution. From data given by slitless surveys with limiting apparent magnitude 19.5, we find that the evolutionary function takes form of ρ = ρo(1+z)6.5±1. The analysis has also showed that the observational redshift distribution of quasars is compatible with cosmological principle.
Subsamples of galaxies with different morphological types have been sorted out from Stromlo-APM redshift survey. Two-point correlation function for each subsample has been calculated. The two-point correlation functions for all subsamples show very large scale fluctuation. We show that the two-point correlation function with fluctuation could be fitted by a modified power spectrum with power excess at wave number comparable to the scale of the fluctuation.
Observational data increasingly indicate that the mergers of galaxies, even minor mergers, can trigger the formation of a set of SSCs within galaxies. the follow-up, dynamical evolution of SSCs in a configuration of dark matter (DM) dominated systems would be basically similar to what we simulated in this work. the scenario that we propose yields a series of results comparable to the relevant observations. Most notable are two points. One is that the low bulge detection rate in very late-type galaxies is in favour of soft-core DM profiles in galaxies of this kind. On the other hand, the observed young ages of nuclear clusters provide evidence supporting cuspy-core profiles. in conclusion, both the soft- and cuspy-core DM density profiles are suitable to relevant dwarf galaxies based on comparisons with observations.
Typical scales in the distribution of IRAS galaxies have been searched for with the unnormalized pair count method given by Mo et al.1. Samples consist of a) galaxies from QDOT with | b | ≥ 20°; b) galaxies from the IRAS faint source catalog(FSC) with f60 ≥ 0.3 Jy and | b | ≥ 30°. Galaxies with b ≥ 0 and b ≤ 0 were treated as independent samples in our analysis.
Applying a discrete wavelet transformation (DWT)1 to the spiral (SP) and elliptical+lenticular (EL) galaxies in A PM bright galaxy catalog (APMBGC)2, we investigated the scale-dependence of bias parameter b in the linear bias model
We have completed spectroscopic observations (Wu et al. 1997a) of a sample of 73 very luminous infrared galaxies (log(LIR/L⊙) ≥ 11.5;H0 = 50 km s−1 Mpc−1) from the 2-Jy catalogue (Strauss et al. 1992) using the 2.16m telescope at the Beijing Astronomical Observatory. Spectral and interacting classifications are performed for the sample (Wu et al. 1997b). These statistical results provide strong evidence for the idea that interactions trigger nuclear activity and enhance the infrared luminosity. With the decrease of nuclear separation, relative velocity and specific angular momentum decrease rapidly, while on the contrary, both infrared luminosity and Hα equivalent width increase. Dynamical friction plays an important role even when two galaxies have large separation. This provides a favorable condition for strong star formation. We construct a simple merger sequence, from interaction class 1 to 4, to class 5 and 6 and then to the class 0 regarded as being in the stage of advanced merger. Along this sequence, spectral types change from HII-like to AGN-like. Considering the strong correlation of very luminous infrared galaxies in spectral classification schemes, it is reliable that infrared luminous galaxies evolve from HII-like galaxies to AGN-like galaxies. The different properties of infrared luminous Seyfert 1s and optically selected Seyfert 1s suggest that infrared luminous galaxies could evolve into optical Seyfert 1s in the last stage.
The ultraluminous infrared galaxies (ULIRGs) are strong interacting or merging galaxies. Statistical study shows that about ten percent of ULIRGs are QSOs or Seyfert 1 galaxies, and high–resolution HST images suggest that they are likely to be at the post merger stage. We investigate the optical spectroscopic properties for a complete sample of 28 QSOs/Seyfert 1s selected mainly from the IRAS galaxy redshift survey QDOT and 1.2 Jy catalogs. The optical spectra were obtained with the 2.16 m optical telescope of the Beijing Astronomical Observatory between October 1998 and the end of 1999. Statistical results for both continuum and emission lines show the following:
1. Most of our sample galaxies are strong or extremely strong FeII emitters with a ratio of FeII/Hβ larger than 2. There also exists an anti-correlation of the ratio of FeII/Hβ with EW(OIII) and FWHM(Hβ).
2. We fit the continuum for all sample galaxies. Aside from a few objects which could be fitted well by a power-law model, the continuum for most sample Seyfert 1 galaxies can be fitted well by a blackbody model or by composites of power–law and blackbody models. For Seyfert 1 galaxies which fit a power–law, E(B-V) is small and in the range of optically selected Seyfert 1 galaxies. However, for Seyfert 1 galaxies fitting a blackbody model, the temperature increases as E(B-V) increases. This is strong observational evidence to support the evolutionary scenario from starbursts to optical QSOs/Seyfert 1s.
3. We also discuss the possible mechanism for strong FeII emission from the point of view of evolution of mergers to AGNs.
We perform photometric measurements on a large HST snapshot imaging survey sample of 97 ultraluminous infrared galaxies (ULIRGs). We classify all the sources into three categories with multiple, double and single nucleus/nuclei, mainly based on a quantitative criterion of I-band luminosity. The resultant fractions of multiple, double and single nucleus/nuclei ULIRGs are 18%, 39% and 43%, respectively. This supports the multiple merger scenario as a possible origin of ULIRGs, in addition to the commonly-accepted pair merger model. Further statistical studies indicate that the fraction of AGN increases from multiple (18%) to double (39%) and then to single (43%) nucleus/nuclei ULIRGs. For the single nucleus category, there is a high luminosity tail in the luminosity distribution, which corresponds to a Seyfert 1/QSO excess. This supports the statement that active galactic nuclei tend to appear at final merging stage. For multiple and double mergers, we also find a considerably high fraction of very close nucleus pairs (e.g., 2/3 for those separated by less than 5 kpc). This strengthens the conclusion that systems at late merging phase preferentially host ULIRGs.