اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدA method to constrain the characteristic angular size of the brightest cosmic-ray sources observed above 57 $times$ 10^{18} eV
128
0
0.0
(
0
)
تأليف
Patrick Younk
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We introduce a method to constrain the characteristic angular size of the brightest cosmic-ray sources observed above 57 times 1018 eV. By angular size of a source, we mean the effective angular extent over which cosmic-rays from that source arrive at earth. The method is based on the small-scale (< 10circ) self-clustering of cosmic-ray arrival directions. The method is applicable to sparse data sets in which strong localizations of CR* directions are not yet observed. We show that useful constraints on the source size can be made in the near future and that these constraints are not strongly dependent on the assumed spatial distribution and luminosity function of the cosmic-ray sources. We suggest that an indication of the source size is quite telling. For example, an indication of the source size can be used to infer limits on the particle charge and intervening magnetic fields (not independently), both of which are not well constrained so far. This is possible because the source size is similar in scale to the magnetic deflection.
قيم البحث
اقرأ أيضاً
The sources of ultra-high energy cosmic rays are not yet known. However, the discovery of anisotropic cosmic rays above 57x10^18 eV by the Pierre Auger Observatory suggests that a direct source detection may soon be possible. The near-future prospect
s for such a measurement are heavily dependent on the flux of the brightest source. In this work, we show that the flux of the brightest source above 57x10^18 eV is expected to comprise 10% or more of the total flux if two general conditions are true. The conditions are: 1.) the source objects are associated with galaxies other than the Milky Way and its closest neighbors, and 2.) the cosmic ray particles are protons or heavy nuclei such as iron and the Greisen-Zatsepin-Kuzmin effect is occurring. The Pierre Auger Observatory collects approximately 23 events above 57x10^18 eV per year. Therefore, it is plausible that, over the course of several years, tens of cosmic rays from a single source will be detected.
We report a measurement of the energy spectrum of cosmic rays for energies above $2.5 {times} 10^{18}~$eV based on 215,030 events recorded with zenith angles below $60^circ$. A key feature of the work is that the estimates of the energies are indepen
dent of assumptions about the unknown hadronic physics or of the primary mass composition. The measurement is the most precise made hitherto with the accumulated exposure being so large that the measurements of the flux are dominated by systematic uncertainties except at energies above $5 {times} 10^{19}~$eV. The principal conclusions are: (1) The flattening of the spectrum near $5 {times} 10^{18}~$eV, the so-called ankle, is confirmed. (2) The steepening of the spectrum at around $5 {times} 10^{19}~$eV is confirmed. (3) A new feature has been identified in the spectrum: in the region above the ankle the spectral index $gamma$ of the particle flux ($propto E^{-gamma}$) changes from $2.51 pm 0.03~{rm (stat.)} pm 0.05~{rm (sys.)}$ to $3.05 pm 0.05~{rm (stat.)} pm 0.10~{rm (sys.)}$ before changing sharply to $5.1 pm 0.3~{rm (stat.)} pm 0.1~{rm (sys.)}$ above $5 {times} 10^{19}~$eV. (4) No evidence for any dependence of the spectrum on declination has been found other than a mild excess from the Southern Hemisphere that is consistent with the anisotropy observed above $8 {times} 10^{18}~$eV.
A measurement of the cosmic-ray spectrum for energies exceeding $4{times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{circ}$ detected with the Pierre Auger Observatory between 1 January 2004
and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{times}10^{18}$ eV, the ankle, the flux can be described by a power law $E^{-gamma}$ with index $gamma=2.70 pm 0.02 ,text{(stat)} pm 0.1,text{(sys)}$ followed by a smooth suppression region. For the energy ($E_text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_text{s}=(5.12pm0.25,text{(stat)}^{+1.0}_{-1.2},text{(sys)}){times}10^{19}$ eV.
Cosmic rays are atomic nuclei arriving from outer space that reach the highest energies observed in nature. Clues to their origin come from studying the distribution of their arrival directions. Using $3 times 10^4$ cosmic rays above $8 times 10^{18}
$ electron volts, recorded with the Pierre Auger Observatory from a total exposure of 76,800 square kilometers steradian year, we report an anisotropy in the arrival directions. The anisotropy, detected at more than the 5.2$sigma$ level of significance, can be described by a dipole with an amplitude of $6.5_{-0.9}^{+1.3}$% towards right ascension $alpha_{d} = 100 pm 10$ degrees and declination $delta_{d} = -24_{-13}^{+12}$ degrees. That direction indicates an extragalactic origin for these ultra-high energy particles.
We report a measurement of the energy spectrum of cosmic rays above $2.5{times} 10^{18}$ eV based on $215,030$ events. New results are presented: at about $1.3{times} 10^{19}$ eV, the spectral index changes from $2.51 pm 0.03 textrm{ (stat.)} pm 0.05
textrm{ (sys.)}$ to $3.05 pm 0.05 textrm{ (stat.)}pm 0.10textrm{ (sys.)}$, evolving to $5.1pm0.3textrm{ (stat.)} pm 0.1textrm{ (sys.)}$ beyond $5{times} 10^{19}$ eV, while no significant dependence of spectral features on the declination is seen in the accessible range. These features of the spectrum can be reproduced in models with energy-dependent mass composition. The energy density in cosmic rays above $5{times} 10^{18}$ eV is $(5.66 pm 0.03 textrm{ (stat.)} pm 1.40 textrm{ (sys.)} ) {times} 10^{53}~$erg Mpc$^{-3}$.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
