We use the distance sum rule method to constrain the spatial curvature of the Universe with a large sample of 161strong gravitational lensing systems,whose distances are calibrated from the Pantheon compilation of typ...We use the distance sum rule method to constrain the spatial curvature of the Universe with a large sample of 161strong gravitational lensing systems,whose distances are calibrated from the Pantheon compilation of typeⅠa supernovae using deep learning.To investigate the possible influence of mass model of the lens galaxy on constraining the curvature parameterΩ_(k),we consider three different lens models.Results show that a flat Universe is supported in the singular isothermal sphere(SIS)model with the parameterΩ_(k)=0.049_(-0.125)^(+0.147).While in the power-law(PL)model,a closed Universe is preferred at the~3σconfidence level,with the parameterΩ_(k)=-0.245_(-0.071)^(+0.075).In the extended PL model,the 95%confidence level upper limit ofΩ_(k)is<0.011.As for the parameters of the lens models,constraints on the three models indicate that the mass profile of the lens galaxy could not be simply described by the standard SIS model.展开更多
From the Main galaxy data of the SDSS Data Release 4 （SDSS4）, we have identiffed close galaxy pairs at neighbourhood radius R = 100 kpc by three-dimensional cluster analysis. Using the criterion that an ＂isolated g...From the Main galaxy data of the SDSS Data Release 4 （SDSS4）, we have identiffed close galaxy pairs at neighbourhood radius R = 100 kpc by three-dimensional cluster analysis. Using the criterion that an ＂isolated galaxy pair＂ must be separated from its ＂nearest neighbor＂ by more than 500 kpc, we constructed an isolated galaxy pair sample of 1158 pairs. We also constructed a random pair sample by randomly selecting 1158 galaxy pairs from the Main galaxy sample, which has the same redshift distribution as the isolated galaxy pair sample, and in which the two components of any pair have the same redshifts. Comparative studies of luminosity and size between the members of the galaxy pairs are performed. We find and further confirm there is no tendency for paired galaxies to have similar luminosities or sizes. From the isolated pair sample we also selected a subsample with the magnitude limit of the primary raised by 2 magnitudes, so as to include pairs in which the secondary is 2 magnitudes fainter than the primary. This subsample contains 82 pairs. A random pair sample is similarly constructed.展开更多
We present disk thicknesses, some other parameters and their statistics of 108 nonedge-on spiral galaxies. The method for determining the disk thickness is based on solving Poisson＇s equation for a disturbance of mat...We present disk thicknesses, some other parameters and their statistics of 108 nonedge-on spiral galaxies. The method for determining the disk thickness is based on solving Poisson＇s equation for a disturbance of matter density in three-dimensional spiral galaxies. From the spiral arms found we could obtain the pitch angles, the inclination of the galactic disk, and the position of the innermost point （the forbidden region with radius r0 to the galactic center） of the spiral arm, and finally the thickness.展开更多
文摘We use the distance sum rule method to constrain the spatial curvature of the Universe with a large sample of 161strong gravitational lensing systems,whose distances are calibrated from the Pantheon compilation of typeⅠa supernovae using deep learning.To investigate the possible influence of mass model of the lens galaxy on constraining the curvature parameterΩ_(k),we consider three different lens models.Results show that a flat Universe is supported in the singular isothermal sphere(SIS)model with the parameterΩ_(k)=0.049_(-0.125)^(+0.147).While in the power-law(PL)model,a closed Universe is preferred at the~3σconfidence level,with the parameterΩ_(k)=-0.245_(-0.071)^(+0.075).In the extended PL model,the 95%confidence level upper limit ofΩ_(k)is<0.011.As for the parameters of the lens models,constraints on the three models indicate that the mass profile of the lens galaxy could not be simply described by the standard SIS model.
基金Supported by the National Natural Science Foundation of China.
文摘From the Main galaxy data of the SDSS Data Release 4 （SDSS4）, we have identiffed close galaxy pairs at neighbourhood radius R = 100 kpc by three-dimensional cluster analysis. Using the criterion that an ＂isolated galaxy pair＂ must be separated from its ＂nearest neighbor＂ by more than 500 kpc, we constructed an isolated galaxy pair sample of 1158 pairs. We also constructed a random pair sample by randomly selecting 1158 galaxy pairs from the Main galaxy sample, which has the same redshift distribution as the isolated galaxy pair sample, and in which the two components of any pair have the same redshifts. Comparative studies of luminosity and size between the members of the galaxy pairs are performed. We find and further confirm there is no tendency for paired galaxies to have similar luminosities or sizes. From the isolated pair sample we also selected a subsample with the magnitude limit of the primary raised by 2 magnitudes, so as to include pairs in which the secondary is 2 magnitudes fainter than the primary. This subsample contains 82 pairs. A random pair sample is similarly constructed.
基金the National Natural Science Foundation of China.
文摘We present disk thicknesses, some other parameters and their statistics of 108 nonedge-on spiral galaxies. The method for determining the disk thickness is based on solving Poisson＇s equation for a disturbance of matter density in three-dimensional spiral galaxies. From the spiral arms found we could obtain the pitch angles, the inclination of the galactic disk, and the position of the innermost point （the forbidden region with radius r0 to the galactic center） of the spiral arm, and finally the thickness.
