In the neutral hydrogen(H I)galaxy survey,a significant challenge is to identify and extract the H I galaxy signal from the observational data contaminated by radio frequency interference(RFI).For a drift-scan survey,...In the neutral hydrogen(H I)galaxy survey,a significant challenge is to identify and extract the H I galaxy signal from the observational data contaminated by radio frequency interference(RFI).For a drift-scan survey,or more generally a survey of a spatially continuous region,in the time-ordered spectral data,the H I galaxies and RFI all appear as regions that extend an area in the time-frequency waterfall plot,so the extraction of the H I galaxies and RFI from such data can be regarded as an image segmentation problem,and machine-learning methods can be applied to solve such problems.In this study,we develop a method to effectively detect and extract signals of H I galaxies based on a Mask R-CNN network combined with the PointRend method.By simulating FAST-observed galaxy signals and potential RFI impact,we created a realistic data set for the training and testing of our neural network.We compared five different architectures and selected the best-performing one.This architecture successfully performs instance segmentation of H I galaxy signals in the RFI-contaminated time-ordered data,achieving a precision of 98.64%and a recall of 93.59%.展开更多
This paper presents the design,calibration,and survey strategy of the Fast Radio Burst(FRB)digital backend and its real-time data processing pipeline employed in the Tianlai Cylinder Pathfinder Array.The array,consist...This paper presents the design,calibration,and survey strategy of the Fast Radio Burst(FRB)digital backend and its real-time data processing pipeline employed in the Tianlai Cylinder Pathfinder Array.The array,consisting of three parallel cylindrical reflectors and equipped with 96 dual-polarization feeds,is a radio interferometer array designed for conducting drift scans of the northern celestial semi-sphere.The FRB digital backend enables the formation of 96 digital beams,effectively covering an area of approximately 40 square degrees with the 3 dB beam.Our pipeline demonstrates the capability to conduct an automatic search of FRBs,detecting at quasi-realtime and classifying FRB candidates automatically.The current FRB searching pipeline has an overall recall rate of88%.During the commissioning phase,we successfully detected signals emitted by four well-known pulsars:PSR B0329+54,B2021+51,B0823+26,and B2020+28.We report the first discovery of an FRB by our array,designated as FRB 20220414A.We also investigate the optimal arrangement for the digitally formed beams to achieve maximum detection rate by numerical simulation.展开更多
The Tianlai Dish Pathfinder Array is a radio interferometer array consisting of 16 six-meter dish antennas.The original digital backend integration time is at the seconds level,designed for H I intensity mapping exper...The Tianlai Dish Pathfinder Array is a radio interferometer array consisting of 16 six-meter dish antennas.The original digital backend integration time is at the seconds level,designed for H I intensity mapping experiment.A new digital backend with millisecond response is added to enable it to search for fast radio burst during its observations.The design and calibration of this backend,and the real time search pipeline for it are described in this paper.It is capable of forming 16 digital beams for each linear polarization,covering an area of 19.6 square degrees.The search pipeline is capable of searching for,recording and classifying FRBs automatically in real time.In commissioning,we succeeded in capturing the signal pulses from the pulsars PSR B0329+54 and B2021+51.展开更多
Cross-correlating the data on neutral hydrogen(HⅠ)21 cm intensity mapping with galaxy surveys is an effective method to extract astrophysical and cosmological information.In this work,we investigate the cross-correla...Cross-correlating the data on neutral hydrogen(HⅠ)21 cm intensity mapping with galaxy surveys is an effective method to extract astrophysical and cosmological information.In this work,we investigate the cross-correlation of MeerKAT single-dish mode HⅠintensity mapping and China Space Station Telescope(CSST)spectroscopic galaxy surveys.We simulate a survey area of~300 deg~2 of MeerKAT and CSST surveys at z=0.5 using MultiDark N-body simulation.The PC A algorithm is applied to remove the foregrounds of HⅠintensity mapping,and signal compensation is considered to solve the signal loss problem in HⅠ-galaxy cross power spectrum caused by the foreground removal process.We find that from CSST galaxy auto and MeerKAT-CSST cross power spectra,the constraint accuracy of the parameter productΩ_(HⅠ)b_(HⅠ)r_(HⅠ,g)can reach~1%,which is about one order of magnitude higher than the current results.After performing the full MeerKAT HⅠintensity mapping survey with5000 deg~2 survey area,the accuracy can be enhanced to<0.3%.This implies that the MeerKAT-CSST cross-correlation can be a powerful tool to probe the cosmic HⅠproperty and the evolution of galaxies and the Universe.展开更多
The China Space Station Telescope(CSST)is the next-generation Stage IV survey telescope.It can simultaneously perform multiband imaging and slitless spectroscopic wide-and deep-field surveys in ten years and an ultra-...The China Space Station Telescope(CSST)is the next-generation Stage IV survey telescope.It can simultaneously perform multiband imaging and slitless spectroscopic wide-and deep-field surveys in ten years and an ultra-deep field(UDF)survey in two years,which are suitable for cosmological studies.Here we review several CSST cosmological probes,such as weak gravitational lensing,two-dimensional(2D)and three-dimensional(3D)galaxy clustering,galaxy cluster abundance,cosmic void,Type Ia supernovae(SNe Ia),and baryonic acoustic oscillations(BAO),and explore their capabilities and prospects in discovering new physics and opportunities in cosmology.We find that CSST will measure the matter distribution from small to large scales and the expansion history of the Universe with extremely high accuracy,which can provide percent-level stringent constraints on the property of dark energy and dark matter and precisely test the theories of gravity.展开更多
基金support by the National SKA Program of ChinaNo.2022SKA0110100+1 种基金the CAS Interdisciplinary Innovation Team(JCTD-2019-05)the science research grants from the China Manned Space Project with No.CMS-CSST-2021-B01。
文摘In the neutral hydrogen(H I)galaxy survey,a significant challenge is to identify and extract the H I galaxy signal from the observational data contaminated by radio frequency interference(RFI).For a drift-scan survey,or more generally a survey of a spatially continuous region,in the time-ordered spectral data,the H I galaxies and RFI all appear as regions that extend an area in the time-frequency waterfall plot,so the extraction of the H I galaxies and RFI from such data can be regarded as an image segmentation problem,and machine-learning methods can be applied to solve such problems.In this study,we develop a method to effectively detect and extract signals of H I galaxies based on a Mask R-CNN network combined with the PointRend method.By simulating FAST-observed galaxy signals and potential RFI impact,we created a realistic data set for the training and testing of our neural network.We compared five different architectures and selected the best-performing one.This architecture successfully performs instance segmentation of H I galaxy signals in the RFI-contaminated time-ordered data,achieving a precision of 98.64%and a recall of 93.59%.
基金support of the National SKA program of China(Nos.2022SKA0110100 and 2022SKA0110101)the National Natural Science Foundation of China(NSFC,Grant Nos.1236114814,12203061,12273070,and 12303004)。
文摘This paper presents the design,calibration,and survey strategy of the Fast Radio Burst(FRB)digital backend and its real-time data processing pipeline employed in the Tianlai Cylinder Pathfinder Array.The array,consisting of three parallel cylindrical reflectors and equipped with 96 dual-polarization feeds,is a radio interferometer array designed for conducting drift scans of the northern celestial semi-sphere.The FRB digital backend enables the formation of 96 digital beams,effectively covering an area of approximately 40 square degrees with the 3 dB beam.Our pipeline demonstrates the capability to conduct an automatic search of FRBs,detecting at quasi-realtime and classifying FRB candidates automatically.The current FRB searching pipeline has an overall recall rate of88%.During the commissioning phase,we successfully detected signals emitted by four well-known pulsars:PSR B0329+54,B2021+51,B0823+26,and B2020+28.We report the first discovery of an FRB by our array,designated as FRB 20220414A.We also investigate the optimal arrangement for the digitally formed beams to achieve maximum detection rate by numerical simulation.
基金supported by the Ministry of Science and Technology(MOST)2018YFE0120800the National Key R&D Program 2017YFA0402603+2 种基金the National Natural Science Foundation of China(NSFC)grants 11633004 and 11473044the Chinese Academy of Sciences(CAS)grant QYZDJ-SSW-SLH017the Hebei Key Laboratory of Radio Astronomy Technology(HKLRAT)。
文摘The Tianlai Dish Pathfinder Array is a radio interferometer array consisting of 16 six-meter dish antennas.The original digital backend integration time is at the seconds level,designed for H I intensity mapping experiment.A new digital backend with millisecond response is added to enable it to search for fast radio burst during its observations.The design and calibration of this backend,and the real time search pipeline for it are described in this paper.It is capable of forming 16 digital beams for each linear polarization,covering an area of 19.6 square degrees.The search pipeline is capable of searching for,recording and classifying FRBs automatically in real time.In commissioning,we succeeded in capturing the signal pulses from the pulsars PSR B0329+54 and B2021+51.
基金the support of 2020SKA0110402,MOST-2018YFE0120800National Key R&D Program of China No.2022YFF0503404+5 种基金the National Natural Science Foundation of China(NSFC,Grant Nos.11822305,11773031 and 11633004)support of the National Natural Science Foundation of China(NSFC,Grant Nos.11473044 and 11973047)the Chinese Academy of Sciences grants QYZDJ-SSW-SLH017,XDB23040100,XDA15020200supported by the National Research Foundation of South Africa under Grant Nos.150580,120385 and 120378NIThe CS program“New Insights into Astrophysics and Cosmology with Theoretical Models confronting Observational Data”supported by the science research grants from the China Manned Space Project with NO.CMS-CSST-2021-B01 and CMS-CSST-2021-A01。
文摘Cross-correlating the data on neutral hydrogen(HⅠ)21 cm intensity mapping with galaxy surveys is an effective method to extract astrophysical and cosmological information.In this work,we investigate the cross-correlation of MeerKAT single-dish mode HⅠintensity mapping and China Space Station Telescope(CSST)spectroscopic galaxy surveys.We simulate a survey area of~300 deg~2 of MeerKAT and CSST surveys at z=0.5 using MultiDark N-body simulation.The PC A algorithm is applied to remove the foregrounds of HⅠintensity mapping,and signal compensation is considered to solve the signal loss problem in HⅠ-galaxy cross power spectrum caused by the foreground removal process.We find that from CSST galaxy auto and MeerKAT-CSST cross power spectra,the constraint accuracy of the parameter productΩ_(HⅠ)b_(HⅠ)r_(HⅠ,g)can reach~1%,which is about one order of magnitude higher than the current results.After performing the full MeerKAT HⅠintensity mapping survey with5000 deg~2 survey area,the accuracy can be enhanced to<0.3%.This implies that the MeerKAT-CSST cross-correlation can be a powerful tool to probe the cosmic HⅠproperty and the evolution of galaxies and the Universe.
基金the support of the National Key R&D Program of China(Grant Nos.2022YFF0503404,and 2020SKA0110402)the CAS Project for Young Scientists in Basic Research(Grant No.YSBR092)+4 种基金the support of the National Natural Science Foundation of China(Grant No.12361141814)the Chinese Academy of Sciences(Grant No.ZDKYYQ20200008)the support of the National Natural Science Foundation of China(Grant No.12133006)the National Key R&D Program of China(Grant Nos.2023YFA1607800,and 2023YFA1607801)supported by the Science Research grants from the China Manned Space Project(Grant Nos.CMS-CSST-2021-B01,CMS-CSST-2021-A01,and CMS-CSST-2021A03)。
文摘The China Space Station Telescope(CSST)is the next-generation Stage IV survey telescope.It can simultaneously perform multiband imaging and slitless spectroscopic wide-and deep-field surveys in ten years and an ultra-deep field(UDF)survey in two years,which are suitable for cosmological studies.Here we review several CSST cosmological probes,such as weak gravitational lensing,two-dimensional(2D)and three-dimensional(3D)galaxy clustering,galaxy cluster abundance,cosmic void,Type Ia supernovae(SNe Ia),and baryonic acoustic oscillations(BAO),and explore their capabilities and prospects in discovering new physics and opportunities in cosmology.We find that CSST will measure the matter distribution from small to large scales and the expansion history of the Universe with extremely high accuracy,which can provide percent-level stringent constraints on the property of dark energy and dark matter and precisely test the theories of gravity.
