Large scale spectroscopic surveys such as that using Large-sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) have collected spectra of millions stars in the Milky Way.Utilizing this huge sample of stars to s...Large scale spectroscopic surveys such as that using Large-sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) have collected spectra of millions stars in the Milky Way.Utilizing this huge sample of stars to study the assembling history and structure of our Galaxy requires accurate estimates of distance,extinction,age,and mass for individual stars.Combining the parallax constraint from Gaia EDR3 with Bayesian inference,we have estimated the distance and extinction for stars observed in LAMOST DR7,as well as the stellar mass and age for evolved stars in this data release.We validated the accuracies of the stellar parameters by comparing our results against various measurements,including the star-pair technique,asteroseismology,globular clusters,and isochrone fits to main sequence stars and subgiants.This is a valuable catalog of stellar parameters under a Bayesian framework estimated using the data from Gaia EDR3 and LAMOST spectroscopic data.With this data set we explored the stellar population of the Galactic massive substructure Gaia-Sausage-Enceladus(GSE).The kinematically selected members of GSE have a median metallicity of [Fe/H] =-1.29 and a median age of 11.6 Gyr.展开更多
Quasars are very important in materializing the reference frame.The excess emission of active galactic nuclei(AGNs) in the mid-infrared band can be used to identify quasar candidates.As extremely distant and point-lik...Quasars are very important in materializing the reference frame.The excess emission of active galactic nuclei(AGNs) in the mid-infrared band can be used to identify quasar candidates.As extremely distant and point-like objects,quasars also could be further selected by an astrometry method.Increasing the number of reliable quasar candidates is necessary in characterizing the properties of Gaia astrometric solution and evaluating the reliability of Gaia’s own quasars classification.We identify quasars by using appropriate All WISE [W1-W2] color and different combinations of astrometric criteria.Together with the contamination and completeness,the magnitude,astrometric properties,density distribution,and the morphological indexes of these selected quasars are evaluated.We obtain a quasar candidate catalog of 1,503,373 sources,which contains 1,186,690 candidates(78.9%) in common with the Gaia EDR3_AGN catalog and 316,683 newly identified quasar candidates.The completeness of this catalog is around 80% compared to LQAC5,and the purity of the overall catalog is about 90%.We also found that the purity of quasar candidates selected by this method will decrease in the crowded sky area and the region with less WISE observations.展开更多
基金The Guo Shou Jing Telescope(the Large-sky Area Multi-Object Fiber Spectroscopic Telescope,LAMOST)is a National Major Scientific Project built by the Chinese Academy of Sciences.Funding for the project has been provided by the National Development and Reform Commissionsupported by the National Natural Science Foundation of China(NSFC,Grant No.12073047)。
文摘Large scale spectroscopic surveys such as that using Large-sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) have collected spectra of millions stars in the Milky Way.Utilizing this huge sample of stars to study the assembling history and structure of our Galaxy requires accurate estimates of distance,extinction,age,and mass for individual stars.Combining the parallax constraint from Gaia EDR3 with Bayesian inference,we have estimated the distance and extinction for stars observed in LAMOST DR7,as well as the stellar mass and age for evolved stars in this data release.We validated the accuracies of the stellar parameters by comparing our results against various measurements,including the star-pair technique,asteroseismology,globular clusters,and isochrone fits to main sequence stars and subgiants.This is a valuable catalog of stellar parameters under a Bayesian framework estimated using the data from Gaia EDR3 and LAMOST spectroscopic data.With this data set we explored the stellar population of the Galactic massive substructure Gaia-Sausage-Enceladus(GSE).The kinematically selected members of GSE have a median metallicity of [Fe/H] =-1.29 and a median age of 11.6 Gyr.
基金supported by the Youth Innovation Promotion Association CAS with Certificate Number 2022259the grants from the Natural Science Foundation of Shanghai through grant 21ZR1474100+1 种基金the National Natural Science Foundation of China(NSFC)through grants 12173069,and 11703065the science research grants from the China Manned Space Project with NO.CMS-CSST-2021-A12 and NO.CMS-CSST-2021-B10。
文摘Quasars are very important in materializing the reference frame.The excess emission of active galactic nuclei(AGNs) in the mid-infrared band can be used to identify quasar candidates.As extremely distant and point-like objects,quasars also could be further selected by an astrometry method.Increasing the number of reliable quasar candidates is necessary in characterizing the properties of Gaia astrometric solution and evaluating the reliability of Gaia’s own quasars classification.We identify quasars by using appropriate All WISE [W1-W2] color and different combinations of astrometric criteria.Together with the contamination and completeness,the magnitude,astrometric properties,density distribution,and the morphological indexes of these selected quasars are evaluated.We obtain a quasar candidate catalog of 1,503,373 sources,which contains 1,186,690 candidates(78.9%) in common with the Gaia EDR3_AGN catalog and 316,683 newly identified quasar candidates.The completeness of this catalog is around 80% compared to LQAC5,and the purity of the overall catalog is about 90%.We also found that the purity of quasar candidates selected by this method will decrease in the crowded sky area and the region with less WISE observations.
