The space environment background of various particle fluxes of the Hard X-ray Imager(HXI), one of the payloads of the Advanced Space-based Solar Observatory(ASO-S) spacecraft, is investigated and presented. Different ...The space environment background of various particle fluxes of the Hard X-ray Imager(HXI), one of the payloads of the Advanced Space-based Solar Observatory(ASO-S) spacecraft, is investigated and presented. Different approaches are used to obtain the input information on various space environment particles(protons, alpha particles, electrons, positrons, neutrons, and photons). Some special regions(SAA and radiation belt) are also taken into account. The findings indicate that electrons are the primary background source in the radiation belt. Due to the large background flux generated by electrons, HXI cannot effectively observe solar flares in the radiation belt.Outside the radiation belt, primary protons and albedo photons are the main sources of background at low and high magnetic latitudes respectively. The statistical analysis of the flare and background spectra shows that the errors of the flare energy spectrum observation are mainly concentrated in the high energy band, and the detector still has a certain spectrum observation capability for flares of C-class and below in the low energy band of the non-radiation belt. The imaging observation of flares of C-class and below is significantly affected by the accuracy of background subtraction. The energy band with the best signal-to-noise ratio is from 10 to 50 ke V, which can be used to monitor the formation and class of flares.展开更多
The cross-correlation between the high-redshift 21 cm background and the Soft X-ray Background （SXB） of the Universe may provide an additional probe of the Epoch of Reionization. Here we use semi-numerical simulatio...The cross-correlation between the high-redshift 21 cm background and the Soft X-ray Background （SXB） of the Universe may provide an additional probe of the Epoch of Reionization. Here we use semi-numerical simulations to create 21 cm and soft X-ray intensity maps and construct their cross power spectra. Our results indicate that the cross power spectra are sensitive to the thermal and ionizing states of the intergalactic medium （IGM）. The 21 cm background correlates positively to the SXB on large scales during the early stages of the reionization. However as the reionization develops, these two back- grounds turn out to be anti-correlated with each other when more than - 15% of the IGM is ionized in a warm reionization scenario. The anti-correlated power reaches its maximum when the neutral fraction declines to 0.2-0.5. Hence, the trough in the cross power spectrum might be a useful tool for tracing the growth of HII regions during the middle and late stages of the reionization. We estimate the detectability of the cross power spectrum based on the abilities of the Square Kilometre Array and the Wide Field X-ray Telescope （WFXT）, and find that to detect the cross power spectrum, the pixel noise of X-ray images has to be at least 4 orders of magnitude lower than that of the WFXT deep survey.展开更多
The history of the cosmological reionization is still unclear. Two ionizing sources, stars and QSOs, are believed to play important roles during this epoch. Besides the 21 cm signals, the infrared emission from PopⅢ ...The history of the cosmological reionization is still unclear. Two ionizing sources, stars and QSOs, are believed to play important roles during this epoch. Besides the 21 cm signals, the infrared emission from PopⅢ stars and X-ray photons from QSOs can be powerful probes of the reionization. Here we present a cross-correlation study of the 21 cm, infrared and X-ray backgrounds. The advantage of doing such crosscorrelations is that we could highlight the correlated signals and eliminate irrelevant foregrounds. We develop a shell model to describe the 21 cm signals and find that PopIII stars can provide higher 21 cm signals than QSOs. Using the ROSAT data for X-ray and AKARI data for infrared, we predict various cross power spectra analytically and discuss prospects for detecting these cross-correlation signals in future low frequency radio surveys. We find that, although these cross-correlational signals have distinct features, so far, they have been difficult to detect due to the high noise of the soft X-ray and infrared backgrounds given by ROSAT and AKARI.展开更多
基金supported by the Strategic Priority Research Program on Space Science,Chinese Academy of Sciences (No.XDA 15 320 104)National Natural Science Foundation of China (NSFC, Grant Nos. 11973097, 12173100 and 12022302)the Youth Innovation Promotion Association CAS (Nos.2021317 and Y2021087)。
文摘The space environment background of various particle fluxes of the Hard X-ray Imager(HXI), one of the payloads of the Advanced Space-based Solar Observatory(ASO-S) spacecraft, is investigated and presented. Different approaches are used to obtain the input information on various space environment particles(protons, alpha particles, electrons, positrons, neutrons, and photons). Some special regions(SAA and radiation belt) are also taken into account. The findings indicate that electrons are the primary background source in the radiation belt. Due to the large background flux generated by electrons, HXI cannot effectively observe solar flares in the radiation belt.Outside the radiation belt, primary protons and albedo photons are the main sources of background at low and high magnetic latitudes respectively. The statistical analysis of the flare and background spectra shows that the errors of the flare energy spectrum observation are mainly concentrated in the high energy band, and the detector still has a certain spectrum observation capability for flares of C-class and below in the low energy band of the non-radiation belt. The imaging observation of flares of C-class and below is significantly affected by the accuracy of background subtraction. The energy band with the best signal-to-noise ratio is from 10 to 50 ke V, which can be used to monitor the formation and class of flares.
基金supported by the National Natural Science Foundation of China(Grant Nos.11473031,11261140641 and 11173028)the 973 Program(Grant No.2013CB837900)
文摘The cross-correlation between the high-redshift 21 cm background and the Soft X-ray Background （SXB） of the Universe may provide an additional probe of the Epoch of Reionization. Here we use semi-numerical simulations to create 21 cm and soft X-ray intensity maps and construct their cross power spectra. Our results indicate that the cross power spectra are sensitive to the thermal and ionizing states of the intergalactic medium （IGM）. The 21 cm background correlates positively to the SXB on large scales during the early stages of the reionization. However as the reionization develops, these two back- grounds turn out to be anti-correlated with each other when more than - 15% of the IGM is ionized in a warm reionization scenario. The anti-correlated power reaches its maximum when the neutral fraction declines to 0.2-0.5. Hence, the trough in the cross power spectrum might be a useful tool for tracing the growth of HII regions during the middle and late stages of the reionization. We estimate the detectability of the cross power spectrum based on the abilities of the Square Kilometre Array and the Wide Field X-ray Telescope （WFXT）, and find that to detect the cross power spectrum, the pixel noise of X-ray images has to be at least 4 orders of magnitude lower than that of the WFXT deep survey.
基金supported by a CAS grant KJCX3-SYW-N2.References
文摘The history of the cosmological reionization is still unclear. Two ionizing sources, stars and QSOs, are believed to play important roles during this epoch. Besides the 21 cm signals, the infrared emission from PopⅢ stars and X-ray photons from QSOs can be powerful probes of the reionization. Here we present a cross-correlation study of the 21 cm, infrared and X-ray backgrounds. The advantage of doing such crosscorrelations is that we could highlight the correlated signals and eliminate irrelevant foregrounds. We develop a shell model to describe the 21 cm signals and find that PopIII stars can provide higher 21 cm signals than QSOs. Using the ROSAT data for X-ray and AKARI data for infrared, we predict various cross power spectra analytically and discuss prospects for detecting these cross-correlation signals in future low frequency radio surveys. We find that, although these cross-correlational signals have distinct features, so far, they have been difficult to detect due to the high noise of the soft X-ray and infrared backgrounds given by ROSAT and AKARI.
