Photometric redshifts of galaxies obtained by multi-wavelength data are widely used in photometric surveys because of their high efficiency.Although various methods have been developed,template fitting is still adopte...Photometric redshifts of galaxies obtained by multi-wavelength data are widely used in photometric surveys because of their high efficiency.Although various methods have been developed,template fitting is still adopted as one of the most popular approaches.Its accuracy strongly depends on the quality of the spectral energy distribution(SED)templates,which can be calibrated using broadband photometric data from galaxies with known spectroscopic redshifts.Such calibration is expected to improve photometric redshift accuracy,as the calibrated templates will align with observed photometric data more closely.The upcoming China Space Station Telescope(CSST)is one of the Stage IV surveys,which is aiming for high precision cosmological studies.To improve the accuracy of photometric redshift estimation for CSST,we calibrated the CWW+KIN templates using a perturbation algorithm with broadband photometric data from the CSST mock catalog.This calibration used a training set consisting of approximately 4500 galaxies,which is 10%of the total galaxy sample.The outlier fraction and scatter of the photometric redshifts derived from the calibrated templates are 2.55%and 0.036,respectively.Compared to the CWW+KIN templates,these values are reduced by 34%and 23%,respectively.This demonstrates that SED templates calibrated with a small training set can effectively optimize photometric redshift accuracy for future large-scale surveys like CSST,especially with limited spectral training data.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
Galaxy photometric redshift(photoz)is crucial in cosmological studies,such as weak gravitational lensing and galaxy angular clustering measurements.In this work,we try to extract photoz information and construct its p...Galaxy photometric redshift(photoz)is crucial in cosmological studies,such as weak gravitational lensing and galaxy angular clustering measurements.In this work,we try to extract photoz information and construct its probability distribution function(PDF)using the Bayesian neural networks from both galaxy flux and image data expected to be obtained by the China Space Station Telescope(CSST).The mock galaxy images are generated from the Hubble Space Telescope-Advanced Camera for Surveys(HST-ACS)and COSMOS catalogs,in which the CSST instrumental effects are carefully considered.In addition,the galaxy flux data are measured from galaxy images using aperture photometry.We construct a Bayesian multilayer perceptron(B-MLP)and Bayesian convolutional neural network(B-CNN)to predict photoz along with the PDFs from fluxes and images,respectively.We combine the B-MLP and B-CNN together,and construct a hybrid network and employ the transfer learning techniques to investigate the improvement of including both flux and image data.For galaxy samples with signal-to-noise ratio(SNR)>10 in g or i band,we find the accuracy and outlier fraction of photoz can achieve σ_(NMAD)=0.022 and η=2.35% for the B-MLP using flux data only,and σ_(NMAD)=0.022 and η=1.32% for the B-CNN using image data only.The Bayesian hybrid network can achieve σ_(NMAD)=0.021 and η=1.23%,and utilizing transfer learning technique can improve results to σ_(NMAD)=0.019 and η=1.17%,which can provide the most confident predictions with the lowest average uncertainty.展开更多
The measurement of cosmological distances using baryon acoustic oscillations(BAO)is crucial for studying the universe’s expansion.The China Space Station Telescope(CSST)galaxy redshift survey,with its vast volume and...The measurement of cosmological distances using baryon acoustic oscillations(BAO)is crucial for studying the universe’s expansion.The China Space Station Telescope(CSST)galaxy redshift survey,with its vast volume and sky coverage,provides an opportunity to address key challenges in cosmology.However,redshift uncertainties in galaxy surveys can degrade both angular and radial distance estimates.In this study,we forecast the precision of BAO distance measurements using mock CSST galaxy samples,applying a two-point correlation function(2PCF)wedge approach to mitigate redshift errors.We simulate redshift uncertainties of σ_(0)=0.003 andσ_(0)=0.006,representative of expected CSST errors,and examine their effects on the BAO peak and distance scaling factors,α_(⊥)andα_(||),across redshift bins within 0.0<z≤1.0.The wedge 2PCF method proves more effective in detecting the BAO peak compared with the monopole 2PCF,particularly forσ_(0)=0.006.Constraints on the BAO peaks show thatα_(⊥)is well constrained around 1.0,regardless of σ_(0),with precision between 1%and 3%across redshift bins.In contrast,α_(||)measurements are more sensitive to increases inσ_(0).Forσ_(0)=0.003,the results remain close to the fiducial value,with uncertainties ranging between 4%and 9%;forσ_(0)=0.006,significant deviations from the fiducial value are observed.We also study the ability to measure parameters(Ω_(m),H_(0)r_(d))using distance measurements,proving robust constraints as a cosmological probe under CSST-like redshift uncertainties.These findings demonstrate that the CSST survey enables few-percent precision measurements of D_(A)using the wedge 2PCF method,highlighting its potential to place tight constraints on the universe’s expansion history and contribute to high-precision cosmological studies.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 from the Shanghai Science and Technology Foundation Fund under grant No.20070502400the support from the Innovation Program of Shanghai Municipal Education Commission(grant No.2019-0107-00-02-E00032)+4 种基金the support from National Key R&D Program of China grant Nos.2022YFF0503404,2020SKA0110402the CAS Project for Young Scientists in Basic Research(No.YSBR-092)support from the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning and the Shuguang Program of Shanghai Education Development Foundation and Shanghai Municipal Education Commissionsupported by the National Natural Science Foundation of China(NSFC,Grant Nos.U1931210,12141302,12173026,and 11933002)China Manned Space Project with grant Nos.CMS-CSST-2021-A01,CMS-CSST-2025-A02,CMS-CSST2025-A03,CMS-CSST-2025-A05 and CMS-CSST-2025-A20。
文摘Photometric redshifts of galaxies obtained by multi-wavelength data are widely used in photometric surveys because of their high efficiency.Although various methods have been developed,template fitting is still adopted as one of the most popular approaches.Its accuracy strongly depends on the quality of the spectral energy distribution(SED)templates,which can be calibrated using broadband photometric data from galaxies with known spectroscopic redshifts.Such calibration is expected to improve photometric redshift accuracy,as the calibrated templates will align with observed photometric data more closely.The upcoming China Space Station Telescope(CSST)is one of the Stage IV surveys,which is aiming for high precision cosmological studies.To improve the accuracy of photometric redshift estimation for CSST,we calibrated the CWW+KIN templates using a perturbation algorithm with broadband photometric data from the CSST mock catalog.This calibration used a training set consisting of approximately 4500 galaxies,which is 10%of the total galaxy sample.The outlier fraction and scatter of the photometric redshifts derived from the calibrated templates are 2.55%and 0.036,respectively.Compared to the CWW+KIN templates,these values are reduced by 34%and 23%,respectively.This demonstrates that SED templates calibrated with a small training set can effectively optimize photometric redshift accuracy for future large-scale surveys like CSST,especially with limited spectral training data.
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 MOST-2018YFE01208002020SKA0110402+10 种基金NSFC-11822305NSFC-11773031NSFC-11633004CAS Interdisciplinary Innovation Teamsupport from the National Natural Science Foundation of China(NSFC,Grant Nos.11473044 and 11973047)the Chinese Academy of Science grants QYZDJ-SSW-SLH017,XDB 23040100 and XDA15020200support from NSFC grant 11933002the Dawn Program 19SG41the Innovation Program 2019-0107-00-02-E00032 of SMECsupported by the science research grants from the China Manned Space Project with No.CMS-CSST-2021-B01 and CMS-CSST-2021-A01funded by the National Natural Science Foundation of China(NSFC,Grant No.11080922)。
文摘Galaxy photometric redshift(photoz)is crucial in cosmological studies,such as weak gravitational lensing and galaxy angular clustering measurements.In this work,we try to extract photoz information and construct its probability distribution function(PDF)using the Bayesian neural networks from both galaxy flux and image data expected to be obtained by the China Space Station Telescope(CSST).The mock galaxy images are generated from the Hubble Space Telescope-Advanced Camera for Surveys(HST-ACS)and COSMOS catalogs,in which the CSST instrumental effects are carefully considered.In addition,the galaxy flux data are measured from galaxy images using aperture photometry.We construct a Bayesian multilayer perceptron(B-MLP)and Bayesian convolutional neural network(B-CNN)to predict photoz along with the PDFs from fluxes and images,respectively.We combine the B-MLP and B-CNN together,and construct a hybrid network and employ the transfer learning techniques to investigate the improvement of including both flux and image data.For galaxy samples with signal-to-noise ratio(SNR)>10 in g or i band,we find the accuracy and outlier fraction of photoz can achieve σ_(NMAD)=0.022 and η=2.35% for the B-MLP using flux data only,and σ_(NMAD)=0.022 and η=1.32% for the B-CNN using image data only.The Bayesian hybrid network can achieve σ_(NMAD)=0.021 and η=1.23%,and utilizing transfer learning technique can improve results to σ_(NMAD)=0.019 and η=1.17%,which can provide the most confident predictions with the lowest average uncertainty.
基金supported by the National SKA Program of China(Grant Nos.2022SKA0110200 and 2022SKA0110202)the National Key Research and Development Program of China(Grant Nos.2023YFA1607800,2023YFA1607802,2023YFA1607804,and 2022YFF0503400)+6 种基金the National Natural Science Foundation of China(Grant Nos.12103037 and12273020)the 111 Project(Grant No.B20019)Shanghai Natural Science Foundation(Grant No.19ZR1466800)the science research grants from the China Manned Space Project(Grant Nos.CMS-CSST-2021-A02,CMS-CSST-2021-A03,and CMS-CSST-2021-B01)the Fundamental Research Funds for the Central Universities(Grant No.XJS221312)supported by Science Research Project of Hebei Education Department No.BJK2024134supported by the High-Performance Computing Platform of Xidian University。
文摘The measurement of cosmological distances using baryon acoustic oscillations(BAO)is crucial for studying the universe’s expansion.The China Space Station Telescope(CSST)galaxy redshift survey,with its vast volume and sky coverage,provides an opportunity to address key challenges in cosmology.However,redshift uncertainties in galaxy surveys can degrade both angular and radial distance estimates.In this study,we forecast the precision of BAO distance measurements using mock CSST galaxy samples,applying a two-point correlation function(2PCF)wedge approach to mitigate redshift errors.We simulate redshift uncertainties of σ_(0)=0.003 andσ_(0)=0.006,representative of expected CSST errors,and examine their effects on the BAO peak and distance scaling factors,α_(⊥)andα_(||),across redshift bins within 0.0<z≤1.0.The wedge 2PCF method proves more effective in detecting the BAO peak compared with the monopole 2PCF,particularly forσ_(0)=0.006.Constraints on the BAO peaks show thatα_(⊥)is well constrained around 1.0,regardless of σ_(0),with precision between 1%and 3%across redshift bins.In contrast,α_(||)measurements are more sensitive to increases inσ_(0).Forσ_(0)=0.003,the results remain close to the fiducial value,with uncertainties ranging between 4%and 9%;forσ_(0)=0.006,significant deviations from the fiducial value are observed.We also study the ability to measure parameters(Ω_(m),H_(0)r_(d))using distance measurements,proving robust constraints as a cosmological probe under CSST-like redshift uncertainties.These findings demonstrate that the CSST survey enables few-percent precision measurements of D_(A)using the wedge 2PCF method,highlighting its potential to place tight constraints on the universe’s expansion history and contribute to high-precision cosmological studies.
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.
