【摘要】：河外伽馬射線背景起源是一個重要但是沒有解決的問題，它可能是由一些真正的彌散源所貢獻(xiàn)，也可能是一些未被分解的點(diǎn)源所貢獻(xiàn)。真正彌散源包括暗物質(zhì)湮滅或衰變所輻射的伽馬光子，或宇宙大尺度結(jié)構(gòu)形成過程中激波所加速的高能粒子的輻射等。費(fèi)米伽馬射線太空望遠(yuǎn)鏡上天后，盡管其靈敏度、角分辨率和有效面積相比以前的儀器有著革命性的提高，探測到了更多的河外點(diǎn)源，但是這些點(diǎn)源總的流量只是河外伽馬射線背景的一小部分，距離直接分解河外伽馬射線背景還有很大的距離。 圖像疊加法是一種可以大大提高圖像信噪比，從而充分利用現(xiàn)有數(shù)據(jù)的方法。我們利用此方法對一些可能的、還未被直接探測到的伽馬射線點(diǎn)源樣本疊加，然后利用最大似然法求其總流量，從而得出它們對河外伽馬射線背景的貢獻(xiàn)。 我們首先對AT20G樣本進(jìn)行疊加，發(fā)現(xiàn)其對河外伽馬射線背景貢獻(xiàn)為8.4%，小于由射電流量和伽馬射線流量相關(guān)關(guān)系得到的比例。但是我們的方法更加直接。這表明由某類天體其它波段流量（或光度）和伽馬射線流量（或光度）相關(guān)關(guān)系來得到其對河外伽馬射線背景貢獻(xiàn)有很大的不確定性。 然后我們對FIRST進(jìn)行疊加，，此樣本對河外伽馬射線背景貢獻(xiàn)為61.4%.但是其低射電流量的子樣本的伽馬射線流量不可忽略�？紤]到FIRST樣本為一流量限樣本且在低流量處并不完備，則可以預(yù)期，如果此樣本流量限更低且更加完備，則樣本對河外伽馬射線背景的貢獻(xiàn)將會更大。但是具體貢獻(xiàn)值則很難確定，這依賴于更暗源的數(shù)密度分布以及射電、伽馬射線流量關(guān)系，然而兩者目前都不確定。但是考慮到一些不能被FIRST示蹤類型源，例如普通星系、射電寧靜類星體等也可以貢獻(xiàn)一部分河外伽馬射線背景，可以認(rèn)為點(diǎn)源即使不能完貢獻(xiàn)全部也可也貢獻(xiàn)絕大部分的河外伽馬射線背景，標(biāo)準(zhǔn)天體物理模型可以解釋全部的河外伽馬射線背景起源。
[Abstract]:The origin of extragalactic gamma-ray background is an important but unsolved problem. It may be contributed by some real diffusing sources or some undecomposed point sources. The true dispersion sources include gamma photons emitted by the annihilation or decay of dark matter, or the radiation of high-energy particles accelerated by shock waves during the formation of the large-scale structure of the universe. The Fermi Gamma-Ray Space Telescope, though revolutionary in its sensitivity, angular resolution and effective area, detected more extragalactic point sources than previous instruments. However, the total flux of these point sources is only a small part of the background of the extragalactic gamma rays, and there is still a long way to go for the direct decomposition of the background of the gamma rays outside the river. Image superposition method is a method which can greatly improve the signal-to-noise ratio (SNR) of images and make full use of existing data. We use this method to superposition some possible gamma ray point source samples which have not been directly detected, and then use the maximum likelihood method to calculate the total flow rate, so as to obtain their contribution to the background of gamma rays outside the river. We first superposition the AT20G samples and find that their contribution to the background of gamma rays beyond the river is 8.4, which is less than the ratio obtained from the correlation between radio and gamma ray flows. But our approach is more straightforward. This indicates that there is great uncertainty about the contribution to the background of extragalactic gamma rays from the correlation between the other band flux (or luminosity) and the gamma ray flux (or photometry) of a certain type of celestial body. We then superimposed the FIRST, which contributed 61.4 to the extragalactic gamma ray background. But the gamma ray flux of the subsample of its low radio current can not be ignored. Considering that the FIRST sample is a flow-limited sample and is not complete at a low flow rate, it can be expected that if the flow limit of the sample is lower and more complete, the contribution of the sample to the off-river gamma-ray background will be greater. However, it is difficult to determine the specific contribution value, which depends on the number density distribution of the darker source and the relationship between radio and gamma ray flux, but both are uncertain at present. But considering that some types of sources that cannot be traced by FIRST, such as ordinary galaxies, radio tranquil quasars, and so on, can also contribute part of the off-river gamma-ray background, It can be considered that the point source can contribute most of the extragalactic gamma-ray background even if it can not complete the contribution, and the standard astrophysical model can explain the origin of all the extragalactic gamma-ray background.
【學(xué)位授予單位】：中國科學(xué)院研究生院（云南天文臺）
【學(xué)位級別】：博士
【學(xué)位授予年份】：2013
【分類號】：P172.3

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相關(guān)期刊論文 前1條

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