We explore the feasibility of H I galaxy redshift surveys with the Five-hundred-meter Aperture Spherical Telescope(FAST) and its proposed Core Array interferometry.Using semi-analytical simulations,we compare the perf...We explore the feasibility of H I galaxy redshift surveys with the Five-hundred-meter Aperture Spherical Telescope(FAST) and its proposed Core Array interferometry.Using semi-analytical simulations,we compare the performance of the FAST single-dish and Core Array modes in drift scan (DS) and on-the-fly (OTF) observations across different redshifts.Our results show that the FAST single-dish mode enables significant H I detections at low redshifts (z■0.35) but is limited at higher redshifts due to shot noise.The Core Array interferometry,with higher sensitivity and angular resolution,provides robust H I galaxy detections up to z~1,maintaining a sufficient number density for power spectrum measurements and BAO constraints.At low redshifts (z~0.01–0.08),both configurations perform well,though cosmic variance dominates uncertainties.At higher redshifts (z>0.35),the Core Array outperforms the single-dish mode,while increasing the survey area has little impact on single-dish observations due to shot noise limitations.The DS mode efficiently covers large sky areas but is constrained by Earth’s rotation,whereas the OTF mode allows more flexible deep-field surveys at the cost of operational overhead.Our findings highlight the importance of optimizing survey strategies to maximize FAST’s potential for H I cosmology.The Core Array is particularly well-suited for high-redshift H I galaxy surveys,enabling precise constraints on large-scale structure and dark energy.展开更多
The main goal of the gamma-ray spectrometer（GRS） onboard Chang＇E1（CE-1） is to acquire global maps of elemental abundances and their distributions on the moon,since such maps will significantly improve our underst...The main goal of the gamma-ray spectrometer（GRS） onboard Chang＇E1（CE-1） is to acquire global maps of elemental abundances and their distributions on the moon,since such maps will significantly improve our understanding of lunar formation and evolution.To derive the elemental maps and enable research on lunar formation and evolution,raw data that are received directly from the spacecraft must be converted into time series corrected gamma-ray spectra.The data correction procedures for the CE-1 GRS time series data are thoroughly described.The processing procedures to create the time series gamma-ray spectra described here include channel processing,optimal data selection,energy calibration,gain correction,dead time correction,geometric correction,orbit altitude normalization,eliminating unusable data and galactic cosmic ray correction.Finally,descriptions are also given on data measurement uncertainties,which will help the interested scientists to understand and estimate various uncertainties associated with the above data processing.展开更多
We analyzed a sample of 66 gamma-ray bursts(GRBs)and statistically confirmed the prediction on the time curve of the hardness ratio of GRBs made by Qin et al.based on the curvature effect.In their analysis,GRB pulses ...We analyzed a sample of 66 gamma-ray bursts(GRBs)and statistically confirmed the prediction on the time curve of the hardness ratio of GRBs made by Qin et al.based on the curvature effect.In their analysis,GRB pulses are divided into three types according to the shape of their raw hardness ratio(RHR)time curves,defined as to include the background counts to the signal counts,so as to make use of counts within small time intervals.Of the three types,very hard sources exhibit a perfect pulse-like profile(type 1),hard bursts possess a pulse-like profile with a dip in the decay phase(type 2),and soft bursts show no pulse-like profile but have only a dipped profile(type 3).In terms of the conventional hardness ratio,type 3 sources are indeed generally softer than those of type 1 and type 2,in agreement with the prediction.We found that the minimum value of RHR is sensitive in distinguishing the different types.We propose that GRB pulses can be classified according to the minimum value of RHR and that the different type sources may be connected with different strengths of the shock or/and the magnetic field.展开更多
基金the support of the National SKA Program of China (Nos.2022SKA0110200 and 2022SKA0110203)the National Natural Science Foundation of China (NSFC,Nos.12473091 and 12473001),and 111 Project (No.B16009)the support of the Fundamental Research Funds for the Central Universities (No.N2405008)。
文摘We explore the feasibility of H I galaxy redshift surveys with the Five-hundred-meter Aperture Spherical Telescope(FAST) and its proposed Core Array interferometry.Using semi-analytical simulations,we compare the performance of the FAST single-dish and Core Array modes in drift scan (DS) and on-the-fly (OTF) observations across different redshifts.Our results show that the FAST single-dish mode enables significant H I detections at low redshifts (z■0.35) but is limited at higher redshifts due to shot noise.The Core Array interferometry,with higher sensitivity and angular resolution,provides robust H I galaxy detections up to z~1,maintaining a sufficient number density for power spectrum measurements and BAO constraints.At low redshifts (z~0.01–0.08),both configurations perform well,though cosmic variance dominates uncertainties.At higher redshifts (z>0.35),the Core Array outperforms the single-dish mode,while increasing the survey area has little impact on single-dish observations due to shot noise limitations.The DS mode efficiently covers large sky areas but is constrained by Earth’s rotation,whereas the OTF mode allows more flexible deep-field surveys at the cost of operational overhead.Our findings highlight the importance of optimizing survey strategies to maximize FAST’s potential for H I cosmology.The Core Array is particularly well-suited for high-redshift H I galaxy surveys,enabling precise constraints on large-scale structure and dark energy.
基金supported by the National High Technology Research and Development Program of China (Grant Nos. 2008AA12A212 and 2010AA122202)the National Natural Science Foundation of China (Grant Nos. 41040031 and 40904024)
文摘The main goal of the gamma-ray spectrometer（GRS） onboard Chang＇E1（CE-1） is to acquire global maps of elemental abundances and their distributions on the moon,since such maps will significantly improve our understanding of lunar formation and evolution.To derive the elemental maps and enable research on lunar formation and evolution,raw data that are received directly from the spacecraft must be converted into time series corrected gamma-ray spectra.The data correction procedures for the CE-1 GRS time series data are thoroughly described.The processing procedures to create the time series gamma-ray spectra described here include channel processing,optimal data selection,energy calibration,gain correction,dead time correction,geometric correction,orbit altitude normalization,eliminating unusable data and galactic cosmic ray correction.Finally,descriptions are also given on data measurement uncertainties,which will help the interested scientists to understand and estimate various uncertainties associated with the above data processing.
基金the National Natural Science Foundation of China(Grants 10533050 and 10573030)
文摘We analyzed a sample of 66 gamma-ray bursts(GRBs)and statistically confirmed the prediction on the time curve of the hardness ratio of GRBs made by Qin et al.based on the curvature effect.In their analysis,GRB pulses are divided into three types according to the shape of their raw hardness ratio(RHR)time curves,defined as to include the background counts to the signal counts,so as to make use of counts within small time intervals.Of the three types,very hard sources exhibit a perfect pulse-like profile(type 1),hard bursts possess a pulse-like profile with a dip in the decay phase(type 2),and soft bursts show no pulse-like profile but have only a dipped profile(type 3).In terms of the conventional hardness ratio,type 3 sources are indeed generally softer than those of type 1 and type 2,in agreement with the prediction.We found that the minimum value of RHR is sensitive in distinguishing the different types.We propose that GRB pulses can be classified according to the minimum value of RHR and that the different type sources may be connected with different strengths of the shock or/and the magnetic field.
